Sound Glossary

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kHz - Abbrev. f. "kilohertz," one-thousand (1,000) cycles per second. Humans are generally thought to hear frequencies up to 20kHz. The AM radio broadcast band lies between 530kHz and 1600kHz.

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Magnetic Induction - Physics- the generation of an electrical current in a conductor caused by motion between the conductor and external magnetic fields. This is how hydroelectric power generators work-- pressurized steam is passed through a fan, around whose axle is a large magnet. Stationary electrical conductors surround the magnet; as the fan turns, the magnetic field changes in relation to the conductors, and induces a current. The opposite is also true-- this is how a motor works.

Masking - In audio or musical terms, masking is the obscuring of one sound by another sound that is usually higher in amplitude (level). In theatre sound terms, masking can be defined as any soft-good designed to muffle or baffle sound.

Matrix - Similar to the mathematical tool, a "matrix" is part of an output section found on some mixing desks. Matrices can be thought of as the final output section of the mixing desks, fed in different amounts by the subgroups, creating different mixes of audio signals to different destinations.

Maximum SPL (Sound Pressure Level) - A specification often encountered in microphone specifications. Maximum SPL is an indication of the highest sound pressure level a microphone can handle before distortion occurs in the microphone's electronics. Usually, this maximum SPL point is referenced to other values in order to properly compare microphones. It is important when choosing a microphone to remember the intended use and ensure that the microphone will be adequate in the given application.

Meyer Sound SIM System - A computer-based system utilizing several fast-Fourier transform processors developed by Meyer Sound Labs. The SIM System takes an input (usually a direct output from the console), and utilizing several microphones located in the environment in question, compares the original signal to the sound the microphones pick up. The data can then be utilized to correct for phase differences, delay times, and frequency response over time.

MHz - Abbrev. f. "megahertz," one-million (1,000,000) cycles per second. The FM radio broadcast band lies between 76MHz and 108Mhz. UHF radio-frequency wireless microphones fall somewhere between 400MHz and 900Mhz. European mobile telephones operate at 900MHz and 1800MHz (which is 1.8GHz). The newest revision of the PowerPC G4 processor runs at 500MHz.

Mic Level -The electrical level (voltage) of signal generated by a microphone. In contrast to line levels, which are typically around 1.23 V or 0.316 V, an unamplified microphone level may be around 2 mV.

Microphone - A transducer used for converting acoustic, sound pressure energy into electrical energy. See Input Devices for more information.

Microphonic - Describes an undesirable characteristic of certain audio components in which the components become sensitive to vibration and translate that vibration into audio signals. Most vacuum-tubes exhibit this tendency, as do all audio cables. Microphonics are the result of capacitance changes between the conductors of an audio cable and between the conductors and the shield.

MIDI - Acronym for "musical instrument digital interface." A digital communications standard established in 1984 by musical instrument manufacturers Yamaha, Roland, and a few others. Enables communication (i.e. note on, note off, velocity, etc.) between musical instruments. MIDI has expanded to include communication with lighting boards, computers, sequencers, consoles, effects processors, and the like.

MIDI Show Control - A data and control standard developed upon the MIDI standard that integrates processes other than musical instruments: stage machinery, lighting, et al., into the existing MIDI standard.

Midrange Driver - A loudspeaker component specifically designed to generate middle-range frequencies (600 Hz - 4kHz), designed to complement dedicated woofers and tweeters.

Mixer - All kitchen definitions aside, at its simplest level, a mixer, or mixing desk, or mixing console, or sound desk, or sound console, or desk, or recording console, is an audio device used to combine multiple inputs into multiple outputs, with controls by which an operator can adjust relative levels. The central "heart" of the sound system or the sound recording system which allows for the human control of the sound system.

Modulation - By definition, modulation is "change." In music technology and synthesis, the term refers to a control signal used to change some parameter of another signal; for instance, a control signal, or voltage, may be used to change, or modulate, the pre-delay time in a reverb processor. In broadcasting, FM (frequency modulation) and AM (amplitude modulation) are both techniques using one parameter of a wave (in FM, the frequency; in AM, the amplitude) to change the waveform of an audible signal, called the carrier.

Monitor -Video- a cathode-ray-tube device on which moving pictures appear. Audio (noun)- often used as another name for "loudspeaker." Often refers to foldback loudspeakers or other loudspeaker systems designed to provide program to onstage talent (e.g. "i need more me in my monitors."). In theatrical situations, the word can also apply to backstage program loudspeakers. Audio (verb)- to pre-fade listen, or otherwise listen to a signal source via a pair of headphones or other loudspeaker system, in order to troubleshoot or cue a signal.

Moving Coil - A type of loudspeaker construction in which a voice coil connected to a speaker cone of paper-like material, interacts within the range of a magnetic field. It is also a standard used in phonograph cartridges in which the reverse principle is applied: the stylus (needle) is directly coupled to a coil which is placed within a magnetic field. The resultant voltage generated by the coil is then fed to the preamplifier in its electronic form. Can also apply to microphone construction, and refer to what we call a dynamic microphone capsule.

Multipair Cable - A term applied to a type of multiconductor cable with a single outer insulation and many internal balanced (twisted-pair) lines. Simply put, it is many microphone cables rolled into a single jacket that is lighter in weight and easier to handle. Also termed "multicore."

Mute - Usually, a pushbutton switch on a mixing desk or other piece of audio equipment that silences the input or output in question. Some mixing desks appear with varying degrees of computer-based automation that can mute many channels or outputs at once, sometimes on a cue-by-cue basis.