Glossary
3D sound See surround sound.
5.1 surround sound An audio format involving five channels of full bandwidth audio: center, left, right, left surround and right surround. A special low frequency effects channel (LFE or “.1”) covers a frequency range from 20 Hz to 120 Hz. The basic setup for music production is defined in ITU 775.
A-D Analog-Digital.
AAC Advanced Audio Coding. Special variant of the MPEG standard.
AB (1) Microphone placement for spaced microphones intended for time difference stereo. (2) Manner in which microphones are provided with power. Also called Tonader. (3) A method for comparison of two versions.
absorption A property of materials that reduces the amount of sound energy reflected; unit: sabin. 1 m2 full absorption (like an open window) equals 1 m2 sabin.
absorption coefficient (symbol: a) The practical unit between 0 (no absorption) and 1 (full absorption) expressing the absorbing properties of a material. This is basically specified per octave or 1/3 octave. Absorption may exceed 100% (or a >1) when the surface area seems larger than the area it covers (applies typically only at high frequencies).
AC Alternating current, as opposed to: DC, direct current.
AC-3 Digital Audio Compression Standard.
acoustics The interdisciplinary science that deals with the study of sound.
ADC Analog to Digital Converter. A circuit that converts an analog signal to a digital signal.
ADPCM Adaptive Differential Pulse Code Modulation. Encoding form for digital signals.
ADR Automatic Dialog Replacement. Automatic replacement of location dialog with studio dialog.
AES Audio Engineering Society. International society for professional audio engineers.
AES/EBU The AES (Audio Engineering Society) and EBU (European Broadcast Union) created jointly a standard for the transfer of two channels of digital sound. The signal is bi-phase modulated, self-clocking and runs on a balanced cable (max. 50 m or 150 ft) or via optical fiber. The standard currently is called AES3.
AF Audio Frequency. Audible frequencies, basically in the range of 20 Hz to 20,000 Hz.
A-filter See A-weighting.
AFM Designation for a video recorder’s frequency-modulated sound track (Audio-FM).
A-format A microphone arrangement with four coincident cardioid capsules. Through use of a dedicated matrix this signal can be converted to B-format. See sound field microphone. AGC Automatic Gain Control. Method by which the amplification in a circuit is controlled by the input voltage or another parameter.
AIFF File format for sound.
AM Amplitude Modulation. Transfer of information by the variation of the amplitude of a carrier wave.
ambience Spatial effect, notably mixing of remotely placed microphones in order to include the atmosphere of the room on the recording.
ambient noise (Acoustic) noise from the surroundings.
Ambisonics A principle that utilizes the sound field microphone involving B-format recording (X, Y, Z, and W).
ampere, A Unit for electrical current.
amplitude For an alternating signal; the size of the variation.
analog Quantities in two separate physical systems having consistently similar relationships to each other are called analogous. One is then called the analog of the other (for example, sound pressure in front of a microphone and the electrical output of that microphone).
anchor element The perceptual loudness reference point or element around which other elements are balanced in producing the final mix of the content, or that a reasonable viewer would focus on when setting the volume control.
anechoic room Room without echo; the reverberation time is ideally close to zero seconds.
ANSI American National Standards Institute. A federation of American organizations concerned with the development of standards.
anti-aliasing Low-pass filter for the removal of frequencies that otherwise would create “alias” frequencies that were not present in the signal originally.
apt-X Bit reduction system from Audio Processing Technologies used by DTS. 4:1 or 3:1 compression.
artifact Unwanted effects that arise due to technical limitations.
ASCII American Standard Code for Information Interchange. Character set encoding used in data transfer.
asynchronous sample rate converter When two (digital) devices cannot be synchronized (for example, a CD player with a mixer) even a small deviation between the clock frequencies of the two devices will cause occasional glitches due to the accumulation of shortages or excesses. This creates a small “crack” in the sound. The asynchronous sample rate converter can perform interpolation, and hence create the missing intermediate values so that glitches are avoided.
ATR Audio Tape Recorder.
ATRAC Adaptive Transform Acoustic Coding. Bit reduction system from Sony for use on MiniDisc. In stereo, 300 kbps is used. The system is also used for films (see SDDS).
ATSC Advanced Television Systems Committee.
attack The beginning of a sound; the initial transient of a musical note.
attenuation Variable or fixed downward adjustment of a signal level.
attenuator A device used to control the level of an electrical signal
audio That part of sound technology that concerns itself with the recording and reproduction of sound.
autolocate Facility on a tape unit’s transport system.
AUX Auxiliary jack, an extra input or output.
A-weighting The connection of an A-filter (IEC-A) for the acoustical and electrical measurement of noise. Produces a result that roughly corresponds to the human ear.
azimuth Angle of a magnetic head gap in relation to the direction of travel of a magnetic tape.
balancing When a signal is run independently of the frame/shielding and both terminals have the same impedance to the frame. See symmetry attenuation.
band-pass filter See filter, band-pass.
bandwidth The distance between the 3 dB cutoff frequencies on a response curve. Expressed either in octaves or in Hz.
batch The number of sound or video media produced in the same fabrication process.
BCD Binary Coded Decimal. Decimal digits converted to the base two system.
bel, B Relative logarithmic unit for the measurement of sound levels. Normally one-tenth of a bel is regarded as the main unit: decibel, dB.
Betacam Video format that uses the Betamax cassette with a tape speed of 10.15 cm/s [4 in./s]. and two analog sound tracks. Betacam SP: two analog and two FM modulated sound tracks. Betacam SP Digital: one analog, two FM, and two digital sound tracks.
B-format (microphones) A recording format virtually based on three orthogonal oriented figure 8 microphones (X, Y, Z) and one omnidirectional microphone (W). By combining these signals a variety of directional characteristics can be obtained. Most B-format microphones are designed with cardioid microphones. See sound field microphone.
bias High-frequency alternating current (typically 100 kHz) that is added to the recording head in a tape recorder together with the sound signal. The use of bias improves the quality of the recording with respect to both the frequency response and the distortion.
binary Number system that only contains two digits
binaural recording Stereo recording using either an artificial head with built-in microphones or a real person with small microphones in, or close to, the ear canals. For correct monitoring, the recording must be reproduced by using headphones to eliminate crosstalk.
biphase modulation A form of modulation that, among other things, is used by the AES/ EBU interface and time code. In the bit stream, each bit shift is marked with a level shift (from high to low or vice versa). If the bit value is high, this is marked with a level shift in the middle of the bit concerned. Some of the advantages include that the DC component in the signal is minimized and the signal is self-clocking.
bit Binary digit in digital technology, “0” or “1”.
bit companding A technique for digital audio via which greater contrast can be obtained for a given number of bits.
bit reduction As linear quantization can result in a larger number of bits per second than there is room for in a transmission channel or on a storage medium, the number of bits is reduced, preferably in a manner so that it cannot be heard in the audio signal.
bit Smallest unit in digital technology, with a value of either 0 or 1.
bit stream converter See Delta-Sigma converter.
BNC connector Baby N-Connector; coaxial connector.
BS.1770 Formally ITU-R BS.1770. This specifies an algorithm that provides a numerical value indicative of the perceived loudness of the content that is measured. Loudness meters and measurement tools that have implemented the BS.1770 algorithm will report loudness in units of “LKFS.”
buffer Circuit for the maintenance or improvement of a function.
bus A common set of conductors where many signals are gathered, for example in a mixer console.
byte Data word, consisting of a number of bits, normally 8.
c/s Cycles per second = Hz.
calibration The process of measuring to determine the accuracy of the measurement chain.
calibrator, acoustic A device that produces a known sound pressure on a microphone in a sound level measurement system.
camcorder A contraction of the words camera and recorder; the recording medium and the camera are built together as a unit.
cartridge Special tape cassette with 1/4-inch tape earlier used for jingles, ads, etc., at radio stations. Format: mono, stereo, or 8-track versions.
CC See Compact Cassette.
center frequency The arithmetic center of a constant bandwidth filter, or the geometric center (midpoint on a logarithmic scale) of a constant percentage bandwidth filter.
center post The center lead in a contact device.
channel separation The attenuation of one channel appearing in neighboring channels.
clean sound Atmospheric sound.
clipper See limiter.
clipping An electrical signal is clipped if the signal level exceeds the capabilities of the signal chain or recording device. It is a distortion of the signal.
comb filter A distortion produced by combining an electrical or acoustic signal with a delayed replica of itself. The result is a series of tops and dips across the frequency response that makes it look like a comb.
Compact Cassette , CC. Registered name for the cassette developed by Philips with a 3.81 mm [0.15 in.] audio tape.
compand Describes a process that involves compression and expansion successively.
compander A contraction of compressor and expander. A device that can perform both functions.
compression Reduction of the dynamic range of recorded audio.
compressor A device or plug-in that provides reduction of the dynamic range of recorded audio.
content 0 Material or essence used for distribution by an operator.
corner frequency Transition frequency of a filter.
CRC Cyclic redundancy check. Error correction.
crest factor The term used to represent the ratio of the peak (crest) value to the RMS value of a waveform. For example, a sine wave has a crest factor of 1.4 (or 3 dB), since the peak value equals 1.414 times the RMS value. Music has a wide crest factor range of 4–10 (or 12–20 dB). This means that music peaks can be 12–20 dB higher than the RMS value, which is why headroom is so important in recording and in audio design.
critical band In human hearing, only those frequency components within a narrow band, called the critical band, will mask a given tone. Critical bandwidth varies with frequency but is usually between 1/6- and 1/3-octave. The ears act like a set of parallel filters, each with its own bandwidth.
critical distance, Dc The distance from a sound source in a room at which the direct sound and the diffuse, reflected sound has the same level.
cross fade The audio equivalent of what is known as dissolve in video.
crossover frequency In a loudspeaker with multiple radiators, the crossover frequency is the –3 dB point of the network dividing the signal energy.
crosstalk When a recording on a different track can be heard on a track.
cue Audio or visual information that concerns timing or synchronization.
cue wheel Control button for use with slow forwards and backwards winding with cueing.
cutoff The cutoff frequency of a filter. The frequency at which a filter begins to attenuate. Often defined by the attenuation being 3 dB at the frequency concerned.
D-A Digital-Analog (digital to analog).
DAC Digital-to-analog converter. A circuit that converts a digital signal to an analog signal. The abbreviation D-A is often used.
DAT Digital Audio Tape (-recorder). Digital tape format (cassette). Normally understood as R-DAT (Rotary head DAT) as opposed to S-DAT (Stationary head DAT), which never became a widespread format.
dB See decibel.
dB FS Decibels, relative to full-scale sine wave (per AES17).
dB TP Decibels, true-peak relative to full scale (per ITU-R BS.1770 Annex 2).
dBm Logarithmic relation with a reference of 1 mW/600 ohm.
dBu Logarithmic relation with a reference of 0.775 V.
dBV Logarithmic relation with a reference of 1 V.
dbx A particular brand of audio processing equipment including noise reduction.
DC Direct current, as opposed to AC, alternating current.
DC offset The change in input voltage required to produce zero output voltage when no signal is applied to a device. Basically this is an unwanted phenomenon in audio; however, DC offset often occurs in lower quality sound cards.
D-connector Multi-conductor plug with D-shaped collar.
decade Ten times any quantity or frequency range. The range of the human ear is about 3 decades.
decay rate A measure of the decay of acoustic signals, expressed as a slope in dB/second. Essentially, the rate at which a signal drops off.
decibel, dB Logarithmic level specification.
decimation Suitable restructuring of data, for example swapping bandwidth (sampling frequency) for bit depth.
de-emphasis See emphasis.
de-esser Signal processing to reduce “S”es, typically in vocal recordings.
delay Time delay. (1) Electrical circuit that can delay a signal, in practice from fractions of a millisecond up to multiple seconds; used for sound effects. (2) Unwanted effect of timeconsuming digital conversion, processing, etc.; see also latency.
Delta-Sigma converter (Δ∑converter) Serial conversion at a high sampling frequency, where each bit specifies whether the current value of the signal is higher or lower than the prior one. After this process, this bit stream is converted to standard values, for example 16-bit format.
DI (1) Digital In, digital input. (2) Direct Injection, intermediate amplifier. (3) Directivity Index, directional index for acoustic transducers.
dialnorm An AC-3 metadata parameter, numerically equal to the absolute value of the dialog level carried in the AC-3 bit stream.
dialog level The loudness, in LKFS units, of the anchor element.
diffraction The distortion of a wave front caused by the presence of an obstacle in the sound field; the scattering of radiation at an object smaller than one wavelength and the subsequent interference of the scattered wave fronts.
diffuse sound The sound field contains no directional information and spreads randomly in the room.
diffuser A device that provides scattering when sound hits the surface.
digital Concerning a state wherein an electrical signal has been converted to a series of impulses according to a specific code. The signal has come to exist in “tabular form.”
digital interface Interface between digital systems. A number of standards exist, of which SP-DIF and AES/EBU are the most used.
DIN plug Contact connection as per the DIN norm.
DIO Digital In/Out, digital input and output.
Directivity factor The ratio of the mean-square pressure (or intensity) on the axis of a transducer at a certain distance to the mean-square pressure (or intensity) that a spherical source radiating the same power would produce at that point.
Directivity Index (DI) Directivity factor expressed in dB (10 $ log (directivity factor)).
dissolve Mixing (of images). Corresponds to crossfade in audio.
distance double law When doubling the distance from a point source, the sound pressure is halved (reduced by 6 dB).
distortion When a signal is changed from its original form, for example due to nonlinearities in the transmission chain.
distortion factor Percentage measure for harmonic distortion, for example, k3 = 3% means that the third harmonic overtone is 3% of the fundamental tone.
distribution amplifier Amplifier that can distribute a signal to multiple inputs without the signal source becoming overloaded.
dither Noise that is added to the lowest bit in the digital signal in order to reduce the distortion at low levels of the audio signal. Dither can be noise shaped, in order to be less audible.
DO Digital Out, digital output.
Dolby E An audio data-rate reduction technology designed for use in contribution and distribution that also conveys Dolby E metadata.
Doppler effect or Doppler shift The apparent upward shift in frequency of a sound as a noise source approaches the listener or the apparent downward shift when the noise source recedes; e.g., when a speedy car passes by.
DRC Dynamic range control.
DRC profile A collection of parameters that describe how dynamic range control metadata is calculated.
drop frame Variant of time code, where a frame is periodically skipped in order to preserve synchronization.
drop-out Short-duration loss of the signal on a tape due to faults in the tape’s magnetic coating.
DSB Digital satellite broadcasting.
DSP Digital signal processor. A circuit that can perform manipulation of data.
D-sub A plug type that can be used, among other things, for the transfer of digital signals. The flange around the connector pins are D-shaped, hence the name.
DTS Digital Theater System. Digital sound system originally for movies. The sound information is stored on a CD-ROM, which is controlled by a time code on the film. Uses APT-X bit reduction.
dubbing Mix of one signal with another.
ducking Automatic compression, for example when a speaker’s insert dims the music signal.
dynamic range The relationship between the strongest and weakest passages in the program material. Used for both the acoustic and the electrical signal.
EBU European Broadcasting Union. An association of European radio broadcasting stations.
echo Sound impulse arising from a reflection with such a strength and time delay after the direct sound that it is perceived as a repetition of it.
edge track Designation for the longitudinal (sound) tracks of a video tape, since these are located on the edge of the tape.
EFM Eight-to-fourteenmodulation. Digitalmodulation form, used for CDsamong other things.
EFP Electronic field production. The production form typically applied for drama and documentaries produced outside the studio.
EIAJ Electronic Industry Association of Japan. An interest organization in Japan that issues some norms.
emphasis A technique often used in analog transmission systems (wireless microphones, FM broadcast, etc.) to enhance dynamic range by raising the level of higher frequencies. Deemphasis is introduced on the receiving side.
ENG Electronic news gathering. News production in which electronic media is used, i.e. video tape, HD, or flash recorders (as opposed to film).
EQ See equalizer, graphic; equalizer, parametric; equalizing.
equal loudness contour A contour representing a constant loudness for all audible frequencies. The contour with a sound pressure level of 40 dB at 1000 Hz is arbitrarily defined as the 40-phon contour.
equalizer, graphic Electronic equipment for “equalizing.” Built from a number of 1/1 octave or 1/3 octave band-pass filters that can each amplify or attenuate, and used to obtain a desired frequency response.
equalizer, parametric. Electronic equipment for “equalizing”. Constructed from a set of filters where the center frequency, bandwidth and amplification/attenuation can be adjusted independently for each filter.
equalizing (1) The process that consists of modifying the frequency balance in the amplifier chain for the purpose of obtaining a flat frequency response, minimizing noise, or achieving an artistic effect. (2) Equalization of nonlinearity (in frequency response).
expander (1) Electronic equipment in which the output signal’s dynamic range is increased in relation to that of the input signal. (2) Designation for a controllable synthesizer without a keyboard.
far field A region in free space at a much greater distance from a sound source than the linear dimensions of the source itself where the sound pressure decreases according to the inverse-square law (the sound pressure level decreases 6 dB with each doubling of distance from the source).
FFT Fast Fourier Transform, an efficient method of estimating the frequency spectrum of a signal.
file-based scaling device A device used to apply an overall gain correction to audio content stored as files.
filter A device or algorithm for separating components of a signal on the basis of their frequency. It allows components in one or more frequency bands to pass relatively unattenuated, and it attenuates components in other frequency bands.
filter, band-pass A filter that passes all frequencies between a low-frequency cutoff point and a high-frequency cutoff point.
filter, high-boost A filter that amplifies frequencies above a specific frequency.
filter, high-cut A filter that attenuates frequencies above a specific cutoff frequency.
filter, high-pass A filter that passes all frequencies above a cutoff frequency but attenuates low-frequency components. They are used in instrumentation to eliminate low-frequency noise, and to separate alternating components from direct (DC) components in a signal.
filter, low-cut A filter that cuts off low frequency signals below the cutoff frequency with a certain attenuation (roll off). In microphones the filters are typically active below 80e300 Hz, and the slope is typically 6 or 12 dB/octave. See also filter, high-pass.
filter, low-pass A filter that passes signals below the cutoff frequency and attenuates the signal above that frequency. An antialiasing filter in a digital system is an example of a low-pass filter with a very steep roll off.
filter, notch Narrow-band filter with very strong attenuation in a very narrow frequency range. Used to remove individual frequencies, for example hum.
filter, octave Filter with a bandwidth of an octave.
filter, shelving A type of filter that gives constant amplification or attenuation from the corner frequency.
filter, third-octave A filter whose upper-to-lower pass band limits bear a ratio of 21/3, which corresponds to 23% of the center frequency.
flanging Sound effect based upon the direct signal mixed together with itself using varying time delays. Originally made using a tape recorder, where the source reel is slowed down by a finger placed on the flange of the reel.
FM Frequency modulation. Modulation principle in which a carrier wave is varied about its center frequency in proportion to the frequency of the modulating wave and where the oscillation of the carrier wave is proportional to the amplitude of the modulating wave.
fold back The musicians on the scene have a need to be able to hear themselves and the others in a quite specific manner. They are given a fold back or monitor loudspeaker, where the sound is specially mixed for the purpose.
frame In video, an image. The smallest unit of a time code.
framesync Short for “frame synchronizer.”
free field An environment in which there are no reflective surfaces within the frequency region of interest and the sound is isotropic and homogeneous.
frequency The number of cycles per second. Its reciprocal is the period. Specified in hertz (Hz).
frequency response Figure that shows the relationship between amplitude and frequency.
frequency weighting Modification of the frequency spectrum of a signal by means of a filter having a conventional characteristic known as A, B, C, D, RLB, K, CCIR/ITU, etc.
fundamental (1) The basic pitch of a musical note. (2) Fundamental frequency, the lowest frequency of a vibrating system. The spectrum of a periodic signal will consist of a fundamental component at the reciprocal of the period and possibly a series of harmonics of this frequency.
gain Amplification (in a circuit).
gate See noise gate.
gear Encompasses all equipment.
glitch When a bit is skipped, it can lead to a little “crack” in the sound.
GPI General Purpose Interface.
graphic equalizer See equalizer, graphic.
Haas effect Also called the precedence effect or principle of first arrival.
harmonic A discrete sinusoidal (pure-tone) component whose frequency is an integer multiple of the fundamental frequency of the wave. If a component has a frequency twice that of the fundamental, it is called the second harmonic, etc.
harmonic distortion Changing the harmonic content of a signal by passing it through a nonlinear device. Clipping results in harmonic distortion (uneven harmonics).
harmonic overtones Tones with the frequency of an integer multiple of the fundamental frequency.
headroom Overloading reserve. The amount of signal above nominal level that can be permitted before overloading arises with distortion as a consequence.
hertz, Hz Measurement unit for frequency.
HF High frequency.
high-boost filter See filter, high-boost.
high-cut filter See filter, high-cut.
high-pass filter See filter, high-pass.
house sync Sync signal that is distributed (in-house) so all digital devices can run at the same speed.
HVAC noise Heating, ventilation, and air conditioning noise. The word is used in connection with requirements concerning noise in control rooms, cinemas, etc.
Hz See hertz.
iCheck Integrity check. Reveals if the signal is spatially compromised, e.g., because of data reduction, such as MP3 or AAC encoded at too low a bit rate.
IEC International Electrotechnical Commission. A standardization commission.
IM Intermodulation.
impedance Electric resistance: a material’s opposition to the flow of electric current; measured in ohms.
impedance matching Maximum power is transferred from one circuit to another when the output impedance of the one is matched to the input impedance of the other. Impedance matching is generally only relevant for RF and electrically coupled digital interfaces.
impulse response The response of a system to a unit impulse. The Fourier transform of the impulse response is the frequency response.
induction The property that an electrical current is produced in a conductor when it is exposed to a varying magnetic field.
inductor Coil wound on an iron core.
infrasound Sound at frequencies below the audible range, that is, below about 16– 20 Hz.
initial time-delay gap (ITDG) The time gap between the arrival of the direct sound and the first sound reflected from the surfaces of the room.
in-phase Two periodic waves reaching peaks and going through zero at the same instant are said to be “in phase.”
insert (1) Insertion of a clip (scene) in an existing recording. (2) A breakpoint in a mixer channel where an external device can be inserted.
interpolation Computation of intermediate values in relation to fixed values (for example, values between two samples).
inverse square law A description of the acoustic wave behavior in which the mean-square pressure varies inversely with the square of the distance from the source. This behavior occurs in free-field situations, where the sound pressure level decreases 6 dB with each doubling of distance from the source.
ips Inches per second.
IR Infrared. IR light is used as a control signal in remote control units.
ISO International Organization for Standardization.
ITU International Telecommunication Union.
jackplug One-legged connector with two or three contacts. Normal dimensions are 6/3.5/2.5mm.
jack-bay A patch panel with jacks that are used to make connections between different devices easy to establish.
jam sync Method for recording new time codes from a source tapez
jitter Expresses that the sample timing deviates from a fixed rate. Jitter is measured in seconds (typically ns or ps). Jitter causes noise in the signal reproduced. The worst kind of jitter is sampling jitter as this cannot be corrected later. Transmission jitter can to some degree be compensated for.
kbps or kb/s Kilobits per second.
kHz, kiloherz One thousand hertz, see hertz.
latency Delay due to processing.
layback A post-production technique where audio is rejoined with the associated video after editing, mixing, or “sweetening.”
LCD Liquid crystal display.
LED Light-emitting diode.
Leq Equivalent continuous sound pressure level.
LF Low frequency, (1) Oscillations in the audible frequency spectrum (below 20 kHz). (2) Oscillations in the low frequency part of the audible frequency spectrum.
limiter A signal processing unit that attenuates the output when the input exceeds a given threshold. This provides a fixed maximum output level.
linear phase response The phase is constant with frequency through the device or circuit.
linear quantization Conversion to a digital signal where all bits represent identical steps in level. (As opposed to nonlinear quantization and bit compression).
line driver Intermediate amplifier for studio and stage use that brings a low voltage (for example, from a guitar pickup) up to line level. At the same time, provides a matching for long cables.
line level The voltage that the signals are amplified up to (for example, in the mixer), before they are routed to an output amplifier (or transmitter).
lip-sync The technique of miming to a prerecorded program in connection with a TV recording, etc.
LKFS Loudness, K-weighted, relative to full scale, measured with equipment that conforms to ITU recommendation 1770.
load If an electric circuit has a well-defined output terminal, the circuit connected to this terminal (or its input impedence) is the load.
locate To find a specific position, for example on a track, digital or analog.
long-form content Show or program related material or essence. The typical duration is greater than approximately two to three minutes.
longitudinal Lengthwise.
loudness A perceptual quantity; the magnitude of the physiological effect produced when a sound stimulates the ear.
loudness level (1) In acoustics; measured in phons it is numerically equal to the median sound pressure level (dB) of a free progressive 1000 Hz wave presented to listeners facing the source, which in a number of trials is judged by the listeners to be equally loud. Loudness level can be calculated according to ISO 532B. (2) In audio production; measured in loudness units (LU) according to ITU 1770.
low-cut filter See filter, low-cut.
low-pass filter See filter, low-pass.
LTC Longitudinal Time Code. The time code that is recorded on a tape’s longitudinal track.
LU Loudness Unit. A weighted measure used in program metering. Defined in ITU-1770.
MADI Multichannel Audio Digital Interface; a.k.a. AES10. Interface standard where up to 64 audio channels can be transferred serially on a cable, coax, or optical. NRZI encoding, 125 Mbps.
magnitude The size of a signal.
matrix A circuit in which the output signal is an encoded version of the input signal. A MSmatrix will transform MS to LR or vice versa.
Mbps or Mb/s Megabits per second.
measured loudness The magnitude of an audio signal when measured with equipment that implements the algorithm specified by ITU-R BS.1770/EBU R-128. It is an approximation of perceived loudness.
meter Designation for a measurement instrument for the control of signal levels.
MIDI Music Instrument Digital Interface.
mixing level Indication of the absolute sound pressure level calibration of the mixing studio that produced the content.
mode (1) A room resonance. Axial modes in rectangular rooms are associated with pairs of parallel walls. Tangential modes involve four room surfaces and oblique modes all six surfaces. Their effect is greatest at low frequencies and for small rooms. (2) A specific setting for a device (like record mode, sleep mode, etc.)
modulation An analog process by which the characteristic properties of a wave (the modulating wave) are mixed into another wave (the carrier wave).
modulation noise Noise in the signal chain that varies with the signal strength. Particularly a problem with audio tape recorders.
MOL Maximum output level. For tapes, the highest attainable output. monitor A control or monitoring device; in this context, a loudspeaker for the assessment of recording quality.
mono Signal in a single channel.
mono compatible A stereo signal, if no significant loss of level and no coloration (comb filtering) occur when summing the channels to one mono signal.
MPEG Motion Picture Experts Group. Standardization organization that sets standards for techniques such as digital audio compression.
MPX Multiplex filter, for removing an FM radio’s stereo pilot tone.
MSB Most significant bit.
MS-technique A stereo recording technique using M (mid) and S (side) signals generally from one cardioid and one figure-8 microphone. To obtain L/R format the signals are processed like this: L = M þ S, R = M – S.
MTC MIDI time code.
MUSICAM Masking pattern adapted Universal Subband Integrated Coding And Multiplexing. An (older) bit reduction system.
mV Millivolt, 1/1000 V.
MVPD Multichannel Video Programming Distributor. Includes DBS service operators, local cable system operators, and cable multiple system operators.
N See newton.
NAB or NARTB National Association of Radio and Television Broadcasters. American standardization organization.
NBC Non-backward compatible. Compression standards that are not backwards compatible, i.e., it is not possible to “unpack” stereo to 5.1 channels having first gone from 5.1 to twochannel stereo.
newton Measurement unit for force.
noise (1) Unwanted sound. (2) Technically, sound without tonal components.
noise floor A measure of the signal created from the sum of all noise sources and unwanted signals within an audio system.
noise gate Special signal processing unit whose output signal is 0 until the input signal exceeds a specific, preset value.
noise shaping A special technique providing frequency weighting of dither used in connection with reducing high-resolution digital audio to a lower bit format.
notch filter See filter, notch.
NR Noise reduction.
NRZ Non-return to zero.
nWb Nanoweber = 10−9 weber. See weber.
octave A range of frequencies whose upper frequency limit is twice that of its lower frequency limit. For example, the 1000 hertz octave band contains noise energy at all frequencies from 707 to 1414 hertz. In acoustic measurements, sound pressure level is often measured in octave bands, and the center frequencies of these bands are defined by ISO and ANSI. The sound pressure level of sound that has been passed through an octave band pass filter is termed the octave band sound pressure level. Fractional portions of an octave band are also often used, such as a 1/3 octave band.
octave filter See filter, octave,
ohm [Ω] Unit for electrical resistance.
one-bit converter See Delta-Sigma converter.
operator A broadcast network, broadcast station, DBS service, local cable system, or cable multiple system operator (MSO).
oscillator Signal generator for the generation of, for example, pure sinusoidal tones with constant amplitude for use in measurements.
output impedance The alternating current resistance a circuit’s output represents. May also be called source impedance.
oversampling The use of a sampling frequency that is a number of times higher than is necessary. This makes it easier to make low-pass filters that ensure that no alias frequencies arise in the sound.
overdub A process whereby a track is recorded while listening to already recorded material on the same or a different tape recorder.
override See ducking.
overtone A harmonic frequency component of a complex tone at a frequency higher than the fundamental. This can involve both harmonic as well as nonharmonic overtones.
PAC Perceptual Audio Coding. Bit reduction system from Lucent: 96 kbps.
pad Circuit in the input module (for example, in a mixer) with the purpose of preattenuating the signal.
PAL Phase Alternation Line. European TV system.
pan-pot Potentiometer in the mixer for “moving” the signal between the left and right channel.
parallel port Digital input or output port with multiple lines, allowing multiple bits of data to be transferred simultaneously.
partial One of a group of frequencies, not necessarily harmonically related to the fundamental, which appear in a complex tone. Bells, xylophone blocks, and many other percussion instruments produce harmonically unrelated partials.
patch Connection of circuits via external connections.
PCM Pulse-code modulation. A form of modulation in which the information is described by the number and duration of impulses.
peak The maximum positive or negative dynamic excursion from zero of any time waveform. Sometimes referred to as “true peak” or “waveform peak.”
peak-hold Circuit that for a shorter or longer period of time is in a position to maintain a peak value display on an instrument.
perceptual coding A principle for low bit rate coding based on the masking abilities of the ears.
periodic signal A signal is periodic if it repeats the same pattern over time. The spectrum of a periodic signal always contains a series of harmonics.
phantom supply Method for DC power supply of electrostatic microphones via the signal cable (normally 48 volt).
phase The different values that alternating current or alternating voltage runs through during a period.
phon Logarithmic unit for loudness.
plug/jack Plug and jack for one conductor and shielding.
pink noise Electrical noise signal for test purposes; contains constant energy per octave.
PIPU Punch In Punch Out.
pitch Subjectively perceived tone frequency.
PLL Phase-locked loop. A circuit that ensures a stable frequency in relation to a reference.
polarity Referring to the positive or negative direction of a signal. In all kinds of stereo and surround sound production it is important that microphones have the same polarity or else the imaging is totally blown.
post production The entire post-processing phase (including editing, sound effects, music, etc.) for video and TV productions.
pot See potentiometer.
potentiometer Adjustable resistance used, for example, in controlling levels.
PPM Peak program meter. A meter with a time constant of 5 or 10 ms.
precedence effect See Haas effect.
pre-emphasis See emphasis.
presence The frequency range around 2e5 kHz. Highlighting of this range causes voices and instruments to stand out in the acoustic image.
pressure zone As sound waves strike a solid surface, the particle velocity is zero at the surface and the pressure is high, thus creating a high-pressure layer near the surface.
psychoacoustics The study of the interaction of the human auditory system and acoustics.
punch-in A rerecording of a short sequence in an already recorded program.
punch-out See punch-in.
Q factor Measure for the slope of a resonance top.
quantization Digitalization of a signal. Conversion of the analog signal to numbers that express the values measured at the time of the samplings.
rack Cabinet or frame in which devices are installed.
RAID Redundant array of inexpensive disks. Method for simultaneous operation of multiple hard disk drives so that they work as a fault-tolerant unit.
RAM Random-access memory. Digital storage where data can be arbitrarily stored and retrieved.
RASTI Rapid Speech Transmission Index. See STI.
R-DAT Rotary-Head Digital Audio Tape recorder.
refraction The bending of a sound wave from its original path, either because it is passing from one medium to another with different velocities or caused by changes in the physical properties of the medium, for example, a temperature or wind gradient in the air.
resolution The number of bits per sample of a digitized signal.
RF Radio frequency. Name for frequencies in the range of 30 kHz to 3000 GHz. This is the range for electromagnetic waves applied to radio communication.
RMS Root mean square, the effective value of a signal.
roll off The attenuation of a high-pass or low-pass filter is called roll off. The term is mostly used for high-frequency attenuation.
room mode The normal modes of vibration of an enclosed space. See mode.
routing switch A switch for the routing of signals.
RT60 Reverberation time based on the 60 dB attenuation of the sound after the sound source has stopped.
RTP Real-time Transport Protocol. Protocol for the transfer of data for immediate use.
S/N See signal-to-noise ratio.
S/PDIF Sony/Philips Digital Interface.
sample rate converter (synchronous) Converts digital signals with the same reference from one sampling frequency to another.
sampling In digital technology, entry of the signal into discrete values in a table. A single value is called a sample.
sampling frequency The number of samples that are extracted per second. In professional sound equipment: 48 kHz. For CDs and the like: 44.1 kHz.
SCART plug A special 21-pin plug/jack on some video tape recorders and TV units.
SCSI Small Computer System Interface. Ultimately a purely computer-related standard, for the controlling of hard disk drives and such like. It can, however, also carry sound information.
SDDS Sony Dynamic Digital System. Digital sound system for movies with a total of 8 sound channels: L, CL, C, CR, R, SL, SR and subwoofer. SDDS is bit-reduced with the ATRAC system.
SECAM Systeme En Couleur Avec Memoire. Television system.
sensitivity Expresses the size of a signal that a device requires in order to reach nominal level.
separationDegree of signal-related separation between tracks, channels, etc.
sequencerA device on which information about sequences can be recorded, but not the sequence itself.
SFXSpecial effects.
shelving filterSee filter, shelving.
short-formcontentAdvertising, commercial, promotional, or public service relatedmaterial or essence. Also termed “interstitial” content. The typical duration is less than approximately two to three minutes.
shuttle modeAs related to tape transport or DAW track handling, the running of the recording back and forth between two points.
signal-to-noise ratioRatio of the nominal signal level to the undesired noise level. Expressed in dB.
sinusoidal toneThe most simple harmonic tone, consisting of only one frequency.
slap backA discrete reflection from a nearby surface.
slatingMarking on a recording before a take.
SMPTESociety of Motion Picture and Television Engineers. International association.
snakeFor PA systems, the bus cable between scene microphones and the mixer in the concert hall.
SNGSatellite news gathering. Direct news transmission to main stations via satellites.
SOLSaturation output ;evel. The magnetization level at which a magnetic tape is saturated.
sound field microphoneA single unit microphone with four cardioid condenser microphone capsules shaped like a tetrahedron. This configuration is also called the A-format. By processing the signals the B-format is formed equivalent to three figure-8 microphones and one omnidirectional microphone, all in a coincident position. A countless number of directional characteristics are obtained by combining the signals in different ways.
sound pressure level (SPL)The sound pressure level of a sound in decibels, equal to 20 times the logarithm to base 10 of the ratio of the RMS sound pressure to the reference sound pressure 20 mPa.
sound pressureA dynamic variation in atmospheric air pressure. Sound pressure is measured in pascals (Pa).
SPSpecial performance. Relates to improved versions of existing video formats.
spherical waveA sound wave in which the surfaces of constant phase are concentric spheres. A small (point) source radiating into an open space produces a free sound field of spherical waves.
splitboxA unit that distributes the signal from a microphone to multiple mixers or tape recorders.
square wavesWaveform for acoustic or electrical signals that in terms of frequency contain a fundamental tone and all the odd-numbered harmonics.
stereoA technique intended to created a spatial sound impression by the use of two or more channels.
STISpeech Transmission Index. Special measurement method and measurement equipment for the objective determination of speech intelligibility in a room. In a good room, the STI value ought to be greater than 0.6 (on a scale of 0 e 1). Practical (reduced) versions that can be implemented in handheld measurement devices are RaSTI (Rapid Speech Transmission Index) and STIPA (Speech Transmission Index, PA systems).
STIPASee STI.
streaming audioSound that can be played back immediately in (almost) real time from the Internet.
subharmonicSubharmonics are synchronous components in a spectrum that are multiples of 1/2, 1/3, or 1/4 of the frequency of the primary fundamental.
supersonicSee ultrasound.
surround soundDesignation for certain multichannel systems for film and TV stereo sound.
sweet spotThe optimum listening position in front of the stereo- or surround speakers.
symmetry attenuationThe attenuation of induced electrical noise signals that is attained in a balanced connection.
synchronizerA unit that by the use of a time code can deliver control signals for the timerelated locking of, for example, tape units.
tape speedThe speed at which a magnetic tape passes the magnetic heads in a sound or video tape recorder. Specified in cm/s or inch/sec.
tape widthThe width of a magnetic tape.
tapingOutlet from mixer channel, for example aux-send. The expression is used by radio broadcasters.
target loudnessA specified value for the anchor element (in some systems dialog level), established to facilitate content exchange from a supplier to an operator.
TBTalk back. A system via which the control room can give oral messages to the studio.
TCSee time code.
TDIFTascam Digital Interface. Factory-initiated interface, 8-channel parallel, unbalanced in a D-sub connector, cable max. 15 m [45 ft].
telephone hybridUnit that adapts a telephone to a mixer console.
THDTotal harmonic distortion.
THD+NTotal harmonic distortion plus noise. An electro-acoustic measure of (unwanted) signals from distortion (occurring, for instance, by the clipping of the signal) and the noise in the given audio channel. Specified in dB below the main signal or in a percentage.
third-octave bandA frequency band whose cutoff frequencies have a ratio of 21/3, which is approximately 1.26. The cutoff frequencies of 891 Hz and 1112 Hz define the 1000 Hz third-octave band in common use.
third-octave filterSee filter, third-octave.
tie-lineConnection line for signals (for example, between editing rooms).
TIMTransient intermodulation distortion; occurs when the feedback circuitry is not acting fast enough when the amplifier is exposed to fast transient signals.
timbreThe quality of a sound related to its harmonic structure.
time codeDigital code that marks time with information on frames, seconds, minutes, hours, etc. Examples: SMPTE, EBU, MTC.
time constantsIn transmission and recording, corner frequencies of de-emphasis are often defined by time constants, for example 3180 ms. The frequency is 50 Hz, since the time constant s ¼ 1/2pf.
tinnitusRinging in the ear or noise sensed in the head typically caused by excessive exposure to high sound levels.
toleranceThe maximum permissible deviation from the specified quantity.
TPAbbreviation for true peak (unweighted). The term is used in digital audio metering and is then related to full scale. See true peak.
transfer functionThe output to input relationship of a structure.
transformerAn electronic device consisting of two or more coils used to couple one circuit to another.
transientA relatively high amplitude, suddenly decaying, peak signal level.
true peakThe maximum absolute level of the signal waveform in the continuous time domain, measured per ITU-R BS.1770. Its units are dB TP meaning decibels relative to nominal 100%, true peak.
truncationCutting off of superfluous bits without weighing their value.
twisted-pairA way to ensure balancing in cables.
ultrasoundSound at frequencies above the audible range, that is, above about 20 kHz.
unbalancedA connection where the chassis/ground is a part of the circuit between electroacoustic devices. Also referred to as single ended.
varispeedVariable speed, generally in playback systems.
VCAVoltage-controlled amplifier.
VCRVideo cassette recorder.
voiceoverSee ducking.
volt, VUnit for electrical voltage.
VppMeasure of the magnitude of an electrical voltage from peak to peak.
VTRVideo tape recorder.
VUVolume Unit, a level meter (standard volume indicator) for audio recording; time constant: 300 ms.
watt, WThe unit of electrical acoustic power.
wavFile format for sound.
waveformThe waveform is the shape of a time domain signal as seen on a DAWscreen or an oscilloscope screen. It is a visual representation or graph of the instantaneous value of the signal plotted against time.
weber, WbMeasurement unit for magnetic flux.
weightingA measurement is weighted when the signal has passed through a filter (for example, an A filter).
white noiseA signal that contains all frequencies, with constant energy per Hz.
wooferBass loudspeaker.
working levelThat signal level at which a circuit is nominally modulated. Also called the “0-level.”
WRMSWeighted RMS value. The abbreviation is also used for the RMS value of the power.
XLRProfessional cable connector for audio. Pin 1: shield, pin 2: +, pin 3: —.
Zwicker LoudnessA technique developed by Dr. E. Zwicker for calculating a real-time estimate for the loudness of sound as perceived by the human ear. This methodology is primarily used in connection with calculation and perception of noise exposure.