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
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
maximally flat magnitude response See: Butterworth
maximally flat phase response See: Bessel
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
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
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 µ.
microbar 1. A unit of pressure equal
to one millionth of a bar.
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
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
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
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
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
(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
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
mute A control found on recording consoles,
some mixers, and certain signal processing
units that silences (mutes) a signal path, or output.