Audio Terminology And Definitions Dictionary

 

Magnetic Flux  The measure of strength of a magnet. Unit of measurement is Gauss (G).

 

Magnetic Soundtrack   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.)

 

Magnetic Shielding  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. 

 

Mastering Studio  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 convincing.

 

Matrix(ing)     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 specifications.

 

MHz   Megahertz (one million cycles per second).

 

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. 

 

Mid-Bass     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.

 

MIDI (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.

 

Midrange 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 convincingly realistic.

 

Midrange Driver   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 format.

 

Mono   Single channel record/replay standard. All commercial recordings were mono until the early 1950's when stereo was introduced.

 

Monopole  A loudspeaker that radiates sound in one direction only, usually directly ahead. (See also: direct-radiating speaker.)

 

Moving Coil  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 driver.).

 

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. 

 

MPEG    MPEG 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.

 

MP3 (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 sound quality.

 

mp3Pro   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.

 

M-T-M Array A loudspeaker with a tweeter centered between two midrange drivers. (See also: D'Appolito configuration.)

 

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.

 

Multi-Track    Two or more independently processed audio signals that are synchronized in time and are intended to be heard simultaneously.

 

mV   MilliVolt. (1000mV = 1V); 1000uV = 1mV)