Audio Terminology And Definitions Dictionary

 

A Common abbreviation for ampere (see ampere).

 

AB Switch A coaxial cable switch capable of switching one cable to one of two branch cables, A or B

 

AAC (Advanced Audio Coding) A computer-audio file format developed as an improvement on the MP3 format. AAC uses more advanced compression and, according to some, delivers better sound at lower bitrates (98 Kbps) when compared to MP3s encoded at higher bitrates (128 Kbps), despite a smaller file size. The current version of AAC was developed as part of the MPEG4 standard. Versions are now used by Apple in their popular iTunes Store, as well as Sony in their PlayStation3 game consoles. Files may appear with the ".m4a" or ".mp4" filename extension.

 

AC  Common abbreviation for alternating current.

 

AC-3 Now called Dolby Digital. A method developed by Dolby Laboratories for "compressing" (or reducing) the amount of bits needed to convey multi-channel, full-bandwidth digital sound for a wide variety of formats, including DVDs, laserdiscs, and television and satellite broadcasts.AC-3's potential benefits include fully discrete sound for five full-bandwidth channels and one low-frequency (subwoofer) channel, as compared to earlier "matrix" formats with mono surround and a derived subwoofer channel. The "AC" stands for "audio codec" while the "-3" identifies this method as the third one developed by Dolby for this purpose. (See also: Dolby Digital and Dolby Stereo Digital.)

 

"A high-frequency filter used in some advanced home theater controllers to compensate for the overly bright soundtrack of many earlier films. This filter operates only in the mono mode and begins attenuating high frequencies just below 2 kHz. It reaches maximum effect (-16 dB) at 10 kHz. Note that the "Academy" filter is not the same as "Re-equalization." Re-equalization is a technique unique to THX processing in which high-frequency content to all front channels (LCR) is reduced less radically.

 

Acoustic Suspension  A completely sealed enclosure that typically houses at least a woofer. Air trapped inside the enclosure acts as a spring to restore the woofer's diaphragm to its equilibrium position after movement. Acoustic suspension enclosures generally provide more linear bass response than horn or bass reflex enclosures. Acoustic suspension speakers are usually characterized by accurate bass response.  

 

A/D (ADC)  Analog/Digital; an integrated circuit device that  converts analog signals to digital signals.

 

AIFF (Audio Interchange File Format)  An audio format for Macintosh operating systems that is commonly used for storing uncompressed, CD-quality sound (similar to WAV files for Windows-based computers). AIFF is considered a lossless container format.

 

ALAC (Apple Lossless Audio Codec)   ALAC is a lossless audio compression format developed by Apple that provides full CD-quality audio in about half the space of the original file.  

 

Alternating Current  Electricity in the form of sine wave (i.e. with positive and negative halves of a continuous waveform).  Mains electricity is in the form of alternating current (AC).

 

Ambience  The surrounding "atmosphere" that frames more intense sounds. In audio reproduction, ambience means the subtle, very low-level sonic cues that describe the acoustic environment in which a recording was made. In video, these very faint sounds (wind or traffic noise) add to the reality of a scene. Often recorded separately from the dialog or main effects tracks, they are usually added later in the "post-production" phase of preparing a film for release. (Sometimes called atmospherics.)  

 

Ambisonics  A recording/replay system developed in the Seventies to improve three dimensional stereo definition by means of a special microphone recording technique, encode/decode electronics and a multiple surround sound loudspeaker playback system.

 

Amplifier  An electronic device or product designed to turn a small signal into a larger one. An integrated amplifier accepts input signals, has source selection and volume controls and provides an output sufficiently high to drive loudspeakers. A power amplifier, simply the loudspeaker driving half of an integrated amplifier. A pre-amplifier, the first half of an integrated amplifier, provides inputs for the various source signals, switching between sources and a number of controls (eg volume, balance, tone and other signal processing). Most hi-fi amplifiers contain two channels (left and right stereo).  A monoblock power amplifier is a single channel amplifier. Two are required to drive a stereo pair of loudspeakers. Multi-channel amplifiers are required for surround sound systems. For instance a fully fledged Home THX system requires five channels of amplification (left, center and right front, plus two rear channels). An extra power amplifier is sometimes required if a subwoofer (very deep bass loudspeaker) is used to supplement the low frequency output of the system.

 

 

Amplitude Modulation  A form of radio broadcast, (abbr: AM); literally means that the carrier frequency is  modulated, or varies, in size (amplitude) according to the content of the transmitted signal.

 

Analog Television This refers to a video display device that receives and displays broadcast television signals. The video portion of an analog TV signal is transmitted in AM, while the audio is transmitted in FM. Analog television signals were (and still are, in some cases, with educational or other low-powered transmissions) broadcast in interlaced format, with the image's odd lines transmitted first, then the even lines. Full-power analog television broadcasting in the U.S. ended in 2009.

 

Anechoic  Non-reverberant. An anechoic chamber is an acoustically dead room designed primarily for the purpose of accurate loudspeaker measurement.

 

Aspect Ratio Aspect ratio defines the horizontal width of a video image or screen in relation to it its vertical height. For example, traditional analog television had an aspect ratio of 4x3 (4 units in width, 3 units of height). HDTVs have a "widescreen" ratio of 16x9. Alternately, 4x3 is often referred to as 1.33:1 (1.33 units of horizontal width against 1 unit of vertical height), and 16x9 is expressed as 1.78:1 (1.78:1 units of horizontal width against 1 unit of vertical height).

 

ATRAC (Adaptive Transform Acoustic Coding) Developed by Sony engineers in the early 1990s for the MiniDisc format, ATRAC is a lossy audio codec that is said to offer near-CD quality sound with relatively small file size. (ATRAC3 and ATRAC3+ are advanced versions of the codec, and they boast even smaller file sizes and reduced bitrates.)

 

ATSC  The Advanced Television Systems Committee, which wrote the specs for high-definition digital television.

 

Attenuate  To reduce or lower the strength or level of a signal. Attenuation can take place at many points in a signal path, the most common of which is the volume control.

 

AU  An audio format commonly used for posting sound clips on the Internet. AU files can be played back on Windows, Macintosh, and other operating systems..

 

Audio  A term used to describe sounds within the range of human hearing. Also used to describe devices which are designed to operate within this range

 

Audio Return Channel (ARC)  A feature of HDMI (version 4.0 and later) that allows a user to transfer audio from the TV back to a home theater receiver in order to listen to TV audio through a home theater speaker array without having to connect a second cable between the TV and home theater system.

 

Audyssey DSX   Audyssey's Dynamic Surround Expansion, which adds front vertical-height speakers, similar to Dolby Pro Logic IIz, and left and right wide speakers positioned between the front left and right and surround left and right speakers.

 

Auxiliary Bass Radiator  A loudspeaker drive unit fitted to a box loudspeaker, coupled acoustically but not electrically to the input signal. Functions somewhat like a port or tuned tube in the loudspeaker cabinet supplementing bass output and aiding loudspeaker sensitivity.

 

A/V Receiver   An AV receiver combines the functions of three components:

· An AM/FM radio tuner and, in some cases, HD (high-definition radio) or SiriusXM satellite radio capability.

· A preamplifier/processor that switches and controls audio and video source selection and routes audio and video signals for further processing as required.

· A built-in multi-channel amplifier (5.1, 6.1, or 7.1 channels) that sends surround sound audio signals and power to the speaker array. 

 

AVCHD  Developed jointly by Panasonic and Sony, AVCHD (Advanced Video Codec High Definition) is a high-definition digital video format for recording 1080i and 720p signals onto MiniDVD discs, MiniDV tape, hard drives, and digital camera memory cards. AVCHD uses a very efficient compression format known as MPEG4 (H264).

 

AVI  A file format for storing and playing back movie clips with sound on Windows computers. An AVI file is organized into alternating ("interleaved") chunks of audio and video data. AVI is a container format, meaning that it specifies how the data will be organized, but it is not itself a form of audio or video compression.

 

AWG  American Wire Gauge; a wire diameter specification, the lower the AWG number the larger the wire diameter.