MTEC-111 Introduction to Music Technology Terms

1/2" Two-Track Tape

stereo, with each track nearly 1/4" wide, used for the highest quality analog stereo master mixes.

Patch Point

A location in a flow chart or the corresponding electronic circuit at which access to the circuit is provided by a jack in the patch bay.

Tweeter

A loudspeaker designed to reproduce high frequencies.

Woofer

A loudspeaker designed to reproduce low frequencies only.

1/4" Half-track (Or Two-Track) Tape

...in which the tape contains two tracks of information, which can be recorded in separate directions as mono tracks, or simultaneously in the same direction as stereo. The professional standard for stereo master mixes.

1/4" Quarter-Track Tape

...with the pairs of stereo tracks (indicated as 1-3 and 2-4 pairs) arranged across the tape in 1-4-3-2 order. Considered a home reel-to-reel format.

Additive Synthesis

(A) Randomly chosen amounts and phases of a fundamental and its second through sixth harmonics; (B) The complex wave created by combining the above waveforms.

Volt

(symbol V) A unit of voltage. The voltage between two points of a conducting wire carrying a constant current of 1 ampere, when the power dissipated between these two points is 1 watt.

Gate

1. A control voltage generated by any key on a synthesizer keyboard that instructs signal generators and other devices to begin operating. 2. Short for noise gate.

Frequency Response

1. A graph of the amplitude vs. frequency, either for an acoustic sound or for a signal passing through any piece of audio equipment. 2. The graph that shows an audio device's output amplitude through a wide frequency band, when the amplitude of the input through that band is constant. So-called "flat" response indicates a horizontal, straight line response "curve" (as it is often called), which in turn means that the device passes all frequencies equally well, or without coloration.

Dynamic Loudspeaker

1. A loudspeaker in which the diaphragm or cone is attached to a coil of wire that moves through a magnetic field in response to the electromagnetic field created when an audio program signal flows through the coil. Also called moving coil loudspeakers. 2. A loudspeaker whose diaphragm is a ribbon, generally mounted between the poles of a large "U" magnet.

Resonance

1. A reinforcement of signal caused when the incoming frequency is equal to the natural frequency of vibration of the acoustic or electric system through which it passes. 2. A specific frequency at which a resonant condition exists.

Decibel (dB)

1. A unit of level used to designate power ratios in acoustic and electric measurements, adapted separately for various power and voltage scales. 2. Loosely, the smallest increment in perceived volume that the average human ear can detect. In early experiments with sound, it was noted that 1/10 bel is very close to this increment; thus, precise measurements of volume are standardized in decibels.

Oscillator

1. An electronic signal generator whose output is a pure sine wave of selectable frequency. Standard test equipment in every studio. Many oscillators also produce square waves and other waveshapes used in testing and maintenance procedures. 2. The basic sound-generating circuit in most traditional synthesizers. A control voltage generated by each key of the keyboard (or other controller) instructs the oscillator what output frequency is required. This can then be processed by any number of other circuits.

Volume

1. Colloquial term for sound pressure level. 2. Short for volume control.

Ground Lift

1. Generally, a three prong AC plug adapter used without its ground connected in an attempt to eliminate the occurrence of a ground loop through the power cord of a piece of equipment. 2. On a D.I. box, the switch that disconnects the common ground between its input and output. Used to help eliminate hums and buzzes in the signal, caused by improper grounding of some instrument pickups, or by the effect of RF fields on magnetic pickups, etc.

Resolution

1. Generally, the measure of photographic sharpness of any image. 2. In motion picture film, this depends on the quality of lenses, the accuracy and stability of registration in the camera and projector, and the grain structure of the emulsion itself. 3. In video, the number of pixels into which a horizontal line of picture is accurately divided. This presumes that the system in use is capable of supplying distinct picture information to all 525 lines (if it is an NTSC system). Home televisions, for example, can deliver no more than 325 lines of vertical resolution, with about 250 pixels per line.

Doubling

1. Sometimes mistakenly used to mean tracking, the recording on multitrack tape of a second performance of an instrumental or vocal part already recorded once (played or sung by the same performers), usually done to achieve a fuller sound. 2. Loosely, creating the aural impression of more players and/or singers than were originally recorded by mixing a slightly delayed duplicate of their track(s) in with the direct signal.

Bandwidth

1. Strictly speaking, the arithmetic difference between the highest and lowest frequencies that are (a) passed by an electronic device, or (b) present in a specific acoustic sound or audio signal. Example: The bandwidth of a telephone is approximately 2.2 kHz-i.e., 2,400 Hz minus 200 Hz. The endpoints of a circuit's or system's bandwidth are those frequencies at which its response or Output is attenuated by 3 dB.

Input

1. The connector by which a signal enters an electronic device, or the signal itself. 2. An electronic operating mode in tape recorders, in which the input signal to various tracks are routed directly to their outputs.

Fundamental (1)

1. The frequency of the first in a series of partials which make up the timbre of a musical sound. This first partial will also have the highest amplitude in the series and will be the frequency we recognize as the pitch of the musical sound. eg.: The fundamental of a complex musical waveshape at A440 will be 440Hz.

Dynamic Range

1. The number of decibels between the levels of the loudest and softest sounds that can be made by an instrument, or between the loudest and softest passages in a live or recorded piece. 2. In a tape recorder, or with respect to a specific type of recording tape, the decible level difference between its inherent noise level and the signal level at which 3% total harmonic or third harmonic distortion is present at the output or on tape.

Overload

1. The type of distortion that occurs when an applied signal exceeds the level at which a system will produce its maximum undistorted output level. Generally results in clipping of the waveform, since the output will be literally cut off at maximum output level. 2. The condition that exists when this distortion is produced.

Sample

1. To take regular measure of an analog signal. 2. Any single measurement of such a voltage. 3. To digitally record one or more sounds intended as a sound source for playback via keystrokes on a synthesizer or other device. One might, for example, sample a frog croaking, and later reproduce the croak at any desired pitch through the various keys of a synthesizer.

Decay

1. Used both for acoustical and electronic sound sources. The characteristic fall-off in output amplitude or volume a sound producing source emits when the force creating the vibrations (or the current powering the oscillator in a synthesizer, for instance) is removed. This term is often confused with release, the fourth section of a sound's envelope. 2. The second of four sections of a sound or signal's envelope. In order, they are attack, decay, sustain, release.

Fundamental (2)

2. The primary frequency, or lowest frequency, present in a sound source or musical note. Frequencies caused by beating between two notes or sound sources, but that are not inherent in either source, are not fundamentals.

Monitor

A loudspeaker in a control room or other listening area. 2. A cathode ray tube (CRT) or, more simply, a television on whose screen programs and data can be displayed (verb) To listen back to a recorded performance or a live performance in the control room.

Attenuation Pad (or Pad)

A resistive network or other circuit generally passive, that is inserted in an audio line to reduce the signal level.

Electrostatic Loudspeaker

A loudspeaker in which a rigid plate is charged by a DC voltage with one electric polarity and a thin metallic membrane charged oppositely. Variations in this steady voltage potential difference are caused by an audio signal mixed with it, in turn causing a variation in the capacitance between the plate and membrane. This moves the membrane toward and away from the plate, creating sound waves that propagate into the surrounding air. Also called capacitor (or condenser) loudspeaker.

Hum

A low-frequency unwanted noise of definite pitch - generally 60 Hz or multiples thereof - that usually imposes itself on a signal through the effect of stray magnetic fields, the proximity of AC lines, or through improper grounding.

BPM Beats per Minute

A measurement used by disc jockeys to determine whether two rock or dance records will blend or mix together smoothly. BPM ratings are often printed by record companies on the labels of promotional copies sent to radio stations, record pools, and individual disc jockeys.

Proximity Effect

A rise in the low frequency response of all non omni-directional microphones, caused when the mic is used very close to the source; e.g., when a singer "swallows" the mic.

Condenser (or Capacitor) Microphone

A microphone in which the vibrating diaphragm is electrically charged and acts as one plate of a capacitor. The movement of the diaphragm or membrane with respect to a rigid plate (charged with the opposite polarity) causes a tiny change in the potential between them. This is amplified by an internal pre-amplifier and sent to the recording console. DC power is required to run the pre-amplifier. Works like an electrostatic speaker in reverse.

Shock Mount

A microphone suspension system that prevents mechanical vibrations of the stand from reaching the mic. Usually made of elastic bands mounted on a metal frame, which together hold the mic in position without rigid mechanical contact with the stand.

Expander

An amplifier whose gain is unity for signals below a specified threshold, then increases for higher input signal levels, or (b) is unity for signals above a designated threshold, then decreases for input signals below that threshold. Most professional units employ the second design. Noise gates are good examples of the lo-type expander.

Overtone

An integer multiple of fundamental frequency. The first overtone is twice the fundamental, the second is three times the fundamental, etc.

Harmonic

An integer multiple of the fundamental frequency of a sound. The first harmonic (also called a "partial") is the fundamental itself the second harmonic is two times the fundamental, etc.

Byte

A sequence of 8 bits of data, established as a standard parcel of information in computing because it can designate any of 63 possible items (2 raised to the 8th power, minus 1). This number is sufficient to uniquely specify any letter in the English alphabet, any single Arabic numeral, and a group of commonly used symbols. For that reason, the byte is used as the basis of the ASCII code.

Voltage-Controlled Oscillator (VCO)

An oscillator whose output frequency varies in proportion to an externally supplied control voltage. The main tone-producing circuit of many synthesizers.

Equal Loudness Contours

A set of superimposed graphs plotting the human ear's sensitivity to sound vs. frequency, each graph representing this phenomenon at a different loudness level. Also called the Fletcher-Munson curves, after the scientists who derived them. A new version, the Robinson-Dadson curves, is gaining favor.

Vibrato

A wavering quality in a steady musical tone or sound, caused by a cyclical change in its musical pitch (or fundamental frequency); above and below its nominal pitch. Often confused with tremolo.

Tremolo

A wavering quality in a steady musical tone or sound, caused by a cyclical change in its volume level;above and below its nominal level. Often confused with vibrato.

Slapback

An unwanted and distracting echo caused by a reflective surface in any environment - e.g., a large window in a recording studio. 2. A tape delay, or the effect it creates.

Series

A wiring configuration by which several circuits or devices may be connected. A signal or power source is first routed to the input of one device. Its output then becomes the input for the second device, and so on. Opposite of parallel wiring.

Magnetic Recording Tape

A medium capable of recording the changes in an electrical signal in the form of varying intensities of magnetism encoded along its length. Magnetic particles, such as iron oxide, are suspended in a paint-like binder and coated onto continuous plastic or other film base. When passed by an electromagnet through which an audio signal flows, the particles are magnetized in proportion to the instantaneous level of the signal. This linear magnetic "record" can then be reproduced as it in turn passes over a sensitive electromagnetic generator creates an electrical signal in proportion to the magnetism present along the length of tape.

Crossover Network

A circuit or device that divides a broad-band audio signal into two or more separate bands, each of which can be sent to separate amplifiers, processors, etc. Used most often in speaker systems to divide the amplifier s output into two or more bands, directing only the proper frequency bands to each type of driver.

Passive Device

A circuit or network that operates without need for any outside power supply - AC components - i.e., resistors, capacitors, and inductors, and as a result of their internal consumption of some of the signal's energy, the audio output level of the device will be lower than the input level.

Electret Microphone

A condenser microphone whose diaphragm and plate are semi-permanently charged during manufacture. The charge can dissipate after several years, which will cause a loss of output level, etc.

Phase Coherency

A condition encountered in the summation of two or more signals, in which the signals combine constructively, with little or no cancellation.

Hard Disk

A data storage and retrieval device consisting of a disk drive and one or more permanently installed, precisely machined rigid disks.

Serial Output

A data transmission mode in which each bit of an e-bit word is delivered to a single pin connector one at a time, in sequence. Opposite of parallel output.

Acoustic Delay

A delay line in which a speaker and microphone are separated by an extended path length, such as by placing them at opposite ends of a long tube. The delay itself is derived from the time it takes the sound to travel through the air in the tube.

Tape Delay

A delay produced by recording and playing back a sound or signal simultaneously on the same recorder, taking advantage of the time it takes the tape to travel from the record to the playback head. Also, the tape and recorder with which this is done. Tape delay was used long before digital and other systems were developed. Because the heads are stationary, the only way to adjust the delay time is by changing the tape speed itself. Sometimes called a slapback.

Direct Box

A device containing an impedance matching transformer (and sometimes a pre-amplifying circuit) that allows the output of an electric instrument to feed the input module of a recording console directly. Also called a D.I. (direct input).

Envelope Generator

A device that produces a control voltage that varies with time according to the user's specifications. This voltage, applied to each note played on a synthesizer, gives notes the desired envelope. Also called a contour generator.

Sound Pressure Level (SPL) Meter

A device used to measure sound pressure levels in any environment, calibrated in decibels, and usually offering a selection of "weighted" scales that allow the reading of levels in specific frequency ranges, such as the high frequencies, which can damage the ear at high levels.

Moving Coil Loudspeaker

A dynamic loudspeaker.

Ribbon Microphone

A dynamic microphone in which the diaphragm is a metallic ribbon. The ribbon is suspended between the poles of a permanent magnet. Audio signals are generated in the ribbon itself as it vibrates through the magnetic field. Because sounds approaching the ribbon's edge (from either side along its surface) will fail to move it, ribbon mics are always bi-directional. Other patterns can be achieved by blocking sounds approaching the ribbon from various directions.

Notch Filter

A filter that severely attenuates a very narrow band of frequencies. Often used to eliminate steep resonances in an instruments' response, or to get rid of motor hums, feedback, room resonances, and other unwanted sounds that may have been present when a signal was recorded.

Comb Filter

A filter that, through phasing cancellation, notches out a series of different frequencies in an incoming signal. This is the principle by which flanging is achieved.

VU Meter

A level meter calibrated in volume units. Most VU meters are calibrated in decibels and % modulation, a linear scale defined such that 100% modulation = 0 dBVU. The ballistics of a VU meter (a function of its components and the inertia of the indicator itself) approximates the response of the human ear to sudden level changes. The ear senses the average level of sounds, not their momentary peaks. Similarly, the VU meter cannot move fast enough to indicate every peak. When the meter bounces up to 0 dBVU, the peak that caused that bounce may actually have reached +10 dBVU or more.

Attenuation

A fixed or variable reduction in signal strength, which may in turn reduce the volume of sound heard.

Digital-to-Analog Converter (DAC)

A group of electronic circuits that reads and decodes sequential numerical voltage samples, then recreates a stepped waveform that approximates the analog waveform existing before initial encoding. The voltage samples may come from any storage medium, tape, RAM, a buffer memory, etc.

Port (or I/O Port)

A jack or plug by which another device or computer can be connected to the computer at hand.

Peak Reading Meter

A level meter driven by a circuit that registers and holds transient peaks in the signal long enough for the pointer or display to show the highest instantaneous level in each peak.

Dynamic Microphone

A moving coil or ribbon microphone, in which the movement of the diaphragm (with its attached coil of very fine wire) or ribbon through the field of a permanent magnet induces a varying output voltage. This voltage is sent to the recording console. Works like a dynamic loudspeaker in reverse.

Pan Pot

A multiple pole potentiometer used to vary the proportion of an incoming signal sent to two or more separate outputs. Generally used to position sounds left to right in a stereo mixdown, or to distribute one signal to two tracks in a multi-track recording. Stereo and quad pan pots are common in audio applications.

Omni-Directional Microphone

A nearly circular pattern, indicating equal sensitivity to sounds approaching from all directions around the microphone.

Patch (noun)

A particular sound produced by a synthesizer, either preset at the factory, or programmed by the performer. Example: A clarinet or harpsichord patch-i.e., the synthesized sound of that instrument.

Protocol

A predetermined procedure or series of rules that ensures sending and receiving units pass data efficiently and accurately.

Mega

A prefix meaning one million times the unit that follows - e.g., a megabyte. Abbreviation, m.

Kilo

A prefix used in the metric system, designating one thousand times the unit of measure that follows. Thus, kilograms are units each containing one thousand grams. Designated by lower case k.

Oversampling

A process by which each audio sample is read from a compact disc more than once, mainly to double-check the accuracy of the first reading, but also to interpolate values between samples, increasing the effective sampling rate. Oversampling rates of 88.2 kHz and 176.4 kHz are available on higher quality players, but there is no proof that the process improves the sound of the output, at least for the average listener.

FM Synthesis

A process of signal production in which the frequency of a carrier wave is modulated by the amplitude of an audio signal, in turn generated in response to control voltages from a keyboard, etc.

Patch Cord

A short length of audio cable with an audio plug on each end, used for signal routing in a patch bay.

Unbalanced Line

A signal line with two conductors: one that carries the signal, the other at ground potential. The ground conductor is often used as the shield. Unbalanced lines are more subject to the effects of ambient magnetic or electric fields than balanced lines.

Compressor

A signal-processing device consisting of an amplifier whose gain decreases automatically as the input signal level increases above a specified threshold. Some models use their own output signal to control gain reduction. The result is a decrease in the dynamic range of the signal from input to output, primarily by reduction of the level of transients or peaks in the signal. This can prevent overload on steep transients and, when the gain prior to compression is greater than unity, provide a boost for very low level signals.

Master Fader

A single fader that controls the level of all the tracks being recorded or mixed.

Serial Interface

A single-wire plug and associated cable through which serial data flows, one bit after another. The RS-232 connector is the current industry standard serial interface.

Wow

A slow variation in the musical pitch of recorded sounds caused by inconstant tape speed. A slower kind of Flutter.

Transient

A sudden, high-amplitude signal peak that decays to the average program level very quickly. Percussive instruments create steep transients with every note.

Floppy Disk

A thin, flexible disk coated with magnetic oxide, and used as a permanent medium for data and/or programs.

XLR Connector

A three-pin grounded and lockable audio connector designed for professional use, especially in balanced lines.

Stereophonic

A type of audio system that uses two or more speakers or channels to reproduce spatial information, giving the listener the illusion of lateral placement of sounds between two speakers and their relative distance from the listener.

Random Access Memory (RAM)

A type of computer memory in which the user can send data to or retrieve it from any single memory address, independently of all other addresses. The number of Kbytes in a computer's RAM limits the complexity of programs to be run, the size of matrices established for spreadsheets, and the amount of text data instantly available for review or editing.

Read-Only Memory (ROM)

A type of computer memory into which data has been factory stored. Hence the user can only read the data. He cannot rearrange or replace it. Used to store programs that (a) comprise the machine's operating system, (b) translate between user languages such as FORTRAN, BASIC, etc. and machine language, (c) telecommunications programs any basic program the user needs in order to run applications software. ROM cartridges and/or cards also store factory designed patches for many synthesizers.

Volatile

A type of computer memory which can only store data when charged with electricity. When power is turned off, the contents of memory are lost.

Spreadsheet

A type of data-based applications software that establishes a matrix in the computer's RAM or CPU. Used mostly for business applications such as budgeting, cost monitoring and control, scheduling, and inventory. The user can assign names and values (costs, number of items required or available, time or scheduling factors, etc. ) to the items in each position of the columns and rows of the matrix. He can also define equational relationships between the items in various columns and rows. By plugging in different test values for each entry, the user can predict how various factors will affect the outcome of the overall program. He can thus computer-optimize cost, time, and other factors in order to achieve specific business goals.

Moving Coil Microphone

A type of dynamic microphone in which the diaphragm is attached to a small coil of very thin wire. The motion of this coil through the field of a permanent magnet produces the output signal.

Pressure Zone (PZM) Microphone

A type of microphone first developed and marketed by Crown Corporation, in which a dynamic or condenser capsule is mounted flush at the surface of a rigid metal plate or other plate several inches on a side. When the plate is taped to a wall, the inside of a piano lid, or other rigid surface, only direct sound can reach the capsule. This eliminates most direct/indirect phasing problems that can be generated by virtue of mic placement itself, and (in theory) leads to a clearer sound. Many companies now make PZM mics.

Phantom Power Supply

A type of microphone power supply that raises the voltage potential of both conductors in a balanced line to the same DC value, the opposite voltage being applied to the shield. Because both signal leads are identically charged, the input channel that receives the mic's output cannot sense a polarizing voltage at all. Hence the name "phantom." Many consoles have internal phantom supplies, individually assignable to any or all mic input lines.

Chorus

A type of signal processing that slightly delays and, by rhythmic flanging, doubles the apparent number of players or singers heard in the signal. Chorusing also adds a vibrato to the resulting signal.

Cardioid Microphone

A uni-directional pattern, with the axis of minimum sensitivity at l80°. The pattern derives its name from its heart-shaped appearance.

Super-Cardioid Microphone

A unidirectional pattern narrower than cardioid, but broader than hyper-cardioid. Minimum sensitivity occurs at about 135° and 225° off-axis.

Volume (Unit)

A unit of signal level corresponding to the ear's subjective judgment of changes in audio program level or loudness.

Voltage-Controlled Filter (VCF)

A variable bandpass filter, the cut-off frequency of which increases or decreases in proportion to an externally supplied DC control voltage. Used in many synthesizers to change the timbre of the output signal.

2" Tape Formats

Because of the expense of the tape transport needed to manipulate such wide tape, are all professional. Most machines are Sixteen or Twenty-Four-Track. 32 and 40-Track configurations have been built.

Equalizer (EQ)

Any signal processing device used to change the frequency response, relative frequency content, or spectrum of signals passing through it. Equalizers are sometimes mistakenly called filters. Filters may be used in equalizer circuits, but only the passive equalizer can properly be called a filter, since it can only detract from the input signal.

Microphone

Any transducer that converts acoustical energy or sound into an electrical audio signal.

Loudspeaker

Any transducer that converts the electrical energy of an audio signal into acoustical energy or sound.

Shelf Equalization

Any type of equalization in which the boost or cut levels off to a constant shelf of the specified number of decibels. A shelf equalization of +5 dB at 5 kHz implies that from 5 kHz to 20 kHz all frequencies will be boosted by 5 dB. The curve by which frequencies below 5 kHz increase from unity gain to +5 dB varies according to the design of the circuit.

Storage Medium

Any type of material on which analog recordings or digital data is permanently saved; i.e., recording tape, floppy disk, hard disk, optical disk or CD, punched paper tape, etc. Technically, even a common LP is a storage medium for analog information.

ADSR

Attack, Decay, Sustain, Release. The four sections of every sound's envelope.

Hertz

Abbreviated Hz. Formerly called cycles per second. The time by which frequency is measured and specified.

ASCII

American Standard Code For Information Exchange. The most common code used for transmitting text data from computer to computer, or to peripherals. The code employs 8-bit binary words, by which each letter of the English language, each Arabic numeral, and each commonly used symbol is uniquely designated.

Noise Reduction System (Dolby, DBX, etc.)

An active signal-processing device that attenuates noise added to a signal by an audio system such as a tape recorder. Almost all N.R. systems are companders, compressing one or more frequency ranges during recording or broadcast, then expanding these ranges to their original dynamics again during playback or reception. In the case of broadcasts, the compression is at the radio station, the expander in the listener's tuner.

Fader

An adjustable level or "volume" control, usually linear in design and operation. Sometimes called a mixer, especially in England and Europe. Functionally, a potentiometer.

Voltage-Controlled Amplifier (VCA)

An amplifier whose gain is controlled by an external voltage having nothing to do with the signal being amplified. Used in some recording consoles for subgrouping, in automated mixing, etc.

Balanced Line

An electrical cable with two conductors and a separate shield. When a signal is present, the conductors have the same potential with respect to ground, but opposite polarities.

Ground

An electrical pathway or conductor connected to the earth, or a conductive object so large that its potential is considered zero.

Digital Delay (DDL)

An electronic delay line in which the time delay is created by translating the analog input signal into digital information, which is stored for a determined or adjustable length of time, then reconverted back to an analog signal and sent to the output. Many DDLs allow adjustable regeneration or feedback, causing multiple repeats, and other effects such as flanging or chorusing of the input signal.

Ground Loop

An electronic problem caused if the common return wire of a system has two or more connections to ground. The resulting closed path or "loop" is susceptible to electromagnetic induction from AC fields, resulting in hum or RF pickup by the system.

Microphone (or Mic) Level

An electronic signal level (actually a range of levels) that corresponds to the output level of the "average" microphone. Generally accepted as -50 dBV, although actual microphone output levels vary between -65 dBV for some dynamic models and-35 dBV for a few condenser types.

Parametric Equalizer

An equalizer in which the center of the frequency band that each boost/cut control affects can be continuously varied over a wide range. The amount of boost or cut for each band is separately adjustable. Sometimes the bandwidth that each boost/cut control affects can also be varied by a second control. The bandwidth parameter is often erroneously called Q.

Filter

An equalizer that attenuates designated frequencies or bands. These bands may be very narrow or quite wide.

Bandpass Filter

An equalizer that attenuates frequencies above and below a designated band. A low-pass filter thus allows low frequencies but not high frequencies to pass through.

Low-Frequency (or High-Frequency) Shelving

An equalizer that attenuates frequencies uniformly below or above the designated turnover frequency, respectively.

Active Equalizer

An equalizer that employs active electronic components such as transistors or ICs in its processing circuit(s). A pre-amplifying circuit generally follows each stage of actual equalization, boosting the signal level to restore unity gain. If the unit allows overall adjustment of output level, the engineer can A-B the flat and equalized signal.

Passive Equalizer

An equalizer that employs only passive electronic components: i.e., resistors, capacitors, and/or inductors. Since these components consume some of the signal internally, passive equalizers can only cut each operating band. The output signal is thus lower in level than the input.

Shelving Equalizer

An equalizer that raises or lowers frequencies beyond its turnover frequency by a fixed and continuous amount. A shelf boost of 6 dB above 5 kHz will thus increase all frequencies in the signal above 5 kHz by dB.

Cut-Off Filter

An equalizer that sharply attenuates all frequencies that are above or below a designated limit.

Graphic Equalizer

An equalizer whose controls are a set of sliding pots, usually arranged in a row, and each of which adjusts the amount of boost or cut in a specified band of the input signal's overall frequency content. The positions of all the controls gives a "graphic" representation of the frequency response curve that is applied to any input signal.

Dynamic Filter

An equalizer whose operating bandwidth changes automatically in response to changes in program level, frequency content, or some other parameter.

Noise Gate

An expander whose threshold can be set to totally eliminate or attenuate low-level signals, such as noise. Current models allow the user to select the threshold level (i.e., the lowest signal level that will "open" the gate or pass through it unaltered), the rates at which the gate "opens" and "closes" to allow program signal through (called attack and release times), the amount of attenuation in effect when the gate is "closed" (called the floor), and other variables.

Resonant Peak

An increase in amplitude or intensity that occurs when a resonant frequency passes through an acoustic or electronic system. Measured in dB above nominal signal level or SPL for other frequencies.

Shielded Cable

Any audio cable in which the conductors are protected from ambient fields by a surrounding braided or foil metal shielding.

Signal Processing Device

Any audio system used to alter the characteristics of a signal passing through it. Examples: equalizer, compressor, noise gate, etc.

Distortion

Any change in the waveshape of a signal that occurs between the input and the output of an audio device. Strictly speaking, equalization and compression are types of distortion, even though they are used to "enhance" sound or make it more usable. Specific distortion ratings are expressed in percentages, representing the amount of distortion present in the total amplitude of the output waveform.

Applications

Any complex software the user buys to accomplish a repetitive job that is unrelated to the basic nature of his own goals. A word-processing program is a good example, since it is mathematically complex, but its internal operations are functionally irrelevant to the user who is writing letters or a book.

Delay Line

Any device-acoustic or electronic-that intentionally introduces a time delay between its input and output signals.

Sample and Hold Circuit

Any electronic circuit that can take a measurement of the instantaneous voltage (or other parameter) of a signal and hold the value for processing and/or display until the next sample is requested. The time at which the sample is taken may be manually designated, as in certain test equipment, or programmed to happen in response to certain signal events (e.g., as in a peak-reading meter), or repeatedly with respect to time (e.g., in the D-A or A-D circuits of a digital recorder.)

Dynamic Signal Processor

Any electronic device whose type or degree of operation changes in response to level or other characteristic of the input signal-e.g., compressors, noise reduction systems, flangers, etc.

Active Device

Any electronic signal processing device that requires AC or DC current to power its operation, and that generally includes an amplifying stage after its primary processing circuit, allowing the output level to be matched to the input level

Room Resonance

Any frequency whose half-wavelength is equal to one or more dimensions of a room. When propagated in the room, this frequency will cause a resonant condition.

Database

Any large body of information through which the computer can sort to find subsets of data whose members share one or more user-specified characteristics.

Shield

Any material or device used to inhibit the destructive effects an ambient magnetic or electric field may have on a signal path or an entire electronic system. In tape recorders, the heads may be shielded by plates of metal, an alloy impervious to magnetic fields. (b) In electric signal paths, the signal conductors may be wrapped in a thin metallic sheath, either of foil or fine wires, etc.

Analog Recording

Any method of recording in which the recorded waveform is a continuous representation of the original signal. Example: conventional magnetic recording, direct to disc.

Uni-Directional Microphone

Any pattern in which the microphone exhibits more sensitivity to sounds appearing on axis.

ALU

Arithmetic and Logic Unit. The portion of a CPU that actually performs arithmetic and other computational procedures.

Level

Generally, the SPL or "volume" of sound in the listening environment; or the amplitude of the audio signal present on tape, passing through a console or other device, etc. Expressed in decibels according to the various scales that apply to electronic signals or acoustic sound pressure. A potentially misleading term unless the context of its usage is well defined.

CRT

Cathode Ray Tube. Either black and white or color. Although there are all shapes and sizes of CRT's, the most familiar is the picture tube of every television.

CPU

Central Processing Unit. The integrated circuit chip in a computer that actually performs most operations on data. (see ALU.)

Bandwidth 2 (Colloquially...)

Colloquially, the low and high frequencies of any specific frequency band. One might say, "The bandwidth of an electric guitar is 80 Hz to 8 kHz."

CD-ROM

Compact Disk Read-Only Memory. A data storage format for compact discs that enables digital sound and or visual materials to be encoded on the disc. If visuals will accompany audio, the format allows enough memory for about one still image for each 30 seconds of audio. As a publishing medium, CD-ROM offers book publishers vast storage capacity. The Grolier Encyclopedia was the first book available in this format, the entire printed edition fitting on a single CD. Random access availability of data and the enormous indexing capacity of CDs make this a great medium for printed matter. The total storage capacity of a single CD-ROM is about 650 megabytes.

Frequency

Concerning any acoustic sound wave or cyclically varying electric signal, the number of complete vibrations or cycles per unit.

DOS

Disk Operating System (pronounced "doss"). A suffix used by software and hardware manufacturers to describe the way their products organize data and package it for storage. Each manufacturer has its own operating system, although the acronym DOS is often mistakenly taken to imply that there is one universal system.

Fletcher-Munson Curves

Equal loudness contours, which show the volume (or SPL in decibels) of a sound the ear perceives as being of equal loudness as the frequency of the sound increases for 20 Hz to 20 kHz. Since the ear is most sensitive at around 3 kHz, it takes a much higher volume of tones at low and high frequencies before the ear perceives them as being "equal" in volume to a 3 kHz tone.

Signal-to-Noise Ratio

For any audio system, the ratio of maximum undistorted signal voltage level to noise voltage level, usually expressed as the decibel difference between these two levels. This quantity can be measured for any single piece of audio equipment, or for a number of processes performed sequentially on a signal, such as recording and reproducing it.

Threshold

For any dynamic signal processor, the input level at which the device starts functioning.

Track Format

For any tape recorder or recorded tape, the number of tracks, their width and position with respect to the tape, and the overall width of the tape itself. Tape speed is not always included. In general use, some factors are left out if the remaining factors uniquely specify a particular format. For example, "quarter track" uniquely specifies 1/4" tape width with two pairs of stereo tracks, each pair recorded in one direction on the tape. Similarly, 8-track 1" and 24-track uniquely specify two common professional formats.

Envelope

If the amplitude vs. time graph of a musical sound is plotted, the envelope of the sound is the overall shape of this graph. More exactly, the curve and its reflection that enclose the waveforms comprising a sound. A sound's envelope includes its attack, decay, sustain, and release.

Parallel Interface

In Computers, the multipin connector and associated cable through which parallel data flows. The Centronics Corporation defined the current standard parallel interface.

Poly Mode

In MIDI inter-connection of synthesizers, the operating mode in which an instrument can receive several notes on one specified MIDI channel, generating a polyphonic output with all notes sounding the same patch. Also called omni-off/poly mode.

Pre-Amplifier or Preamp

In a console or other audio system, the first stage of amplification, in which very low level input signals, such as from a phonograph cartridge or microphone, are boosted to line level (or some usable level). Many pre-amplifiers contain circuits to equalize signals whose source has a known imbalance in frequency content, again such as a phonograph record.

Patch Bay

In a recording console or equipment rack, one or more rows of female input and output jacks, used in conjunction with patch cords to route signals through outboard signal processing gear, or to reroute signals inside the console itself. Synonym for jack bay.

Normalled Connection

In a recording console or other electronic device, a predesignated and continuous signal routing connection that can be interrupted by insertion of a patch cord at the corresponding point in the patch bay. The normalled connection is then "broken," allowing the engineer to reroute as he desires.

Solo Button (noun)

In a recording console, a switch that disconnects the output of the normal monitor system from the monitor amp input. Instead, it routes the signal passing through the circuit or module containing that solo button directly to the monitor amp. The result is that only the signal from that source or module will be heard.

Speed of Sound

In air, sound travels at about 1,087 feet per second at 32°F and 30% humidity. This velocity changes by about 1 ft/sec, increasing as temperature goes down and decreasing as temperature goes up.

Word Processor

In computers, software that allows the computer to accept, edit, format, and then send data to a printer for finished text and/or graphic presentation. It enables the user to input long text programs, to electronically shuffle various parts of the text into a satisfactory order, then specify the format in which it will be printed, including margins, justification, characters, and line spacing, etc.

Operating System

In computers, the software system that organizes the underlying computational and memory resources of the computer and makes them available to the user via a specific set of command names and functions called languages; e.g., BASIC, COBOL, FORTRAN, and other computer languages. Specific applications software can then be written in such a language.

Buffer Memory

In digital circuits, an intermediate storage device (or memory) that can receive and dispense data at different rates, or merely hold data until the following device is prepared to accept it. Often used to adapt the output rate of one device - e.g., a computer-to the input rate of another e.g., a printer. One use of buffer memories in digital recording occurs in error correction circuitry, where such a device holds data read from tape until it can be checked for accuracy, at which point it is decoded and reproduced. Buffers are also used to re-sequence data in de-interleaving, and to reduce wow and flutter in digital playback.

Analog-to-Digital Converter (ADC)

In digital recording, the group of circuits that sample the analog waveform, measure its instantaneous voltage, and convert this decimal value to its binary equivalent, in preparation for storage on tape (or on floppy disk, in random access memory, etc.).

Record or Playback Equalization

In tape recording, the internal and complimentary alteration of the frequency response of input signals prior to recording and output signals after playback. By boosting highs prior to record and reducing them after playback, some tape noise is eliminated. In addition, the equalization curve can compensate for nonlinear response of the specific type of recording tape in use. The NAB, C.C.I.R., and I.E.S. established standard record/playback curves used in the United States, Europe and elsewhere.

Parallel

In the connection of one signal or power source to more than one device or destination, the wiring configuration in which the input leads of all the devices meet at a common electrical point. Signal or power routed to this point flows directly to each device. Opposite of series wiring, in which the source is wired to the input of one device, whose output becomes the input for the next, etc.

Hexadecimal

In the hexadecimal numbering system, any of the sixteen symbols (the arabic numerals 0 through 9 and capital letters A through F) can be used to express numbers 0 through 15.

LED

Light Emitting Diode. An electronic component that allows current to flow in only one direction through itself, and emits light whenever current is flowing.

Monophonic (Mono)

Literally, single sound. In monophonic recording or playback, all sounds are blended together on one channel or track, or heard from a single loudspeaker.

Crossover Frequency

Loosely, the frequency above and below which an audio signal is divided into two bands, each of which is directed to a separate destination. Strictly speaking, the frequency at which each of these two bands is attenuated 3 dB by the crossover network.

LFO

Low-Frequency Oscillator. A circuit whose output is generally used to control some parameter of another signal-generating or signal-processing device. LFO output, when applied to audio signal level, produces a tremolo. When used to modulate delay time, an LFO produces flanging, etc.

MIDI

Musical Instrument Digital Interface. A digital data format or scheme in which control signals generated by the keyboard commands played on one synthesizer can trigger the tone-generating circuits of other synthesizers. One player can thus simultaneously draw on the unique sound settings or patches of several synthesizers to create combined effects that would otherwise be impossible.

Tape Hiss

Noise that is characteristic of analog tape recordings, produced by the random fluctuations in the positioning of magnetic particles along the tape, and heard as low-level hiss during playback. The noise, although broadband, is most noticeable in the high frequencies.

LED Display

One or more LEDs used to indicate the operational status of a piece of electronic equipment, or the varying level of a signal being processed, or simply peak or VU levels. The series of LEDs must be driven by a circuit that senses these levels or conditions, turning on only the appropriate LEDs at each moment.

1/4" Full-Track (Mono) Tape

Tape in which a single track is recorded across the entire tape width.

Limiter

Technically, a compressor whose ratio is infinite-i.e., its output level will never exceed a specified value no matter how much the input level increases over the threshold. Practically, any compressor whose ratio is greater than 10:1.

Oxide

The actual magnetic material applied to one side of all recording tape. It is made of small particles of iron oxide (specifically gamma ferric oxide) or other magnetic material stirred into and suspended in viscous binder liquid which is applied evenly to the tape and allowed to dry.

Room Equalization

The alteration of the frequency response of signals that will be sent to speakers or monitors, done in order to compensate for resonances or other response problems inherent in the room itself. These problems are generally identified by sending pink noise to the speakers, then adjusting the frequency response of the resulting sound that arrives at the listening position. Real-time analysis and other lab tests are often tempered by human judgment in setting room EQs.

Loudness

The apparent intensity of sound as judged by the listener.

Trim (noun)

The attenuation control associated with the first stage of amplification in each module of a console, and by which the incoming level of a mic or line input can be lowered.

Phase Cancellation

The attenuation that results when two acoustic or electric waves of the same frequency but opposite or nearly opposite polarity combine.

Bi-Directional Microphone

The axes of maximum sensitivity are at 0° and 180°; minimum sensitivity is at 90° and 270°. In three dimensions, the pattern resembles two eggs end to end; maximum sensitivity along the line through their long axes, minimum sensitivity along the plane between them.

Cue Mix

The blend of live inputs and/or previously recorded tracks sent hy the engineer to the headphones of performers playing or singing in the studio. Also called the headphone mix.

Flanging

The characteristic sound created by mixing a direct signal with the same signal, slightly delayed by a continuously varying amount of time. As the delay time varies, certain frequencies in the signal are reinforced or completely phased out. These frequencies travel up or down throughout the entire spectrum as the delay time varies, "combing" the spectrum. Originally discovered when playing two copies of the same tape synchronized on separate decks, then manually applying drag to the flanges of one tape reel or the other so that a small delay is introduced between the two identical programs. Flanging is one of a number of effects called "comb filters."

Patch (verb)

To route a signal in via a desired path, usually by use of the patch bay and patch cords.

Sound Pressure Level (SPL)

The decibel rating of acoustic pressure of a sound wave. The threshold of hearing is defined as 0 dB SPL. The threshold of pain for most people is near 140 dB SPL. SPL meters are often equipped with filters to give weighted as well as flat readings.

Voltage

The difference in the electrical potential of two points in a circuit.

MIDI Code

The digital data-transmission format by which MIDI-generating or MIDI-receiving devices communicate with each other. Exactly 31,250 BPS, with word length of 30 bits. Or the MIDI data itself.

Spectrum

The distribution of frequencies present in a specific sound, or reproducible by a certain medium or device.

Signal

The electric current that carries audio information.

Polar Pattern

The graph of the sensitivity of a transducer.

Nyquist Frequency

The highest audio program frequency that can be accurately sampled by any specific sampling rate. By definition, one-half the sampling frequency.

Peak Level

The instantaneous highest level of the transient in any signal or series of signals. Because these transients are so short, meters designed to read peak levels have circuitry built in that remembers and holds the level on display long enough for the meter itself to reach the peak's full level and be observed by the engineer.

Decay Time

The length of time it takes for echoes or reverberation of a sound to diminish 60 dB below its original level, effectively to inaudibility. More precisely known as reverberation time or T-60.

Magnetic Field

The magnetic flux (or lines of force) surrounding a magnet or any magnetic material, such as recording tape.

Transient Response

The measure of the accuracy with which an audio system reproduces transients. For example, each hit of the snare drum in a digitally recorded rock cut may have a transient 12-15 dB above the average signal level.

Chip

The miniaturized signal-processing heart of an integrated circuit, or any of the thumbnail sized data storage or data-processing circuits in computers, digitally controlled devices, etc.

Hyper-Cardioid Microphone

The narrowest of unidirectional patterns, narrower even than super-cardioid, indicating very low off-axis sensitivity. There is usually a small lobe of sensitivity around 180°. Thus, minimum sensitivity occurs at about 110° and 250° away from the axis.

Word Length

The number of bits composing each word of digital data. The more bits in each digital audio sample, for instance, the greater the number of quantizing increments by which the incoming analog wave can be represented. This, in turn, affords greater accuracy in recording and reproduction of the original waveform.

Decay Rate

The number of decibels per second by which echoes or reverberation of a sound diminish once the sound has stopped. Depending on the sound source and environment, the decay rate may be linear (e.g., a steady number of dB per second), or it may begin to decay slowly and then fall off rapidly, or the reverse. In addition, various frequencies in the sound may decay at different rates.

Sampling Rate (or Sampling Frequency)

The number of samples a digital recorder takes per second for each signal channel or track. Expressed in hertz, although this term does not exactly apply, since sampling, though a repetitive process, has nothing to do with audio frequencies per se. Various professional digital recorders sample at 48,000 or 50,000 Hz. CD players have a 44.1 kHz sampling rate, while digital audio recorded on NTSC video formats is sampled at 44,056 Hz (due to the corresponding 29.97 frame per second rate of the NTSC standard itself).

Compression Ratio

The numerical ratio of the decibel increase in input level of a compressor (above the threshold) that produces a one decibel increase in output level. Example: If the increase in input level is 5 dB for every 1 dB increase in output, the compression ratio is 5:1.

1" Eight Track

The only pro format of tape.

Digital Recording

The original analog waveform is sampled, yielding a voltage value for each sample. These values are converted to binary numbers which are encoded on tape as a biphase signal. Upon playback, the voltage values are reconstructed, then filtered and smoothed. Sampling at a rate less than the nyquist frequency results in an incorrect replica of the original waveform. Sampling at or above the nyquist frequency results in a duplicate of the original waveform.

Composite Equalization

The overall frequency response modification produced when a signal passes through more than one equalizing circuit in the same device, or through several equalizers in series.

Diaphragm

The part of a microphone (the membrane) or loudspeaker (the cone) that moves in response to sound waves or an incoming signal, respectively.

Equalization ("EQ")

The process by which one electronically modifies the frequency response of an audio system, and thereby the relative frequency content or energy distribution curve of an audio signal passing through it.

Subtractive Synthesis

The process of creating sounds by taking some of the overtones or partials out of a very complex original signal, such as a square or sawtooth wave. Most analog synthesizers generate sounds subtractively.

Gain

The ratio of the signal level at the output of an audio device to the signal level at its input. Normally expressed in decibels (dB), but sometimes as a ratio of voltages. Unity gain, for instance, denotes identical input and output levels. A gain of 6 dB indicates that a device amplifies signals by 6 dB, equivalent to a doubling of the signals' voltage. The voltage ratio here is thus 2:1.

Cue Send

The section of the recording console that controls the source and volume of the signal to be sent to the cue box. There are normally cue send volume controls at each module, all of which are mixed and fed via the cue bus(es) to a master cue send volume control located in the monitor or master control module.

Mixing Board (Console or Desk)

The set of F controls (and the enclosure containing them) by which the recording engineer selects various input signals (mic, line, or tape playback), adjusts their relative volume, tone, etc., and routes them, either to multi-track tape, mixdown, control room monitors, studio headphones, or other destination.

Bit

The smallest unit of information that can be stored, transmitted, or processed by any digital circuit - e.g., a computer. Each bit is a "1" or "0" and corresponds to a single yes/no, on/off, or other similar decision. Abbreviated from BInary digiT.

Timbre

The specific tone color or quality of a sound, including its timing, harmonic structure, envelope, and other identifying aural characteristics.

Compression

The squeezing together of air molecules during the first half of each complete cycle of a sound wave. It corresponds to the portion of the wave that appears above the axis when graphed. Opposite of rarefaction.

Delay

The time interval between the initial occurrence of a sound or signal and its repeat or echo.

Phase

The time relationship of two or more sound waves reaching the same point in space simultaneously, or of two or more signals passing through the same point in an electronic circuit simultaneously. If the two sounds or signals are of identical frequencies, they are "inphase" if the peaks and troughs of the waves occur simultaneously. They are "out? of phase" if the peaks of one partially or fully cancel the peaks of the other. The degree of "out-of-phaseness" is designated in degrees (x°) such that 0° phase difference indicates two sounds or signals exactly "inphase," and 180° phase difference indicates the two are completely "out-of-phase," cancelling each other completely.

Print-Through

The unwanted transfer of signal from one layer of magnetic tape to another. Noticed particularly when a very loud sound on one layer of tape can be heard during very soft sounds or pauses on the adjacent layers.

Partials

The upper harmonics or overtones in a complex waveform or sound. The partials of a flute, for example, include the sound of the player's breath passing over the embouchure or mouthpiece, in addition to the higher frequencies emanating from the instrument's body.

Sine Wave

The waveform of pure tone or single frequency. One of the three basic waveforms produced by synthesizers, the others being square and sawtooth waves.

Trim (verb)

To attenuate the incoming level of a signal. For example, "Trim the mic in module number three."

Mute

To cut off a sound, input, or track suddenly. Also, to reduce monitor level by a known amount via a pre-set button on the console, normally to facilitate verbal communication in the control room.

Format

To designate the parameters that control how and where a computer stores data on a floppy disk or other so-called hard memory. Formatting parameters include the types of data, data density on the disk, size of any matrices, how data is grouped for easy retrieval, etc. Compatibility among computers often depends on their formatting, rather than internal operation.

Solo Button (verb)

To press a solo button on a recording console in order to hear only the signal passing through one module or channel.

1/2" Eight- and Sixteen-Track Tape

considered semi-pro formats, and used mainly in making demos.

1/2" Four-Track Tape

used for quadraphonic mixdowns and the production of stereo mixes with separate SMPTE or other synchronizing tracks.