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Glossary of Audio Terms: R - S



RAM: Random Access Memory. This is a type of memory used by computers for the temporary storage of programs and data, and all data is lost when the power is turned off.

R-DAT: Digital tape machine using a rotating head system.

REAL TIME: An audio process that can be carried out as the signal is being recorded or played back. The opposite is off-line, where the signal is processed in non-real time.

RELEASE: The time taken for a level or gain to return to normal. Often used to describe the rate at which a synthesized sound reduces in level after a key has been released.

RELEASE ( RECOVERY): Time taken for a compressor or limiter to return to a non compressing state below the set threshold.

RESISTANCE: Opposition to the flow of electrical current. Measured in Ohms.

RESOLUTION: The accuracy with which an analogue signal is represented by a digitising system. The more bits are used, the more accurately the amplitude of each sample can be measured, but there are other elements of converter design that also affect accuracy. High conversion accuracy is known as high resolution. 

RESONANCE: The characteristic of a filter that allows it to selectively pass a narrow range of frequencies

REVERB: The persistence of sound due to repeated reflections at the boundaries.

RF: Radio Frequency.

RIBBON MICROPHONE: Type of microphone in which currents are generated by the movements of a metal ribbon suspended in a magnetic field.

ROLL-OFF: The rate at which a filter attenuates a signal once it has passed the filter cut-off point.

ROM: Read Only Memory. Memory having fixed contents which cannot be altered.

E-PROM: (Erasable Programmable Read Only Memory) Similar to ROM, but the information on the chip can be erased and replaced using special equipment.

ROOT MEAN SQUARE (RMS): A method of calculating the voltage and current to obtain the average power.

RELEASE ( RECOVERY): Time taken for a compressor or limiter to return to a non compressing state below the set threshold.

RING MODULATOR: Device used to produce sum and difference frequencies of two signals applied to the input. Most recognizable use is the sound of the Daleks in Doctor Who

RMS: (Root Mean Square) A method of specifying the behaviour of a piece of electrical equipment under continuous sine wave testing conditions.



SAFETY COPY: Copy or clone of an original tape for use in case of loss or damage to the original.

SAMPLE: The process carried out by an A/D converter where the instantaneous amplitude of a signal is measured many times per second (44.1kHz in the case of CD).

SAMPLE: A digitised sound used as a musical sound source in a sampler or additive synthesizer.

SAMPLE RATE: The number of time’s per second that samples are taken of an analogue signal in a A/D converter. ( 44.1Khz, 48Khz 88.1 etc)

SAMPLE AND HOLD: Usually refers to a feature whereby random values are generated at regular intervals and then used to control another function such as pitch or filter frequency. Sample and hold circuits were also used in old analogue synthesizers to 'remember' the note being played after a key had been released.

SCSI: Small Computer Systems Interface. An interfacing system for using hard drives, scanners, CD-ROM drives and similar peripherals with a computer. Each SCSI device has its own ID number and no two SCSI devices in the same chain must be set to the same number. The last SCSI device in the chain should be terminated, either via an internal terminator, where provided or via a plug-in terminator fitted to a free SCSI socket.

SESSION TAPE: The original tape made during a recording session.

SEQUENCER: Device for recording and replaying MIDI data, usually in a multitrack format, allowing complex compositions to be built up a part at a time.

SHORT CIRCUIT: A low resistance path that allows electrical current to flow. The term is usually used to describe a current path that exists through a fault condition.

SIBILANCE: High frequency whistling or lisping sound that affects vocal recordings. De-esser is the equipment used to try and combat this effect.

SIDE-CHAIN: A part of the circuit that splits off a proportion of the main signal to be processed in some way. Compressors use the side-chain signal to derive their control signals.

SIGNAL: Electrical representation of input such as sound.

SIGNAL CHAIN: Route taken by a signal from the input to a system to the output.

SIGNAL-TO-NOISE RATIO: The ratio of maximum signal level to the residual noise, expressed in dBs.

SINE WAVE: The waveform of a pure tone with no harmonics.

SINGLE ENDED NOISE REDUCTION: A device for removing or attenuating the noise component of a signal, but that doesn't require previous coding, as in the case of Dolby or dbx.

SLATE (SLATING): Term used for recording spoken take numbers or cues on tape by analogy with chalked cues on a film clapperboard.

SLAVE: A device under the control of a master device.

SMPTE: Society of Motion Picture and Television Engineers. Time code developed for the film industry but now extensively used in music and recording. SMPTE is a real-time code and is related to hours, minutes, seconds and film or video frames rather than to musical tempo.

S/PDIF : Sony/Philips Digital Interface. 

SPL: Sound Pressure Level measured in dBs.

STEMS: When mixing complex audio material it is often useful to divide the tracks into related sections and mix those sections separately before combining the whole. In mixing film soundtracks, the material would often be grouped as a dialogue stem, a music stem, an effects stem and so on. Each stem might be mono, stereo or multichannel, as appropriate to the situation. In music mixing, stems might be used for the rhythm section, backline instruments, frontline instruments, backing vocals, lead vocals and effects — or any other combination that suited the particular project.

STEP TIME: A system for programming a sequencer in non-real time.

STEREO: two-channel system feeding left and right loudspeakers.
STRIPE: To record time code onto one track of a multitrack tape

SQUARE WAVE: A symmetrical rectangular waveform. Square waves contain a series of odd harmonics.

SAWTOOTH WAVE: So called because it resembles the teeth of a saw, this waveform contains both odd and even harmonics.

SUB BASS: Frequencies below the range of typical monitor loudspeakers. Some define sub-bass as frequencies that can be felt rather than heard.

SUBCODE: Hidden data within the CD and DAT format that includes such information as the absolute time location, number of tracks, total running time and so on. 

SURGE: Sudden increase in mains voltage.

SUSTAIN: Part of the ADSR envelope which determines the level to which the sound will settle if a key is held down. Once the key is released, the sound decays at a rate set by the Release parameter. Also refers to a guitar's ability to hold notes which decay very slowly.

SWEET SPOT: The optimum position for a microphone, or for a listener relative to monitor loudspeakers.

SWITCHING POWER SUPPLY: A type of power supply that uses a high frequency oscillator prior to the transformer so that a smaller, lighter transformer may be used. These power supplies are commonly used in computers and some synthesizer modules.

SYNC: A system for making two or more pieces of equipment run in synchronism with each other.

SYNTHESIZER: Electronic musical instrument designed to create a wide range of sounds, both imitative and abstract.