Basic Terms in Sound Engineering

Basic Terms in Sound Engineering

3-to-1 Rule: – When using multiple microphones, the distance between microphones should be at least 3 times the distance from each microphone to its intended sound source

‘A’ signal: – In stereo, it is the signal to be fed to the left-hand loudspeaker of a two speaker system.

Absorption: – This is the dissipation of sound energy by losses due to sound absorbent materials.

Acoustics: – The study of sound behavior within a giving space. The acoustics of an enclosed space depend on its size and shape, and the number and position of absorbers and reflectors.

Active Circuitry: – Electrical circuitry which requires power to operate, such as transistors and vacuum tubes.

     A/D: – Analogue-to-digital signal conversion.

                 Ambience: – Room acoustics or natural reverberation.

Ambient Noise: – In any location, from quiet studio, quiet live sound venues or living room to busy street, there is a background  of sound.

Amplifier: – A device for increasing the strength of a signal by means of a varying control voltage.

                 Amplitude: -The strength or level of sound pressure or voltage.

Analogue: – Any system in which a continuous electrical waveform mimics that of the original sound. Microphones and loudspeakers are examples of analogue transducers.

Audio Chain: – The series of interconnected audio equipment used for recording or PA.

Atmosphere: – The background sound at any location. This can enhance authenticity and give listeners a sense of participation in an event.

     Attenuation: – Fixed or variable losses (usually in an electrical signal).

Axis (either of microphone or loudspeaker):- Line through center of diaphragm which is at a right angle to it.

‘B’ signal: – In stereo, the signal to be fed to the right-hand loudspeaker of a two speaker system.

Back Plate: -The solid conductive disk that forms the fixed half of a condenser element.

Baffle: – (a) A  rigid  screen  around a  loudspeaker diaphragm, extending the acoustic path from front to rear in order to reduce the flow of air around the edge of the speaker at low frequencies, an effect that causes serious loss of bass. (b) A small acoustic screen that causes a local variation in the acoustic field close to the microphone diaphragm.

Balance: – (a) A circuit that carries information by means of two equal but opposite polarity signals, on two conductors. (b) The relative placing of microphones and sound sources in a given acoustic, designed to pick up an adequate signal, discriminately against noise, and provide a satisfactory ratio of direct to indirect sound. (c) The distribution of a sound between A and B stereo channels

Balance test: – One or several trial balances, judged by direct comparison.

Bass: – Lower end of the musical scale. In acoustics it is generally taken as the range (below 200 Hz, say) in which difficulties (principally in the production or reproduction of sound) are caused by the large wavelengths involved if not regulated.

Bass Management: – A system uses crossover networks at about 120 Hz or below that splits off low frequency sound in stereo or surround channels and routes it to a subwoofer with a separate amplifier.

Bass Tip-Up (UK) or Proximity Effect (US): – Increase in bass response of directional microphones when they are situated in a sound field that shows an appreciable loss of intensity in the distance travelled from front to back of microphone.

Beats: – It can be seen as two tones that differ only slightly in frequency and have approximately the same amplitude

 

Bidirectional Microphone: – A microphone that picks up equally from two opposite directions.  The angle of best rejection is 90 deg. from the front (or rear) of the microphone, that is, directly at the sides. The polar response is a figure-of-eight.

Boom: – A telescopic arm (often attached to a floor mounting) from which a microphone is slung.

Boomy: – Subjective description of a sound quality with resonances in the low frequencies, or a broad band of bass lift. Expressions with similar shades of meaning are ‘tubby’ or, simply, ‘bassy’.

Boundary/Surface Microphone: – A microphone designed to be mounted on an acoustically reflective surface.

Bright surface: – A surface that reflects sound strongly, particularly at high frequencies.

Bus: – A line to which a number of separate channels are fed and combined: this may go on to an amplifier, recorder, effects processor, group or master fader, remote location, broadcast or other output.

Cancellation: – Partial or complete opposition in phase, so that the sum of two signals approaches or reaches zero.

Capacitance: – The ability of an electrical component, or components, to store static charge.

Capsule: – (a) Removable pick-up head. (b)  The diaphragm assembly of a condenser microphone.

Cardioid Microphone: – A unidirectional microphone with moderately wide front pickup 131 degree. Angle of best rejection is 180 deg. from the front of the microphone, that is, directly at the rear. Its polar diagram is like a heart-shaped.

Cartridge (Transducer): -The element in a microphone that converts acoustical energy (sound) into electrical energy (the signal).

Compact Disc (CD): – A digital medium, recorded (‘burned’) and read optically by laser, that has largely replaced vinyl discs as a medium for recorded music.

CD-R, CD-RW: – These are CDs that are recordable (once) or rewritable (several times). Term also used for the PC, domestic or higher quality equipment to record/rewrite CDs.

Channel: – (a) Complete set of (professional) recording equipment. (b) Recording room (or part of recording room that can operate independently to record a program). (c) The series of controls within an individual signal path- way in a control console: like Microphone channel.

Chorusing: – It is a process of combining an original track with a slightly de-tuned and delayed copy, in order to add strength and harmonic complexity.

Clean feed (US: mixed-minus): – A cue feeding back to a programed source that includes all but the contribution from that source.

Clean sound: – Actuality sound of an event, without super- imposed commentary.

     Close Pickup: -Microphone placement within 2 feet of a sound source.

     Clip: – To overload and cause distortion.

Codec: – A compression system that removes information that is physically present in the original sound but may be masked or otherwise redundant when it reaches the ears.

Comb Filtering: – An interference effect in which the frequency response exhibits regular deep notches.

Combination Tones: – It results when two loud tones differ by more than 50Hz.

Condenser Microphone (electrostatic or capacitor microphone):- A microphone that generates an electrical signal when sound waves vary the spacing between two charged surfaces: the diaphragm and the back plate.

Cone: – In a loudspeaker, a piston of stiff felted paper or possibly of plastics. It should be light and rigid. Paper cones are often corrugated to reduce any tendency to ‘break up’ radially and produce sub harmonic oscillations.

Console: – A desk (or ‘panel’) that includes a mixer and associated controls.

Contact microphone: – Transducer attached to a solid surface.

Control room: – A switching center; other- wise, the sound mixing room.

Copyright: – The law in relation to the ownership of creative works, which is initially vested in the author, composer or artist.

Critical Distance: – In acoustics, the distance from a sound source in a room at which the direct sound level is equal to the reverberant sound level.

Crossover: – This is a device or component that the frequency at which a signal is split in order to feed separate parts of a loudspeaker.

Current: – Charge flowing in an electrical circuit. It is analogous to the amount of a fluid flowing in a pipe.

dB:-  Decibel

Dead acoustic: – An audio environment in which a substantial loss is introduced at every reflection.

Decibel (dB): – A number used to express relative output sensitivity. It is a logarithmic ratio. In brief it is a measure of relative intensity, power or voltage.

Delay line: – Device that electronically delays a signal.

Dl: – This has two approaches (a) Direct injection (box) used in popular music balance: converting from unbalance to balance and giving you access to control level of noise input. (b) Directivity index: in microphone design, this is a measure of forward response.

Diaphragm: – The part of a microphone upon which the pressure of a sound wave acts. In size it should be small enough not to suffer substantial high-frequency phase cancellation for sound striking the diaphragm at an angle, and big enough to present a sufficiently large catchment area to the pressure of the wave. It is in summary the thin membrane in a microphone which moves in response to sound waves.

Diffraction of sound: – A sound wave re-forms after it has passed an object that is small compared to its wavelength, almost as though the object were invisible to it.

Diffusion of sound: – The degrees to which sound waves are broken up by uneven surfaces, and by absorbers that are scattered in all parts of a studio or hall rather than clustered together. A high degree of diffusion is desirable in a sound studio.

Digital Audio workstation (DAW): – A system that uses a hard disk for recording, mixing, editing or creating digital masters.

Digital signal processing (DSP): – This is performed by digital devices that offer a wide (and apparently ever-increasing) range of effects.

Directivity pattern: – Polar diagram.

Diffraction: – The bending of sound waves around an object which is physically smaller than the wavelength of the sound.

Direct Sound: – Sound which travels by a straight path from a sound source to a microphone or listener.

Distance Factor: – The equivalent operating distance of a directional microphone compared to an omnidirectional microphone to achieve the same ratio of direct to reverberant sound.

Distant Pickup: – Microphone placement farther than 2 feet from the sound source.

Distortion: – Unwanted changes of sound quality, in the frequency response, or by the generation of unwanted products.

Dissonance: – The sensation produced by two tones that are about a semitone or full tone apart.

Dropout: – Loss of signal often due to a localized fault in tape coating or other media.

Dry acoustic: – Lacking in reverberation. By way of mixed metaphor, the opposite is ‘warm’ or ‘bright’.

Dubbing (UK): – This is when copying sound which is arranged as a material to be available in convenient form e.g. transferring music from disc to tape.

DVD-Audio: – This offers a variety of (uncompressed) options, some with far higher fidelity than standard CD.

Dynamics: – The way in which volume of sound varies internally within a musical work (or in a speech or speech-and-music presentation). It may refer to the variation of levels within the work as a whole, or from note to note, or in the envelope of a single note.

Dynamic Microphone: – A microphone that responds directly to the air pressure on its diaphragm on one side only. Most moving coil microphones work in this way, but other principles can also be adapted to do so.

Dynamic Range: – The range of amplitude (range of volumes in an audio signal) of a sound source or the range of sound level that a microphone can successfully pick up. It may be measured as the range of peak values the range of average volume.  It may refer either to the range of the original sound, or to what remains after compression.

Earphone/Earpiece: – A speaker for ear fitting or for the hearing aid type.

Echo: – Discrete repetition of a sound, produced  by a single reflected sound wave, or a combination  of such waves that is delayed long enough (more than about 50 msec.) in which the return is coincident in time and at least 20ms after the original sound. Delay of, typically, 35ms or more may be used to create the effect of an echo.

Effects: – Simulated incidental sounds occurring (a) in the location portrayed (usually recorded effects) or (b) as a result of action (usually Foley or spot effects those created on the spot).

Electret: – A material (such as Teflon) that can retain a permanent electric charge.

Electronic Music: – A work constructed from electronic source materials by arranging them in a formal pattern (which may be beyond the range of conventional instruments or musicians).

Electrostatic loudspeaker: – An application of electro static principles to the movement of air in bulk.

Electrostatic  Microphone: –  Like Condenser microphone.

Enclosure: – Commonly, a loudspeaker cabinet. Its most important function is to improve bass response.

Envelope: – The manner in which the intensity of a sound varies with time. The term may also refer to the envelope of frequency content, or of an imposed frequency characteristic, as in a format.

Equalization (EQ): – The use of a filter network to compensate for frequencies. This to create tone control to shape frequency response in some desired way.

Establish: – Establishing a sound effect, etc., is allowing it sufficient time (and volume, which may be greater than that subsequently used) for it to register in the listener’s mind.

Exponential: – An exponential curve is one that follows the progress of a particular form of natural, unrestrained growth or decay.

Extinction frequency: – Frequency at which there is complete loss of signal when the dimension of a component matches signal wavelength.

Fade: – Gradual reduction or increase in the signal. This is accomplished by means of a fader (i.e. a potentiometer – or ‘pot’ for short.  Faders used in audio work are logarithmic over their main working range.

Feedback: – This is the addition of some fraction of the output to the original input signal. In a P.A. system consisting of a microphone, amplifier, and loudspeaker, feedback is the ringing or howling sound caused by amplified sound from the loud speaker entering the microphone and being re-amplified.

Flanging: – It is the Effect produced by playing two recordings almost in sync but with one running slightly slower than the other, so that phase cancellation sweeps through the audio-frequency range. Originally, it is produced manually by a digital signal processor.

     Flat: – No extras.

Flat Response: – A frequency response that is uniform and equal at all frequencies.

Flutter: – It is the Rapid fluctuation in pitch, having a warble frequency of say, 8 Hz or more due to a fault in equipment.

Fold Back: – A feed of selected sources to a studio or monitor loudspeaker or headphones to be heard by performers.

Foley Artist: – US film industry term for a post-production specialist in matching footsteps and other sound effects.

Formant: – A characteristic resonance region: a musical instrument may have one or more such regions, fixed by the geometry of the instrument.

Frequency: – The rate of repetition of a cyclic phenomenon such as a sound wave. This can be seen also as the number of complete excursions an air particle makes in one second  (formerly described as cycles per second, c/s or cps, now as hertz, Hz).

Frequency Correction: – The change required in the frequency characteristics of a signal to restore it to its original form. The term is also used ambiguously to indicate the application of desired deliberate distortion of the response (often by increasing some range of the upper middle frequencies).

Frequency Response Tailoring Switch: – A switch on a microphone that affects the tone quality reproduced by the microphone by means of an equalization circuit (Similar to a bass or treble control on a hi-fi receiver.)

Frequency Response:  – in brief it the variation in gain or loss with frequency. This can be seen as a graph showing how a microphone responds to various sound frequencies.  It is a plot of electrical output (in decibels) vs. frequency (in Hertz).

Fundamental– The note associated with the simplest form of vibration of an instrument, usually the first and lowest member of a harmonic series. It is also the lowest frequency component of a complex waveform such as musical note. It establishes the basic pitch of the note.

Gain: – Amplification of sound level or voltage. It is also ratio of output voltage to input voltage. It is most conveniently calculated in decibels.

Gain-Before-Feedback: – The amount of gain that can be achieved in a sound system before feedback or ringing occurs.

Gate: – A switching circuit that passes or cuts off a signal in response to some external control, e.g. to whether or not an applied voltage is above or below a given threshold.

Graphic Filter: – Filter in which the signal is divided into narrow bands, perhaps of a third of an octave, each con- trolled by a slide fader

Groove: – The pulse of the song and how the instruments dynamically breathe with it. It can be seen also as a Track on a record that carries a mono audio signal in the form of a lateral displacement, and stereo in a combination of two 45degree displacements.

Ground: – A switch on some audio devices (mostly guitar amps and direct boxes) used to decrease hum.

     Ground Loop (US): – More of Earth loop.

Group fader (US: sub master fader): – A fader though which the combined output of several individual faders is fed.

Haas effect: – When a sound is heard from two loudspeakers in different directions and there is a time delay on one path, all the sound seems to come from the other loudspeaker unless the delayed sound is increased in volume to compensate

Harmonic: – A series of frequencies that are all multiples of a particular fundamental frequency. They are produced by the resonances of air in a tube (e.g. woodwind, brass, and organ) or of a vibrating string, etc. It is also seen as Frequency components above the fundamental of a complex waveform. They are generally multiples of the fundamental which establish the timbre or tone of the note.

Headphones: – A pair of electro-acoustic transducers (e.g. moving coil) held to the ears by a headband. Alternatively, devices similar to hearing aids may be used in one ear (e.g. for listening to talkback instructions

Headroom: – The safety margin (in decibels) allowed, primarily when recording an audio signal.

Hearing: – Essentially, the ear acts like an instrument for measuring frequencies and volumes of sound logarithmically (so they appear linear in octave scales and decibels). The subjective aspect of frequency is pitch: judgment of pitch is not entirely independent of volume.

     Hertz (Hz): – The measure of frequency

High-Pass Filter: – An electronic device that allows the high frequencies to pass through while is attenuating the low frequencies. Used to eliminate low frequency artifacts like hum and rumble.

Hiss: – High-frequency noise.

     Hum: – Low-frequency noise.

Hyper cardioid: – A unidirectional microphone with tighter front pickup 105 degree than a super cardioid, but with more rear pickup. Angle of best rejection is about 110 deg. from the front of the microphone.

     I/O: – The input/output of a device.

Impedance: – In an electrical circuit, opposition to the flow of alternating current, measured in ohms. It can be further explain simple as a combination of d.c. resistance with inductance and capacitance that responds to an alternating current as a resistance does to a direct current. An inductive impedance increases with increasing frequency; a capacitative impedance decreases with frequency. Either type introduces change of phase.

Indirect Sound (in microphone balance): – Sound that is reflected one or more times before reaching the micro- phone.

Inductance: – The resistance of (in particular) a coil of wire to rapidly fluctuating alternating current. The field built up by the current resists any change in the rate of flow of the current. This form of resistance increases with frequency.

Insert point: – A point in a signal path where there are two jacks, wired so that when an external device is plugged in, the signal is diverted through it – or where a pair of switches performs the same function.

Intensity of sound: – It is the sound energy crossing a square meter.  Relative sound intensities, energies or pressures may all conveniently be measured in decibels.

Interference: – Destructive combining of sound waves or electrical signals due to phase differences.

Inverse Square Law: – States that direct sound levels increase (or decrease) by an amount proportional to the square of the change in distance.

ISDN: – Integrated Digital Switched Network

     Isolation: – Freedom from leakage; ability to reject unwanted sounds.

Joint: – A place on a connection where two physically separate butt ends have been joined together more of a terminal.

Lavalier: – Personal microphone originally worn suspended around the neck or a piece of cloth like pendant jewelry.

     Leakage: -Pickup of an instrument by a microphone

Level: – Volume of electrical signal as picked up by micro- phone(s) or signal inputs and passed through preamplifiers and mixer faders.

LFE: – Low-frequency effects, generally below 120 Hz, on the sixth track in 5.1 surround sound: this goes directly to a subwoofer, where bass fed from the loudspeaker system’s bass management system

Limiter: – An automatic control that stops volume exceeding a predetermined level, for some artistic purpose or to prevent over modulation.

Line: – This is a send and return path for an electric signal. In its simplest form a line consists of a pair of wires.

     Live angle: – Angle within which reasonable sensitivity is obtained

Live side (of microphone): – The face of the microphone that must be presented to a sound source for greatest sensitivity.

M signal: – The combined A + B stereo signal. It corresponds to the signal from a single ‘main’ microphone.

Main Gain Control (US: grand master or overall master control): – Final fader to which the combined outputs of all group (US: sub master) or individual faders are fed.

Matching: – It is an arrangement that the impedance presented by a load is equal to the internal impedance of the generator, unless this is done there will be some loss of power, and the greater the mismatch the greater the loss.

Masking: – this is the phenomenon by which loud signal prevents the ear from hearing softer sounds.

MDM: – The modular digital multitrack recording system is a way-station on the relentless advance of digital memory and processing power

Meter: – Device for measuring voltage, current, etc. In audio, several types of meter are used for measuring program volume.

     Microphone: – An electro-acoustic transducer.

Microphone channel: – The preamplifier, equalization circuit, fader, etc. in a mixer that is collectively available for each microphone. The channel may also include facilities for ‘pre-hear’, and feeds for echo, fold back and public address.

MIDI: – A ‘musical instrument digital interface’ is data communications hardware that is used to link electronic musical instruments by means of a digital signal with each other and with computers.

MIDI cable: – A shielded, twisted pair of wires, up to a maximum of 15 m (50 ft) in length.

     Mil: – A thousandth of an inch, about 25 microns.

Mix: – Combine the signals from different sources through a path, signal processors, replay devices and other sources then all combine together.

     Mix-minus, mixed-minus (US): – Clean feed.

Modulation: – Superimposition (of sound wave) on a carrier, which may be a high-frequency   signal (e.g. by amplitude modulation, AM, or frequency modulation, FM, q.v.) or (on a record) a smooth spiral groove

Monitoring: –  (a)  Checking sound quality, operational techniques, program content, etc., by listening to the material as it leaves the studio (or at subsequent points in the chain, or by a separate feed, or by checking from a radio receiver (b) Listening to other broadcasts for information.

Mono (monophonic sound): – Sound heard via a single channel. This is defined by the form of the recording or transmission, not by the number of loudspeakers.

Moving-coil (microphone, loudspeaker or pick-up): – These all use a small coil that can move within the field of a permanent magnet. In the microphone or pick-up the movement generates a current in the coil; in the loudspeaker the current cause’s movement that is transmitted to a cone (q.v.) that drives the air.

Mute (UK) (US: MOS): – An on/off switch for sound. To mute something means to turn it off.

NAG: -Needed Acoustic Gain is the amount of gain that a sound system must provide for a distant listener to hear as if he or she was close to the unamplified sound source.

Near field: – The listening area where there is more direct than reflected sound.

     Newton’s per Square Meter (N/m2): – A unit of sound pressure.

Noise: -This is generally defined as unwanted sound or acoustic interference.

     Noise Canceling: -A microphone that rejects ambient or distant sound.

Noise reduction systems: – Digitally encoded audio signals are intrinsically less susceptible to noise and distortion.

Noise Rejection: – The difference (in dB at a given angle off-axis) between on-axis wanted sound and off-axis unwanted noise.

NOM: – Number of open microphones in a sound system. This decreases gain-before-feedback by 3dB every time NOM doubles.

Normalization: – A process, used in CD mastering, in which the highest instantaneous level is determined and contained, so that the transfer never exceeds the maximum coding level but the need for headroom is eliminated.

Obstacle Effect: – Obstacles tend to reflect or absorb only those sounds with a shorter wavelength than their own dimensions.

Off-microphone: – On a dead (i.e. insensitive) side of a microphone, or at much more than the normal working distance on a live side.

Omnidirectional Microphone: – A microphone that picks up sound equally well from all directions. Or a mic that is equally sensitive in all directions.

Oscillator: – A device that produces an alternating signal, usually of a particular frequency (or harmonic series). An audio oscillator produces a pure sine tone at any frequency in the audio range.

Overdub: – Added recording (usually on a separate track) made while listening to replay of tracks already recorded.

Overload (over drive): – Exceeding the signal level capability of a microphone or electrical circuit.

Overtone: – A partial in a complex tone, so called because such tones are normally higher than the fundamental.

Pad: – Attenuator of fixed loss. It is also an electronic circuit that attenuates the signal (usually either 10 or 20dB) in order to avoid overload.

PAG: – Potential Acoustic Gain is the calculated gain that a sound system can achieve at or just below the point of feedback.

Panning or steering: – Splitting the output from a mono-phonic microphone between stereo A and B channels. Pan pot: a potentiometer (fader) arranged to do this. For surround, an extra pan pot (or a joystick) may be used.

Pascal: – International unit of sound pressure, equal to 1 newton per square meter or (in older units) 10 dynes/ cm2

     Patch (US): – Cross-plug.

     PCM: – Pulse code modulation

     Peak: – A short period of high volume.

Peak Program Meter (PPM): – A device for measuring the peak values of audio volume. In Europe it is the main volume control aid.

Perspective: – Distance effects, which may be simulated by varying the levels and the proportions of direct and indirect sound.

PFL: – Pre-fade listen.

Phantom Power: – A method of providing power to the electronics of a condenser microphone through the microphone cable.

Phase: – The “time” relationship between cycles of different waves. This is the stage that a particle in vibration has reached in its cycle. Particles are in phase when they are at the same stage in the cycle at the same time.

     Phase shift: – The displacement of a waveform in time.

Phon: – A somewhat archaic unit of perceived loudness. Phons are the same as decibels at 1000 Hz, and at other frequencies are related to this scale by contours of equal loudness.

Pick-up: – The electromechanical transducer of a gramo- phone. The movement of a stylus in the record groove gives rise to an electrical signal.

Pickup Angle / Coverage Angle:-The effective arc of coverage of a microphone, usually taken to be within the 3dB down points in its directional response.

Pitch: – The subjective aspect of frequency (in combination with intensity) that determines its position in the musical scale. This is the fundamental or basic frequency of a musical note.

Polar Pattern (Directional Pattern, Polar Response): – A graph showing how the sensitivity of a microphone varies with the angle of the sound source, at a particular frequency. Also it is seen as the response of a microphone, loudspeaker, etc., showing its sensitivity (or volume of sound) in relation to direction.

Polarization: – The charge or voltage on a condenser microphone element.

Pop Filter: – An acoustically transparent shield around a microphone cartridge that reduces popping sounds. Often a ball-shaped grille, foam cover or fabric barrier.

Pop: – A thump of explosive breath sound produced when a puff of air from the mouth strikes the microphone diaphragm. Occurs most often with “p,” “t,” and “b” sounds.

Popping: – Breakup of the signal from a microphone which is caused by blowing the diaphragm beyond its normal working range.

Portamento: – Used in musical performance,   a slide in frequency to reach a note or from one note to another. It is also provided in some synthesizers. It is measured in octaves per second.

     Pot (pot meter, potentiometer): – Fader

Power (of sound source): – The total energy given out by a source (as distinct from intensity, which is energy crossing unit area). Power is the rate of doing work and in an electrical circuit equals voltage times current.

     PPM: – Peak program meter.

Preamplifier: – Amplifier in circuit between a source and the source fader.

Pre-emphasis: – Increasing the relative volume of part of the frequency response (usually HF) in order to make the best use of some segment of a recording or transmission system (e.g. VHF radio). This is compensated by matched de-emphasis after the link or component in question.

Pre-fade (UK) or dead-roll (US): – Playing closing music from a predetermined time in order to fit exactly the remaining program time, and fading up at an appropriate point during the closing words or action.

Pre-hear (Pre fade-Listen, PFL): – A facility for listening to a source either on headphones or on a loudspeaker of a quality characteristically different from the main monitoring loudspeaker. The source can thereby be checked before fading it up to mix it in.

     Pre-mix: – A mix made of several but not all components of a final mix,

Pre-recording: – Recording made prior to the main recording and replayed into it.

Presence: – A quality described as the bringing forward of a voice or instrument (or the entire composite sound) in such a way as to give the impression that it is actually in the room with the listener. This is achieved by boosting part of the 1-8 kHz frequency range.

Presence Peak: – An increase in microphone output in the “presence” frequency range of 2000 Hz to 10,000 Hz. A presence peak increases clarity, articulation, apparent closeness, and “punch.”

Pressure Gradient Microphone: – One with a diaphragm open to the air on both front and back, and which therefore responds to the difference in pressure at successive points on the sound wave (separated by the path difference from front to back).

Pressure microphone: – One with a diaphragm opens to the pressure of the sound wave on one side and enclosed on the other. If the diaphragm and casing is sufficiently small, the microphone is omnidirectional.

Pressure Zone Microphone (PZM): – Proprietary name for a range of boundary microphones that are attached or very close to a hard reflecting surface, so that interference effects are virtually eliminated.

Pro Tools: – A proprietary set of computer programs that simulate many of the operational systems available on sophisticated consoles. The simulation includes visual displays that often look like the physical controls they replace. Also acts as the host platform to further programs that may be added as ‘plug-ins’.

Proximity Effect: – The increase in bass, usually occurring with most unidirectional microphones when they are placed close to an instrument or vocalist (within 1 ft.). It does not occur with omnidirectional microphones.

Public Address (PA): – A loudspeaker system installed for the benefit of an audience. The output of selected microphones is fed at suitable levels to directional loudspeakers.

Punchy: – A description for a quality of sound that infers good reproduction of dynamics with a strong impact. Sometimes means emphasis in the 200Hz and 5 kHz areas.

     Q: – Bandwidth of a filter or equalizer.

Quad, quadraphony: – A system that provided four-channel sound surrounds the listener. Two speakers were placed to the front (left and right) and two to the rear.

Ratio: – A parameter control on a compressor/limiter that determines how much compression or limiting will occur when the signal exceeds threshold.

Range: – On a gate or expander, a control that adjusts the amount of attenuation that will occur to the signal when the gate is closed.

Rear Lobe: – A region of pickup at the rear of a super-cardioid or hyper-cardioid microphone polar pattern. A bidirectional microphone has a rear lobe equal to its front pickup.

Recall: – A system that memorizes the position of all pots and switches on a console. The engineer must still physically reset the pots and switches back to their previous positions as indicated on a video monitor.

Recording: – An inscription of an audio signal in permanent form, usually on magnetic tape or disc or hard disk. The term record implies commercial disc.

Reflection: – The bouncing of sound waves back from an object or surface which is physically larger than the wavelength of the sound.

Refraction: – The bending of sound waves by a change in the density of the transmission medium, such as temperature gradients in air due to wind.

Reinforcement (in sound balance): – The strengthening of direct sound reaching a microphone by the addition of indirect sound.

Resistance: – The ratio of EMF (electromotive force) to current produced in a circuit; the ratio of voltage drop to current flowing in a circuit element. It can also be seen as the opposition to the flow of current in an electrical circuit.  It is analogous to the friction of fluid flowing in a pipe.

Resonance: – A natural periodicity or the reinforcement associated with it. The frequencies (including harmonics) produced in many musical instruments (e.g. vibrating strings or columns of air) are determined by resonance.

Resonant Frequency: – A particular frequency or band of frequencies that are accentuated, usually due to some extraneous acoustic, electronic, or mechanical factor.

Response: – Sensitivity of microphone, etc. such as Frequency response; Polar characteristic.

    Ring: – Un-damped resonance.

Roll off: – A gradual decrease in response below or above some specified frequency.

Rumble: – Low-frequency mechanical vibration picked up by an audio system.

Reverberation: – The sum of many reflections of sound in an enclosed space that it becomes non-directional and persists for some time after the source has stopped. The amount of reverberation depends on the relative. Reverberation time is the time taken for sound to die away to a millionth of its original intensity.

    Signal- the received input or send output

S signal: – The stereo difference signals A – B. The S does not stand for stereo (of which it is only part) but for ‘side’ response, such as may be obtained by a side fire bidirectional microphone used sometimes in combination with a ‘main’ microphone to produce stereo.

SACD: – Super Audio Compact Disc. It is an advanced CD format with two layers on one side of the disc.

Sampling: – Recording a short audio segment and storing it for subsequent processing and playback (often several times) as part of another work.

Scale: – Division of the audio-frequency spectrum by musical intervals (i.e. frequency ratios).

Screen (US: flat, gobo): – A free-standing  sound-absorbent or reflecting panel that may be used to vary acoustics  locally, or  to  cut  off  some  of  the  direct  sound travelling  from  one  point  to  another  in  a  live hall or a studio.

Screening (electrical): – Protection from stray fields. It may take the form of an earthed mesh wire surrounding a conductor carrying a low level signal.

    Segue (pron. ‘segway’): – This is a musical term meaning follow on.

Sensitivity: – The ratio of response to stimulus, usually measured in decibels relative to some given reference level. Or to a mic, it is the electrical output that a microphone produces for a given sound pressure level.

Separation: – Ensuring that the sound from one source does not spill excessively on to the microphone for another.

Sequencer: – Originally, a digital program for ordering data from electronic sources in order to create a musical work. Now it may be a powerful software system for integrating digital audio and MIDI, also providing related musical processes (and even notation).

Shaped Response: – A frequency response that exhibits significant variation from flat within its range. It is usually designed to enhance the sound for a particular application.

Shelf: – At high or low frequency, a pre-set higher or lower level that lies beyond a rise or fall from the main volume level.

     SI: – International system of measurement

Sibilance: – The production of strongly emphasized ‘f’, ‘s’,  ‘sh’  and ‘ch’  sounds  in speech. These may in turn be accentuated by microphones having peaks in their high-frequency response.

Side-fire: – Orientation of diaphragm within a microphone such that the axis of directional pick-up is at a right angle to its length. The forward axis is usually marked.

Signal: – The fluctuating electrical current or digital data stream that carries audio information (program).

Signal-to-noise ratio: – The difference in decibels between signal and noise levels. A standard reference level is 1 Pa (94 dB at 1 kHz).

Sine tone (pure tone): – A sound (or electrical signal) that contains one frequency, and one alone. This corresponds to an air particle executing simple harmonic motion, and its graphical representation (waveform) as that of s.h.m. (i.e. a sine wave).

Slung microphone: – One that hangs by wires or by its own cable from a ceiling or grid fitting (or from a boom or lazy arm).

SMPTE: – Society of Motion Picture Engineers. Defined the American 30-frame time code standard, but ‘SMPTE’ may also be used to refer to time code at any frame rate.

Snake: – A cable that carries a number of signal sends and returns with input and output channels.

     Solid-state device: – A circuit element such as a transistor

Sound: – A series of compressions and rarefactions travelling through air or another medium, caused by some body or bodies (sound sources) in vibration.

     Sine tone: – Velocity of sound.

Sound card: – A circuit, plugged in to a computer, which converts between analogue audio and digital data (A/D and D/A conversion).

Sound Chain: – The series of interconnected audio equipment used for recording or PA.

     Sound effects: – The application of Effects.

Sound Pressure Level (SPL): – It is the acoustic pressure that builds up within a defined atmosphere area. It is the loudness of sound relative to a reference level of 0.0002 microbars.

     Sound Reinforcement-Amplification of live sound sources.

Spaced pair: – Two separated microphones used to pick up stereo. Phase distortion effects occur, but many balancers regard these as tolerable, or even as adding to the richness of the stereo sound.

Spatialization: – Phase-change effects that distort a stereo image to make it appear wider than the distance between the two loudspeakers.

Speed of Sound: – The speed of sound waves, about 1130 feet per second in air.

Spill (US: leakage): – Sound reaching a microphone other than that intended, thereby reducing separation.

Spin: – The combination of original and delayed signals with multiple repetitions.

Spot Effect (US: Foley artist): – A sound effect created in the studio.  It may be taken on a separate microphone or on the same microphone as the main action.

Spotting: – Reinforcement of a particular element in a stereo balance using a monophonic   microphone (US: accent microphone). The balance is usually very close, to avoid ‘tunnel’ reverberation effects and other problems.

Standing Wave: – A stationary sound wave that is reinforced by reflection between two parallel surfaces that are spaced a wavelength apart.

Stereo (stereophonic sound): – A form of reproduction in which the apparent sources of sound are spread out. The word ‘stereo’ implies ‘solid’. Stereo may be used to simulate the spread of direct sound of an orchestra or a theatre stage.

     Sting: – Musical punctuation pointing dramatic or comic mood.

Stops: – A term referring back to the stud positions on a stud fader, and the markings associated with them, and so, by extension, to the corresponding arbitrary divisions of a continuous fader.

Stray field: – Un-wanted a.c. field that may generate a signal in some part of the equipment where it should not be. The use of balanced wiring discriminates against this, and so also, where necessary, does screening (in which an earthed conductor surrounds parts that might be affected).

Studio (sound studio): – Any room or hall that is primarily used for sound production, manipulation and reproduction works.

Sub-harmonic: – A partial of frequency that lies below the fundamental frequency.

Subwoofer: – A loudspeaker delivering frequencies so low that their wavelengths are comparable with the size of a small auditorium. Its position should not be obvious: in a large auditorium it will generally be at the front evenly positioned, but in a smaller room it can be anywhere convenient.

Super cardioid Microphone: – A unidirectional microphone with tighter front pickup angle 115 degrees than a cardioid, but with some rear pickup. Angle of best rejection is 126 degree.

Surround Sound: – One of several systems that feed loudspeakers set on all sides of the audience.

Synchronization: – When two devices, usually storage devices such as tape machines, DAWs, or sequencers, are locked together in respect to time.

Sync Take: – Film shot with sound, using a synchronous recording system.

Talkback: – This is a communication circuit from control console to studio or live stage used mainly for the direction of performers. Reverse talkback is a secondary circuit for communication from studio to console.

Tape: – Recording medium consisting of a magnetic coating on a  plastic backing.

Tent: – A group of screens, arranged to trap (and usually to absorb) sound in the region of the microphone.

Threshold: – The point at which an effect takes place. On a compressor/limiter for instance, the threshold control adjusts the point at which compression will take place.

Threshold of Hearing: – This is the minimum sound pressure level that produces the phenomenon of hearing in most people which differ due to some natural and artificial factor.

Threshold of Feeling: – This is when the sound pressure level is about 118dB between a particular frequency and starts to cause discomfort to the listener

Threshold of Pain: – it is when the sound pressure level is high that it causes pain usually at about 140dB and above at a particular frequency.

Timbre: – Tone quality. It is the distribution of frequencies and intensities in a sound. Or it is also the characteristic tone of a voice or instrument; a function of harmonics.

Time code: – A recorded time signal that can be electronically read and displayed.

Time constant: – For a capacitor of C farads, charging or discharging through a resistance of R ohms (as in a PPM, limiter, etc.), the time constant, t = CR seconds. (Similarly, for an inductance of H henries and resistance, R ohms, t = HIR seconds.)

Tone: – Imprecise term for sound considered in terms of pitch (or frequency content). A pure tone is sound of a particular frequency.

Tone control: – Preamplifier control for adjusting the frequency content of sound (usually bass or treble) on domestic equipment.

Top: – High frequencies in the audio range, particularly in the range 8-16 kHz.

Top Response: – Ability of a component to handle frequencies at the higher end of the audio range.

Track: – (a) To move a camera or boom toward or away from the performance area. (b) An individual recording among several on a record.  (c) One of several (typically, up to eight, 16 or 24) recordings made side by side on multitrack platform.

Transducer: – A device for converting a signal from one form to another. The system in which the power is generated or transmitted may be acoustic, electrical, mechanical (disc), magnetic (tape), etc. Thus, microphones, loudspeakers, pick-ups, tape heads, etc., are all transducers.

Transient: – The initial part of any sound, before any regular waveform is established. The transient is an important part of any sound and in musical instruments helps establish an identifiable character.

Transient Response: -The ability of a device to respond to a rapidly changing input

Transistor: – A semiconductor device that performs most of the functions of a valve (vacuum tube), but differs from it principally in that (a) no heater is required,  so that the transistor is always ready for immediate  use and no significant unproductive power is consumed, (b) it is much smaller in size, (c) input and output circuitry are not so isolated as in a valve, and (d) there is normally no phase reversal  in a transistor,  as the control voltage is used to promote flow of  current, not to reduce  it. A range of designs and functions of transistors (as with valves) is available. Although the circuit associated with a transistor is some- what different from that for a valve. Transistors are more sensitive to changes of temperature than valves. Power transistors, which generate heat, need to be well ventilated.

Transport: – Tape transport (on a tape recorder and play- out machine) is controlled by a series of buttons, usually marked with conventional symbols, to record, play, pause, stop, fast forward or rewind a  tape.

Tremolo: – A regular variation in the amplitude of a sound, e.g. of electric guitar, generally at a frequency between 3 and 30 Hz. Sometimes, it is confused with vibrato.

Tube (US): – Vacuum tube, or valve.  When used as a component of a head amplifier of archaic design in an early condenser microphone or replica, the term has been applied to the microphone itself.

Tunnel effect: – Monophonic reverberation associated with an individual source in stereo.

Tweeter: – High-frequency loudspeaker used in combination with a low-frequency unit or ‘woofer’ and possibly also a mid-range unit (sometimes called a ‘squawker’).

Unbalanced: – A circuit that carries information by means of one signal on a single conductor.

Unidirectional Microphone: – This may refer either to a cardioid or near-cardioid type of response that is live on one face and substantially dead on the other, or a microphone that is most sensitive to sound coming from a single direction in front of the microphone. Cardioid, super cardioid, and hyper cardioid microphones are examples of unidirectional microphones.

Valve (US: vacuum tube): – In its simplest form, the valve is a diode and it conducts electricity whenever there is a flow of electrons into the cathode (on every other half-cycle of an alternating signal).Used in electronic equipment before the advent of the transistor, and still found in some older or repro microphones.

Velocity (or speed) of sound: – In air at room temperature this is about 344 m/s (1130 ft/s) at 20o C (68o F), increasing with temperature or, more precisely, 331.4 m/s plus 0.607 for each degree Celsius. For Imperial measures it can be calculated roughly as 1087 + 1.1T ft/s, where T is degrees Fahrenheit. Humidity also makes a slight difference: in fully saturated damp air it is about 1 m/s (3 ft/s) faster than in very dry air. In liquids and solids it is much faster than in air.

     VHF: – Very High Frequency.

Vibrato: – Rapid cyclic variation in pitch at a rate of about 5-8 Hz, used by musicians to enrich the quality of sustained notes.

Vocal Stop: – A short break in vocalized sound that precedes certain consonants. e.g. when cutting ‘bu/’ (for ‘but’) on to the beginning of a sentence.

Voice Coil: – Small coil of wire attached to the diaphragm of a dynamic microphone.

Voltage: – The potential difference in an electric circuit. It is Analogous to the pressure on fluid flowing in a pipe.

Wave (sound wave): – A succession of compressions and rarefactions transmitted through a medium at a constant velocity. In representing this graphically, displacement is plotted against time, and the resulting display has the appearance of a transverse wave (like the ripples on a pool).

Wave, WAV: – An uncompressed PC audio file format suitable for recording on hard disk, the file suffix is ‘.wav’.

Wavelength: – The physical distance between the start and end of one cycle of a sound wave.

Weighted and un-weighted: – Different ways of indicating levels of noise or hum relative to signal, with particular reference to their bass content.

     Wild Track: – Film sound recorded without picture.

Windshield (US: windscreen): – Shield that fits over the microphone and protects the diaphragm from ‘rattling’ by wind, and also contours the microphone for smoother airflow round it.

Wireless Microphone: – A term that is more often used in America for radio microphone. (In Britain, ‘wireless’ was the early word for radio, but is now felt to be archaic.)

     Woofer: – Low-frequency unit in a loudspeaker.

Woolly: – Sound that lacks clarity at high frequencies and tends to be relatively boomy at low.

Wow: – Cyclic fluctuation in pitch due to mechanical faults in recording or reproducing equipment (or physical fault in a disc).

XLR Connector: – A rugged type of connector that is widely used in sound connection.

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