racket A loud distressing noise. [AHD]
rack unit See "U"
radar (radio detecting and ranging) 1. A method of detecting distant objects and determining their position, velocity, or other characteristics by analysis of very high frequency radio waves reflected from their surfaces. 2. The equipment used in such detection. [AHD] Compare with sonar and sodar.
radian 1. Mathematics. A unit of angular measure equal to the angle subtended at the center of a circle by an arc equal in length to the radius of the circle, approximately 57°17'44.6 [AHD] 2. Filters. Frequency is measured in radians/second. One cycle (360°) equals 2π (pi) radians.
radiation error Loudspeakers. All inclusive term describing the total lobing and cancellation error occurring in a loudspeaker response due to crossover and multiple driver effects. An ideal crossover applied between two sources would exhibit no lobing error and no cancellations off axis. [Coined by Justin Baird and David McGrath, Lake Technology, in their paper "Practical Application of Linear Phase Crossovers with Transition Bands Approaching a Brick Wall Response for Optimal Loudspeaker Frequency, Impulse and Polar Response," presented at the 115th Convention of the Audio Engineering Society, New York, NY October 10-13, 2003, Preprint 5885.]
radicalism "The conservatism of tomorrow injected into the affairs of today." -- Ambrose Bierce.
radio The wireless transmission through space of electromagnetic waves in the approximate frequency range from 10 kilohertz to 300,000 megahertz. [AHD]
radio button A graphical user interface style based on old automobile analog radio designs.
Radiolab Broadcast. Popular public radio program that describes itself this way: "Radiolab believes your ears are a portal to another world. Where sound illuminates ideas, and the boundaries blur between science, philosophy, and human experience. Big questions are investigated, tinkered with, and encouraged to grow. Bring your curiosity, and we'll feed it with possibility."
radix Mathematics. The number base, such as 2 in the binary system and 10 in the decimal system. [AHD]
radix point The binary equivalent of the decimal point -- think of it as a "binary point."
Ragone chart A useful way to compare such things as batteries, this chart plots storage device energy density versus power density on a log-log graph with discharge times represented as diagonal lines.
RAID (Redundant Array of Independent Disks) [Originally: Redundant Array of Inexpensive Disks] A technology providing greater storage functions and reliability using redundancy. Hit the link for details. Finding its way into pro audio studio use by such companies as Glyph's Portagig 62.
rail-switcher A term used to describe audio power amplifier designs utilizing more than one power supply for the output, and a means of switching between them based upon the input signal. This scheme improves efficiency. See Class G Amplifiers and compare with tracking power amplifiers.
rail-to-rail® Registered trademark of Nippon Motorola, Ltd. for their op amp designs having maximum input and output levels equal to the power supply voltages. See RRIO.
rainstick Musical Instrument. English translation for the original Chilean instrument called palo de lluvia.
raised cosine filter A low-pass filter found most often in data communication systems. A perfect raised cosine filter is characterized by a frequency response that is symmetrical about 0 Hz, with a flat low frequency passband, then a smooth rolloff following a cosine curve to zero through the transition region and staying at zero (infinite attenuation) throughout the stopband. The response of real world filters (usually DSP FIR designs) approximate this response, with the most noticeable deviation being ripple in the transition region, limiting attenuation to, say, 70 dB, or so, depending on the number of filter taps used. The first known use of this technology in pro audio occurred with a proprietary filter based on raised cosine design used in the Lake Contour™ system.
Randall, Don (1917-2008) American entrepreneur who co-founded Fender in 1946 along with Leo Fender. Beginning in the 1970s he started his own company using the Randall brand.
RaneNotes A series of technical notes written by Rane's technical staff.
Rankine scale A scale of absolute temperature using degrees the same size as those of the Fahrenheit scale, in which the freezing point of water is 491.69° and the boiling point of water is 671.69°. After William John Macquorn Rankine below. [AHD. Sounds handy to me.]
Rankine, William John Macquorn (1820-1872), Scottish engineer and physicist.
RAQ (rarely asked questions) The really important questions that should be asked, but never are. The answers to RAQs are kept hidden within government and corporate walls.
rarefaction 1. A decrease in density and pressure in a medium, such as air, caused by the passage of a sound wave. 2. The region in which this occurs. [AHD]
RASTI (room acoustics speech transmission index) [Originally spelled RaSTI, with lower-case a, which was an acronym for rapid speech transmission index.] A speech intelligibility performance technique developed in 1973 by Dr. Steeneken in Holland, it is simpler than the more complex STI (speech transmission index), however overtime this procedure proved unreliable and was removed as a IEC standard with the 2011 revision to IEC 60268-16. Compare with %ALCONS.
rationalism 1. Reliance on reason as the best guide for belief and action. 2. Philosophy The theory that the exercise of reason, rather than experience, authority, or spiritual revelation, provides the primary basis for knowledge. [AHD] [The optimist says the glass is half full. The pessimist says the glass is half empty. The rationalist says the glass is twice as big as it needs to be.]
rave Music. Unannounced, unadvertised dance party, often illegal, held in an unmarked location, usually a warehouse; spread by word of mouth.
Rayleigh distance Acoustics. "The geometric nearfield of a finite acoustic radiator is the area around the radiator where the sound pressure level does not follow spherical or cylindrical spreading ... The Rayleigh distance D = ka²/2, where k = 2f/c, f is the frequency, c is the sound speed, and a is half the largest dimension, has been used to approximate the size of the geometric nearfield of plane radiators." From Kuntz, Hixson and Ryan, "The Rayleigh distance and geometric nearfield size of nonplane sound radiators," Jour. Acoust. Soc. Amer., Nov., 1983.
Rayleigh, Lord (1842-1919), Third Baron. Title of John William Strutt. British physicist. He won a 1904 Nobel Prize for investigating the density of gases and for discovering argon with Sir William Ramsay.
Rayleigh scattering Physics. The scattering of electromagnetic radiation by particles with dimensions much smaller than the wavelength of the radiation, resulting in angular separation of colors and responsible for the reddish color of sunset and the blue of the sky. [AHD]
R&B See: rhythm & blues.
RC (room criteria) rating A new noise criteria adopted by ASHRAE to replace the NC criteria. The RC rating is based on ASHRAE sponsored studies of preference and requirements for speech privacy ratings for "acoustical quality." RC ratings contain both a numerical value and a letter to describe the expected spectral quality of the sound. The numerical part is called the speech interference level (SIL) equal to the arithmetic average of the measured SPL in the 500 Hz, 1 kHz and 2 kHz octave bands, and the letter part denotes the timbre or sound quality as subjectively described by an observer as neutral (N), rumbly (R), hissy (H) or acoustically induced vibration noise (RV). The RC curves serve as optimum spectrum shapes for background sound in buildings. Octave band analysis that meet a specific RC curve are considered neutrally balanced, i.e., they have the desired amounts of low-, mid- and high-frequency content to be heard as not offensive. RC curves are straight lines set at -5 dB/octave slopes (of course -- couldn't be 6, had to be 5). The RC rating standard is Criteria for Evaluating Room Noise, ANSI S12.2. See Trane's excellent summary "How To Determine The RC Noise Rating," for a step-by-step tutorial.
RCA jack See connectors.
RCDDTM (Registered Communications Distribution Designer) A designation for individuals who demonstrate expertise in the design, integration, and implementation of telecommunications (voice, data, video, audio, and other low-voltage control) transport systems and their related infrastructure components.
RC time constant Electronics. One time constant equals the time required for the output voltage to increase to 63%, or decrease to 37%, of the final value, due to a step input voltage change. This action is fundamentally controlled by a resistor-capacitor pair. [Although not obvious, time (in seconds) equals resistance (in ohms) times capacitance (in farads).]
R-DAT or DAT (rotary head digital audio tape recorder) A digital audio recorder utilizing a magnetic tape cassette system similar to that of a video recorder.
RD-taper See: potentiometer.
REACH (Registration, Evaluation and Authorization of Chemicals) The EU's latest legislation bans additional chemicals from electronic products.
reactive power Same as apparent power.
Reado The name of the first FAX machine, introduced by Crosley Radio in 1940.
real part Mathematics. See: complex number.
real power The total circuit power in watts (resistive load). Contrast with apparent power.
real-time analyzer See RTA.
real-time operation What is perceived to be instantaneous to a user (or more technically, processing that completes in a specific time allotment).
reamplifying Originally this term meant to take an already recorded guitar sound and use it to drive another different sounding guitar amp -- literally reamplifying it as a means of changing the original recorded sound. Now used on any recorded sound with a real amplifier or virtual plug-in.
rearaxial softspeaker Term coined by Electro-Voice for their mythical loudspeaker, the SP13.5TRBXWK. Claimed by many to be the speaker that couldn't be made, it might have changed all future loudspeaker design, but it didn't. Characterized by being undirectional, the designer's claimed it produced silken highs and woolen lows. The only loudspeaker known to incorporate both "presence" and "absence" controls. Based on a ridiculously simple principle that still cannot be explained, the SP13.5TRBXWK was only heard once, during the Rane demo of their PI 14 Pseudoacoustic Infector, coupled by a Jensen JE-EP-ERs Multi-denomial Transpedance Informer to a Crown Belchfire BF-6000SUX amplifier. No one survived.
rebab Musical Instruments. A type of bowed or plucked string instrument indigenous to the Middle East.
Recklinghausen, Daniel von (1925-2011) American engineer and audio inventor who was associated with the AES for over 50 years. Famous for his quote: "If it measures good and sounds bad, it is bad; if it measures bad and sounds good, you've measured the wrong thing." Here is a list of his major engineering contributions while at H. H. Scott.
reconstruction filter A low-pass filter used at the output of digital audio processors (following the DAC) to remove (or at least greatly attenuate) any aliasing products (image spectra present at multiples of the sampling frequency) produced by the use of real-world (non-brickwall) input filters.
recording console See mixer.
recording history See History of Recording.com.
recording terminology See the Recording Institute of Detroit, who claims to have posted the largest glossary of recording terms on the web.
rectifier An electronic component used to convert from alternating current (AC) to direct-current (DC). Works by only conducting current in one direction which allows inversion or suppression of alternate half cycles. Several types exist from early selenium rectifiers to modern semiconductor diodes. See full-wave and half-wave.
rectifying junction See: junction, rectifying.
recursive A data structure that is defined in terms of itself. For example, in mathematics, an expression, such as a polynomial, each term of which is determined by application of a formula to preceding terms. [AHD] Pertaining to a process that is defined or generated in terms of itself, i.e., its immediate past history.
Red Book Nickname for the Philips and Sony's ECMA-130 standard document that defines the format for CD-Audio (compact disc-digital audio) discs; available only to licensees. Compare with Green Book and Yellow Book.
red noise See noise color.
reed Music. 1. A primitive wind instrument made of a hollow reed stalk. 2. a. A flexible strip of cane or metal set into the mouthpiece or air opening of certain instruments to produce tone by vibrating in response to a stream of air. b. An instrument, such as an oboe or clarinet, that is fitted with a reed. [AHD]
reflection Acoustics. Sound that is reflected. See link.
reflection phase grating See: grating.
reflectors In acoustics, an object or surface that reflects, or bounces back the original signal. A perfect reflector would reflect with no loss of energy. A diffuser is a special kind of reflector.
refraction Acoustics. The bending of sound waves caused by entering a medium where the speed of sound is different. See link.
refrigerator There is no "d" in this word -- it is quickly becoming the most misspelled word in the United States.
reggae Music. Jamaican English, ragged clothing. Popular music of Jamaican origin having elements of calypso and rhythm and blues, characterized by a strongly accentuated offbeat. [AHD]
reggaeton Music. A genre of dance music characterized by Entertainment Weekly as "a Spanish-language, pan-American fusion of Stateside hip-hop rhymes, Puerto Rican salsa flourishes, and Jamaican dancehall rhythms." Compare with Jawaiian.
REL (Rights Expression Language) A unified vocabulary for individuals to express copyright law rights.
relay Electronics. An electromechanical device with a coil that when energized creates a magnetic field that either opens or closes metal contacts, for making or breaking electrical connections. Invented by Joseph Henry in 1835.
reluctance Magnetics. A measure of the opposition to magnetic flux, analogous to electric resistance. [AHD]
R.E.M. (Remember Every Moment) Music. Athens, Georgia band formed in 1980 by Michael Stipe, Mike Mills, Bill Berry, and Peter Buck. Upon being inducted into the Rock and Roll Hall of Fame in 2007, Michael Stipe disclosed that the band's name came from a favorite saying of his mother.
remixing DJ Recording. An alternate variation of one or more original song (or video, etc.) compositions created by manipulating the original using various recording techniques to create a new version.
REO Speedwagon Music. American rock group formed in 1967. REO Speedwagon took its name from the Reo Speed-Wagon, a truck manufactured by the REO automobile company. ("REO" are initials the company's founder, Ransom Eli Olds, who also lent his name to the Oldsmobile division of General Motors.)
resistance See impedance.
resistor Electronics. Circuit symbol: R 1. An element within a circuit that has specified resistance value designed to restrict the flow of current. 2. A device with the primary purpose of introducing resistance into an electric circuit. (A resistor as used in electric circuits for purposes of operation, protection, or control, commonly consists of an aggregation of units. Resistors, as commonly supplied, consist of wire, metal, ribbon, cast metal or carbon compounds supported by or embedded in an insulating medium. The insulating medium may enclose and support the resistance material as in the case of the porcelain tube type or the insulation may be provided only at the points of support as in the case of heavy duty ribbon or cast iron grids mounted in metal frames.) [IEEE] See: color-code and standard component values.
resistor standard values See values.
resonance 1. Electronics. In an LRC circuit, it is the condition where the inductive and capacitive reactances are equal; this is called the resonant frequency. 2. Physics. The increase in amplitude of oscillation of an electric or mechanical system exposed to a periodic force whose frequency is equal or very close to the natural undamped frequency of the system. [AHD] A dynamic condition which occurs when any input frequency of vibration coincides with one of the natural frequencies of the structure. That is, the inclination of any mechanical or electrical system to vibrate (resonate) at a certain frequency when excited by an external force, and to keep vibrating after the excitation is removed. 3. Acoustics. Intensification and prolongation of sound, especially of a musical tone, produced by sympathetic vibration. 4. Linguistics. Intensification of vocal tones during articulation, as by the air cavities of the mouth and nasal passages. [AHD]
resonant frequency Electronic Circuits. See above.
resonator guitar Invented by John Dopyera, who founded the Dobro Manufacturing Company with his brothers Rudy, Emile, Robert and Louis, after leaving the National String Instrument Corporation, a company he cofounded.
return loss Category wiring. The ratio of the transmitted signal strength to the reflected signal strength. A characteristic often degraded due to excessive bending of the cable.
reverb Recording. Shortened form of reverberator, or reverberation unit. Any electronic or acoustical device designed to simulate, or capture, the natural reverberation of a large hard-surfaced (echoic) room, and mix it back with the original recorded sound. Reverb today is accomplished by digital devices using complex DSP algorithms; previously done using a chamber, a plate, or springs. See: algorithmic reverb and convolution reverb for DSP techniques..
reverberation The total sound field remaining in a room after the original source is silenced. The length of time of this collapsing sound field is called the reverberation time and is defined below. Contrast with echo and ambience. "Reverberation represents the energy decay process after the initial echoes" [Blesser].
reverberation time also RT60 and more often today as T30 Reverberation is all sound remaining after the source stops. The time it takes for this sound to decay is called the reverberation time, and it is quantified by measuring how long it takes the sound pressure level to decay to one-thousanth of its original value. Since one-thousanth equals a 60 dB reduction, reverberation time is abbreviated "RT60," however since most all acousticians measure the decay time for a 30 dB reduction and then doubles the number to express it as RT60, it is more accurately called T30. Now this is a very simplified definition; for a very thorough discussion see: Averaging RT60 Values for Room-Acoustics by Eric Desart.
reverse mixing Live Sound. A term coined by Rick Chinn of Uneeda Audio who defines it this way: "Reverse Mixing refers to the practice of listening to a mix and NOT raising the level of something that you can't hear sufficiently but instead looking for the source that is masking what you can't hear and bringing its volume down. This is a good strategy to avoid Climbing Fader Syndrome."
RFID (radio frequency identification) Technology using RF signals to ID individuals. It uses silicon chip tags with radio frequency functions and on-board memory that holds unique ID numbers, allowing it to ID and track just about anything.
RF-Lite See ZigBee.
rhonchisonant Imitating the noise of snorting. [Kacirk]
rhythm The only English language word containing two syllables with no natural vowels. [Thanks GS.]
rhythm & blues Abbr. R&B Music. Phrase coined by Jerry Wexler, who would go on to become a famous record producer for Atlantic Records.
RIAA (Recording Industry Association of America) A professional trade organization representing the U.S. recording industry. RIAA® members create, manufacture and/or distribute approximately 90% of all sound recordings produced and sold in the United States.
RIAA equalization curve The standard first proposed by the RIAA (see above) and adopted by the disc recording industry in 1953, reaffirmed in 1964 by both the RIAA and NAB and issued as international standard IEC 60098 (old IEC 98) by the IEC, which remains in effect today. The curve is used in cutting vinyl records and its inverse is required in phono playback preamplifiers. The curve attenuates low frequencies and amplifies high frequencies (relative to a 1 kHz reference point) in order to achieve the maximum dynamic range for a lateral cut vinyl disc (as opposed to the older method of vertical cutting). The grooves in a stereo phonograph disc are cut by a chisel shaped cutting stylus driven by two vibrating systems arranged at right angles to each other. The cutting stylus vibrates mechanically from side to side in accordance with the signal impressed on the cutter. The resultant movement of the groove back and forth about its center is known as groove modulation. The amplitude of this modulation cannot exceed a fixed amount or "cutover" occurs. Cutover, or overmodulation, describes the breaking through the wall of one groove into the wall of the previous groove. Since low frequencies cause wide undulations in the groove, they must be attenuated to prevent overmodulation. At the other end of the audio spectrum, high frequencies must be amplified to overcome the granular nature of the disc surface acting as a noise generator, thus improving signal-to-noise ratio.
ribbon controller (aka pitch ribbon) Synthesizers. A touch-sensitive strip used to vary pitch. The most popular design is a variable resistor shaped into a linear controller where the resistance is continuously variable from one end to another. This form was popularized by Moog synthesizers in the '60s, but early ribbon controllers date back to the late 1920s with models by Hellertion, Ondes-Martenot, and Trautonium.
ribbon microphone Invented in 1923 by Walter Schottky (the same German physicist who invented the famous diode) and Erwin Gerlach of Siemens Halske (German pioneering telegraph company), it is constructed using a very thin metal foil ribbon (~0.002 mm [really] and pleated or corrugated to reduce its longitudinal stiffness, to obtain the lowest resonant frequency so the ribbon is mass-controlled) attached between the poles of a permanent magnet. The acoustic signal (sound pressure variation) causes the ribbon to move and interact with the stationary magnetic field inducing a voltage into the ribbon proportional to the amplitude and frequency of the audio signal.
ribbon tweeter Also invented by Schottky and Gerlach simply by reversing the physical effects of their microphone; it is the inverse of the ribbon microphone described above. It creates a high frequency loudspeaker consisting of a paper-thin metal foil ribbon suspended in a magnetic field (i.e., placed between the poles of a permanent magnet). The audio voltage signal drives the ribbon causing a current to flow creating a magnetic field that reacts with the stationary magnet to create sound proportional to the applied waveform. Very similar in principle to the dynamic loudspeaker, only much smaller, with the ribbon replacing the voice coil and cone arrangement.
Rickenbacker Guitars. Name for the company credited with producing the first commercially available electric guitar in 1931 (ten years before Les Paul's innovations). The company was founded by Adolph Rickenbacker (WWI flying legend Eddie Rickenbacker's cousin) and George D. Beauchamp with the original name being the Electro String Instrument Corporation.
Ricky Guitars. Popular nickname for Rickenbacker guitars (see above) but a term hated by the founder.
Rights Expression Language See REL.
ring it up Phrase coined from the first cash registers that ran a bell for emphasis when the drawer opened, signifying the end of the calculation.
ring modulator Synthesizers. An effects generator with two inputs and one output. The output is the sum and difference frequencies of the two input signals, and does not contain the original signals -- only the sum and difference signals. These signals are harsh and inharmonious. Input signals rich in harmonics such as square, rectangular and sawtooth waves create complex output signals that makes clangor-type, bell-like sounds.
ring out Acoustics. Shorten form of "ring out a room," slang meaning for locating and treating a sound system's resonant and feedback frequencies.
ring-right-red Old mantra from the early telephone days meaning the ring of a telephone jack always connects to the right terminal, and is red. Now used by audio designers and installers to remind that the right channel is always the ring in a 1/4" TRS connector and the red RCA phono jack and cable.
ring topology A network topology where all nodes are daisy chained together (connected) in a closed loop.
RISC (reduced instruction set computer) A computer design that achieves high performance by doing the most common computer operations very quickly, utilizing a high speed processing technology that uses a far simpler set of operating commands. Primarily found in workstations and PowerPCs. The alternative to CISC (complex instruction set computing), the original way of doing computing.
ritardando Music. Gradually slowing in tempo; retarding. Used chiefly as a direction. [AHD]
(Registered Jacks) As in RJ-12 the ubiquitous modular telephone
jack, or RJ-45 the connector and wiring used for connecting Ethernet devices. [Note that the RJ designation specifies both the wiring configuration and the connector. Hit the link for more details.]
RLA (Richard Long Associates) See Long, Richard.
RLB-weighting See: weighting filters.
RMM (Recreational Music Making) Music making just for the fun of it. It is for those who never thought of themselves as musical and just want to learn and play in a fun manner. Recreational Music Making does not compete with traditional music instruction; it is a alternative concept for playing music. [Think a bunch of naked men in the forest beating drums ... hmm ... maybe not.]
rms See root mean square.
rms power No such thing. A misnomer, or application of a wrong name. There is no such thing as "rms power." Average or apparent power is calculated using rms values but that does not equal "rms power;" it equals continuous sine wave power output into a resistive load.
roar Acoustics. Term for noise in the 125 Hz to 500 Hz range. [Things like fans and pumps.]
rock and roll (seen more often as rock 'n' roll)
In 1922, the words "rock" and "roll", which were black slang for sexual intercourse, appear on record for the first time, Trixie Smith's "My Man Rocks Me (With One Steady Roll)". [Rock 'n' roll Timeline 1877-1959] [Note: Alan Freed did not create the phrase, he just applied it to a (then) new music genre.]
rock crusher Accordion. [Decharne]
rock journalism See Zappa, Frank Vincent.
Rogowski coils Electronics. (after Walter Rogowski) A type of current transformer used for measuring alternating current or high-speed current pulses through a conductor.
rolloff rate Filters. The rate at which low-pass, high-pass and bandpass filters attenuate frequencies outside the passband. Expressed in dB/octave, it is a measure of the attenuation slope. Slopes occur in 6 dB/octave increments (due to the natural storage effects of capacitors and inductors), e.g., 12 dB/oct, 18 dB/oct, 24 dB/oct, etc.
ROM (read-only memory) A memory from which data, after initial storage, may only be read out, but new data cannot be written in. The normal audio CD is an example of a read-only system.
room modes or eigentones (from German eigen meaning "self" or "own") Acoustics. The acoustic resonances (or standing waves) in a room (or any enclosed space) caused by parallel surfaces. It is the dimensional resonance of a room, where the distance between the walls equals half the wavelength of the lowest resonant frequency (and resonates at all harmonic frequencies above it). Room modes create uneven sound distribution throughout a room, with alternating louder and quieter spots. See room ratios.
room ratios Acoustics. The ratios of dimensions for a rectanguloid room recommended to ensure a uniform distribution of low-frequency room modes (see above). There are standards (few) and there are disagreements (many). See link for excellent overview and details. A rough summary follows:
root mean square Abbr. rms (lowercase) Mathematics. The square root of the average of the squares of a group of numbers. [AHD] A useful and more meaningful way of averaging a group of numbers.
ro-ro Short for road dog.
rosenfeld A proposed unit defined as electricity savings of 3 billion kilowatt-hours a year, i.e., equivalent to the amount generated by a 500-megawatt coal-fired plant in one year. After Arthur H. Rosenfeld, who is referred to as the godfather of energy efficiency.
Rosie DJ Mixers. First stereo DJ mixer developed by Alex Rosner, named after the designer and for its red paint.
rotary equalizer A multi-band variable equalizer using rotary controls as the amplitude adjustable elements. Both active and passive designs exist with rotary controls. Center frequency and bandwidth are fixed for each band.
router Audio. An audio device used to selectively assign any input to any output, including the ability to add inputs together. In this way, one input could go to all outputs, or all inputs could go to just one output, or any combination thereof. An n x m matrix forms the core of any router, where there are n inputs and m outputs. Typically, level controls are provided on all inputs and outputs; balanced and unbalanced designs exist. More elaborate designs are called matrix-mixers. Networks. Wired or wireless network routers are devices that connect multiple networks. Also see: gateway.
RPM (Remote Programmable Multiprocessor) Rane Corporation's trademark for their line of DSP multiprocessor-based digital audio signal processing devices.
RRIO (rail-to-rail input & output) Term created to indicate op amps with maximum input and output levels equal to the power supply voltages, without violating the registered term rail-to-rail®.
RS (Recommended Standard) As in RS-232 serial interface standard, et al.
RS-232 The standard serial interface (EIA/TIA-232-E)used on most personal computers. A format widely supported for bidirectional data transfer at low to moderate rates. The most common interface method used to connect personal computers with peripheral hardware and instruments. Use is restricted to one peripheral at a time and short distances. The standard originally called for DB-25 connectors, but now allows the smaller DB-9 version.
RS-422 The standard adopted in 1978 by the Electronics Industry Association as EIA-422-A, Electrical characteristics of balanced voltage digital interface circuits. A universal balanced line twisted-pair standard for all long distance (~1000 m, or ~3300 ft) computer interconnections, daisy-chain style. [See NSC AN 759 for RS-422 vs. RS-485 comparison.]
RS-485 The standard describing the electrical characteristics of a balanced interface used as a bus for master/slave operation. Allows up to 32 users to bridge onto the line (as opposed to RS-422's need to daisy chain the interconnections). Same as EIA-485. [See NSC AN 759 for RS-422 vs. RS-485 comparison.]
RS-490 The standard adopted in 1981 by the EIA entitled Standard Test Methods of Measurement for Audio Amplifiers. The power amp testing standard for consumer products.
RT60 See reverberation time.
RTP See: real-time transport protocol.
RU (rack unit) See "U."
ruan Musical Instrument. A Chinese four-stringed round lute that dates back to the Qin Dynasty (221 BC - 206 BC).
rubato Music. Rhythmic flexibility within a phrase or measure; a relaxation of strict time. [AHD]
Rube Goldberg (1883-1970) American cartoonist famous for his contraptions that accomplished something very simple in extremely complicated ways. His name is recognized as an adjective defined as: "Of, relating to, or being a contrivance that brings about by complicated means what apparently could have been accomplished simply." [AHD]
rubidium A soft silvery-white metallic element of the alkali group that ignites spontaneously in air and reacts violently with water, used in photocells and in the manufacture of vacuum tubes. [AHD] Used in pro audio applications to create the most precise and stable atomic audio clocks for recording studios. See for example Stanford Research Systems Perfection 10.
rumba shakers See: maraca.
rumble Acoustics. Term for noise in the 31.5 Hz to 125 Hz range. [Air turbulence, for example.] Phonographs. A quantitative measure of phonograph turntable noise and vibration resulting from performance imperfections. The rms voltage is measured at the cartridge while playing a blank (silence) record, and the answer expressed in dB below a reference point.
rumble filter See infrasonic filter.
ruthenium Chemistry. Symbol Ru A hard silver-gray acid-resistant metallic element that is found in platinum ores and is used to harden platinum and palladium for jewelry and in alloys for nonmagnetic wear-resistant instrument pivots and electrical contacts. Atomic number 44; atomic weight 101.07; melting point 2,310°C; boiling point 3,900°C; specific gravity 12.41; valence 0, 1, 2, 3, 4, 5, 6, 7, 8. [AHD] In audio world it is found in the Ultrasone Edition 8 headphones used as a coating on the outer ear cups.
RYTMO (Reaching Youth Through Music Opportunities) "An after school music program designed to provide a positive, creative and professional environment for underserved youth who demonstrate musical, technical and/or business potential in the arts."