Now looking at definitions starting with letter "r"
R-DAT : Rotary-head Digital Audio Tape: A standard for digital audio tape recording which employs a rotating head mechanism similar to that of video recorders. Two channels of 16-bit digital audio information, plus subcode and track information, can be recorded onto a tape ap-proximately 3mm wide, traveling at a very low speed of about 50 cpm. The tape is housed in a case similar to a video cassette, though much smaller. R-DAT machines offer three sampling rates: 32kHz, 44.1kHz, and 48kHz. Maximum continuous record time for a cassette is two hours at standard play and four hours at long play, with reduced quality. See also DAT.
rack : A type of shelving, usually with enclosed sides and back, to which audio components can be attached vertically, one on top of the other. Components are normally screwed into front-mounted, tapped metal strips with holes which are spaced so as to accommodate the height of devices of various U-sizes. Racks are usually 19" wide and have their height denominated in U-units.
radiation impedance : The acoustic impedance that acts as a load on a loudspeaker, opposing the motion of the cone.
radiation pattern : (1) The polar pattern that graphs a loudspeaker’s directional characteristics for a group of specific test frequencies. (2) The three-dimensional graph of the intensity with which any sound source emits various frequencies at all angles around itself.
radio frequency (RF) : An alternating AC current or voltage having a frequency above about 100kHz, so-called because these frequencies are radiated as electro-magnetic waves by radio and television, and as high as 30 GHz (30,000 MHz). The constant frequency of the carrier wave (the frequency which you tune into) falls within this range. This is then modulated by the audio (or other) signal, according to some process such as AM or FM.
radio microphone : A mic with a built-in RF transmitter used instead of a cable connection to give a performer increased mobility. A receiver system picks up the transmitted signal for distribution to a PA, etc.
Radio Monitor : radio reception when tape is set for fast-forward or rewind.
RAID Redundant Array of Inexpensive Disks. RAID is when you take a bunch of hard drives and run them either in parallel or arranged so that your data is spread across them with duplicate (redundant) information that lets the system reconstruct all the data if any of drives fails.
ramp wave : See sawtooth wave.
random access : Storage systems where data may be stored and accessed in any order, independent of the ordinal position of the data when it was originally recorded. This is the opposite of linear (3) access, or linear recording media such as magnetic tape which necessarily preserves the sequential relation of the data as it is recorded, and depends on this sequential relation for accurate playback. See non-linear recording.
random noise : Sound where there is no predictable relationship between the frequency or amplitude of the waveform over time. See white noise, pink noise.
rarefaction : The spreading apart of air molecules which lowers the local air pressure, during the second half of each complete cycle of a sound wave. This corresponds to the portion of the wave that appears below the x-axis when graphed. The opposite of compression.
raster : The characteristic patterns of horizontal lines formed by the scanning beam of the TV picture tube. Also, the actual electronic circuit that creates the scanning spot that traces these lines on the TV screen.
rate : In a digital delay or flanger, a circuit and control that enable varying of the length of time during which the depth circuit completes one full increase or decrease cycle of the nominal delay time. To the ear, the rate control varies the speed of the apparent vibrato added to the input signal by the depth circuitry.
rate control : An envelope parameter which controls the rate or timing of certain synthesizer actions, such as the attack, decay and release portions of an ADSR envelope. Compare with level cl control.
rated bandwidth : The frequency range, normally 20Hz-2kHz, over which the performance of an audio device is rated with respect to specification rated characteristics such as power output bandwidth, harmonic dc distortion, etc.
rated load : The load impedance into which a power amplifier or loudspeaker is designed to operate safely, and upon which other rated characteristics are based. See power bandwidth.
RCA Radio Corporation of America. Used with most consumer audio gear, developed by RCA. Commonly used for unbalanced line-level connections of with coaxial cable for S/PDIF connections. ("Phono-connector" in Dilettante’s Dictionary)
RCA connector : See phono connector.
RDS : Radio Data System: traffic information system on fm radio. RDS shows station name display (PI/PS) and delivers traffic bulletins (TP/TA). Also locks onto best possible frequency for a station in a particular part of the country (AF). Can display time and date on receiver (CT). Sets with PTY (Program Type) will automatically tune into a station broadcasting pop, classical, News etc.
re-laying : To post-stripe a video master tape, recording the mixed film soundtrack back onto the tape after it has been striped for post-dubbing or the addition of narration, music, and/or effects. See layback recorder.
re-recording : The process of mixing all edited DME stems, sync and non-sync, of a film or video production to mono, stereo, multichannel or whatever audio format is desired for the final print master with the picture, also known as dubbing. Usually done at a re-recording stage.
re-recording stage : The facility where re-recording is done. Contrary to what one might think, there is rarely a stage/platform/dais involved. See dubbing theater.
reach : The clear pick-up of quiet, distant sounds by a microphone due to a high S/N ratio. See self-noise. The higher the SPL of the sound source at the mic, the higher the S/N ratio. Given an SPL of 94dB, a S/N spec of 74dB is excellent, 64dB is good. The higher the S/N ratio, the cleaner (more noise-free) is the signal, and the greater the reach of the microphone.
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