GLOSSARY

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In acoustics, absorption is what happens when sound waves are absorbed by a surface, as opposed to bouncing off the surface (reflection). Absorptive materials in a control room, for example, tend to “deaden” the sound of the room because the sound energy is absorbed rather than reflected. (See also “Reflection.”)

Absolute Phase

This term describes a perfect polarity between an original signal (into the microphone) and the reproduced signal (through the speaker). When positive pressure exerted upon the microphone is translated as positive pressure to the loudspeaker, the two are in “absolute phase.”

AC

See “Alternating Current.”

Accelerometer

A device that measures the acceleration to which it is subjected and creates an electric signal to match it. In music and audio, accelerometers are found in such things as microphones and guitar pickups.

Acorn Tube

Named for its acorn-like shape, an acorn tube is a small vacuum tube used in ultra high frequency (UHF) electronics such as tube amplifiers.

Background Noise

Refers to either 1) The ambient noise in a room unrelated to the instrument(s) or vocal(s) being recorded; or 2) The system noise unrelated to the recorded signal. (All electronics emit a level of noise.)

Baffles

Sound absorbing panels that are used to prevent sound waves from entering or leaving a space.

Balance

1) The relative level of two or more instruments in a mix, or the relative level of audio signals in the channels of a stereo recording. 2) To even out the relative levels of audio signals in the channels of stereo recording.

Balanced Cable

A cable consisting of three wires (two signal wires and a ground wire) and two connectors. The two signal wires carry the same signal in opposite polarities, providing protection against interference and noise in a balanced system. Examples of balanced cables include tip-ring-sleeve (TRS) stereo cables and XLR cables.

Balanced Mixer

A circuit or device that generates the sum and difference frequencies of two input signals.

Band

1) A range of frequencies, often identified by the center frequency of the range. 2) A group of musicians playing together.

Cable

A group of one or more insulated conductors, optical fibers, or a combination of both within an enveloping jacket, typically for transmitting electrical signals of different types.

Cable Assembly

Cable that is ready for installation in specific applications and usually terminated with connectors.

Cable Harness

A grouping of cables or wires used to interconnect electronic systems.

Cable Sheath

Conductive protective cover that is applied to cables.

Capacitor

An electronic device made of two plates separated by an insulator, designed to store electrostatic energy. The capacitor is a key component in condenser microphones, for example.

Capstan

A mechanical part of a magnetic tape recorder that controls the speed of the tape as it passes across the tape heads.

D/A

Abbreviation for Digital to Analog conversion, which changes digital data numbers (digital audio signal) into discrete voltage level. The reverse process of A/D.

Daisy Chain

The connection of three or more devices in a series, where the audio signal passes through one device to reach a second, and through the second to reach the third, etc.

D-Sub Connector

Abbreviation for “D-subminiature connector,” a D-sub is a multipin connector that is most often used to connect a computer to a VGA monitor, but also used occasionally in digital audio applications in the recording studio.

Damping

The reduction of energy in a vibrating system, through friction. Can refer to the reduced amplitude in an electrical signal, or the stifled vibrations of a musical instrument (for example, the damper pedal on an acoustic piano).

Damping Factor

Describes an amplifier’s ability to restrain the pushback motion (back-EMF) of the loudspeaker cone when the audio signal stops.

DAW

An abbreviation for Digital Audio Workstation, a device or software program designed for recording and mixing audio digitally.

Early Reflections

The first sound waves that reach a listener’s ear after bouncing off a surface in the room, usually heard almost immediately after the initial sound. The first stage of reverberation.

Echo

The distinct repetition of an initial sound, caused by the reflection of the sound waves upon a surface. We recognize a sound as an echo when the distance between the source and the reflection is far enough apart that we can detect the time delay between one and the other. Essentially, reverberation is the combination of many echoes occurring too rapidly to hear each individually. In the studio, echoes can be reproduced acoustically or simulated by a digital signal processor.

Echo Chamber

An enclosed room designed with reflective, non-parallel surfaces for the purpose of creating acoustic echoes (reverberation).

Edit

To change one or more parameters of a recorded sound after the fact. This can take many forms, including “punching in” a section of the music that is re-recorded to replace the original version; altering the shape/size of waveforms graphically; changing the sequence of playback; and many others. Analog editing would typically involve splicing the magnetic tape on which the audio signals were recorded. These days, almost all editing in the studio is done via computer using a digital audio workstation (DAW).

Effects

1) Various ways an audio signal can be modified by adding something to the signal to change the sound. 2) Short for the term Sound Effects (sounds other than dialogue, narration or music like door closings, wind, etc.) added to film or video.

Effects Track

1) In film production audio, a recording of the mixdown of all the sound effects ready to be mixed with the dialogue and music. 2) In music recording, one track with a recording of effects to be added to another track of a multitrack recording.

Fade

A gradual reduction of the level of the audio signal, or a gradual change of level from one pre-set level to another.

Fader

A control which adjusts the level (gain or attenuation) of an incoming signal to a channel or grouping of channels on a console.

Far Field

The region away from a loudspeaker at which the sound drops 6dB for each doubling of the distance, up to the critical distance. The beginning of the far field varies according to the size of the speaker, but in most cases the far field begins around 3 feet from the sound source. Audio engineers often use both near field and far field monitoring when fine-tuning a mix. (See also “Critical Distance,” “Near Field.”)

Feed

To send an audio or control signal to.

Feedback

The return of a portion of the output signal back into the input of a system. This can be done in a controlled manner through a feedback circuit to alter the sound of an instrument (most commonly electric guitars or analog synths). It can also describe the unwanted feedback loop created when an open microphone is picking up the sound from a nearby speaker, generating a loud, oscillating frequency that increases in intensity until the feedback loop is broken by turning off the mic or speaker, or by use of an equalizer to attenuate the frequency.

Feedback Control

The control on a delay line or delay effects device that controls the amount of feedback into the system.

Gain

1) The amount of increase in audio signal strength, often expressed in dB.

Gain Control

A device that changes the gain of an amplifier or circuit, often a knob (potentiometer) that can be turned. In a mixing console, each channel usually has its own gain control to regulate the gain of the signal coming into the board—not to be confused with the channel “fader,” which regulates the output of an already-amplified signal.

Gain Reduction

The action of a compressor or limiter in regulating the amplitude of the audio signal.

Gain Structure

A term that describes the interconnection of multiple components in an audio system, and the amount of gain increase or reduction that occurs at each point. A configuration with a good gain structure means that the components are working properly together to provide optimal gain with minimal distortion or noise.

Gate

(Also called Noise Gate) A type of expander that completely (or almost completely) attenuates a signal once it drops below a certain level, rather than simply reducing the level. (See also “Expander.”)

Generation

A term used to describe the number of times that the recorded audio signal has been copied.

Haas Effect

(Also called Precedence Effect) Simply stated, a factor in human hearing in which we perceive the source of a sound by its timing rather than its sound level. In his research, Helmut Haas determined that the first sound waves to reach our ears help our brains determine where the sound is coming from, rather than its reflection or reproduction from another source. The reflection of the sound must be at least 10dB louder than the original source, or delayed by more than 30ms (where we can perceive it as an echo), before it affects our perception of the direction of the sound. This is what helps us distinguish the original sound source without being confused by reflections and reverberations off of nearby surfaces. Understanding the Haas effect is particularly useful in live audio settings, especially in large venues where loudspeakers are time-delayed to match the initial sound waves coming from the source.

Half-Normalled

See “Normalled.”

Half Step

A change in pitch equivalent to adjacent keys on a piano. Also known as a “semitone.”

Hall Program

A setting of a digital delay/reverb effects unit that approximates concert halls. Hall programs are characterized by pre-delay of up to 25 ms.

Hard Knee

In compression, refers to a more abrupt introduction of compression of the signal once the sound level crosses the threshold. (See also “Knee.”)

Harmonic Distortion

The presence of harmonics in the output signal of a device which were not present in the input signal, usually for the purpose of changing the instrument’s timbre.

IC

See “Integrated Circuit.”

IM Distortion

See “Intermodulation Distortion.”

Imaging

Refers to the ability to localize a specific sound within the sound space. In recording environment, it refers to “placing” instruments within the stereo or surround field so that it when the sound is played through speakers, it fools our ears into thinking the sound source is in emanating from a specific point instead of from the speakers. In live audio and sound reinforcement, the principle of imaging is the same, the goal being to make the audience perceive the sounds as coming from performers on the stage, rather than from the speakers.

Impedance

Refers to the resistance of a circuit or device to alternating current, which can be mathematically described as the ratio of voltage to current. Differences in impedance between devices in the studio can affect how they work together. Impedance is abbreviated by the letter Z, and measured in ohms (W).

In Phase

The desirable situation in which two or more devices (and their respective audio signals) are on the same side of the polarity spectrum, producing waveforms that do not conflict or cancel each other out.

Inductance

A characteristic of electrical conductors in which electrical charge (voltage) is produced or stored magnetically due to the natural resistance to change in the electrical current. Inductance is an electromagnetic principle that can either assist in audio applications (as in loudspeakers) or cause resistance (as in using speaker wire whose gauge is too low for the application).

Jack

A connector mounted on the case of a device or on a panel.

Jam Sync

A process available on some clock or syncing devices which reads an external time code and recreates (or “jams”) a new time code identical to the original external code for the syncing of devices. This function is mainly used for replacing code that has become degraded.

Key

1) In music, the note scale in which a piece of music is written or played, identified by the first note (tonic) of the scale, as in, “Key of C.” 2) The control of a dynamics processing device by an external audio signal through the use of a side chain. 3) A digital or data code that unlocks the use of a device or software. Example: Pro Tools is licensed through an iLok ID via the use of a physical USB key.

Keyboard

Any musical instrument or computer controlled by pressing a key.

Keyboard Controller

A piano-styled keyboard that sends out MIDI signals to control other MIDI devices. Most keyboard instruments are equipped with MIDI control capabilities, but dedicated MIDI keyboard controllers emit no audio signals, only MIDI data.

kHz

An abbreviation for kilohertz (1000 Hz, or 1000 cycles per second). Example: 2000 Hz = 2 kHz. Most commonly used in the studio for describing audio frequency ranges or digital sampling rates.

Kick/Kick Drum

The bass drum on a trap drum set, so called because it is played with a kick pedal.

Knee

A function on a compressor that determines how abruptly or gradually compression begins once the sound level crosses the threshold. So-called because the graphic “bend” in the response curve is reminiscent of a knee. “Hard knee” refers to an abrupt activation of the compressor, while “soft knee” refers to a more gradual change.

Layering

Refers to almost any blending of similar multiple musical parts or sounds at once, often combined on one channel or assigned to one controller. In audio recording, layering usually involves recording similar takes of the same instrument or vocal (or duplicating parts with slight delays or chorusing effects) to create a fuller, richer sound than the vocal/instrument by itself. In sound design, it also refers to blending multiple samples (example: two or more drum sounds) to create a fuller sound.

Lead

The musical instrument that plays the melody, including the vocal.

Lead Sheet

A shorthand form of music notation (similar to a chord chart) that displays the basic essential elements of a song so musicians can follow along without the full notation of every note or expression. Lead sheets most commonly include a melody line written in music notation with chord changes above the staff, and lyrics below it. (See also “Chord Chart.”)

Leakage

Sounds from other instruments and sound sources that were not intended to be picked up by the microphone.

Level

The amount of signal strength; the amplitude, especially the average amplitude.

Limiter

A type of compressor that sharply reduces (limits) the gain of the signal when the audio level reaches a certain threshold, typically used to prevent overload and signal peaking. A compressor effectively becomes a limiter when its ratio is 10:1 or higher. (See also “Compressor.”)

Magnetic Tape

Recording tape consisting of a plastic strip coated by magnetic materials, finely ground iron oxide (rust) particles. Commonly used for analog recording.

Magnetism

A natural attractive energy of iron based-materials toward other iron-based materials.

Margin

ee “Headroom.”

Masking

The characteristic of hearing by which loud sounds prevent the ear from hearing softer sounds of similar frequency. Also refers to the obscuring of softer sounds by louder ones.

Master

1) The main output control of a console or DAW, setting the level of the mixed signal as it leaves the console. (Also called “master fader.”) 2) The final-mixed original recording from which copies are made.

Mastering

The final process of fine-tuning and “sweetening” the mix on a song or collection of songs, from which the master will be created.

Nanowebers per Meter (NW/m)

The standard unit in measuring the amount of magnetic strength on analog tape. A Weber is a unit of magnetic strength, but it is too large a unit to apply to the magnetism in tape recorders, so nanowebers is used instead. Nanowebers per meter of tape effectively describes the signal strength that is being recorded to tape.

Narrowband Noise

Noise (random energy) that occurs over a limited frequency range.

Near-Coincident Miking

A stereo miking technique in which two microphones are placed near each other at an outward angle to create a stereo image (as opposed to “Coincident Miking” which angles the microphones toward each other). Common versions of near-coincident miking include DIN stereo (90-degree angle, 20cm apart), NOS stereo (90-degree angle, 30 cm apart) and ORTF (110-degree angle, 17 cm apart).

Near Field

The area between 1-5 feet from the sound source. Studio monitors are generally considered “near-field” speakers because they are meant to be listened to at close range. (See also “Far Field.”)

Negative Feedback

A portion of the output signal that is fed back to the input of an amplifier with its phase inverted from the original output signal. This has a dampening effect on the output, effectively cancelling out a portion of the volume.

Noise

Describes any unpleasant, objectionable or unintended sound frequencies present in the audio signal. All electronic equipment produces some type of noise, which may be described as a hiss or buzz that can be heard during quiet or otherwise silent passages. (See also “Noise Floor.”) Bad connections, improper grounding, radio interference and other issues can also cause introduce noise into the signal. Engineers may also deliberately run a noise signal through a sound system for testing purposes. (See also “White Noise, “Pink Noise.”)

Octave

An interval or difference of pitch of 12 half-steps. In our standard tuning system, the higher note in an octave is exactly double the frequency of the lower note.

Off Axis

Veering away from the imaginary line (axis) directly in front of the receiving end of a microphone. Measured as degrees of an angle. (For example, a sound coming from directly behind the microphone is said to be 180 degrees off-axis.)

Offset Time

1) The SMPTE time that will trigger a MIDI sequencer to begin. 2) The amount of position difference needed to get two reels to play the music in time.

Ohm (W)

The unit used to measure the amount of opposition (impedance) to electrical current flow in a signal or device. (See also “Impedance.”)

Ohm’s Law

The mathematical relationship between voltage, current and resistance.

Omni

A prefix meaning “all.”

Pad

1) A device or circuit that attenuates an incoming signal, usually to prevent overload of an amplifier that follows along the signal path. (Also sometimes called “Attenuator pad.”) 2) A device with a surface that can be hit by a drum stick; hitting the pad produces an output signal pulse (or MIDI command) that causes a drum machine or synthesizer to sound a drum sound. 3) A type of synthesizer patch/program used to create sustained background or atmospheric sounds.

Pan (Panning)

The process of “placing” a particular sound within the stereo field. This is accomplished by controlling the balance of the signal between the left and right speakers so the ear hears the sound as coming from a particular point in the sonic space between left and right. This sonic space is sometimes called the “stereo panorama,” from which the word “panning” is derived. In surround sound, panning occurs in a 360° sound space, not just left-right.

Panpot (or Pan Pot)

Short for “Panoramic Potentiometer,” a panpot is a knob in the channel strip that controls the panning of the audio signal in the stereo (or surround) space by controlling how much of the signal is sent to each speaker or channel.

Parallel Jacks

Several jacks that are wired so that each connection is wired to the corresponding connection of other jacks.

Parallel Port

A connector that is able to transmit and receive digital data at the same time though different pins.

Parameter

Each characteristic of a sound, signal or device that is possible to change.

Quadraphonic

A now rarely-used system of four-channel sound where the channels are designated as left front, left back, right front, right back, intended to deliver sound from all four corners of a room. Quadraphonic sound was a precursor to the surround-sound systems of today.

Quantization

1) In digital music, the process of adjusting the rhythmic performance of music by moving the notes to precise locations on the time line, effectively “rounding” the note occurrences to the nearest defined increment. 2) In analog-to-digital conversion, the use of the same mathematical quantization principles to convert an analog signal into a smaller set of steps (a digital quantity).

Quantization Distortion/Quantization Error

The effective “error in translation” between an analog signal and its sampled counterpart due to the rounding of a large number of analog values to the nearest digital quantity. This often results in additional random frequencies in the sound, often heard as noise.

Quantization Noise

The modulation noise in a signal resulting from quantization error.

RackRack (or Equipment Rack)

A cabinet or framework with rails, used to mount and house various components of outboard gear.

Rack EarsRack Ears/Rack Flanges

Mounting brackets that can are attached to equipment so it can be mounted in a standard equipment rack.

Rack-Mounted

Describing outboard gear that can be housed in an equipment rack.

Radiation

The angle and pattern of coverage of a speaker.

Radiation Pattern

A graphic depiction of speaker coverage. This is not unlike the polar pattern of a microphone, with the exception that a polar pattern describes the area where sound arrives at the microphone, while a radiation pattern describes how sound is dispersed from the loudspeaker.

Ramp Wave (Sawtooth Wave)

See “Sawtooth Wave.”

Safe

A setting on an analog multitrack tape recorder that will prevent a track from recording when the record button is pressed.

Sample

1) In digital recording, the numerical measure of the level of a waveform at a given instant of time. Analog music is represented digitally by many samples taken in rapid succession. 2) A short segment of audio recorded for the purpose of reproducing and manipulating the sound digitally.

Sample Dump Standard (SDS)

See “MIDI Sample Dump Standard.”

Sample Rate

In digital recording, the number of times per second that samples are taken. The higher the sample rate, the more realistic the digital reproduction of the sound, and the higher frequencies of the sound can be reproduced. In digital audio, the quality and resolution of a digitally reproduced sound are described as a combination of sample rate and bitrate. (See also “Bitrate.”)

Sample Rate Conversion

The conversion of digital audio taken at one sample rate to a different sample rate without first converting the signal to analog.

Sampler

A device that records and plays samples, often with features for editing, manipulating and storing the samples.

Tach/Tachometer

In analog tape recording, a device on the recorder that measures and regulates tape speed by emitting pulses as the tape moves across the head.

Tails Out

A method of winding audio tape so that the end of the last recorded selection is at the outside of the reel.

Take

The recording that is done between one start and stop of a tape recorder or DAW.

Take Notation

Writing down the takes of the tune being recorded on a take sheet or on the track log with comments. Take notation was/is recommended for analog tape recording, but in most studios, this function is now accomplished on the DAW.

Talk Box

An effects unit that enables a musician to modulate the sound of his/her instrument via a tube placed into the mouth. Historically, talk boxes have been used as an effect for guitars, but they can be used to modify other instruments, as well.

Talkback

A microphone in the control room carried on a separate circuit from the recorded channels, allowing the engineer to communicate with the musicians in the live room or sound booths through the monitoring system.

Unbalanced Cable

A cable with two conductors (a signal wire and a ground wire) and connectors on each end. Unbalanced cables are often susceptible to electromagnetic interference and noise. Examples of unbalanced cables are guitar/instrument cables (also called tip-sleeve or TS cables) and RCA cables.

Unidirectional Pattern

A microphone pick-up pattern which is more sensitive to sound arriving from one direction than from any other.

Unison

Several performers, instruments or sound sources that are sounding at the same time and with the same pitch.

Unity Gain

The scenario in which there is no increase or decrease in signal strength at the output of an amplifier or device compared to the signal strength at the input (typically described as 0 dB).

Vacuum Tube

A diode, a glass tube with the gases removed, through which electrical current can flow. In audio, vacuum tubes are used in amplifiers, oscillators, and other analog devices.

Vamp

A part of a song or chord progression that is repeated, usually at the end of the song, and usually the chorus or part of the chorus.

Vamp and Fade

A method of ending the recording of a song where the music has a repeating part and the engineer reduces volume until the music fades out.

Vari-Speed

A control on a tape machine that changes the play speed.

Variable-D

A trademarked, patented technology of ElectroVoice in its microphone designs to vary the proximity effect in its microphones. Variable-D places several ports along the microphone body, each of which has a reduced level of sensitivity to higher frequencies the further they are placed from the microphone’s diaphragm.

VCA

Shorthand for “Voltage Controlled Amplifier,” an amp whose gain is affected by an external voltage fed to it.

Watt

Unit of electrical power.

Waveform

A visual representation or graphic of a sound wave, audio signal or other type of wave, showing the wave’s oscillations above and below the zero line.

Wavelength

The physical length of one cycle of a wave, measured in feet, inches, etc. The longer the wavelength of a sound wave, the lower its frequency; the shorter the wavelength, the higher the frequency.

Weighting

An equalization curve used in audio tests that compensates for the Fletcher Munson Curve at various levels. (See also “Fletcher-Munson Curves.”)

Wet

Refers to a signal that has the full amount of an effect (like reverb) applied to it, as opposed to “dry,” which refers to the un-effected sound. Many times, the preferred sound in mixing will be a blend of wet and dry signals. (See also “Dry.”)

White Noise

A noise signal containing an equal spread of energy across all audible frequencies. Like pink noise, engineers often send a white noise signal through audio equipment for tuning and calibration purposes, or in EQ-ing a live audio space. (See also “Pink Noise.”)