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If your like me when reading or talking to more experienced users in the Home Theater or Audiophile Videophile world, you are a little confused by some of the abbreviations and jargon that they use. That is why I've decided to add this 'Glossary' page to my site. To help 'us' learn more and aid in conversation. (with Salesmen too!) It starts with 'abbreviations' followed up with a 'glossary of terms' with definitions. Enjoy...and if you notice any that aren't here...e-mail me at the bottom of the page with it!

Here are some of the various technical 'abbreviations' that you will find in conversation, articles, and in forums. 'Click' the letter of the alphabet that you wish to find and you will jump down or just scan through the list! (...or on to the Glossary)


480i 480 scan lines, interlaced
480p 480 scan lines, progressive
720p 720 scan lines, progressive
1080i 1080 scan lines, interlaced

A, amp: Ampere
AAC: Advanced Audio Coding
A/D: Analog To Digital
A/V: Audio/Video
A: Amperes
AC: Alternating Current
AC-3: Audio Code 3
ADC: Analog-To-Digital Converter
adj-ch: Adjacent-channel
adj-ch: Adjacent-channel Selectivity
AE: Auto Exposure
AES: Audio Engineering Society
AFC: Automatic Frequency Control
AGC: Automatic Gain Control
alt-ch: Alternate-channel
alt-ch-sel: Alternate-channel Selectivity
AM: Amplitude Modulation
amp: Amplifier or Ampere
AM rej: AM Rejection
ANSI: American National Standards Institute
APL: Average Picture Level
ATRAC: Adaptive Transform Acoustic Coding
ATSC: Advanced Television Systems Committee
aux: Auxiliary
A/V: Audio / Video
AWG: American Wire Gauge

B-frame: Bidirectional Frame
BJT: Bipolar Junction Transistor
B-Y: Blue Minus Luminance
BPF: Bandpass Filter
bps: Bits Per Second

C: Chrominance or Color
CATV: Cable TV
CCD: Charge-coupled Device
CCTV: Closed Circuit TV
CD: Compact Disc
CD-R: Recordable CD (unerasable)
CD-ROM: Computer Data CD
CD-RW: Rewritable CD
CEA: Consumer Electronics Association
CG: Character Generator or Computer Graphics
ch: Channel
CIE: Commission International de l'Eclairage (Int'l Commission on Illumination)
CPU: Central Processing Unit
CrO2: Chromium Dioxide
CRT: Cathode-Ray Tube

D/A: Digital To Analog
DAB: Digital Audio Broadcasting
DAC: Digital-to-Analog Converter
dB: Decibel
dBA: Decibel, A-weighted
dBf: Decibel re 1 Femtowatt
dBFS: Decibel re Digital Full Scale
DBS: Digital Broadcast Satellite
dBSPL: Decibel of SPL
dBW: Decibel re 1 Watt
DC: Direct Current
DCDi: Directional Correlation Deinterlacing
DCT: Discreet Cosine Transform
DD: Dolby Digital
D-ILA: Direct-drive Image Light Amplifier
DIN: Deutsche Industrie Normen (German Industry Standards)
DLP: Digital Light Processing
DMAT: Digital Music Access Technology
DMD: Digital Micro-mirror Device
DPL: Dolby Pro Logic
DSD: Direct Stream Digital
DSP: Digital Signal Processing
DSS: Digital Satellite System
DTS: Digital Theater Systems
DTS-ES: DTS Extended Surround
DTV: Digital Television
DV: Digital Video
DVD: Not officially an abbreviation, often interpreted as "digital video disc"
DVD-R, DVD+R: Recordable DVD (unerasable)
DVD-RAM, DVD+RW, DVD-RW: Types of re-writable DVD
DVI: Digital Visual Interface

EBU: European Broadcasting Union
ECC: Error-correction Code
EDTV: Enhanced Definition TV
EIAJ: Electronic Industries Association of Japan
EMI: Electromagnetic Interface
EPG: Electronic Program Guide
EQ: Equalizer, Equalization

F: Farad, Fahrenheit
f: Femto (one quadrillionth)
f/: F-stop
FET: Field Effect Transistor
FFT: Fast Fourier Transform
FL: Focal Length
FM: Fequency Modulation
fps: Frames Per Second
FR: Frequency Response
ftL: Footlambert

G: giga (one billion or 1,073,741,824)
GHz: Gigahertz (1,000,000,000 Hz)
GUI: Graphical User Interface

HD: High Definition
HDCD: High Definition Compatible Digital
HDR: Hard-disk Recorder
HDTV: High Definition TV
Hx: Headroom Extension
Hz: Hertz, or Cycles Per Second

I/O: Input/Output
IC: Integrated Circuit
IEC: International Electrotechnical Commission
IEEE: Institute of Electrical & Electronic Engineers
IEEE 1394: Firewire or i.Link Interface
IEEE 958: SPDIF Interface
IF: Intermediate Frequency
I-frame: Interpolated Frame
IHF: Institue of High Fidelity
IM: Intermodulation (distortion)
imp: Impedance
IR: Infrared
IRD: Integrated Satellite Receiver/Decoder
IRE: Institute of Radio Engineers
ISDN: Integrated Services Digital Network
I2S: Inter-IC Sound
ISO: International Standards Organization

JFET: Junction Field Effect Transistor
JPEG: Joint Photographic Experts Group
K: Kelvins
k: Kilo, (one thousand, or 1,024)
kbps: Kilobits Per Second
kHz: Kilohertz
LCD: Liquid Crystal Display LCOS: Liquid Crystal On Silicon LD: Laserdisc LED: Light-Emitting Diode LFE: Low Frequency Effects lm: Lumen
LNB: Low-Noise Block Downconverter
L/R: Left/Right
LSB: Least Significant Bit
LSI: Large Scale Integrated Circuit
Lt/Rt: Left Total/Right Total
lx: Lux

M: Mega (one million
m Mter or Milli(one thousandth)
mA mAh: Milliampere Hours
MB: Megabyte
Mbps: Megabits Per Second
MC: Moving-coil
MD: MiniDisc
MDF: Medium Density Fiberboard
MDLP: MiniDisc LP Mode
mH: Millihenry
MHz: Megahertz
mic: Microphone
MIDI: Musical Instrument Digital Interface
MIPS: Million Instructions Per Second
mm: Millimeter
MM: Moving-magnet
MMC: Multi-Media Card
MOL: Maximum Output Level
MOSFET: Metal Oxide Semi-Conductor Field-Effect Transistor
MP3: MPEG-1 Layer 3 Audio Encoding
MPEG: Moving Picture Experts Group
MPX: Multiplex
ms: millisecond
MSB: Most-significant Bit
MTS: Multichannel Television Sound
mV: millivolt
mW: milliwatt

n: Nano (one billionth)
NAB: National Association of Broadcasters
ND: Neautral Density
Ni-Cd: Nickel Cadmium
Ni-Mh: Nickel Metal Hydride
NR: Noise Reduction
NTSC: National Television System Committee
nWb: Nanoweber

OFC: Oxygen Free Copper
OFHC: Oxygen Free High-conductivity Copper
: Ohm

p: pico (one trillionth)
PAL: Phase-Alteration Line
PCM: Pulse-Code Modulation
PC-OCC: Pure Copper, Continuous Casting
PDM: Pulse Density Modulation
pF: Picofarad
P-frame: Predicted Frame
PIP: Picture-In-Picture
PLL: Phase Locked Loop
PLUGE: Picture Line-Up Generator
poly: Polypropolene
PPV: Pay-per View
PVC: Poly-vinyl Chloride
PVR: PWM: Pulse-width Modulation

RAM: Random Access Memory
RC: Resistor Capacitor
RDS: Radio Data System
re: Referred to, In Referrence To
R-Y: Red Minus Luminance
RF: Radio Frequency
RFI: Radio Frequency Interface
RGB: Red, Green, and Blue
RGB+H/V: Red, Green, and Blue plus Horizontal & Vertical Sync
RIAA: Recording Industry Association Of America
RISC: Reduced Instruction-Set Computer
rms: Root Mean square
ROM: Read Only memory
rpm: Revolutions Per Minute
RPTV: Rear-Projection TV
RTA: Real-Time Spectrum Analyzer

s or sec: Second
SACD: Super Audio CD
SAP: Secondary Audio Program
SBR: Styrene-Butadiene Rubber
SCA: Subsidiary Communications Authorization
SCMS: Serial Copy Management System
SD: Secure Digital Memory Card
SDDS: Sony Dynamic Digital Sound
SDTV: Standard Definition (digital) TV
SECAM: Sequential Color With Memory
sel: Selectivity
sens: Sensitivity
sep: Separation
SMPTE: Society of Motion Picture and Television Engineers
S/N or SNR: Signal-To-Noise Ratio
SPDIF: Sony/Phillips Digital Interface
SPL: Sound Pressure Level
SPL/W/m: SPL w/ A 1-Watt Input Measured At 1 Meter
SVCD: Super Video CD

TBC: Timebase Corrector
TCXO: Temperature-controlled Crystal Oscillator
THD: Total Harmonic Distortion
THD+N: THD plus Noise
TIM: Transient Intermodulation (distortion)
TOC: Table Of Contents
TTL: Through-The-Lens

USB: Universal Serial Bus

V: Volt
VA: Volt-ampere
VCD: Video CD
VCR: Video Cassette Recorder
VBI: Vertical Blanking Interval
VHS: Video Home System
VU: Volume Unit

W: Watt
W&F: Wow & Flutter
WAV or .wav: Windows Audio File Format
W/ch: Watts Per Channel
WMA: Windows Media Audio
wrms:Weighted Root Mean Square
wtd: Weighted

XDS: Extended Data Services

Y: Luminance
Y/C: Luminance & Chrominance
YCbCr: Digital Luminace + Color Difference
YPbPr: Analog Luminace + Color Difference

Here are some of the various technical 'terms' that you will find in conversation, articles, and in forums. 'Click' the letter of the alphabet that you wish to find and you will jump down or just scan through the list! (MORE COMING SOON! :)...this will take a while... )


AAC (Advanced Audio Coding): An audio codec, first developed by the Fraunhofer Institute (which first developed MP3) and others, that's being used increasingly for downloaded music files, streaming-media, and satellite-radio applications.

accessory shoe: A connector on the top of a camcorder that can hold a floodlamp, external microphone, or other accessories.

acoustic-suspension: A speaker enclosure design that uses the air trapped inside a sealed cabinet to provide a portion of a driver's restoring force; see infinite-baffle.

AC-3:see Dolby Digital.

active crossover: An electronic component that divides the signal from a source component into frequency bands (low & high, for example) before each band is separately amplified.

active scan lines: Those scan lines in a video frame that carry picture information rather than being used for other data (such as closed captioning) or for synchronization.

adjacent-channel selectivity (adj-ch sel): A measure of how well an FM tuner rejects signals from stations one channel up or down (0.2 MHz away) from the tuned frequency; higher figures are better.

AES/EBU interface: The professional standard for transmitting digital audio signals between components, jointly specified by the Audio Engineering Society (AES) and the European Broadcasting Union (EBU).

alternate-channel selectivity (alt-ch sel): A measure of how well an FM tuner rejects signals from stations two channels (0.4 MHz) away from the tuned frequency; higher figures are better.

ambience: The acoustical character of a listening or performing space, determined mainly by the timing, level, frequency balance, and directions of the sound reflections in it. Some digital signal processors can synthesize ambience by generating artificial reflections.

AM rejection (AM rej): A measure of a tuner's ability to ignore amplitude caused by multipath and other types of interference; higher figures are better.

ampere (A, amp): The primary measurement unit of electrical current, which is the rate of flow of elcectrical charges.

amplifier: A separate component, or a section built into an integrated component, that increases the electrical signal (increases its amplitude). A power amplifier, which is designed to drive speakers, must be connected to a preamplifier (or "control amplifier") to switch and process the sound.

amplitude modulation (AM): A technique in which the level, or amplitude, of a high frequency carrier signal is varied according to the level of a much lower frequency signal so that the envelope of the carrier follows the waveform of the modulating signal. Commonly used to impress an audio or video signal onto a radio-frequency (RF) carrier.

analog: A type of component or recording medium that operates with continuously varying waveforms directly analogous to the signals they representl; see digital

analog-to-digtial (A/D) converter(or ADC): An electronic circuit that converts an analog electrical signal into a series of binary numbers.

anamorphic: A means of recording a widescreen image using special lenses or processing such that the image is distorted in the medium but restored to proper proportions during playback.

aperture grille:see Shadow Mask

aperture: In a vieo camera, an adjustable opening in the optical pathway that controls both the amount of light reaching the image sensor and the image's depth of field.

aspect ratio: The rate of width to height of a screen or image; expressed in whole numbers (4:3, 16:9) or divided out (1.33, 1.78).

assemble edit: An editting process by which a program segment is added to the end of an already existing segment; see insert edit.

AT&T ST connector:see ST.

ATRAC (Adaptive Transform Acoustic Coding): The codec used in the Minidisc (MD) format as well as in Sony's SDDS theater sound sytem. MD equipment that supports the long play MDLP option also use the new ATRAC3 codec. Sony's NetMD devices use ATRAC3 as well, it is also incorporated in Real Audio 8 streaming media when that is operated at certain bit rates.

ATSC (Advanced Television Systems Committee): The industry/government body that issued the US digital TV standard.

attenuate: To reduce or lower a signal's strength.

Audible: A spoken-word format delivered from the internet to computers and portable players that also play MP3 files.

audio/video: Any system or component that involves both audio and video elements, like a receiver or peramplifier that switches video signals and processes multichannel audio signals (including surround sound decoding) for for a home theater system.

autofocus: A camcorder subsytem that focuses the image without user intervention by moving the focusing elements of the lens.

autoreverse: A feature of some cassette decks that enables them to play or record both sides of a cassette without its having to be manually turned over.

aux (auxilliary): An input on a receiver, an integrated amplifier, or peramplifier that can be used to connect line level source components; also, any general purpose A/V input.

A-weighted: A standard equalization curve applied in sound-level meters and signal-to-noise (S/N) measurements to make the readings conform more closely with percieved loudness, particularily at low levels, since human hearing is not equally sensitive at all levels and frequencies.

azimuth: The angle between the magnetic gap of a tape head and the direction of the tape travel, ideally 90 degrees. It often varies slightly from one tape deck to another, and any difference between recording and playback azimuth will result in a loss of treble response.

backlight compensation: A video-cameara function designed to reduce the shadowed effect of the main subject, when the subject is brightly lit from behind.

back surround speaker: One or a pair of surround channel speakers that are placed directly behind the listening position in a 6.1-channel system.

balance: A control that changes the relative volume level in two or more volumes.

balanced line: An interference-rejecting connection technique in which the audio signal is carried on two out-of-phase conductors.

band: A particular continuous segment of a frequency spectrum. For example, a graphic equalizer may divide the audio spectrum (20 Hz to 20 kHz) inot ten bands).

bandpass enclosure: A dual-chamber enclosure for a woofer that creates sharp acoustical rolloffs above and below its operating range, minimizing or eliminating the need for a crossover.

bandpass filter: A circuit that removes signals above and below a certain frequency range.

bandwidth: The range of frequencies a component can reproduce.

bass: The lowest part of the audio spectrum, from 20Hz to 150 or 200 Hz; see treble and midrange.

bass-reflex: A type of speaker enclosure in which the sound emitted from the back of the woofers diaphragm is used to augment low-frequency output by being fed through a port or passive radiator; same as a "vented" enclosure.

Bessel filter: A type of filter with excellent phase characteristics but a very shallow rolloff slope.

biamping or biamplification: The use of separate power amplifiers to feed the woofer and midrange/tweeter in a speaker; see biwiring.

bias: In analog audio tape recording, an ultrasonic tone applied during recording to reduce distortion; in amplifiers, a small current applied to a tube or transistor to reduce crossover distortion.

binary: The base-2 number system, whose numerals are 1 and 0, that forms the basis of all digital computation and electronics. The binary system is electronically useful since it's two numerals can be easily represented by two simple electronic states.

binaural: An audio recording, recording system, or playback system (such as headphones) that carries signals picked up by two microphones places in the "ears" of an acoustically accurate mannequin; theoretically, the only "perfect" record/playback scheme.

bipole: A type of speaker that radiates sound equally and in phase in two directions.

bit: The basic unit of information in digital audio or video, corresponding to on or off, 1 or 0; a contraction of "binary digit".

bit rate: The rate of transmission of digital data of any type, measured in bits per second (see data rate). A stated bit rate may or may not include data for formatting, synchronization, and so on in addition to the audio or video data makinng up the program material proper.

bitstream: A signal that contains digital data in its undecoded state; often referring to SPDIF output from a DVD, when it carries Dolby Digital or DTS signals.

biwiring: The use of separate wires between a single power amplifier and a woofer and the midrange/tweeter in a speaker; see biamping.

black-level control: On a video monitor, a control that adjusts the amount of light put out by the display when it receives the video signal for black (often called the "brightness" control). On a DVD player, a control that adjusts the video output voltage that's generated when it reproduces data representing black.

black-tint picture tube: A CRT in a direct-view TV whose glass has been tinted black in order to heighten contrast in the displayed image.

blue minus luminance (B-Y): Part of a component video signal; see color difference.

BNC connector: A bayonet-type connector used on some A/V gear.

bridged: A stereo multichannel amplifier design that allows the hookup of pairs of output channels to drive one speaker with considerably boosted power.

brightness: see black-level control.

buffer: A temporary storage area for data, especially data read from a disc or downloaded from the internet, so that playback can continue uninterrupted if the data floe is intermittent.

burn: The process of recording with a laser on optical media in computer drives and standalone CD or DVD recorders. Nothing actually burns, but chemical reactions caused by the heat of the tightly focused laser beam produce spot-like changes in the disc's reflectivity that can be "read" like pits in a pressed disc.

Butterworth filter: A type of filter know for it's maximum flat frequency response in its passband.

byte: A cluster or group of eight bits that are transmitted, processed, or interpreted together.

camcorder: A portable, handheld combination video camera and video recorder.

capstan: A rotating shaft in a tape recorder that, in conjunction with a pinch-roller, pulls the tape across the heads. A closed-loop, dual-capstan machine has capstans at both ends of the tape-head assembly.

capture ratio: A measure, in decibels, of an FM tuner's ability to reject all but the strongest signal on a tuned frequency; lower figures are better.

cardioid microphone: A microphone who's highest sensitivity is directly perpendicular to its diaphragm, usually straight ahead, and that rejects sound from the sides and rear (compare omnidirectional microphone or shotgun microphone) the most common type of microphone in a camcorder.

carrier: A high frequency sine wave whose alterations in amplitude, frequency, or phase are used to convey (carry) the information in a much lower-frequency signal or band of signals.

cassette deck: An analog tape recorder, or deck, that uses standard-size audio cassettes.

CAV Laserdisc: A type of laserdisc that spins at a constant angular velocity (constant rpm) such that the laser pickup reads one video frame per revolution, allowing a variety of special effects; also called standard play; see CLV.

CD: A polycarbonate disc 12 centimeters (approx. 4 3/4 inches) in diameter that can store more than 80min of stereo sound in 16-bit linear PCM digital format. A laser pickup reads refelctions from the microscopic "pits" and "lands" on its internal metallized information layer.

CD Text: Artist names, track titles, and the disc title stored as text on some CD's; you need a CD Text-capable CD player to read and display this information.

center channel: A third front channel used to compliment the front left and right stereo channels in multi-channel audio/video or surround sound system; its primary purpose is to stabilize the center of the reproduced soundstage for off-center listeners.

channel: In audio, a distinct path for a signal; stereo and binaural signals have two channels; multichannel systems such as Dolby Digital, DTS, and Dolby Surround (Pro Logic) use additional channels for a center speaker in front and surround speakers at the the sides or rear. In Dobly Digital or DTS, an LFE channel is devoted to loud low-frequency sound effects. In broadcasting, a channel is a specified frequency band assigned to carry a station's signal.

channel separation: A measure of the amount of signal leakage between audio channels, expressed in decibels; higher figures are better,.

charge-coupled device (CCD): A semiconductor technology used to make, among other things, solid state image sensor's.

chip: An intigrated circuit, so called because it is usually a small piece of silicon chipped off a larger 'wafer' that may contain hundreds of other circuits.

chrominance (chroma, C): A video signal carrying only the point-to-point color, both hue and saturation, of a video image and not its brightness; see luminance.

Class A: An amplifier operating design in which the output devices conduct current at all times - an inefficient technique, but one that eliminates crossover distortion.

Class AB: A very common amplifier configuration that is designed to minimize crossover distortion at low signal levels while maintaining higher operating efficiencey than a Class A design.

Class B: A more efficient type of amplifier configuration that Class A or Class AB in which no current flows through an output device when it is not carrying a signal. While prone to crossover distortion, Class B designs have been successfully used as amplifiers in powered subwoofers.

clipping: Overload distortion that occurs when an electronic device cannot accomodate the maximum level requirements of the input signal, shearing off ("clipping") the waveform peaks.

clone: A digital copy that is a perfect (bit-accurate) numerical reproduction of an original digital signal.

closed captioning: A sytem that transmits caption or subtitle text and symbol data during the non-image portion of a video signal. This requires special circuitry.

closed-loop: A drive system used in tape decks in which the tape is pulled by dual capstans, one on either side of the tape head, so that the part being played or recorded is held tight and is fully isolated from the reel hubs.

coaxial: A type of cable construction in which and inner conducting wire is surrounded by a shielding cylindrical outer conductor; commonly used in digital audio and video connections. Connectors maintaining this construction can also be referred to as coaxial. Aslo refers to a speaker configuration in which two drivers (speakers) are mounted one behind the other so that their centers are in line.

codec: Short for coder-decoder, a circuit or computer program designed to reduice the amount of digital data it takes to transmit an audio or video signal.

coloration: A frequency-response anomaly that alters the percieved timbre of sound.

color balance: see white balance

color control: A video-monitor adjustment that changes the amount of chrominance applied to the image; see Saturation

color difference: A system of transmitting video information in which the color signals contain the difference between a given primary color (red, green, or blue) and the luminance signal. The color information on DVD's and in component video signals is encoded in this way.

color temperature: The specific shade of white produced by a video monito in response to a pure white (luminance only) input signal, measured in kelvins (K). Low color temperatures produce a "white" that's tinted reddish-orange compared with the bluish "white" at high color temperatures.

comb filter: In video equipment, a circuit that separates the chrominance from the luminance signals contained in a composite video signal. Audio producers use comb filters to produce "phasing" and "flanging" effects.

combi-player: A component that plays two partly or largely incompatible formats such as DVD-Video discs and Super Audio CD's or DVD's and VHS tapes.

component: A seperate piece of audio or video equipment, with its own chassis and power supply, that performs one specific function or a set of related functions.

component video: A method of transmitting video signals that continuously keeps the various color components separate from each other. Consumer component-video connections carry luminance and two color-difference signals.

compression: A reduction of an audio signal's dynamic range or of the size of digital audio of video data files. Not all compression is bad: dynamics can be uncomfotably wide (soft sounds get lost in room noise, while loud sounds are deafening), and digital files can be much bigger than they need to be to convey audio and video of aparent high fidelity.

continuous average power: The maxiumum undistorted power that an amplifier can deliver on a sustained basis. This specification is meanigful only when accompanied by the load impedance into which the power is delivered, the frequency range over which the power can be delivered, and the maximum distortion at the rated power.

contrast: In general, the range between the brightest and darkest parts of an image; on a video-monitor a control that adjusts the overall gain of the video signal on its way to the display.

convergence: Adjustments in a CRT-based projection monitor that align the primary-color images produced by the three internal CRT's. In a direct-view color TV, convergence refers to the alignment of the beams generated by the three electron guns.

crossover (crossover network): A circuit or component comprising of low-pass, high-pass, or bandpass filters that separate lower-frequency signals from the higher frequency ones. A crossover is used in a speaker that uses more than one driver. In a two-way speaker the crossover sends the low frequencies to the woofer, and the high frequencies to the tweeter. see Active Crossover & Passive Crossover

crossover (switching) distortion: A type of distortion that can occur in an amplifier when a signal code does not smoothly swing from positive to negative or vice versa as it is passed (switched) from one output device to another.

crossover frequency (or point): In a crossover network, the point at which frequencies are divided so that they can be routed to the appropriate drivers (low's to woofers & high's to tweeter's for example).

CRT (cathode-ray tube: A vaccum tube in which electrons emitted by a hot cathode are focused into beams and are scanned across a fluorescent screen to produce a picture.

crystal: see quartz.

current: The rate of flow of electrical charges in a circuit, measures in amperes.

cutoff frequency: A frequency at which a rolloff begins to take effect. It is normally specified at the point at which the output falls by -3 or -6 dB, depending on the rolloff. see rolloff.

damping: The application of mechanical impedance, such as from a rubber or silicone material, to the suspension of a a speaker diaphragm (or the cantilever pivot of a phono cartridge) to reduce the amplitude of a resonance.

damping factor: The ratio of a speaker's nominal impedance (usually 8 ohms) to the output impedance of tha mplifier driving it. In amplifier specifications, higher numbers are better.

data rate: The rate at which digital information is transmitted or received; typically measured in kilobits per second (kbps) or megabits per second (Mbps).

dBf: Decibels referred to a standard level of 1 femtowatt (one quadrillionth of a watt) at a tuner or receiver's FM-antenna terminals.

dBFS: Decibels referred to a 0-dB level of digital full scale, the maximum numerical signal level encodable by a digital audio system.

decibel: The most commonly used measurement unit in audio, a decibel is a logarithmic unit expressing the ratio of two powers, currents, voltages, or sound-pressure levels (SPL's). An increase in 10dB represents an tenfold increase in power, and an increase of 20dB represents a tenfold increase in voltage. Doubling the power in watts delivered to a speaker raises it output SPL by about 3 dB.

decorrelation: A process that scrambles the relative phase of the signals sent to the surround speakers in a home theater system in order to increase the sense of sound field envelopement; part of the Home THX standard.

defeat: To bypass the the actions of a signal processor, tone controls, or other circuitry.

defect tracking: A measure of how well a DVD or CD player's laser pickup and tracking circuits handle flaws on a disc.

deinterlacing: The process of converting a field-based image (ie. the video on a DVD) to a frame-based image ( as would be delivered from a DVD player's progressive scan output).

diaphragm: The moving surface in an audio transducer such as a speaker or microphone.

digital: A digit is a number, and digital devices use numbers in some way. A digital tuner, for example, may use numbers only in it's front panel display, or it may use digital frequency-synthesis tuning circuits. Digits can also be used to represent analog signals as in digital audio or video. A CD carries a pattern representing a series of 16-bit binary numbers (16-digit strings of 1's & 0's); a CD player converts these numbers into a continuously changing voltage that represents the recorded music.

digital audio tape (DAT): A rotary-head digital playback fornmat whose cassettes are about half the size of a standard audio cassette.

Digital 8: A developement of the 8mm videocassette system that uses standard 8mm cassettes but records DV-type digital signal. Digital 8 camcorders will play both Digital 8 and 8mm analog tapes.

digital filter: A circuit that alters the frequency content of a waveform by arithmetic manipulation of its digital representation.

Digital Light Processing (DLP): A technology developed by Texas Instruments that utilizes a Digital Micro Mirror Device to project video signals.

Digital Micro-mirror Device (DMD): A chip whose surface is covered by more than half a million tiny movable mirrors.

Digital Music Access Technology (DMAT): A scheme developed by the Recording Industry Association of America (RIAA), in conjunction with recording and computer industries, for distributing music via the internet that wraps layers of financial tansactions and various anticopying/antipiracy safeguards around the music signal; aslo know as the Secure Digital Music Initiative (SDMI).

digital output: A coaxial or fiber-optic output found on some CD and DVD players and digital recorders that is used to send digital audio signals to a component with digital audio input; see SPDIF.

digital signal processing/processor (DSP): A general term for the mathematical manipulation of signals that are in digital form. DSP can be used for a wide variety of tasks, including ambience enhancement, equalization, filtering, time alignment, and noise reduction of audio and video signals. A digital signal processor can be either a seperate component or a part of one.

digital to analog (D/A)convertor (or DAC): An electronic circuit that converts a series of binary codes (or digital "words") into a continuous analog voltage.

Digital Visual Interface (DVI): A high-speed digital interface for digital data (both video and still images), typically used in connecting a computer with a desplay device but also on some HDTV monitors.

digital TV: Broadcast of digital television signals in the U.S. following the standards of the ATSC, which specify the 18 formats to be used. The most common high-deinition (HDTV) formats are variants of 1080i (1,080 scan lines) and 720p (720 progressive scan lines), while the enhanced-definition (EDTV) formats all use 480 progressive scan lines (480p) and the standard-definition (SDTV) formats used 480 interlaced scan lines (480i). Though the EDTV and SDTV formats can have both widescreen (16:9) and conventional (4:3) aspect ratios, the HDTV formats are widescreen only.

digitizing: the process of analog-to-digital conversion, which consists of separate processes of sampling and quantization.

D-ILA (Direct-drive Image Light Amplifier): A reflective liquid-crystal technology suitable for high-resolution displays, also know as LCOS (liquid crystal on silicon).

dipole: A type of speaker that radiates sound equally in two directions but with opposite phase or polarity (see bipole); often used today for the surround speakers in a home theater system.

direct-radiating speaker: Basically, any kind of speaker that is not a 'Dipole' or a 'Bipole'; until dipole speakers became popular most speakers were direct-radiating.

Direct Stream Digital (DSD): A Delta-Sigma system used for recording high-quality digital audio, used in professional recording equipment and the Super Audio CD system.

direct-view TV: Usually refers to a CRT set whose single picture tube is intended for viewing head on, not projected onto a screen.

dispersion: A characteristic of a speakers radiation pattern, particularly at high frequencies, expressed in degrees or in terms of the frequency-response rolloff at various angles relative to the on-axis response.

Dolby B, Dolby C, and Dolby S: Noise reduction (NR) system developed by Dolby Laboratories for use in analog consumer audio tape recorders. Dolby S is the most effective (and rare), followed by Dolby C, and then Dolby B; the most common and oldes NR system.

Dolby Digital: The Dolby Labs format for digital surround sound providing up to 5.1 channel; used in DVD's the digital TV system, and some laserdiscs; formerly called AC-3 (Audio Code 3)

Dolby Digital EX: A system of encoding a quasi-6.1-channel within the 5.1 channel framework of a standard Dolby Digital data stream. The sixth channel is encoded by matrix techniques on the left and right surround channels of the DD signal.

Dolby Pro Logic (DPL): An enhancement to Dolby Surround decoding that extracts a center channel and improves channel separation by means of logic-steering-circuitry.

Dolby Surround: The consumer name for the Dolby Stereo system used for movie soundtracks. Basic Dolby surround extracts the single surround channel to feed a pair of speakers at the back or sides of a room.

dot pitch: The horizontal repititions of the red, green, and blue phosphor pattern in a color CRT.

driver: An individual woofer, midrange, or tweeter, or other transducer within a speaker.

DTS: A multichannel codec developed by Digital Theater Systems and used to carry a 5.1 channel soundtrack on DVD's, CD's and laserdiscs.

DTS Extended Surround (DTS-ES): A developement of DTS that adds 6.1 channel capability.

dubbing: The process of copying a recording, the result being a "dub".

DVD: A high-capacity optical-disc format that enables vast amounts of audio, video or computer data be encoded on a laser-read disc the size of a CD.

DVD-Audio: A music-oriented DVD format that can carry up to six channels of audio at up to 24 bits resolution, with or without video or interactive content.

DVD-RAM: A recordable high-data-density disc system based on the DVD.

DVD-RW: A recordable high-data-density disc system based on the DVD, playable on most of today's players.

DVD-Video: A DVD format used almost exclusively for movies or image-intensive program material; most movie DVD's offer up to 5.1 channels of surround sound, and today most come in widescreen format.

dynamic-headroom: The amount, in decibels, by which an amplifier can exceed its rated continuous average power at 1kHz in short, 20 millisecond bursts.

dynamic range: The difference, in decibels, between the highest and lowest levels of sound or a recording, or between the overload level and the noise floor of a component or a recording medium; higher figures are better.

dynamic speaker: A speaker using the most common type of driver technology, in which the diaphragm is driven by a voice coil.

dynamics: A subjective term describing the ability of a component to render loud and soft musical passages.


early reflections: Reflected sounds in any listening space that reach the ear within the first few milliseconds after the first sounds; see late refelctions & reverberation.

EDTV: see enhanced-definition TV.

EDTV monitor: A TV that can display a 480p-format enhanced-definition degital signal when connected to an outboard tuner/decoder.

efficiency: The percentage of electricall input power going to a speaker that is converted into acoustic energy.

electron gun: A subassembly of a CRT responsible for generating and launching high-velocity electrons aimed at the phosphors on the face of the picture tube.

electrostatic: Speakers and headphones that produce sound by moving a thin, electrically charged diaphragm suspended in a high-voltage electrical field.

enclosure: The box or other construction that makes up the outer shell of a speaker. It's principal purpose is to hold the drivers in alignment and to prevent the sound from a back of a woofer from reaching the front in an uncontrolled way that would result in cancellation of low frequencies.

enhanced CD: A fornmat that adds computer-readable graphics or non-audio data to a music CD.

enhanced-definition TV (EDTV): A subset of the digital TV system that is superior to standard-definition TV mainly because it uses 480p formats at up to 60fps for display.

equalization: Deliberate alteration of frequency response. LP's for instance, require a specific type of playback equaliazation; see RIAA.

error correction: Mathematical reconstruction of of corrupted digital data based on redundant data supplied in the recording or transmission.

expander: A device that increases the dynamic range of incoming signals.

Extended Data Service (XDS): Text and other ancillary data included with a broadcast or cable TV signal, such as time checks, content ratings (see V-Chip), station identification, and more; requires and XDS-capable receiver to display or use the information.

external 5.1-channel (or multichannel) input: An analog connection allowing the hookup of a source component supplying multiple output channels, such as a DVD-Audio or Super Audio Cd player, or a DVD-Video player with full Dolby Digital decoding.

fade: A video transition technique in which a scene gradually recedes into black (fade out) or emerges out of black (fade in).

feedback: In electronics, negative feedback is the return of a small amount of the output signal to the input, in reversed polarity, usually to reduce distortion, obtain a specific frequency response, or to stabilize a circuit. Positive feedback is used in sine-wave oscillators and other test-tone generators.

ferrofluid: A ferromagnetic liquid (magnetic particles suspended in Oil) used in some speaker drivers, espe- cially tweeters, to conduct heat away from the voice coil and improve damping and power handling.

fiber-optic: A transmission medium in which signals are carried through a special plastic, or glass-fiber cable in the form of light; the primary benefit is immunity to electrical noise. See Toslink, ST.

field: A video image containing half of the scan lines of an intertacad frame.

field-effect transistor (FET): A semiconductor ampli- fying device that behaves more like a triode vacuum tube than like a bipolar transistor.

50-dB quieting sensitivity: A tuner specification that indicates the RF signal strength (in microvolts or dBf) required for an incoming FM signal to produce a back- ground noise level 50 dB below the audio output at full modulation; lower figures are better.

filter: A circuit that boosts, attenuates, or removes se- lected frequencies from audio signals.

FireWire: see IEEE 1394.

first-surface mirror: A mirror whose reflective coating is on the top, the first surface the light hits, unlike the typical second surface' bathroom mirror; used in rear- projection TVs.

5.1-channel: The conventional designation for a medium or system thst carries six channels of sound information: front left/center/right, surround left/right, and a restricted-bandwidth (hence the “.1”) LFE channel.

flash memory: A type of nonvolatile random-access memory; flash memory can be embedded in circuitry or placed on a removable card.

flat: Applied to frequency response, a condition in which all input frequencies emerge from the device or medium with the the same relative levels as when they entered. Also a selling, as of an equalizer or tone control, that results in a flat frequency response.

flutter: Rapid, small, pitch fluctuations that are caused by speed irregularities in a turntable or tape deck; ex- pressed as a percentage of variation from the correct speed; see wow-and-flutter.

flying erase head: An erase head mounted on a video recorder's rotating head drum that can selectively erase the video information only, without disturbing the tape's audio, timing, and synchronization signals; allows accurate, glitch- and noise-tree video editing.

focal length: The distance between the optical center of a lens to its focus point.

footcandle: A unit of illumination; 1 footcandle is the amount of light falling on the surface of a sphere of 1- foot radius from a light of 1 candlepower located et its center.

4:3, 4x3: see aspect ratio.

frame: A complete, individual picture on a motion-pic- ture film or contained in a video signal.

frame rate: The rate at which frames are diplayed. In typical modern movies the frame rate is 24 per second; in color NTSC video it Is 29.97 per second.

frequency: Rate of vibration or oscillation, measured in cycles per second, or Hertz (Hz). The audio spectrum is generally taken to be 20 to 20,000 Hz (20Hz-20kHz) which encompasses all of the frequencies that humans can hear. In radio it refers to the signal of the station, such as 88.1 Mhz for an FM station, 770kHz for an AM station.

frequency modulation(FM): A technique in which the frequency of a high-frequency carrier is varied according to the level of much lower-frequency signal. Commonly used to impress an audio signal onto a radio-frequency (RF) carrier.

frequency response: The range of frequencies (or bandwidth), expressed in hertz (Hz), that a component can handle, within specified limits of amplitude error, expressed in decibels (dB).

frequency synthesis: The process by which the various reference frequencies required by a tuner are derived by division of a single reference frequency, usually obtained from a stable quartz oscillator (see phase-locked loop). Frequency synthesis tuner features as digital frequency readouts and station presets along with improved audio performance.

front end: The first stage of a tuner, responsible for selecting and amplifying the desired radio or television signal.

front projector: A type of video display in which the projector elements are housed in a separate unit, not connected to the screen and mounted in front of it, much like a movie projector; front projector; front projectors are often mounted on the ceiling.

f-stop (f/): A number describing the relative size of a lens aperture in a camera, It is derived focal length divided by the aperture diameter and it is normally rated in standardized discrete steps separated by a factor of the square-root of 2(1, 1.4,2.0, 8, and so on). Moving from one f-stop to the next lower stop theoretically doubles the amount of light falling on an image sensor. Commonly referred to as the “speed” of a lens, a misnomer.

gain: The amount by which the amplitude of incoming signals is changed by a circuit or antenna, pressed in decibels (dB). Gain can be positive, for amplification; negative, for attenuation; or 0 dB for no change, or "unity gain."

gamma: A numerical specification for the nonlinearity of the signal/light intensity of video transducers (image sensors, CRTs, LCDs, DLPs). Ideally, the various gammas of a video system should cancel each other out so that the final displayed image has a linear light output.

gigs (G): The metric prefix for billion. In refererence to digital data, giga usually stands for 1073,741, 824 (2 to the 30th power)

gigabyte (GB): 1,073,741,824 bytes; a measure of digital information storage capacity; commonly specifies the data-storage capacity of such media as DVD’s and hard-disk drives.

graphic equalizer: An equalizer with control bands that are fixed in frequency but variable in level; the slide controls for the various bands provide a rough graphic representation of the selected frequency response curve.

graphical user interface (GUI): Any “point-and-click” control system for an electronic component that uses menus and icons displayed on the screen instead of (or in addition to) physical physical push buttons and other controls.

ground: In an electrical circuit, the reference for 0 volts, above and below what other (AC) signals may vary.

hard-disk drive: A digital data storage/retrieval device utilizing a rigid, rapidly rotating disk coated with a magnetic recording surface. Thanks to the rapid rotation rate, the read/write head(s) float on a cushion of air very near the disk's surface, allowing almost instantaneous cueing to any desired location without touching the surface.

hard-disk recorder (HDR): A device using the immense data capacity of a computer-type hard-disk drive to record audio or video signals (or both) in digital form. The video-oriented HDR’s usually have versatile programming options for unattended recording and playback options that can let you zip past commercials or watch a program from the beginning even while its still being recorded; these are sometimes called “personal video recorders" (PVRs).

harmonic distortion: Spurious output signals at whole-number multiples of the frequency of the input signal; see distortion total harmonic distortion (THO).

HDCD (High Definition Compatible Digital): An audio recording system for ODs developed by Pacific Microsonics; when decoded, HDCD recordings are said to have greater bandwidth and dynamic range than standard COs.

HDTV monitor: A TV set that can display full-resolution widescreen high-definition images when connected to an outboard HDTV tuner; see EDTV monitor.

HOTY set: An HDTV monitor that has a built-in high definition tuner.

HDTV tuner: An outboard, usually set-top, digital TV tuner/decoder that can receive high-definition TV programs broadcast over the air as well as from a satellite receiver or cable service and then decode the signals for display in full resolution on a widescreen HDTV monitor.

head: see tape head.

head drum: A rotating cylinder inside a VCR or camcorder around which the tape is wrapped; two or more heads are mounted on the head drum for video recording and playback, hi-fl audio recording and playback, and erasure; see flying erase head.

headphones: A pair of miniature speakers that fit over a listener's ears; "open-air" headphones do not block outside sound or keep sound from the phones from leaking out, whereas "circumaural" (around-the-ear) phones sometimes do both. Even tinier head phones that fit inside the listener's ears are called "earbuds" or "earphones."

headroom: The difference between the signal level at any moment and the maximum level an audio device can handle without clipping or other significant distortion; expressed in decibels (dB).

helical scan: A videotape recording system in which the tape is wrapped around a spinning head drum (forming a helix) so that the recorded tracks trace diagonally across the width of the tape.

hertz (Hz): The standard unit ot frequency, representing cycles per second, or changes away from a basic state and back again. In audio, the basic state is defined as either ordinary air pressure (without sound) or its electrical equivalent: a constant-level (DC) signal, often 0 volts, or ground. For a sound in the audible range, the higher the frequency in hertz, the higher the pitch. In video, frequency usually relates to horizontal luminance resolution; the higher the frequency, the finer the detail and the higher the resolution. A kilohertz (kHz) is a thousand hertz, a megahertz (MHz) a million hertz, and a gigahertz (GHz) a billion hertz.

HI8: A development of the 8mm videocassette system that has extended luminance resolution.

hi-fi: High fidelity, used to refer to an audio system that can reproduce recorded sound with substantial fidelity to the original, VHS Hi-Fi is an audio recording system for VCRs that uses frequency-modulation techniques for improved sound quality.

high-definition TV (HDTV): A specific subset of the digital TV standard that features increased horizontal and vertical resolution, choice of interlaced or progressive scan, and widescreen images; see enhanced-definition TV and standard-definition TV.

high-pass filter: A circuit, as in a speaker's crossover network, that progressively attenuates signals below its cutoff frequency, passing those above unaltered; see filter and low-pass filter.

home theater system: A collection of audio and video components designed and configured to reproduce something like the picture and sound quality that would be experienced from a movie in a good cinema. A home theater is generally expected to include a TV screen of reasonable size and a surround sound audio system. See also Dolby Digital, Dolby Surround, DolbyPro Logic, and DTS.

horizontal luminance resolution: Measured in lines, this is the most common parameter for characterizing the reproduction of fine detail in video. (Do not confuse these "lines" with scan lines).

hue: A color's position in the visible spectrum from red to blue, or its gradation of tint; the professional name for a video monitor's tint control.

HX Pro: see Dolby HX Pro.

IEEE 1394: The Institute of Electrical and Electrical Engineers (IEEE) standard for high-speed, high-capacity digital connections of audio and video components, computers, and peripherals; better known as FireWire (the official brand name) or i.Link.

IF rejection: A measurement of a tuner's ability to reject external interference at the intermediate frequency; higher figures are bailer.

i.Link: see IEEE 1894.

image rejection: A measure of a tuner's ability to reject the sum or difference frequency of its own intermediate and oscillator frequencies; poor suppression results in reception at false frequencies; higher figures are better.

image sensor: The image-to-electricity transducer in a video camera. All consumer video cameras, camcorders, and digital still cameras now use solid-state sensors, usually charge-coupled devices (CCDs).

image stabilizer: A system that removes shakiness in a handheld camcorder image either by varying the readout pattern of the image sensor or by optical compensation with counter-movement of a prism.

imaging: The ability of an audio system to reproduce sounds in a spatially realistic manner.

impedance (imp): In electronics, the total resistance of a component or circuit to the flow of alternating current (AC), expressed in ohms. In addition to pure resistance, it may include reactive (capacitive or inductive) elements that cause its value to vary with frequency. In mechanical engineering (still relevant to speaker design), impedance is something that resists motion by transforming energy, like a spring or shock absorber; see reactance.

index search: A VCR feature that allows automatic rapid cueing to index points recorded on a videotape.

infinite-baffle: A speaker enclosure that is sealed in order to isolate the speaker's front radiation from the back radiation of its drivers. Acoustic-suspension is a special type of infinite-baffle design.

infrared (IR): Light whose wavelength is longer than visible red. "Near infrared" wavelengths close to the visible-tight range are used by line-of-sight remote controls and sensed by come camcorders.

infrasonic filter: A type of high-pace fitter used to attenuate frequencies below about 20 Hz; often celled a "subsonic" filter, a misnomer.

insert edit: An editing process by which a new program segment is inserted into an already recorded segment, replacing the overlapping material; see assemble edit.

integrated amplifier: A component that combines the functions of a preamplifier and power amplifier.

integrated circuit (IC): A miniature, one-piece, solid state device containing many transistors and other electronic components; it is the basic building block of most modern electronics; see chip.

interlaced scan: A video component or signal that assigns alternating scan lines in a video frame to one of two fields, which are then displayed separately (the opposite of progressive-scan), Interlacing reduces picture flicker without the transmission of additional video information.

intermediate frequency (IF): In a tuner, the standard frequency to which the front end converts any tuned carrier for demodulation, 10.7 MHz for FM or 455 kHz for AM.

intermodulation (IM) distortion: A type of distortion whose components are at frequencies that are sums and differences of the input frequencies; lower figures are better.

I2S: Inter-IC Sound: a type of digital audio data format used to transmit signals between ICs.

jack: A female connector that serves as a receptacle for a male connector, or plug; see RCA connector.

Kapton: A plastic material widely used in the manufacture of speaker voice-coil formers.

kelvin (K): A unit on the Kelvin temperature scale, which is the same "size" as a degree on the centigrade/Celsius scale but starts from "absolute zero" (0K = -273'C = -45.7'F) rather than the freezing point of water.

kilo (k): The metric prefix for thousand. In reference to digital data, kilo usually stands for 1,024 (2 to the 10th power).

kilobits per second (kbps): A statement of bit rate or data-transfer speed, usually encountered in reference to downloaded music tiles in MP3 and other compressed-audio formats, where 128 kbps is often cited as the "standard" for acceptable sound quality, though the quality at that rate can actually vary considerably depending on which codec was used. See codec and MP3, AAC, RealAudio, and Windows Media Audio.

kilobyte (kB): 1,024 bytes; a measure of digital information-storage capacity.

laser: A device that generates a coherent, monochromatic beam of light. These two characteristics allow a laser beam to be focused down to very small areas, a trait essential to its use in the CD, DVD, MD, and other optical or magneto-optical data-storage systems.

laserdisc: A laser-read videodisc, usually 12 inches in diameter. Most laserdisc players play CDs as well; see CA V laserdisc and CLV disc.

late reflections: Echoes in an enclosed space that reach the ear after multiple reflections and, consequently, have a relatively long delay time; see early reflections and reverberation.

LCD (liquid-crystal display): Color LCD panels are used in some flat-screen TVs and computer monitors as well as in some video-projection systems. Mono-chrome LCD readouts are used on the faceplates of some A/V components and remote controls.

LOOS (liquid crystal on silicon): A reflective liquid-crystal technology suitable for high-definition displays.

LEO (light-emitting diode): A semiconductor device used as an indicator light on many components.

lenticular: In video, anything containing many small lenses; commonly used to describe video projection screens optimized to produce high picture brightness in certain viewing directions.

letterboxing: The scaling of a widescreen image to fit within a 4:3 aspect ratio screen by shrinking the image's vertical dimension so that the width fits exactly and tilling the resulting spaces above and below the image with black bars. Critics of the technique think that the screen area is being wasted" by the letterboxing bars; see pan-and-scan.

LFE (low-frequency effects) channel: This is the '0.1-channel of a 5.1-channel surround sound sys-tem, containing only very low frequencies; in movie soundtracks it is used primarily for loud sound effects.

limiter: A circuit that prevents a signal from exceeding a certain amplitude.

line doubler: A device that doubles the number of scan lines in a video image, possibly in conjunction with progressive-scan processing; line triplers and line quadruplers are also available.

line interpolation: A process by which additional scan lines are synthesized out of the original scan lines pre-sent in a video image; used to increase the apparent vertical resolution; see line doubler.

linearity: Describes the accuracy with which a component's output signal tracks the input signal; a device whose output varies in direct proportion to the input is said to be linear.

line-level: Signal voltages in the range delivered from the outputs of most audio source components (such as CD players) and preamplifiers; also known as low-level or preamp-level.

LNB (low-noise block downconverter): A device mounted at the focal point of a satellite dish that amplifies the microwave signals collected by the dish and converts them to a lower frequency that's sent to a satellite receiver over standard coaxial cable. An LNBF is an LNB with an integrated feedhorn.

logic: In a surround sound system, “logic-steering" is used to improve separation between multiple channels derived from matrix-encoded two-channel signals. In cassette decks, "full logic controls" indicates the ability to switch from one transport function, such as fast for-ward, to another, such as rewind, without pressing the stop button; doing this in decks without logic controls can damage the tape.

loudness compensation: A form of equalization that progressively emphasizes low frequencies (and some-times high frequencies) as volume is reduced. Loud-ness-compensation circuits are designed to offset the ear's loss of low-frequency sensitivity as the sound level decreases.

low-pass filter: A circuit, as in a speaker's crossover network, that progressively attenuates signals above its cutoff frequency, passing those below unaltered; see filter and high-pass filter

LP: A long-playing vinyl phonograph record.

lumen (lm): A unit for the rate of flow of visible light.

luminance (luma, Y): A video signal that encodes the point-to-point brightness - not the overall brightness and not the color (chrominance) - of a video image. Black-and-white TVs display only luminance signals.

lux (lx): A unit of illumination, equal to one lumen per square meter.

macro: A lens or zoom setting on a camera or camcorder that is optimized for extreme closeups; also, a series of operations programmed to be executed with just one button push on a remote control.

Macrovision: A set of alterations of a standard video signal designed to prevent copying it or, tailing that, to severely degrade the quality of any copies made. DVD players usually apply two types of Macrovision processing to their outputs, pseudo pulse" and "color striping," via circuitry enabled by instructions on the disc.

magazine: The removable module in a CD changer into which six discs are loaded for play and can also be stored (some older magazine changers held five or ten discs per magazine); often called a cartridge."

matrix: A type of circuit commonly used in surround sound encoders and decoders to squeeze three or more channels of information into two or to extract multiple channels from an encoded two-channel signal; also used to describe similar circuits that can synthesize an ambience channel from a non-encoded stereo recording. The term 'matrix" derives from the mathematics involved.

MDLP: A long-playing version of the MiniDisc format utilizing the ATRAC3 codec to provide more than 5 hours of stereo recording time per disc.

mega (M): The metric prefix for million. In reference to digital data, mega usually stands for 1048,~76 (22c).

megabyte (MB): 1048~76 bytes; a measure of digital information-storage capacity.

megachanger: A CD or DVD changer that holds 50 or more discs at a time in a jukebox-like mechanism.

MemoryStick: A flash-memory format developed and promoted by Sony.

MicroMV: A digital camcorder format using MPEG-2 compression that records an hour of video on a tiny cassette about the size of an audio micro-cassette.

microphone: A transducer that converts acoustical energy info an electrical signal; see cardioid micro-phone and shotgun microphone.

microprocessor: An integrated circuit containing a complete central processing unit (CPU) of a computer. A microcomputer is a complete computer (comprising a CPU, memory, and input/output circuitry) on a single IC chip.

midbass: The segment of the audio frequency spectrum covering sounds produced in the upper-bass and lower-midrange regions.

midrange: The segment of the audio frequency spectrum between the bass and treble, which includes most of the fundamental tones of the human voice and of most musical instruments; it runs from approximately 150 or 200 Hz to around 3kHz.

midrange driver: A speaker driver designed to reproduce frequencies from 200 Hz or so up to 2 to 3 kHz.

MiniDisc (MD): A magneto-optical digital audio re-cord/playback format based on the ATRAC family of codecs; more than 5 hours of audio information can be stored on and retrieved from a 2½-inch magneto-optical disc housed in a caddy like those used for computer floppy disks. MD is not compatible with any other disc format.

monitor: In audio, a speaker used in recording or other professional applications; in video, the term can refer to any display device, including TVs, but is often used specifically to denote a display device without tuning functions.

mono (monaural or monophonic): A recording or signal containing one channel of audio. In a component, it indicates that only one channel is handled, as in a mono power amplifier.

MOSFET (metal-oxide-semiconductor field-effect transistor): A type of field-effect transistor, used both in power amplifiers and in digital integrated circuits (such as microprocessors).

moving-coil (MC) cartridge: A magnetic phono cartridge, typically of very low output, in which the magnet is fixed and the coils are attached to the stylus cantilever.

moving-magnet (MM) cartridge: A magnetic phono cartridge in which the coils are fixed and the magnet is attached to the stylus cantilever.

MP3: The common term for the audio codec officially known as MPEG-1 Layer 3. Originally used for sound data in computer-related applications and now popular for music files ripped from CDs or downloaded from the Internet and played on a computer or portable digital device; also see MPEG-2.

MPEG (Moving Picture Experts Group): A commit-tee of engineers and scientists formed to issue standards for reduced-bit-rate digital audio and video.

MPEG-2: The standard reduced-bit-rate audio/video encoding scheme for digital TV, DVDs, and certain digital satellite transmissions.

MPEG-4: A data-encoding standard incorporating advancements to MPEG-2 and AAG in addition to facilities for the synthesis and manipulation of audio and video "objects" (shapes, textures, sounds, and soon).

MTS (multi-channel television sound): The encode/decode system devised by Zenith and dbx and used for stereo analog TV broadcasting in the U.S. An MTS decoder is built into all stereo TVs and VCRs sold in the U.S. Also see SAP.

muddy: A subjective term describing reproduced sound, usually in the bass region, that isn't as clear as it should be.

multi-channel: An audio system or component using more amplifier/speaker channels than a stereo pair.

Multi-Media Card (MMC): A flash-memory format used in many MP3 players.

multi-path: When a broadcast radio or TV signal reaches the receiving antenna over two or more paths of differing lengths ("multiple paths"), usually because it has been reflected from buildings or other objects between the transmitter and the receiver. The resulting interference causes distortion on FM and "ghosts" on standard TV, and may prevent reception of digital TV signals altogether.

multiplex (MPX): Two or more channels transmitted on a single carrier so that they can be independently recovered by the receiver. Usually, as in TV and stereo FM, this is achieved by means of sub-carriers, signals on the main carrier that are themselves modulated by other signals. Some cassette decks have an MPX filter that removes the 19-kffz pilot tone from stereo FM broadcasts to prevent it from interfering with noise-reduction systems for analog tape.

Multi-room system: A system that directs music or video programs from one or more sources to secondary listening/viewing spaces, or zones.

negative feedback: see feedback.

neutral density (ND): Commonly denoting filters that dim the amount of tight reaching a camcorders image sensor without changing the balance of colors.

noise reduction (NR): A system designed to reduce the noise added to a signal during recording or play- back.

noise: Any unwanted signals that are not strongly correlated with the desired signal and that usually arise from a random process. Hiss and hum are typical examples of audible noise. In video programs, noise appears as "snow" onscreen or graininess in the image.

noise shaping: A digital signal processing technique used in digital filters, analog-to-digital converters, and digital-to-analog converters that reduces quantization noise at the frequencies where it is most audible, at the expense of increasing the noise at other frequencies.

nonvolatile memory: A type of digital memory circuit that does not lose its data content when the power is removed .

NTSC (National Television System Committee): The industry/government body that issued the U.S. analog color TV standard that was approved by the FCC (Federal Communications Commission) in 1g53; thus, any video signal or component that operates according to that standard.

octave: A ratio of 2:1 or 1:2 in frequency (measured in hertz). The ear hears changes in frequency of equal multiples or fractions of an octave as equal changes in musical pitch. A one-third-octave interval, used in acoustical measurements, is equal to the musical in- terval ot a major third.

ohm (a): The basic unit of electrical resistance; also see impedance.

omni-directional: Equally sensitive or effective in all directions; might be said of an antenna, a microphone, or a speaker.

1-bit 0/A converter: A circuit that translates a digital signal into an analog waveform using a digital delta- sigma modulator followed by a POM or PWM output converter; see digit al-to-analog (0/A) converter.

optical (fiber-optic) input-output: A special type of jack that accepts fiber-optic connectors; see ST and Toslink.

output-current capability: A rating, in amperes, of the maximum current an amplifier can supply.

output level: A measure of the strength of the output signal of a component.

output transformer: A transformer used to couple the output stage of a power amplifier to a speaker. Output transformers are usually essential in tube amplifiers but are almost never used in solid-state amps.

oversampling: Any digital signal processing tech- nique that generates or uses a sampling rate greater than that required by theory to encode the maximum frequency of interest; used in CD and OVO players' audio digital-to-analog (0/A) converters and output filters. In a 0/A converter, a technique whereby multiple "samples" are mathematically generated from each real sample, which permits the use of digital filters to augment a simple, shallow analog output filter instead of the complex and very "steep" analog filter that would otherwise be required.

PAL (phase-alternating line): The analog TV standard for Western Europe except France (see SECAM) and much of the rest of the world except Japan and North America (see NTSG)

pan (or panorama): A video shooting technique that swings the camera horizontally over a scene or tracks a horizontally moving object.

pan-and-scan: A technique for making a widescreen movie till a 4:3 aspect ratio screen by showing only selected parts of the original image, re-cropped scene by scene to focus in on what seems moat significant to the action. Critics of this technique think the re-cropping compromises the director's intent.

parametric equalizer: An equalizer that has variable parameters - such as center frequency, level, and filter sharpness (or Q) - typically to accentuate or re- duce its action on user-determined frequency bands.

passband: The range, or band, of frequencies that a filter lets pass through.

passive crossover: A network, typically built into a speaker, comprising some combination of capacitors, inductors (coils), and resistors that divides the audio signal into frequency bands (low, high, and possibly midrange) after it is amplified; see active crossover.

passive radiator: In a speaker, an un-powered diaphragm that is driven by the buck wave from a woofer; it functions like the mass of sir in the port of a bass-re- flex enclosure.

PCM: see pulse-code modulation.

peak (or peak-level) indicator: A visual indicator on a recorder that indicates when transient signal levels have exceeded the recorder's ability to handle them without distortion.

peak-reading meter: A recording-level meter that rises rapidly and declines more slowly so the user can more easily judge the levels of transient peaks.

perceptual coder: see codec.

peripheral: A device or system hooked up to (Or some- times inside of) a computer, like a monitor, printer, hard drive, CD or DVD drive, or speakers.

phase: The timing relationship among a set of wave- forms or among the components that make up the spectrum of a single waveform. Also, a control that changes polarity. See phase shift, polarity.

phase-locked loop (PLL): A circuit used in tuners to lock the received frequency to a synthesized reference frequency; see frequency synthesis.

phase shift: A change in the timing relationship among a set of waveforms (inter-channel) or among the components that make up the spectrum of a single wave- form (intra-channel).

phono: Abbreviation for phonograph,' a pre-digital device that plays vinyl-disc recordings on a turntable; raters to the low-level signals produced by a phono cartridge and to the special input where these signals are fed to a preamplifier, integrated amplifier, or receiver. The RCA connectors used for phono inputs, and now used for a wide range of analog and digit al A,V gear, were originally called phono jacks.

phono cartridge: A small component mounted on the end of the tonearm on a turntable; it holds the sty- us, which vibrates in a record groove. The cartridge converts the vibrations into an electrical voltage.

phono preamp: A component or part of a component that amplifies the low-level audio signals from phono cartridges, raising them to the same level as signals from other audio source components (called line-level) and also applying the necessary RIAA equalization.

phosphor: A chemical lining the inside face of a CRT that glows when struck by electrons fired by an electron gun. Color CRTs have a repeating pattern of red, green, and blue phosphors named after the colors they emit when irradiated. See dot pitch.

picture-in-picture (PIP): A TV-receiver function that allows the simultaneous display of two or more differ- ant programs on the same screen, usually with a small image of the subsidiary program(s) superimposed over that of the main program.

piezoelectric: A kind of speaker driver (usually a tweet- er) employing a ceramic or other element that bends in response to an applied voltage, generating sound.

pink noise: Random noise with equal energy in each octave, used as a lest signal; see white noise.

pixel (picture element): The smallest subunit of an image that's treated separately in a digital video sys- tem or a non-CRT video display. Pixel counts are often quoted in specs for image sensors, LCD viewfinders, and LCD and DLP projection TVs; see front projector and rear-projection TV.

plasma: A type of video display that employs an enormous array of tiny cells of ionized gas (plasma), which is used to activate each cell's colored phosphor.

polarity: An electrical convention that describes one side of a circuit connection as positive and the other as negative. Reversing, or inverting, the polarity of an audio connection is equivalent to a wideband phase shift of 1 8O~; see reverse polarity.

port: An opening (also called a vent( in the cabinet of a bass-reflex speaker that enables the sound wave from the back of a woofer to reinforce the sound wave from the front; equivalent to a passive radiator.

power: The rate of transfer or absorption of energy per unit time in a system. Electrical power is usually measured in watts, as in the output specifications for a power amplifier.

power amplifier: A component, or part of a component, that strengthens the audio signal from a preamplifier so that it can drive speakers.

powered speaker: A speaker, usually a subwoofer, that has an amplifier built in.

power supply: A subsection of a component that takes AC line voltage and converts it to one or more DC voltages to operate the real of the circuitry. In audio, power-supply design can have an enormous influence on noise levels and the maximum output power an amplifier can produce.

power tower: A floor-standing speaker that includes a built-in powered subwoofer, either instead of a conventional passive woofer or in addition to one.

preamplifier: A component, or part of a component, that switches and processes signals from a variety of source components.

pre-emphasis: Boosting or cutting a range of frequencies with the expectation that reciprocal equalization (de-emphasis) will be applied later to restore flat response. The usual purpose is noise reduction.

preset: A memory circuit that is programmed by the user. For example, tuner presets store the frequencies of radio or TV stations so they can be recalled instantly.

programming: The process of entering instructions for a component to carry out at a later time. For in- stance, many CD players can be programmed to play selected tracks in any order; see macro.

progressive scan: A video component or signal that processes or displays each scan line of a video frame in sequence; the opposite of interlaced scan.

pulse-code modulation (PCM): Representation of an analog signal by a sequence of multi-digit binary numbers. PCM, used for CBs, is the most common digital encoding scheme.

pulse-density modulation (PDM): A signal-generation method, used in the outputs of some 1-bit digital- to-analog converters, in which all of the extremely short signal pulses are of the same amplitude and duration but are either positive or negative; the output must be low-pass-filtered to recover the original analog waveform.

pulse-width modulation (PWM): A signal-generation method, used in the outputs of some I-bit digital-to-an- slog converters, in which all of the signal pulses are of the same amplitude but of varying duration, or width; the output must be low-pass-filtered to recover the original analog waveform.

Q: In an equalizer, Q is a number that specifies the width of the frequency band relative to its level; the higher the Q, the narrower the band. In a speaker, Q refers to the sharpness of the speaker's low-frequency resonance and is inversely proportional to damping.

quantization: In digital audio, the representation of a continuous analog signal by a sequence of discrete numbers. In POM, the dynamic range of the system is determined by the number of possible values available to represent various levels of signal amplitude, which is in turn determined by the number of bits used to rep- resent each sample. In the GD data format, the resolution of the quantization is 16 bits, which means that each sample can have any whole-number value between -32768 and +32767.

quantization noise: A form of distortion unique to dig- ital signals, it is the difference between a quantized signal (which can only take certain discrete numerical or voltage values) and the original analog signal.

quartz: A form of crystalline silicon dioxide that can be used to construct very stable radio-frequency (RF) oscillators and clocks.

Radio Data System (RDS): A system for transmitting test information along with the audio in a radio broad- cast for display on an RDS-equipped tuner or receiver.

radio-frequency (RF): The high-frequency electro- magnetic signals used to broadcast radio and TV pro- grams, or any very high-frequency signal, whether in- tended for broadcast or not.

random access: The ability to go directly to the beginning of s numbered or labeled song, track, chapter, disc, or program without having to scan the intervening material.

RCA connector/plug/jack: The most common kind of audio connector, using a small, single-pin plug and a coaxial shield.

reactance: The portion of the electrical impedance in an AC circuit that is not due to pure resistance. Capacitive reactance causes impedance to rise as the frequency of the signal decreases, whereas inductive reactance causes impedance to rise as the frequency of the signal increases.

RealAudio: A codec system promulgated by RealNetworks. At certain bit rates, RealAudio 8 utilizes the ATRAC3 upgrade of the ATRAC codec.

rear-projection TV (RPTV): A TV set that beams the output of video transducers (GRTs, DLPs, LCDs) in the rear of its cabinet onto an angled mirror, which in turn reflects it onto a large screen (from 40 to 80 inches diagonal) at the front of the cabinet.

receiver: An audio component that receives radio broadcasts, switches and processes audio signals, and amplifies the selected signal to drive speakers; also see A/V receiver. A television receiver is a monitor that contains a tuner for TV signals.

recording-level meter: An indicator that displays the audio signal levels being recorded from moment to moment. record loop: see tape monitor.

red, green, and blue (RGB): The three primary additive colors of most video systems (such as NTSC and DTV); also, the three color signals used by computer monitors. An RGB video connection (usually RGB plus sync, or RGB+HN) provides each color as a discrete signal.

red minus luminance (A - Y): Part of a component- video signal; see color difference.

regional coding: A feature" of the DVD system that gives program producers the ability to restrict the geo- graphical areas in which a OVO can be played. The U.S. and Canada are Region 1, Eur.

resistance: Electronic 'friction" that turns the flow of electrical charges into heat; resistance is impedance that is the same for all frequencies.

resolution: A measure of the ability of a video system to convey tine image details. Most resolution specifications or measurements are for horizontal luminance resolution, but there can be vertical luminance and color resolution figures as well.

resonance: The tendency of a mechanical or electrical system to vibrate ala certain frequency when excited by an external force, and to keep vibrating even after the exciting force is removed. Resonances are undesirable in audio equipment and listening rooms because they can produce colorations.

reverberation: A dense pattern of diffuse and multiply reflected sounds that results when sound is created in an enclosed space. The more reflective the walls and surfaces of the listening space, the louder and longer lasting the reverb; the perceived effect of reverberation depends on the size of the room and how long it per- slats. Reverberation influences both the clarity or intelligibility of the sound (the more, the muddier) and the feeling of spaciousness or ambience (the less reverb, the more closed-in the sound will seem).

reverse polarity: An electrical condition in which the "positive" and 'negative" wires running to one speaker in a stereo pair are reversed relative to the other; this causes the sound waves emanating from the speakers to be out of phase with one another, which weakens bass output by cancellation and impairs stereo imaging.

RF interference (RFI): When a radio or TV broadcast or other radio-frequency signal interferes with the operation of a component.

RGB+H/V: see red, green, and blue.

RIAA (Recording Industry Association of America): A trade and lobbying group based in Washington, DC, that has been one of the moving forces behind the Serial Copy Management System (SOMS) and Secure Digital Music Initiative (SDMI). Decades ago, the RIAA set standards for the equalization used on vinyl records to minimize noise and prevent over-cutting.

ribbon speaker: A form of speaker driver using a light, conductive ribbon suspended in a strong magnetic field; it produces sound by vibrating when a signal cur- rent is passed through it.

rip: To extract the digital audio data from a CC, often using a computer; also applied to the process of converting such data to a compressed audio format, typically MP3.

ripper: Computer software used to rip audio CDs for storage on a hard disk.

rms (root mean square): The most accurate way of averaging voltage and power measurements.

rolloff: A gradual attenuation of a signal above or be- low a certain frequency.

RS-232: A standard for serial communications ports on computers and some A/V components.

rumble: Low-frequency background noise in recordings made in concert halls and churches; also, low-frequency noise caused by imperfections in the drive mechanism of a turntable.

sample: The value of a signal at an instant in time.

sampling: Repeatedly and regularly obtaining samples of a waveform, such as a soundwave, in order to digitize it; see quantization.

sampling frequency (or rate): In digital audio, the number of times a signal is sampled each second. The standard sampling rate for the CD format is 44.1 kHz, which means that the voltage of the audio waveform for each channel is measured 44,100 times per second. The sampling rate must be at least twice the highest frequency to be recorded.

SAP (secondary audio program): A separate mono channel broadcast along with the two stereo channels in the MTS system for stereo analog TV. The SAP channel can be used for an alternative-language soundtrack or descriptions for the sight-impaired.

saturation: In video, saturation is the intensity of a color, specifically defined as its "distance" from white (for example, a lightly saturated pink vs. a deeply saturated red); also, the professional name for a video monitor's color control. In audio, saturation is a condition that occurs when an analog tape becomes fully magnetized and an increase in signal input level does not produce a corresponding increase in recorded level; saturation can also occur in the magnetic structure of the tape heads.

scaler: A circuit or digital signal processing program that converts a video signal from one image format to another (for instance, from 480/to 720p).

scan: A tuner feature used to audition radio stations. On CD and DVD players, scan buttons can be used to move through a track or chapter.

scan doubler: see line doubler.

scan line: One of the thin horizontal strips that together make up a video field or frame. The basic subunit of an analog video image; see pixel.

scan-velocity modulation: In a video monitor, a technique for improving the apparent sharpness of an image by varying the rate at which a scanning electron beam sweeps across the face of a ORT.

SDTV: see standard-def/nit/on TV.

SDTV monitor: A TV set that can display a 480i-for- mat standard-definition digital TV signal when connected to an outboard tuner/decoder.

search: In DVD and CD players, search buttons are used to move quickly from chapter to chapter or track to track. In some cassette decks, fast-forward and rewind buttons can be used to automatically move to the start of the next or the previous track; also known as "music" or "program" search,

SECAM (sequential coulour avec memoire): The broadcast TV standard in France and much of the former Eastern Bloc.

Secure Digital (SD) card: A flash-memory format supported by Toshiba, Panasonic, and others.

Secure Digital Music Initiative (SDMI): The industry forum that developed Digital Music Access Technology for copy-protected downloading.

sensitivity: A speaker measurement that tells how much sound, expressed as sound-pressure level (or SPL) in decibels (dB), is produced at a specified distance (usually 1 meter) from the speaker when It is fed a specified input signal (usually 2.83 volts, equivalent to 1 watt into 8 ohms). A speaker that is 3 dB more sensitive than another requires only half as much amplifier power to deliver the same playback volume.

separation: see channel separation.

Serial Copy Management System (SCMS): Incorporated in all consumer digital audio recorders to limit digital-to-digital copying of copyright material to a single generation. Any number of first-generation digital copies can be made from a digital original, but the resulting copies cannot themselves be copied via a direct digital link.

servo: Short for servomechanism a negative-fee back control system that uses an output signal feedback, comparing it to a reference signal; the difference between them is used to correct the output; servomechanism is sometimes used in powered speakers to reduce distortion.

set-top box: Any of several types of decoder, such for cable TV, digital TV, or Internet functions. designed for hookup to an HDTV/EDTV monitor, a cable-TV fee and so on.

shadow mask: A sheet of metal perforated with thousands of tiny holes that are aligned with the electron guns within a color CRT; the purpose is to prevent the electron beam for one color from hitting the phosphor of another.

sharpness control: A video-monitor control that affects the middle to high frequencies of the luminance signal, which convey the subjective impression sharpness.

shotgun microphone: A long, tubular microphone that is highly sensitive in the direction its tip is pointed and strongly rejects sounds from the aide and rear most often sold as a camcorder accessory.

signal: An electromagnetic wave, current, or voltage whose variations carry audio or video information.

signal processor: A component that manipulates line- level audio signals; equalizers and surround sound processors are the most common varieties.

signal-to-noise ratio (S/N or SNR): Measured in decibels (dB), the difference in level between a signal (usually at a standard level) and the residual noise of the component through which it is passed; higher numbers are better.

6.1-channel: Any system that has provisions for a back surround channel, reproduced by one or two speakers centered behind the listening position, in addition to the conventional left and right surround channels of a 5.1-channel system.

16:9, 16x9: see aspect ratio.

slew rate: The rate at which a signal changes amplitude, or the maximum rate at which an amplifier can change the amplitude of its output; usually expressed in volts per microsecond.

slope: The rate at which a filter or crossover attenuates out-of-band frequencies, in decibels per octave. Typical slopes are 6, 12, 18, and 24 dE per octave, which are also referred to as first- through fourth-order filters, respectively; the higher the order, the faster the rolloff.

SmartMedia card: A flash-memory format used in many MP3 players and digital still cameras.

solid-state: Electronic circuits whose active elements are transistors and integrated circuits, and specifically not vacuum tubes.

Sony Dynamic Digital Sound (SDDS): A mul-tichannel audio reproduction system for movie theaters utilizing ATRAC encoding and featuring as many as five front channels along with two surround channels and an LFE channel.

Sony/Phillips Digital Interface (SPDIF): The standard format for exchanging digital audio signals between consumer audio components Connections can be co- axial or optical.

sound-pressure level (SPL): A measure of physical loudness, usually encountered in speaker sensitivity ratings; expressed in decibels.

soundstage: The virtual space created by an audio system; originally, in audio usage, this term referred only to the imaging of a stereo pair of speakers at the front of a room, but today it can refer just as well to the three-dimensional sound field created by all of the speakers in a multi-channel home theater system. Of course, a soundstage is also the real space where a movie soundtrack is recorded.

speaker (or loudspeaker): A component that accepts audio signals from a receiver or amplifier and converts them into sound waves for listening at some distance (unlike headphones); see driver.

speaker-level: Audio signals that have been sufficiently amplified to drives speaker; see line-level.

specification (spec): A manufacturer's numerical rating of a component's performance in terms of a discrete, measurable characteristic such as frequency response or distortion.

spectrum: The frequency and amplitude distribution of the various pure-tone components that make up a complex waveform; commonly shown in a graph with amplitude on the vertical axis and frequency on the horizontal.

Standard-definition TV (SDTV): A subset of the digital TV (DTV) standard covering digital signals that will yield picture quality at least as good as that of analog NTSC television: see high-definition TV (HDTV) and enhanced-definition TV (EDTV).

ST (AT&T ST) connection: A fiber-optic digital audio connector that uses glass fibers rather Than plastic; see Toslink.

stereo: The use of two or more audio channels to pro- vioe spatial realism or directional effects; nowadays 'stereo' usually refers only to two-channel programs, equipment, or systems. See imaging, binaural, multi- channel.

streaming media: Digital audio or video data down- loaded from the Internet for simultaneous decoding and playback.

stylus: A cone-shaped piece of hard material, usually diamond, on the cantilever of a phono cartridge; its vibration as it traces grooves on a vinyl record is translated by the cartridge into an electrical audio signal.

Subsonic filter: A misnomer for infrasonic filter.

subwoofer: A speaker designed to reproduce only low-bass frequencies. A powered subwoofer contains an amplifier and an electronic crossover.

Super Audio CD (SACO): A high-density audio disc, developed by Sony and Philips, that uses Direct Stream Digital (DSD) audio encoding. Special hybrid SACD pressings are playback-compatible with 00th SACD and standard CD players.

supertweeter: A tweeter used to reproduce only extremely high frequencies.

Super VHS (S-VHS): A development of the VHS videocassette system that originally required special tape to obtain its extended luminance resolution.

surround: Channels or speakers in a multi-channel audio system whose purpose is to create a sense of sonic envelopment or all-around directionality. Also a compliant suspension at the Outer edge of a speaker driver's diaphragm.

surround sound: A reproduced sound field that is three-dimensional instead of a soundstage being heard primarily in front of the listener; an audio system or part of a home theater system that creates such a sound field.

S-VHS ET: A development of the Super VHS system that can use standard VHS videotape to record S-VHS signals.

S-video: A connector that separately carries the luminance and chrominance information for a single video image: a set of video signals divided into luminance and chrominance components.

sync: That pan of a video signal that tells a video component what part of the picture is being processed. Sync signals are usually carried on a luminance wave- form except in computer video signals and some wide- band component video, where they are completely separate; see red, green, and blue (PBS).

tape deck, tape recorder: A component that stores an audio signal on a magnetic tape; see cassette decks, digital audio tape (DAT).

tape heads: Small electromagnets that imposes magnetic pattern on a tape (for recording) or detect one that is already there (for playback). Most tape recorders have a separate head for erasing tapes by randomizing the magnetic pattern.

tape monitor: A switch on a tape recorder or preamplifier that enables the user to listen to a tape as it is being recorded to monitor the quality of the recording; on a preamplifier or receiver, it may also be used to connect an external signal processor.

3-D comb filter, 3-D Y/C separator: Circuits used to extract the luminance and chrominance signals from a composite-video signal. The three dimensions are left, right, and time.

through-the-lens (TTL): Any camcorder function that operates on signals obtained from light entering the lens, including auto-focus, white balance, and exposure controls (aperture, shutter speed); also an obsolescent type of digital circuitry (transistor-to-transistor logic).

THX: A certification for audio components of a home theater system that adhere to standards and specifications developed by Lucasfilm THX and can reproduce soundtracks with very high fidelity to what is obtained in a movie sound studio. There are two grades of certification, THX Ultra (for price-no-object setups) and THX Select (for modest room sizes and budgets).

THX Surround EX: Lucasfilm THX was the first official licensor of technology for home decoding of Colby Dig- ital Surround EX signals for 6.1-channel playback, and equipment using circuitry it has approved carries the THX Surround EX logo.

tilt: A video-camera shooting technique that swings the camera vertically over a scene; see pan.

time-alignment: A speaker design in which all of the drivers are arrayed, or their crossover delays adjusted, so that their sound reaches the listener's ears at the same time.

tint control: The consumer video-monitor control that adjusts the general coloration of an image; see hue.

titler: A camcorder function or video accessory that displays user-entered text over a video image.

tone controls: A kind of rudimentary equalizer included in most receivers, and in some preamplifiers and integrated amplifiers as well, that allows changing the relative balance among preset frequency bands, usually bass and treble but sometimes also midrange.

Toslink: The most common type of fiber-optic connector for digital audio inputs and outputs; uses plastic fibers.

total harmonic distortion (THO): The percentage of an audio output signal that consists of spurious harmonics, or whole-number multiples, of the input frequencies that mere introduced by an amplifier or another component through which the signal passed; lower numbers are better.

total harmonic distortion plus noise (TI-f D+N): The sum of all distortion and noise, expressed as a percentage of the output signal; lower is better.

tracking: The ability of a CD or DVD player to follow the pattern recorded on a disc in the presence of physical or optical disturbances.

transformer: A passive electrical device that raises or lowers AC voltages (as in a power supply), or changes input or output impedances; used ,n some amplifiers to match their output impedance to that of the speakers.

transistor: The basic solid-state amplifying element used in most audio components; see so/id-state, field- effect transistor (FET), and MOSFET.

transport: The parts of a DVD/CD player or a tape deck' VCR that move the disc or tape, including the motor(s), spindle, reel hubs, and other mechanisms.

treble: The upper part of the audio spectrum, from 2 or 3 kHz up to 20 kHz; see bass and midrange.

tuner: A component, or part of a component, that re- calves radio or TV signals from an antenna or cable connection, allows the user to selects station, and de-modulates the audio or audio/video signs from the broadcast radio-frequency (RF) signal.

turntable: A component that turns an analog phonograph record at a constant speed so that the recorded signal contained in the groove can be read by a phono cartridge, carried by a tonearm.

tweeter: A speaker driver designed to reproduce tre- ble frequencies.

universal remote control: A remote that can operate multiple devices, not simply a single component, and usually from more than one brand or manufacturer. Universal remotes are either preprogrammed with control codes for a multitude of specific products from most popular brands, or they can be "taught" the infra- red codes used by the dedicated remotes you already have, thus replacing them.

Universal Serial Bus (USB): A general-purpose standard connection for transferring digital audio, video, or control signals between AN components, computers, and computer peripherals. USB2 is a newer version of the interface capable of much higher data rates.

V-chip: An integrated circuit built into a TV vet that allows parents to automatically restrict the viewing of objectionable material, It works in conjunction with pro- gram-content codes transmitted with the TV signal.

Video CD: A forerunner to the DVD system designed to produce VHS-quality' video using a standard-size CD and MPEG-i video encoding; also see MPEC-2.

vent: see bass-reflex, port.

VHS (Video Home System): The JVC-developed helical scan analog videocassette recording system that uses .2-inch-wide tape.

VHS-C: A development of the VHS system that uses a miniaturized videocassette compatible with standard VHS machines using a special adapter.

viewfinder: A display device uses to monitor the image while recording with a camcorder; common types range from simple optical lenses to miniature CRTs or LCD screens viewed through magnifying optics.

virtual surround sound: A system that can simulate the effect of multi-channel surround sound using only two speakers or headphones. Many of these systems work well if you sit exactly in the "sweet spot,' but the illusion diminishes or vanishes if you wove.

voice coil: In a dynamic speaker or microphone, a hollow cylinder wound with wire that is immersed in the field of a permanent magnet and attached to a diaphragm. In a speaker, current through the wire from the amplifier creates an alternating magnetic field in the coil that causes it and the diaphragm to move back and forth according to changes ,n the input signal. In a microphone, sound moving toe diaphragm also moves the coil, generating a signal voltage in it that is fed to a recorder or directly to a sound system for amplification.

voltage: The measure, in volts, of the strength of an electrical field; voltage can be thought of as pressure pushing electrical charges through a circuit, forming a current.

watt (W):The primary unit of electrical power.

watts per channel (W/ch): A specification of the out- put power an amplifier or receiver can deliver to each speaker connected to it. WAV (.wav) file: A Microsoft Windows file format for storage of audio data, typically, but not necessarily, in linear-PCM form; often applied to other file formats that also at ore PCM audio data.

waveform: A graphical representation of an audio signal as the curve that results when the instantaneous voltage (vertical axis), representing sound pressure, is plotted across time (horizontal axis); the positive-going portion of a waveform moves upward and the negative-going portion downward.

white noise: A type of random noise characterized by equal energy per hertz (in contrast to pink noise). White noise is naturally generated by analog electronics, and the ear hears it as a treble-dominated hissing.

wide-angle lens: Any lens of shorter than normal lo- cal length, which offers a wider-than-normal field of view; wide-angle accessory lenses are available for many camcorders.

wideband component video: An output on a DVD player or other device that can generate or pass pro- gressive-scan or high-definition video signals to a TV set or monitor able to display them.

wind-noise filter: A high-pass filter in the microphone circuit of a camcorder that is designed to reduce rumble caused by wind passing over the microphone's diaphragm.

widescreen: A piece of program material or a component that contains or operates with images of wider than normal aspect ratio (which is 4:3). High-definition TV's mid-screen aspect ratio is 16:g. Display of wider images on a 4:3 screen requires letterboxing or pan-and-scan techniques.

Windows Media Audio (WMA): An audio codec, developed by Microsoft, used for downloaded music files and streaming media applications.

wipe: A video transition technique in which a new scene gradually replaces the old scene at a boundary that moves over the image.

woofer: A speaker driver designed to reproduce bass or bass/midrange frequencies.

wow-and-flutter (W&~): A specification indicating the speed variation of mechanical components like turntables and tape decks. Wow consists of slow variations, flutter of fast ones; lower numbers are better. Digital media usually have un-measurably low wow-and-flutter.

XLR: A three-conductor balanced-line connector; also called a Cannon connector.

YC,Cb: Digital component-video signals as recorded by professional digital video recorders and encoded by an MPEG-2 encoder for recording on a DVD; often confused with YP~Pb.

YP,Pb: Analog component-video signals as obtained at the outputs of a DVD-Video player or a digital TV set-top box.

zone: A listening/viewing area in a multi-room audio or A/V system.

zoom lens: A lens of variable focal length, usually ranging from a mild wide-angle setting to a telephoto setting. Often the lens's optical zoom range is supplemented by an electronic zoom function that enlarges the center of the image on the OCO.


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