Audio Terminology And Definitions Dictionary
Magnetic Flux The measure of strength of a magnet. Unit of measurement is Gauss (G).
Developed in the early 1950s as a sonic improvement over older
optical techniques, magnetic soundtracks are recorded onto strips of iron oxide
material that are similar to standard recording tape. The strips are applied to
the film after the photographic image has been printed. A projector read the
soundtrack with a separate magnetic head just as a tape playback device does.
Although early magnetic standards included provisions for multiple discrete
tracks, and although they paved the way for further developments in surround
sound, magnetic technology's cost and fragility made it vulnerable to new
developments in optical technology, particularly Dolby Stereo. (See also: Dolby
Stereo and optical soundtrack.)
Technique that prevents a speaker's stray
magnetic flux from interfering with the picture of a direct-view TV set,
particularly when that speaker is placed very close to the TV set. A speaker
designer shields a speaker either by specifying a magnet that is totally encased
in mu-metal (a very expensive alloy with exceptional resistance to magnetic
fields) or by fixing a second flux-canceling magnet to the rear of the primary
magnet. The latter approach is far more common.
For home theater applications based on CRT displays, the
center channel speaker must be
shielded. Flanking (left and right) front speakers may need shielding if
they're placed close to (within 3') a direct view (CRT) monitor. Note
that flat panel displays (plasma, LCD, etc.) are not
affected by stray magnetic fields.
The final link between a recording session and the mass duplication of CDs.
Mastering engineers use carefully constructed listening facilities to critically
evaluate musical material and suggest often-subtle equalization and level
adjustments, changes in song sequences, etc., to make an album more coherent or
The process of mixing two distinct signals with
specific phase and amplitude relationships in order to form one signal so that
the original components of the total signal can be separated at a later time.
For example, the Dolby Stereo Motion Picture Sound Matrix mixes four independent
soundtrack elements (LCRS) into two independent signals (Lt and Rt) in such a
way that the four original LCRS signals can be recovered and reproduced
independently in a movie theater.
Metal Film Resistors
Used for their low-noise superiority, metal
film resistors feature a metal alloy that is deposited on a substrate such as
plastic or ceramic. They are also available in very close tolerance
MHz Megahertz (one million cycles per
Microphony Unwanted microphone like behavior of
components in the audio replay system. In effect sound causes these components to vibrate at their resonant frequency and the vibration modulates the
signal waveform. Tubes (also called valves) are known to behave microphonically but so too do
some solid state components.
The frequency range that occurs between low bass and lower midrange frequencies,
or approximately 75 to 200 Hz. With speakers, too much mid-bass output produces
a heavy or muffled sound, and too little mid-bass results in a thin sound.
(Musical Instrument Digital Interface) A MIDI file doesn't
contain actual audio data, but rather it contains commands that let MIDI-capable
synthesizers re-create a specific musical passage. The MIDI protocol has been
used for years as a way for electronic musical instruments (such as digital
keyboards and sequencers) to communicate with each other. Computer sound cards
typically can interpret MIDI files into music. Since they don't actually contain
any music, but rather the commands used to re-create music, MIDI files are a lot
smaller than audio files such as MP3s, WMAs, or WAVs. MIDI files are small and
manageable enough that it's not uncommon to find them embedded in web pages,
adding a sonic element to the surfing experience. They usually appear with the
.mid filename extension.
The wide band of frequencies running between bass and treble. The midrange band
runs from approximately 200 to 3000 Hertz. Most vocal and instrumental sounds
lie in this region. An audio device must have an accurate flat frequency
response with low distortion throughout the midrange in order to sound
A speaker driver specifically designed to reproduce midrange frequencies.
Midrange drivers used to be called "squawkers" to distinguish them from
woofers and tweeters. (See also: driver,
tweeter, and woofer.)
MiniDisc A record/playback system developed by Sony
using a small silver disc as software and a data reduction technology known as ATRAC. Seen by many as a rival to Philips' Digital Compact
Cassette. MiniDisc is incompatible with CD since it is a magneto-optical record/playback
Mono Single channel record/replay standard. All commercial recordings were mono until the early
1950's when stereo was introduced.
loudspeaker that radiates sound in one direction only, usually directly ahead.
(See also: direct-radiating speaker.)
Can indicate either a type of loudspeaker or a phono cartridge. For our purposes,
the term refers to a type of speaker driver with a "motor" made up of a
voice coil located in the gap of a permanent magnet. The coil, connected (either
directly or through a crossover network) to the amplifier's output, moves in
and out. Because the coil is mounted to the driver's surface (usually a cone
or dome), it pushes or pulls that surface to compress or rarefy air molecules,
thus creating sound waves. (Also called a dynamic
Moving Magnet An alternative and cheaper form of pickup cartridge to the moving coil is the stylus assembly
moves in precise relation to fixed coils causing the generation of analogous electrical signals.
is an acronym for the Moving Picture Experts Group, a committee that sets
international standards for the digital encoding of movies and sound. There are
several audio/video formats that bear this group's name. In addition to their
popularity on the Internet, different MPEG formats are used with different kinds
of A/V gear.MPEG1 is a format that is often used in digital cameras and
camcorders to capture small, easily transferable video clips. It's also the
compression format used to create Video CDs, and it is commonly used for posting
clips on the Internet. The well-known MP3 audio format (see definition later on
in this Glossary) is part of the MPEG1 codec.MPEG2 is a format used in
commercially produced DVD movies, home-recorded DVD discs, and most digital
satellite TV broadcasts due to its ability to deliver a high-quality
picture.MPEG2 is also the form of lossy compression used by TiVo-based hard disc
video recorders. It can rival the DV format when it comes to picture quality.
Because MPEG2 is a "heavier" form of compression that removes a larger
portion of the original video signal than DV, however, it's more difficult to
edit with precision. The MPEG2 codec allows for selectable amounts of
compression to be applied, which is how home DVD recorders and hard disc video
recorders can offer a range of recording speeds. MPEG2 is considered a container
format.MPEG4 is a flexible MPEG container format used for both streaming and
downloadable Internet content. It's the video format employed by a growing
number of camcorders and cameras.
(MPEG1, Audio Layer 3) The most popular codec for storing and
transferring music. Though it employs a lossy compression system that removes
frequencies judged to be essentially inaudible, MP3 still manages to deliver
reasonable sound quality in a file that's only about a tenth or a twelfth of the
size of a corresponding uncompressed WAV file. When creating an MP3 file, you
can select varying amounts of compression depending on the desired file size and
An updated version of the original MP3 codec. Small, low-bitrate mp3Pro files
contain much more high-frequency detail than standard MP3 files encoded at
similar low bitrates. The high-frequency portion of the audio signal is handled
by an advanced and extremely efficient coding process known as Spectral Band
Replication (SBR), while the rest of the signal is encoded as a regular MP3. You
can play an mp3Pro file on software that is not compatible with mp3Pro, but
you'll only hear the non-SBR-encoded portions (and consequently will lose
high-frequency data altogether). However, when encoded and played back using a
fully compatible audio program, such as Windows Media Player, mp3Pro files can
deliver very good sound quality using low bitrates.
A loudspeaker with a tweeter centered between two midrange drivers. (See also: D'Appolito
Multi-bit A type of digital to analogue conversion in which ladder resistor networks are used to read the
14, 16, 20, 24 or 32 bit words of a digital bit stream.
or more independently processed audio signals that are synchronized in time and
are intended to be heard simultaneously.
MilliVolt. (1000mV = 1V); 1000uV = 1mV)