Glossary of Audio Terminology

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Index | References



MADI (multichannel audio digital interface) An AES recommended practice document Digital Audio Engineering - Serial Multichannel Audio Digital Interface (MADI) AES-10-1991 (ANSI S4.43-1991) specifying and controlling the requirements for digital interconnection between multitrack recorders and mixing consoles. The standard provides for 56 simultaneous digital audio channels which are conveyed point-to-point on a single coaxial cable fitted with BNC connectors along with a separate synchronization signal. Fiber optic implementation is specified in document AES-10id-1995, entitled AES information document for digital audio engineering - Engineering guidelines for the multichannel audio digital interface (MADI) AES 10. Basically, the technique takes the standard AES/EBU interface and multiplexes 56 of these into one sample period rather than the original two.

magnitude 1. Mathematics. a. A number assigned to a quantity so that it may be compared with other quantities. b. A property that can be quantitatively described, such as the volume of a sphere, the length of a vector, or the value of a voltage or current waveform.

matrix-mixer A mixer that can assign any input to any output by adjusting the level of each input present in each output.  Some Matrix-mixers provide additional signal processing features on all the inputs and outputs. With these you can not only can you assign inputs to outputs but you may add EQ, compression, delay, etc. Very elaborate models exist with as many as 32-channels in and 8 or more output channels.  Also see: mix-minus.

maximally flat magnitude response See: Butterworth crossover

maximally flat phase response See: Bessel crossover

Mb see Magabit

MCU Multipoint Control Unit A device that connects multiple remote sites for audio and video conferencing. sometimes incorrectly called a digital switch or video bridge

MD (MiniDisc) Trademark term for the Sony digital audio recordable storage system utilizing data compression to reduce disc size. Also used to describe the decks and magnetic disc used with this standard.

MDM (modular digital multitrack) Generic term used to describe any of the families of digital audio multitrack recorders. The most common examples being the Alesis ADAT series and the Tascam DA-88 series.

mega- 1. A prefix signifying one million (10E6). abbreviated M. 2. A prefix used in computer work to signify multiples of 1,048,576 (i.e., 2E20). Meant to distinguish base-2 (binary) from base-10 (decimal) magnitudes. For example, a "16M" memory is actually 16,777,216 bits (i.e., 16 times 1,024,576, or 2E24).

Megabit  16,777,216 bits. See Mega

Megabyte 16,777,216 bytes. See Mega

megaflops also MFLOPS (pronounced "mega-flops") (million floating point operations per second) A measure of computing power. See MIPS

Megahertz (MHz) one million cycles pre second.

MI (musical instrument) A broad term used to describe the musical instrument marketplace in general. Reference is made to "the MI market," or to a specific "MI store." If a store sells musical instruments, for instance, it is an MI store.

micro- Prefix for one millionth (10E-6), abbreviated .

microbar 1. A unit of pressure equal to one millionth of a bar.

microcontroller ...

microprocessor An integrated circuit that performs a variety of operations in accordance with a list of instructions. The core of a microcomputer or personal computer.

MIDI (musical instrument digital interface) Industry standard bus and protocol for interconnection and control of musical instruments. First launched in 1983, now generalized and expanded to include signal processing and lighting control.

milli- Prefix for one thousandth (10E-3), abbreviated m.

minimum-phase filters Electrical circuits From an electrical engineering viewpoint, the precise definition of a minimum-phase function is a detailed mathematical concept involving positive real transfer functions, i.e., transfer functions with all zeros restricted to the left half s-plane (complex frequency plane using the Laplace transform operator s). This guarantees unconditional stability in the circuit. For example, all equalizer designs based on 2nd-order bandpass or band-reject networks have minimum-phase characteristics.

MIPS (million instructions processed per second) A measure of computing power. See megaflops

mix-minus A specialized matrix-mixer where there is one output associated with each input that includes all other inputs except the one it is associated with. (The output is the complete mix, minus the one input.) In this manner, the simplest mix-minus designs have an equal number of inputs and outputs (a square matrix). For example, if there were 8-inputs, there would be 8-outputs. Each output would consists of a mix of the seven other inputs, but not its own. Therefore Output 1, for instance, would consist of a mix of Inputs 2-8, while Output 2 would consist of a mix of Inputs 1 & 3-7, Output 3 would consist of a mix of Inputs 1,2 & 4-7, and so on. Primary usage is large conference rooms, where it is desirable to have the loudspeaker closest to each microphone exclude that particular microphone, so as to reduce the chance of feedback.

mixer At its simplest level, an audio device used to add (combine or sum) multiple inputs into one or more outputs, with level controls on all inputs. May also include signal processing on each of the inputs and outputs or a matrix-mixer for the outputs. Larger full featured mixers are referred to as  consoles.

MLS (maximum-length sequences) A time-domain-based analyzing technique using a mathematically designed test signal optimized for sound analysis. The test signal (a maximum-length sequence) is electronically generated and characterized by having a flat energy-vs-frequency curve over a wide frequency range. Sounding similar to white noise, it is actually periodic, with a long repetition rate. This test signal is most often tailored to be pink noise, as the preferred response for fractional octave analysis. Similar in principle to impulse response testing - think of the maximum-length sequence test signal as a series of randomly distributed positive- and negative-going impulses. See: MLSSA

MLSSA (pronounced "Melissa") (maximum-length sequences system analyzer) Trademarked name for the first MLS measurement instrument designed by DRA Laboratories (Sarasota, FL). Maximum-length-sequences methods were used for room impulse response measurement by M.R. Schroeder in 1979 (based on work dating back to the mid-60's); however, it was not until 1987 that the use of MLS became commercially available. The first MLS instrument was developed and made practical by Douglas Rife, who described the principles in his landmark paper (co-authored by John Vanderkooy, University of Waterloo) "Transfer-Function Measurement with Maximum-Length Sequences" (J. Audio Eng. Soc., vol. 37, no. 6, June 1989), and followed up with new applications described in "Modulation Transfer Function Measurement with Maximum-Length Sequences" (J. Audio Eng. Soc., vol. 40, no. 10, October 1992). Further information available directly from DRA Laboratories .

modem (modulator-demodulator) A peripheral device used to convert digital signals ("1s" and "0s") into analog signals (tones) and vice-versa, necessary for communication using standard telephone lines.

monitor mixer A mixer used to create the proper signals to drive the individual muscian stage loudspeaker monitors. A monitor mix is sometimes referred to as  foldback. Compare: FOH

MPEG (Moving Picture Experts Group) A working group within SMPTE who set, among other things, specifications for compression schemes for audio and video transmission. A term commonly used to make reference to their image-compression scheme (MPEG-2) for full motion video.

MS-DOS (Microsoft disk operating system) Microsoft's registered trademark for their PC operating system.

MSB (most significant bit) The bit within a digital word that represents the biggest possible single-bit coded value.

Multicast To Transmit a message to multiple recipients at the same time.  Multicasting is used in teleconferencing and data communications networks.  Multicasting is a one-to-many transmission that implies sending to several designated recipients, whereas broadcast implies sending to anyone who wants to receive the broadcast on the connected network.

multimedia Generally refers to the combination of audio, video, text, and graphics.

multiplex To interleave two or more signals into a single output; a process of selecting one of a number of inputs and switching its information to the output.

Multiplexer A device that permits subdivision of a given bandwidth transmission media.  For example, a T! Multiplexer may be set to divide a T1 line (1,544Kbps) into tow channels of 768Kbps each.

mute A control found on recording consoles, some mixers, and certain signal processing units that silences (mutes) a signal path, or output.



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