3:1 rule (Also, three to one rule, three-to-one rule)
A miking guideline that states that leakage and phase cancellations can be reduced by keeping the distance between mics at least three times the distance the mikes are placed from their respective sound sources.


Absorption: The dissipation of sound energy at a surface as the sound changes into heat. The absorption of acoustic energy effectively is the inverse of reflection. Whenever sound strikes a material, the amount of acoustic energy absorbed (often in the form of physical heat dissipation), relative to the amount reflected, can be expressed as a simple ratio known as the absorption coefficient.

AES protocol: A professional transmission protocol that conveys two channels of interleaved digital audio data through a single, two- conductor XLR cable (for example, a standard microphone cable).

AIF: The AIFF (Audio Interchange File Format) from Apple Computers has become the standard soundfile format for use on the Macintosh multimedia platform

Alignment: The adjustment of an analog tape machine's tape head and electronic circuitry to standardize playback and record frequency response and signal levels within industry accepted standards for reasons of compatibility.

Alignment tape: A reference reproduction tape used for aligning analog tape machines.

Amplification: The process by which a signal level is increased by a device according to a specific input/output ratio.

Analog-to-digital converter: A device that converts analog signals into digital form.

Applet: A small computer program that's designed to work within another core program to do a specific task.

Assistant engineer: The person normally responsible for microphone and headphone setup, operation of the tape machines, session breakdowns, and, in certain cases, for positioning rough mixes on the console for the engineer. Often, larger studios train future staff engineers by having them work as assistant engineers.

Attack: The initial transient or first part of the envelope of a signal. The beginning of a note.

Attenuate: To reduce the signal level.

Autolocator: A feature that enables a specific cue point location on a tape transport to be stored into and recalled from memory. The autolocator can then shuttle the tape to a time point entered by the operator.

Automated mixdown: Enables the console to remember and re-create any settings or changes (regarding level and other mix-related functions) made by the engineer, while allowing continual improvements until the desired final mix quality is achieved.

Auxiliary sends: Provide the overall effects or monitor sends of a console. These sections (of which up to eight or more sends can be provided on a single input module) are used to create separate and controlled submixes of any (or all) of the input signals to a mono or stereo output.


Balance: The relative level of various instruments within a mix.

Balanced line: A cable having two conductors and a ground connection and often surrounded by a shield. With respect to ground, the conductors are at equal potential but opposite polarity. These lines are often used in professional settings to reduce or eliminate induced noise and interference from external electromagnetic sources.

Bandwidth: The amount of data that can pass through a digital device or transmission medium in a given time. Usually expressed as kilobits per second (kbps) or megabits per second (mbps). Bandwidth can also be expressed in bytes per second (bps).

Bass trap: Used to reduce low-frequency buildup at specific frequencies in a room. These low-frequency attenuation devices are available in a number of design types, such as the quarter- wavelength trap, the pressure zone trap, the functional trap, and the Helmholtz resonator trap.

Bias: An ultrasonic signal mixed with the input signal at the record head of an analog tape recorder to reduce distortion.

Bidirectional microphone: A mic sensitive to sounds arriving from on-axis (front) and 180@deg off-axis (rear), with its maximum rejection occurring at both sides.

Bin-loop high-speed duplication: High-speed duplication in a process in which the duplication takes place without the duplicated tape being housed in cassette shells. The tape is recorded on a hard disk or reel-to-reel machine that's specially designed to transfer audio at high speed ratios.

Bit: A digitally encoded state, represented by a 1 (one) or a 0 (zero).

Black burst generator: A device that produces an extremely stable timing reference. The function of this signal is to precisely synchronize the video frames and time code addresses received or transmitted by every video related device in a production facility to a specific clocking frequency. This process ensures that the frame and address leading edges occur at exactly the same instant in time.

Blumlein pickup: The placement of two coincident bidirectional mics crossed at 90° and aiming 45° left and right of center.

Board: American term for console. (See also: recording console)

Bouncing tracks: Commonly used to mix entire performances onto one track, a stereo pair of tracks, or several tracks. This makes the final mixdown easier by grouping instruments together onto one or more tracks. It also opens up needed tape tracks by bouncing similar instrument groups down to one or a stereo pair of tracks, thereby freeing the originally recorded tape tracks for more overdubs.

Bps: The number of bits (or bytes) that are transmitted or passed through a device in a second.

Bus: A common signal path that routes a signal, throughout a console or connected network, from one or more signal sources to one or more signal destinations.

Byte: A grouping of 8 bits.


Cardioid microphone: A common mic pickup pattern designed to attenuate signals arriving 180° off-axis while picking up fully those sounds that arrive at the front (on-axis).

CD-ROM: A disc capable of holding as much as 680mb or 700mb of any type of computer-based data, including graphics, digital audio, MIDI, text, and raw data. Unlike the CD-Audio disc, a CD-ROM isn't tied to a specific data format; the manufacturer or programmer can specify what's contained on the disc.

Compansion: The process in which an incoming signal is compressed before it is recorded on tape; then, upon reproduction, the signal is reciprocally expanded back to its original dynamic range, with a resulting reduction in background tape noise.

Composite tracks: The result of combining the best "takes" from a number of performances that exist on different tracks onto a final single or stereo pair of tracks. This is done to "open up" tracks for further overdubbing or to ease the number of mix movements that must be performed during mixdown.

Compression ratio: The ratio of signal dynamic range between the compressor input and output (such as 2:1, 4:1, and 8:1) above the device's set threshold point.

Compressor: In effect, an automatic fader. When the input signal exceeds a predetermined level, called the threshold, the gain is reduced by the compressor and the signal is attenuated.

Condenser microphone: A microphone that operates on an electrostatic principle rather than on the electromagnetic principle used in dynamic and ribbon mics. The head, or capsule, of the mic consists of two very thin plates - one movable and one fixed. When the distance between these plates decreases, the capacitance increases; when the distance increases, the capacitance decreases. According to the equation: Q &61; CV where Q is the charge, in coulombs, C is the capacitance, in farads, V is the voltage, in volts.

Control room: In a recording studio, this room serves several purposes: it is acoustically isolated from the sounds produced in the studio and surrounding vicinities, it is optimized to act as a critical listening environment using critically balanced and placed monitor speakers, and it houses the majority of the studio's recording, control, and effects equipment.

Crosstalk: The unwanted leakage of a signal from one channel or track onto another.

Cue send: The auxiliary send used for the musicians' headphone mix.

Cycle: The period in which an acoustic or electrical signal varies over one completed excursion of a wave, which is plotted over the 360° axis of a circle.


DAT: A compact, dedicated PCM digital audio recorder that combines rotary head technology and PCM digital technology to create a professional recorder with a wide dynamic range, low distortion, and immeasurable wow and flutter.

DBm: Decibels referenced to 1 milliwatt. dBu or dBv: Decibels referenced to 0.775 volt. (dBu is preferred.) dBV: Decibels referenced to 1 volt.

De-esser: A frequency-dependent compressor used to reduce excessive sibilance ("sss," "sh," and "ch" sounds).

Decibel: A unit of audio measurement of sound-pressure level (SPL), signal level, and changes or differences in signal level. The decibel is a logarithmic (log) mathematical function that reduces large numeric values into smaller, more manageable numbers. Decibel is calculated as being 10 times the log of the ratio of two powers and 20 times the log of the ratio of two voltages.

Degaussing: The process by which small amounts of residual magnetism are eradicated from an analog magnetic tape head. It's often wise to degauss a magnetic tape head after 10 hours of continuous operation.

Destructive editing: When the audio data recorded on a hard disk is altered and rewritten to disk in such a way that it can't be recovered in its original form.

Diffraction of sound: Sound inherently has the capability to bend around a physical acoustic barrier or go through a hole in the barrier. It bends around an object in a manner that will reconstruct the original waveform in both frequency and amplitude.

Digital console: A console in which analog input signals are converted directly into digital data (or are directly inserted into the console's chain as digital data) and are distributed and processed entirely in the digital domain.

Digital signal processing: The processing of a signal in the digital domain in such a way as to follow basic binary computational rules according to a specialized program algorithm. This algorithm is used to alter the numeric values of sampled audio in a predictable way.

Digital-to-analog converter: A device that converts digital signals into analog form.

Digitally controlled analog console: A console that distributes and processes the signal path in analog form with control over all console parameters being carried out in the digital domain. In most cases, this means that the console's control surface (containing all the knobs, faders, assignment buttons, and so on) will output its control parameters as digital signals.

Direct injection box: A box for converting high-level, high- impedance instrument signals to low-impedance microphone-level signals for direct injection into a console mic input.

Directional response: The variations in microphone sensitivity versus the angle of sound incidence, plotted on a polar graph. The sensitivity on-axis is called 0 dB, and the sensitivities at other angles are relative to that. This chart, known as the polar response or polar pattern of a microphone, shows microphone output with respect to direction and frequency over 360°.

DirectX: A Microsoft software technology that allows 3rd party plug-ins to be used with PC on the Windows platform. (Also known as ActiveX.)

Dither: Adding to a signal small amounts of white noise that are less than the least-significant bit (that is, less than a single quantization step), thereby increasing signal-to-error and reducing distortion.

Dry signal: An unprocessed signal that doesn't contain reverb or echoes.

Dynamic microphone: A microphone that operates by electromagnetic induction to generate an output signal. When an electrically conductive coil of wire or ribbon is made to cut across the flux lines of a magnetic field, a current of specific magnitude and direction is generated within that coil or ribbon.


EBU protocol: A professional transmission protocol that conveys two channels of interleaved digital audio data through a single, two- conductor XLR cable (for example, a standard microphone cable).

Edit decision list: A sequential editlist containing permanent SMPTE time code and related edit information.

Effects send: An auxiliary send feeding an effects device.

Electret microphone: A condenser microphone that has the polarizing charge stored permanently in the diaphragm or on the backplate. Because of this electrostatic charge, no external powering is required to charge the diaphragm or backplate.

Engineer: The person responsible for expressing the artist's music and the producer's concepts through the medium of recording. This job is actually an art form because both music and recording are subjective in nature and rely on the tastes and experiences of those involved.

Equalizer: A frequency-dependent amplifier that enables a recording or mix engineer to control the relative amplitude of various frequencies in the audible bandwidth. Put another way, the equalizer lets you exercise tonal control over the harmonic content or timbre of a recorded sound.

Expander: A device that increases the dynamic range of a signal.


Fade: A slow change in volume - up from silence or down to silence - accomplished manually or by calculation in a DAW or hard-disk recorder. The fading in or fading out of a region is a DSP function carried out by calculating the soundfile's relative amplitude over a defined duration.

Fader: A linear attenuation device or linear volume control.

Feedback: The returning of a loudspeaker signal back into a microphone feeding that loudspeaker. Excessive feedback results in unpleasant, screaming buildups at particular frequencies, which the English call howlround.

Flanging: A process whereby a delayed signal is combined with itself undelayed. The delay is varied to create continual changes in timbre. Also called a comb-filter effect.

Fletcher-Munson curves: A group of curves that plot the subjective sensitivity of humans to various frequencies at different sound- pressure levels.

Flutter: A fast, periodic variation in a tape transport's speed.

Frequency: The rate at which an acoustic generator, electrical signal, or vibrating mass repeats a cycle of positive- and negative-going amplitude. The number of cycles that occurs over the period of one second is measured in hertz (Hz). Often, the perceived range of human hearing is from 20 Hz to 18,000 Hz.

FTP: A digital language that can transfer files between computers over the internet.


Gain: Amount of amplification in dB.

Gate: A device that fully attenuates a signal which falls below a predetermined threshold level. Often used to reduce noise or extraneous pickup leakage.

Ground loop: A condition that exists in an improper grounding situation, whereby a DC current differential exists between one signal path and another, resulting in 60 Hz or 50 Hz (European) hum.


Hard-disk recorder: A system that uses a computer hard disk to record, edit, and reproduce digital data.

Harmonic content: A factor that allows us to differentiate between instruments. The presence of several different frequencies within a complex sound wave, in addition to its fundamental note. The frequencies present in a sound, other than the fundamental, are called partials. Partials higher than the fundamental frequency are called upper partials or overtones. These overtones play an important part in determining the sonic character of an instrument. Harmonics are integral multiples of the fundamental frequency.

Hertz: Frequency measurement unit (cycles/second).

Hiss: Broadband tape or amplifier noise.

HTML: A basic language that's used to create and edit web pages.

HTTP: A basic language for transmitting commands over the internet.


Impedance: The opposition of a circuit to the flow of an alternating current.

Input module: The vertical array of controls on a console that relates to a specific input signal.

Iso-booth: Isolation rooms and the smaller iso-booth are acoustically sealed areas built into and easily accessible from the main studio area. These areas provide improved separation between loud and soft instruments, vocals, and so on.

ISP: Business that provide internet service to individuals and companies over phone, cable and/or wireless communications lines.


Jitter: A time-base error caused by varying time delays in a digital audio circuit path.


Leader tape: A paper tape that can be spliced into analog audio tape for the purpose of inserting silent spaces, visual separation, and identification for various songs or selections.

Leakage: The "spilling" or "bleeding" of sound from one instrument onto another instrument's microphone.

Limiter: A device used to keep signal peaks from exceeding a certain level in order to prevent the clipping or distortion of amplifier signals, recorded signals on tape or disc, broadcast transmission signals, and so on.

Line level: A signal level that is referenced to either 4 dBm (pro) or -10 dBV (semi-pro/consumer). Devices other than mics, speakers, and power-amplifier outputs operate at these levels.


Maintenance engineer: The person who ensures that the equipment in the studio is maintained in top condition, regularly aligned, and repaired when necessary.

Masking: The phenomenon by which loud sounds prevent the ear from hearing softer sounds. The greatest masking effect occurs when the frequency of the sound and the frequency of the masking noise are close to each other.

Mastering: The processing and transferring of a final, sequenced audio tape to a medium for duplication.

MIDI: A digital communications language and compatible hardware specification that allows multiple electronic instruments, performance controllers, computers, and other related devices to communicate with one another within a connected network.

MIDI interface: A digital hardware device used to translate MIDI's serial message data into a structure that can be understood by and communicated to a personal computer's internal operating system.

MIDI machine control: A standardized series of transport- related commands that are transmitted over standard MIDI lines from one controller to one or more other MMC-capable devices within a connected system.

MIDI sample dump standard: A protocol developed and ratified by the MIDI Manufacturers Association that enables the transmission of sampled digital audio and loop information from one sampling device to another.

MIDI time code: Provides a cost-effective and easily implemented means for translating SMPTE time code throughout a MIDI chain as a stream of MIDI messages.

Mixdown: The process in which the separate audio tracks of a multitrack tape machine are combined, balanced, and routed through the recording console. At this point, volume, tone, special effects, and spatial positioning can be artistically set by the engineer to create a stereo or four-channel mix that is then recorded to a master recording device such as a DAT recorder.

Modular digital multitrack recorders: Small, cost-effective multitrack digital audio recorders capable of recording eight tracks of digital audio onto readily available videotape cassettes. They are called "modular" because they can be linked together in a proprietary sync fashion, with a theoretical maximum limit of up to 128 tracks!

Moving-coil microphone: Generally consists of a Mylar diaphragm of roughly 0.35 mil thickness attached to a finely wrapped coil of wire that is precisely suspended within a high-level magnetic field. When an acoustic pressure wave hits the face of this diaphragm, the attached voice coil is displaced in proportion to the amplitude and frequency of the wave, causing the coil to cut across the lines of magnetic flux supplied by a permanent magnet. In so doing, an analogous electrical signal (of a specific magnitude and direction) is generated across the voice coil leads.

MP3: An encoding format for compressing digital audio data by removing information that can't be perceived by the human ear due to masking. MP3 files can reduce file sizes by 12:1 and beyond.

Multitimbral: The capability of an electronic musical instrument to respond to and output multiple voice patches at one time.

Multitrack recording: A process that provides an added degree of production flexibility to the recording process by enabling multiple sound sources to be recorded to and played back from isolated tracks that are synchronously locked in time. The recorded tracks are isolated from one another, so any number of sound sources can be recorded and rerecorded without affecting other tracks.

Mute: To turn off or silence an input signal, tape track, and so on.


Nearfield monitoring: Monitoring with a small bookshelf-style speaker on or slightly behind the meter bridge of a console, close to the engineer and producer. This technique ensures that a greater portion of the direct sound mix is heard relative to the room's acoustics.

Noise gate: A device that acts as an infinite expander, allowing a signal above the selected threshold to be passed through to the output at unity gain and without dynamic processing. When the input signal falls below this threshold level, the device effectively shuts down the signal by applying full attenuation to the output.

Nondestructive editing: Editing a hard-disk soundfile by moving pointers, without altering in any way the digital audio data originally recorded to disk.

Normalizing: A specialized gain-related process that makes the best use of a digital system's dynamic range by automatically determining the amount of gain required to increase the level of the highest amplitude signal to its full-scale amplitude value, and then increasing the level of the selected region or entire file by this gain ratio.

Nyquist Theorem: A theory which states that in order to digitally encode the entire frequency bandwidth, the selected sample rate must be at least twice as high as the highest desired recorded frequency (sample rate 2 x highest frequency).


Omnidirectional microphone: A mic that outputs signals received from all incident angles at the same (or nearly equal) level.

Open tracks: Available tracks on a multitrack recorder.

Operational amplifier: A stable high-gain, high-bandwidth amplifier with a high input impedance and a low output impedance. These qualities enable it to be used as a basic building block for a wide variety of audio and video applications.

Outboard equipment: Signal processing and other devices external to the mixing console.

Overdubbing: Enables one or more of the previously recorded tracks to be monitored while simultaneously recording one or more signals onto other tracks. This process can be repeated until the song or soundtrack has been built up. If a mistake is made, it generally is a simple matter to recue the tape to the desired starting point and repeat the process until you have the best take on tape.

Overload: The distortion that occurs when an applied signal exceeds a system's maximum input level.

Oversampling: A process commonly used in professional and consumer digital audio systems to improve Nyquist filter characteristics, thereby reducing intermodulation and other forms of distortion. This process effectively multiplies the sampling rate by a specified factor - commonly ranging from between 12 to 128 times the original rate. This increased sample rate likewise results in a much wider frequency bandwidth, so a simple, single-order filter can be used to cut off the frequencies above the Nyquist limit.


Pan pot: A dual-potentiometer that can place a single signal source at any point between the left and right channels of a stereo image, or the left/right, front/back quadrants of a surround sound image.

Patch bay: A panel that, under the best of conditions, contains a jack corresponding to the input and output of every discrete component or group of wires in the control room. It acts as a central point where console signal paths, pieces of audio gear, and other devices can be connected.

Patch chord: Short cables used for routing signals through a patch bay.

PCM: The most common encoding scheme for storing digital data onto a medium with a maximum degree of data density.

Peak amplitude: The maximum instantaneous amplitude of a signal.

Peaking filter: Used to create a peak- or bell-shaped equalization curve in the frequency response that can be either boosted or cut at a selected center frequency.

PFL: A monitor function that lets the engineer hear a single instrument or group of instruments without affecting the studio's headphone monitor mix, recorded tracks, or mixdown signal.

Phantom power: Power for a condenser mic that comes directly from the console through balanced mic cables by supplying a positive DC supply voltage of 48V (usually) to both conductors (pins 2 & 3) with respect to pin 1. This voltage is distributed through identical value resistors so that no differential exists between the two leads; therefore, the voltage is electrically invisible to the alternating audio signal. The DC circuit is completed by connecting the negative side of the supply to the cable's grounding shield.

Phase: The degree of progression in the cycle of a wave, where one complete cycle is 360°. Waveforms can be added by summing their signed amplitudes at each instant of time. A cycle can begin at any point on a waveform, so it's possible for two waveforms having the same or different frequency and peak levels to have different amplitudes at any one point in time. These waves are said to be "out of phase" with respect to each other. Phase is measured in degrees of a cycle (divided into 360°) and will result in audible variations of a combined signal's amplitude and overall frequency response.

Phase shift: The difference in degrees of phase angle between corresponding points on two waves.

Ping-ponging: Commonly used to mix entire performances onto one track, a stereo pair of tracks, or several tracks. This makes the final mixdown easier by grouping instruments together onto one or more tracks. It also opens up needed tape tracks by bouncing similar instrument groups down to one or a stereo pair of tracks, thereby freeing the originally recorded tape tracks for more overdubs.

Pitch control: A control that varies the speed of a tape transport or the sample rate of a digital audio device, changing the pitch of the reproduced signal.

Pitch shifting: Used to vary the pitch of a program either upward or downward so as to transpose the relative pitch of an audio source.

Playlist: A sequential list of soundfile regions that can be played as a single, continuous program or sequentially triggered at specific time code addresses.

Polar pattern: A polar graph of the sensitivity of a microphone at all angles of sound incidence relative to the sensitivity on-axis.

Polyphonic: The capability of an electronic musical instrument to output multiple notes at one time.

Pop filter: A foam or wire screen placed between the mic and the instrument or performer to reduce wind and breath blasts.

Potentiometer: A rotary gain, pan, or other type of continuously variable signal control.

Print-through: The transfer of a recorded signal from one layer of magnetic tape to an adjacent layer by means of magnetic induction, which gives rise to an audible false signal (pre-echo or post- echo) on playback.

Producer: The person who handles the scheduling, budgetary, and coordination aspects of a recording project. It is the producer's responsibility to create the best recorded performance and final product possible. In effect, a producer is often chosen for his or her ability to understand the many phases of the overall process of creating a final recorded project, from the standpoints of business, musical performance, and creative insight into recording technology.

Project studio: A high-quality MIDI and/or recording facility in a home, apartment, or personal place of business that is used to record the owner's own projects rather than outside projects.

Proximity effect: A bass boost that occurs with single-D directional mics at close working distances.

Punch-in / punch-out: The entering into and out of record mode on a track that contains existing program material for the purpose of correcting or erasing an unwanted segment.


Quantization: The amplitude component of the digital sampling process. In an A/D converter, the process of generating a binary number (made of 1s and Os) that represents the voltage of the analog waveform at the instant it is measured or sampled.


Recording console: A device that enables the engineer to mix and control most (if not all) of the device input and output signals that can be found in the studio. The console's basic function is to allow for any combination of mixing (control over relative amplitude and signal blending between channels), spatial positioning (left/right, as well as possibly front/back), routing (the capability to send any input from a source to a signal destination), and switching for the multitude of audio input/output signals that are commonly encountered within an audio production facility.

Recording studio: One or more acoustic environments specially designed and tuned for the specific purpose of getting the best sound possible onto tape when using a microphone pickup.

Release: The final portion of a note's envelope, which falls from the sustain signal level to silence.

Release time: Once dynamic processing has begun, the time taken for a dynamic range changer (such as a compressor, limiter, or expander) to return the signal to 63% of its original (unprocessed) level.

Repro: The use of an analog tape machine's record head to play back tracks during the overdub process in order to synchronize with the current tracks being recorded.

Resistance: The opposition to the flow of DC current in a wire or circuit (measured in Ohm

Reverb: The persistence of a signal, in the form of reflected waves in an acoustic space, after the original sound has ceased. These closely spaced and random multiple echoes result in perceptible cues as to size and surface materials of a space and add to the perceived warmth and depth of recorded sound. Reverb plays an extremely important role, both in the enhancement of our perception of music and in proper studio design. The reverberated signal itself can be broken into three components: direct signal, early reflections, and reverberation.

Reverb time: Measurement unit of a room's reverberation. The time taken for a reverberated signal (once the initial signal has stopped) to reduce in level by 60 dB.

Ribbon microphone: A microphone that uses a diaphragm of extremely thin, aluminum ribbon suspended in a strong field of magnetic flux. As sound-pressure variations displace the metal diaphragm in accordance with air-particle velocity, the ribbon cuts across the magnetic lines of flux. This induces a current in the ribbon of proportional amplitude and frequency to the acoustic waveform.


S/PDIF: This digital protocol was adopted for the purpose of transmitting digital audio between consumer digital devices in a manner that is similar to but not identical in data structure to its professional AES/EBU counterpart.

Safety copy: A high-quality analog or digital copy of a production tape or final master recording. Safetys should be carefully stored under moderate temperature and humidity conditions.

Samplefile: A computer file that contains sampled audio data.

Sampler: A device capable of recording, musically transposing, processing, and reproducing segments of digitized audio to and from RAM.

Sampling: The process of taking periodic samples of an audio waveform and transforming these sampled signal levels into a representative stream of binary words that can be manipulated or stored for later reproductio

SCMS: Pronounced "scums". A system implemented in many consumer digital devices in order to prohibit the unauthorized copying of digital audio at 44.1 kHz (standard CD sample rate). With the SCMS, you can often make a digital copy of a commercial DAT or CD, but you cannot make a copy from that copy.

Scratch vocal: A rough vocal track recorded live along with the initial rhythm instruments to help the basic tracks keep in the "groove" of the song. Final vocals can be re-recorded later during overdubs.

SCSI: A sample dump format. A bidirectional communications bus used by many PCs and digital devices to exchange data between systems at high speeds.

SDMI: An industry-wide effort to protect the record company's and artist copyrights and royalties by allowing soundfiles to be securely sold and distributed over the web and other distribution paths.

Sensitivity rating: The output level (in volts) that a microphone will produce given a specific and standardized input signal (rated in dB SPL). This specification implies the degree of amplification required o raise the microphone signal to line level (-10 dBV or- 4 dBm).

Sequencer: A digitally based device used to record, edit, and output performance-related MIDI data.

Servo-driven fader: A resistive attenuator that is driven automatically by a servo motor interface. During the playback of an automated mix, the faders will move on their own, in accordance with the requirements of the mix.

Shelving filter: A rise or drop in frequency response at a selected frequency that tapers off to a preset level and continues at this level to the end of the audio spectrum.

Shock mount: A suspension system that isolates a microphone from stand- and floor-borne noises. A shock mount built into a mic reduces handling noise.

Slate: A verbal identification of the song, take, and other identification on the original master tape tracks.

SMPTE: A standard method for synchronously interlocking audio, video, and film transports. The use of time code allows identification of an exact position on a magnetic tape by assigning a digital address to each specified position. This address code cannot slip and always retains its original location, allowing continuous monitoring of tape position to an accuracy of roughly 1/30th of a second.

SMPTE-to-MIDI converter: Used to read SMPTE time code and convert it into such MIDI-based sync protocols as MIDI time code, Direct Time Lock, or song position pointer.

Solo: A monitor function that lets the engineer hear a single instrument or group of instruments without affecting the studio's headphone monitor mix, recorded tracks, or mixdown signal.

Sound-pressure waves: Sound waves generated by a vibrating body in contact with the air, such as an instrument or loudspeaker. Sound arrives at the ear in the form of a periodic variation in atmospheric pressure. The atmospheric pressure is proportional to the number of air molecules in the area being measured.

Soundfile: A computer file that contains audio data. Rather than being reproduced from a sampler, these files are often played back from a hard-disk-based system.

Spatial perception of direction: The capability of two ears to localize a sound source in an acoustic space. Although one ear is not able to discern the direction from which a sound originates, two ears can. This is called spatial or binaural localization.

Speaker polarity: Speakers are said to be electrically in-phase whenever the same signal applied to both speakers will cause their cones to move in the same direction (either positively or negatively). If they are wired out-of-phase, one speaker cone will move in one direction while the other will move in the opposite direction.

Splice: To join two pieces of analog magnetic tape using a special adhesive, nonbleeding tape called splicing tape.

Standing wave: An apparently stationary waveform created by multiple reflections between opposing room surfaces. At certain points along the standing wave, the direct and reflected waves cancel each other, and at other points, the waves add together or reinforce each other. Standing waves cause boomy sounding peaks in a room's low-frequency response.

Streaming: A system for transmitting audio and/or data through a transmission media (such as the web) in real-time.

Studio management: Business people who are (hopefully) knowledgeable about the inner workings of the music studio, music business, and people. Running a studio requires the constant attention of a studio manager, booking department (to keep track of most of the details relating to studio use, billing, and possibly marketing), and competent secretarial staff.

Submix: A grouped set of signals that can be varied in overall level from a single control or set of controls

Sweetening: Overdubbing strings, horns, chorus, and sometimes percussion to give added impact to a recorded production.

Sync: The locking of relative transport or playback speeds of various devices to allow them to work together as a single, integrated system.

Synthesizer: An electronic musical instrument that uses multiple sound generators to create complex waveforms that synthesize a unique sound character.

Sys-Ex messages: Messages that enable MIDI manufacturers, programmers, and designers to communicate customized information between MIDI devices. These messages communicate device-specific data of an unrestricted length.


T1: A high-speed, high-bandwidth internet connection (1.544 megabits/sec).

Take sheet: A written sheet that notes the position of each take on a tape. Comments are written on the take sheet to describe the producer's opinion of the performance, as well as whether it is a complete take, an incomplete take, or a false start.

Threshold of feeling: An SPL rating that will cause discomfort in a listener 50% of the time and which occurs at a level of about 118 dB SPL between 200 Hz and 10 kHz.

Threshold of hearing: The quietest sound humans can hear: 0 dB SPL. A convenient pressure-level reference that constitutes the minimum sound pressure that produces the phenomenon of hearing in most people. It is equal to 0.0002 microbar. One microbar is equal to one-millionth of normal atmospheric pressure, so it's apparent that the ear is extremely sensitive. The threshold of hearing is defined as the SPL for a specific frequency at which the average person can hear only 50% of the time. threshold of pain An SPL rating that causes pain in a listener 50% of the time. It corresponds to an SPL of 140 dB in the range between 200 Hz and 10 kHz.

Time code: A standard encoding scheme (hours:minutes:seconds:frames) for encoding time-stamped address information. Time code is used for address location, triggering, and synchronization between various analog, video, digital audio, and other time-based media.

Track sheet: A sheet that indicates what instrument (or instruments) is on each track of a multitrack tape. The track sheet should always be stored in the box with the reel.

Transducer: Any device that changes one form of energy into another, corresponding form of energy. For example, a microphone is an example of a transducer because it converts sound waves into an electrical signal.

Transient response: The measure of how quickly a mic diaphragm, speaker, or physical mass reacts to an input waveform.


Unbalanced line: A cable having only one conductor plus a surrounding shield, in which the shield is at ground potential. The conductor and the shield carry the signal.

URL: An addressing format for locating resources, documents, etc. on the web.


Velocity of sound: The speed at which sound waves travel through a medium. At 70°F, the speed of sound waves in air is approximately 1130 feet per second (ft/sec) or 344 meters per second (m/sec).

Voltage controlled amplifier: An amplifier in which audio level is a function of a DC voltage (generally ranging from 0 to 5 V) applied to the control input of the device. As the control voltage is increased, the analog signal is proportionately attenuated. Thus, an external voltage is used to change the audio signal level. Console automation and automated analog signal processors often make extensive use of VCA technology.


WAV: The wave file format from Microsoft has become the standard sound file format for use on IBM-compatible PCs for both pro-audio and multimedia production.

Waveform: A graph of a signal's sound pressure or voltage level versus time. The waveform of a pure tone is a sine wave.

Wavelength: The distance in a medium between corresponding points on adjacent waveform cycles.

Wow: A slow, periodic variation in a tape transport's speed.