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70 volt line See constant-voltage.

SAA (semantic audio analysis) The automatic extraction of meaning from audio and the means for representing it, typically as metadata.

sabin A non-metric unit of sound absorption used in acoustical engineering. One sabin is the sound absorption of one square foot (or one square meter -- a metric sabin) of a perfectly absorbing surface--such as an open window. The sound absorption of a wall or some other surface is the area of the surface, in square feet, multiplied by a coefficient that depends on the material of the surface and on the frequency of the sound. These coefficients are carefully measured and tabulated. The unit honors Wallace Sabine (see below). Sabine used this unit, which he called the open window unit (owu), as early as 1911. [From Rowlett's How Many? A Dictionary of Units of Measurement]

Sabine, Wallace Clement Ware (1868-1919) American physicist and Harvard University professor who founded the systematic study of acoustics around 1895. Regarded as the father of the science of architectural acoustics.

SAC (sound absorption coefficient) See: absorption.

SACD® (Super Audio CD®) Also known as DSD® or Direct Stream Digital®, joint trademark of Sony and Philips for their proposal for the next generation CD-standard. Sony and Philips have split from the DVD ranks to jointly propose their own solution comprised of a 1-bit, 64-times oversampled direct-stream digital SACD format. The original SACD proposal was for a hybrid disc comprising two layers: a high density (HD) DSD layer in the middle, and a standard density CD layer at the bottom. The two layers are read from the same side of the disc; the CD laser reads the bottom reflective layer through the semi-transmissive HD layer, while the middle layer is read by the HD laser delivering high-quality, multichannel sound without sacrificing backward compatibility. The HD layer has three tracks: the innermost is for two-channel stereo; the middle is a six-channel mix; and the outer is for such additional information as liner notes, still images and video clips. Maximum playing time is 74 minutes. This proposal turned out to be too expensive, so the SACD first release is a single-layer SACD-only disc.

SAE (Society of Automotive Engineers) The international trade organization comprised of 80,000 engineers, business executives, educators, and students representing 100 countries that functions as the resource for technical information and expertise used in designing, building, maintaining, and operating self-propelled vehicles for use on land or sea, in air or space.

SAMPA (speech assessment methods phonetic alphabet) A computer-readable phonetic script using 7-bit printable ASCII characters based on the IPA.

sample rate conversion The process of converting one sample rate to another, e.g. 44.1 kHz to 48 kHz. Necessary for the communication and synchronization of dissimilar digital audio devices, e.g., digital tape machines to CD mastering machines.

sample-and-hold (S/H) A circuit that captures and holds an analog signal for a finite period. The input S/H proceeds the A/D converter, allowing time for conversion. The output S/H follows the D/A converter, smoothing glitches.

Sampling (Nyquist) Theorem A theorem stating that a bandlimited continuous waveform may be represented by a series of discrete samples if the sampling frequency is at least twice the highest frequency contained in the waveform. See the RaneNote Digital Dharma of Audio A/D Converters.

sampling frequency or sampling rate The frequency or rate at which an analog signal is sampled or converted into digital data. Expressed in Hertz (cycles per second). For example, compact disc sampling rate is 44,100 samples per second or 44.1 kHz, however in pro audio other rates exist: common examples being 32 kHz, 48 kHz, and 50 kHz.

[Historical note re 44.1 kHz vs. 44.056 kHz: Since the first commercial digital audio recorders used a standard helical scan video recorder for storage, there had to be a fixed relationship between sampling frequency and horizontal video frequency, so these frequencies could be derived from the same master clock by frequency division. For the NTSC 525-line TV system, a sampling frequency of 44,055.94 Hz was selected, whereas for the PAL 625-line system, a frequency of 44,100 Hz was chosen. The 0.1% difference shows up as an imperceptible pitch shift.] See the RaneNote Digital Dharma of Audio A/D Converters.

sampling The process of representing the amplitude of a signal at a particular point in time.

SAN (storage area network) A network connecting host computers to storage servers and systems. SAN technology allows high-speed connection of multiple workstations to a centralized hard-disk network (via fiber optics interconnection), allowing each workstation to access any drive from any location (e.g., control rooms in DAW recording studios).

sanxian Musical Instrument. Chinese 3-string fretless lute.

SAR (successive approximation register) A type of analog-to-digital converter using a digital-to-analog converter to determine the output word successively, bit by bit.

saser (sound amplification by stimulated emission of radiation) The ultrasonic acoustic version of a laser operating in the megahertz to terahertz range. Also see: Hail the sound "lasers."

SAVVI (Sound, Audio Visual, and Video Integrators Council) One of ICIA's councils that focuses on the needs and interests of companies that install and integrate AV systems, and seeks to identify best practices.

sawtooth wave A periodic waveform characterized by a 50% duty cycle and a Fourier series consisting of both even- and odd-ordered, equal phase, sinusoidal harmonic components of its fundamental frequency. The amplitudes (coefficients multiplying the magnitude of the fundamental sine wave) of the odd-ordered harmonics are the same as a square wave, while the amplitudes (re the fundamental) for the even-ordered harmonics are -1/n, where n is the even harmonic number. Therefore the first few even harmonic multipliers are -1/2, -1/4, -1/6, ... etc., and the first few odd harmonic multipliers are 1/3, 1/5, 1/7, ... etc.

Sax, Adolphe (1814-1894) Belgian musical instrument designer and inventor of the saxophone.

SBR (spectral band replication) Audio Compression. An audio coding technology invented by Coding Technologies.

scat Jazz singing using sounds instead of words. A scat singer is defined by Down Beat's Yearbook of Swing, 1939 as a "vocalist who sings rhythmically, but without using accepted English words." [Decharne]

Schmitt, Otto Herbert (1913-1998) American scientist most noted for his inventing the Schmitt trigger, the differential amplifier and the cathode-coupled amplifier. Also see the IEEE tribute here.

Schmitt trigger Electronics. A solid state element that produces an output when the input exceeds a specified turn-on level, and whose output continues until the input falls below a specified turn-off level. [IEEE] The on and off levels have different values, making this a comparator with hysteresis. Invented by Otto Herbert Schmitt in 1934 while still a graduate student, he named it a "thermionic trigger" and didn't get it written up until he published it in 1938 [Otto H. Schmitt, "A Thermionic Trigger," Journal of Scientific Instruments 15 (January 1938): 24-26. A useful but highly technical review of the Schmitt trigger can be found in Bryan Hart, "Picturing Schmitt's Trigger," Electronics World (December 1999): 1040-1046.

Schottky, Walter (1886-1976) German physicist whose work in solid-state physics and electronics resulted in many inventions that bear his name (Schottky effect, Schottky barrier, Schottky diode). He also invented the tetrode and (with Erwin Gerlach) the ribbon microphone and ribbon tweeter.

Schottky noise See: shot noise.

Schroeder diffuser See diffuser.

Schroeder, Manfred R. (1926-2009) German physicist best known in the pro audio world for inventing the acoustic diffuser.

science My favorite example of a common word that violates the "i before e except after c" rule.

SCIN (shield current induced noise) Interconnection Wiring. The term coined by Neil Muncy in 1994 to describe the non-uniform magnetic coupling of shield current in balanced audio cables to the two signal conductors.

SCMS (pronounced "scums") (serial copy management system) The copy protection scheme applied to consumer digital recording equipment -- it does not apply to professional machines. This standard allows unlimited analog-to-digital copies, but only one digital-to-digital copy. This is done by two control bits (the C and L bits) contained within the digital audio data.

Scott, H. H. See: Homer Hosmer Scott.

SCR (silicon controlled rectifier) See: thyristor.

scrap flutter (also called frequency-modulation (friction) noise) Electronics. Frequency modulation of the signal in the range above approximately 100 Hz resulting in distortion which may be perceived as a noise added to the signal (that is, a noise not present in the absence of a signal). [IEEE]

scratching Hip Hop. A turntablist technique originated by Grand Wizzard Theodore developed from Grandmaster Flash.

screech analysis Serious but fun analysis done by MC2 System Design Group. [Check it out; you won't be disappointed.]

screeched Often cited as the longest one-syllable word in the English language, however scratched, scrounged, scrunched, stretched, and the plural nouns straights and strengths (all with nine letters) qualify.

screen Electronics. Alternate term used to mean the same as shield.

scribble strip Mixing Consoles. The location used to identify each input and output of a mixing console. Often a plastic strip that can be labeled with a dry marker and erased and used again, or where temporary tape is applied, removed and new tape applied for the next performance. .

scrim Theater. A transparent fabric used as a drop in the theater to create special effects of lights or atmosphere. [AHD]

scrum (Abbreviation of scrummage.)  Software Engineering. A framework for management of software development projects. [In Rugby, a scrum refers to the manner of restarting the game after a minor infraction.] 1. Sports a. A play in Rugby in which the two sets of forwards mass together around the ball and, with their heads down, struggle to gain possession of the ball. b. The mass or formation of players during such a play. 2. Chiefly British A disordered or confused situation involving a number of people. [AHD]

SCSI port (pronounced "scuzzy") (small computer system interface) A standard 8-bit parallel interface used to connect up to seven peripherals, such as connecting a CD-ROM player or document scanner to a microcomputer.

SD (super density compact disc) See DVD

SDDS® (Sony Dynamic Digital Sound) Sony's competing format for the digital soundtrack system for motion picture playback. The signal is optically printed outside the sprocket holes, along both sides of the print. Sony recently developed a single camera system that records all three digital formats (Dolby Digital, DTS & SDDS) on a single inventory print, thus setting the stage for long term coexistence of all formats.

SDIF (Sony digital interface format) Sony's professional digital audio interface utilizing two BNC-type connectors, one for each audio channel, and a separate BNC-type connector for word synchronization, common to both channels. All interconnection is done using unbalanced 75 ohm coaxial cable of the exact same length (to preserve synchronization), and is not intended for long distances.

SDK (software development kit) Computer Software. A programming set-of-rules that enables development of applications for existing program families or platforms.

SDMI (Secure Digital Music Initiative) A multi-industry group defining a specification to protect digital music distribution.

s-domain Mathematics. The Laplace domain for continuous time systems. Contrast with Z-domain.

SDR (software-defined radio) Take an antenna, plug it directly into an ADC, add DSP, software, and—voilà!—a radio. Click the link for details.

sea organ Musical Instrument. A 230-foot-long organ built into a stone staircase on the shores of Croatia. Located below its steps are 35 tubes with whistle openings that produce sounds when waves push air through the structure.

Seattle sound See grunge.

second (time) Abbr. s also sec A unit of time equal to one sixtieth of an minute (time). Technically defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. [I told you it was technical.]

second (plane angle) Abbr. " A unit of angular measurement equal to one sixtieth of a minute (plane angle).

second-order filter Electronics. An electronic filter described by a transfer function having quadratic equations in the numerator and denominator.

SED (Surface-conduction Electron-emitting Display) Video display technology. Proprietary flat-panel, high-resolution display technology jointly developed by Canon and Toshiba, characterized by low power consumption and a very high quality image comparable to CRT.

Seeger, Pete (1919-2014) American folk music legend who influenced several generations of admirers.

segue Music. To make a transition directly from one section or theme to another. [AHD]

seismic noise Geology. Small vibrations usually thought of as noise are now being used to gather new information about the Earth's crust. Examples include ocean waves crashing on the beach and storms passing by causing small changes in air pressure.

self-noise Microphones. Residual noise, or the inherent noise level of a microphone when no signal is present. Microphone inherent self-noise is usually specified as the equivalent SPL level which would give the same output voltage, with typical values being 15-20 dB SPL.

Sel-Sync™ (Selective Synchronous) Recording. Ampex trademark for their revolutionary 8-track recorder developed in 1955 for Les Paul by Ampex engineer Mort Fujii. Interestingly, upon advice of their attorney, Ampex did not apply for a patent.

SEMA (Specialty Equipment Market Association) An organization for the producers and marketers of specialty equipment products and services for the automotive aftermarket. Today's group grew out of the original SEMA started in 1963, known then as the "Speed Equipment Manufacturers Association" and includes aftermarket audio manufacturers.

semantics 1. Linguistics The study or science of meaning in language. 2. Linguistics The study of relationships between signs and symbols and what they represent. Also called semasiology. 3. The meaning or the interpretation of a word, sentence, or other language form: We're basically agreed; let's not quibble over semantics. [AHD]

semicolon Half of a large intestine.

semitone Music. An interval equal to a half tone in the standard diatonic scale. Also called half-step, half-tone. [AHD] Contrast with whole tone.

Sennheiser, Fritz (1912-2010) German PhD engineer who founded Sennheiser in the late '40s, in post-war Germany.

sensitivity 1. Audio electromechanics. The standard way to rate audio devices like microphones, headphones and loudspeakers. A standard input value is applied and the resultant output is measured and stated.

  • loudspeaker sensitivity The standard is to apply one watt and measure the sound pressure level (SPL) at a distance of one meter. [IEC 60268-5]
  • headphone sensitivity The standard is to apply one milliwatt and then measure the sound pressure level at the earpiece (using a dummy head with built-in microphones). [IEC 60268-7].
  • microphone sensitivity The standard is to apply a 1 kHz sound source equal to 94 dB- SPL (one pascal) and then measure the output level and express it in mV/PA (millivolts per pascal). [IEC 60268-4]

    2. Audio electronics. The minimum input signal required to produce a standard output level.

  • power amplifier sensitivity The input level required to produce one watt output into a specified load impedance, usually 4 or 8 ohms. [EIA-490]
  • radio receiver sensitivity The input level required to produce a specified signal-to-noise ratio.

sensory inhibition See Haas Effect.

separation mastering Recording. A specific group of tracks used in mastering, e.g., drums, bass, vocals, etc. Compare with stems, which are individual tracks instead of a group of tracks.

serial interface A connection which allows transmission of only one bit at a time. An example in the PC world is a RS-232 port, primarily used for modems and mice. A serial interface transmits each bit in a word in sequence over one communication link. See also parallel interface.

serializer A parallel-to-serial data converter; used in buses and networks.

series circuit Electronics Circuits. The connection of components such that the same current passes through each device in completing its path to the source of supply. For example series connection of a battery is made by connecting the positive terminal of each successive cell to the negative terminal of the next adjacent cell so that their voltage are additive. [IEEE]

series-mode surge suppression AC Power. Operates by storing the surge energy in a resonant circuit and slowly discharging it back into the power line. Claimed to overcome shunt-mode surge suppression shortcomings, specifically those of finite lifetimes, degrading with time and coupling noise into the ground system.

server A shared master computer on a local area network (LAN) used to store files and distribute them to clients upon demand.

servo-loop; servo-locked loop; servo-mechanism A self-regulating feedback system or mechanism. Typically a feedback system consisting of a sensing element, an amplifier, and a (servo)motor, used in the automatic control of a mechanical device (such as a loudspeaker). In audio, usually the name applies to a class of electronic control circuits comprised of an amplifier and a feedback path from the output signal that is compared with a reference signal. This topology creates an error signal that is the difference between the reference and the output signal. The error signal causes the output to do whatever is necessary to reduce the error to zero. A loudspeaker system with motional feedback is such a system. A sensor is attached to the speaker cone and provides a feedback signal that is compared against the driving signal to create more accurate control of the loudspeaker. Another example is Rane's servo-locked limiter™ which is an audio peak limiter circuit where the output is compared against a reference signal (the threshold setting) creating an error signal that reduces the gain of the circuit until the error is zero.

servo-locked limiter™ Rane Corporation trademark for their proprietary limiter circuit. See servo-loop.

sesquipedalian n. A long word. adj. 1. Given to or characterized by the use of long words. 2. Long and ponderous; polysyllabic. [I am not.]

SET (single-electron transistor) Solid-state Physics. A working transistor built around a single electron. One application is the quantum microphone.

SFCS (swept frequency capacitive sensing) See: Touché.

SFDR (spurious free dynamic range) A testing method used in quantifying high-speed data converters and high-frequency communication integrated circuits. It is the difference in dB between the desired output signal and any undesired harmonics found in the output spectrum. See Intersil Application Note TB326 for measuring details.

SFG See Shepard function generator.

Shannon, Claude E. (1916-2001) American mathematician and physicist who is credited as the father of information theory (For the mathematically advanced, see his famous paper, "A Mathematical Theory of Communication" published in 1948 in The Bell). In his master's thesis Shannon showed how an algebra invented by the British mathematician, George Boole in the mid-1800s could represent the workings of switches and relays in electronic circuits. His paper has been called "possibly the most important master's thesis in the century." See the RaneNote Digital Dharma of Audio A/D Converters.

shaped triangular See TPDF.

Shearer Horn Loudspeaker. After inventor Douglas Shearer, a huge two-way system that marked the beginning of modern sound systems and found instant fame in motion picture theaters. It received a technical Academy Award in 1936.

sheath See jacket.

shelving response Term used to describe a flat (or shelf) end-band shape when applied to program equalization. Also known as bass and treble tone control responses.

sheng Musical Instrument. A Chinese mouth organ.

Shepard function generator (aka barberpole tone, also Shepard's tone) Synthesizers. A circuit that produces a continuously ascending or descending tone. Named after American psychologist Roger Newland Shepard, who wrote a paper in 1964 describing his cognitive experiments using this technique ["Circularity in Judgments of Relative Pitch," J. Acous. Soc., vol. 36, no. 12, 1964, pp. 2346-2353].

shepherd's pipe Musical Instrument. A miniature bagpipe.

SHF See frequency bands.

shield Electronics. 1. A structure or arrangement of metal plates or mesh designed to protect a piece of electronic equipment from electrostatic or magnetic interference. [AHD] 2. As normally applied to instrumentation cables, refers to the metallic sheath (usually copper or aluminum), applied over the insulation of a conductor or conductors for the purpose of providing means for reducing electrostatic coupling between the conductors so shielded and others which may be susceptible to or which may be generating unwanted (noise) electrostatic fields.

shielding, proper See Steve Macatee's Considerations in Grounding and Shielding and the RaneNote Sound System Interconnection.

shofar Musical Instrument. A trumpet made of a ram's horn, blown by the ancient Hebrews during religious ceremonies and as a signal in battle, now sounded in the synagogue during Rosh Hashanah and at the end of Yom Kippur. [AHD]

short circuit Electronics. The condition where two or more nodes are directly connected together, resulting in zero voltage between the nodes.

shotgun microphone See: microphone polar response.

shot noise Solid-state physics. Noise caused by current fluctuations due to the discrete nature of charge carriers and random or unpredictable (or both) nature of charged particles from an emitter. [IEEE] Also called Schottky noise.

ShotSpotter®  Acoustics. Leaders in gunshot and explosion detection and location. [Amazing technology.]

show control See MIDI show control.

shunt-mode surge suppression AC Power. Technology which shorts surge currents to ground using MOVs and other TVS devices.

SI (International System of Units) The International System of Units, universally abbreviated SI (from the French Le Système International d'Unités), is the modern metric system of measurement. SI is the dominant measurement system not only in science, but also in international commerce. See Barry N. Taylor's Guide for the Use of the International System of Units (SI). This free 86 page document is the definitive source of SI info.

SIAP (System for Improved Acoustic PerformanceAn EAE system developed by this Netherlands company.

sibilant Linguistics. adj. Of, characterized by, or producing a hissing sound like that of (s) or (sh): the sibilant consonants; a sibilant bird call. A sibilant speech sound, such as English (s), (sh), (z), or (zh). [AHD]

SiC (silicon carbide) Semiconductor. The chemical formula for carborundum, a compound of silicon and carbon. Among its many uses is making high-voltage, high-temperature transistors, gaining popularity in Class D power amplifier designs. SiC transistors were first developed by Westinghouse in 1961.

SID (slew-induced distortion) See DIM/TIM.

side-chain In a signal processing circuit, such as one employing a VCA, a secondary signal path in parallel with the main signal path in which the condition or parameter of an audio signal that will cause a processor to begin working is sensed or detected. Typical applications use the side-chain information to control the gain of a VCA. The circuit may detect level or frequency or both. Devices utilizing side-chains for control generally fall into the classification of dynamic controllers.

sidetone Telephony. The feature of a telephone handset that allows you to hear yourself talk, acting as feedback that the phone is really working. Sidetones are actually short line echoes bled back into the earpiece. Too much sidetone sounds like an echo and too little sounds so quiet that people think the phone is broken. Sidetones are good for people but can cause acoustic feedback in teleconferencing systems if not treated properly.

siemens Abbr. S A unit of electrical conductance in the International System, equal to one ampere per volt. [After Siemens, Ernst Werner von.]

Siemens, Ernst Werner von (1816-1892) German engineer who made notable improvements to telegraphic and electrical apparatus, and founded the company, Siemens. He patented the first loudspeaker in 1877. His brother Karl Wilhelm, later Sir Charles William Siemens (1823-1883), invented a regenerative steam engine and designed a steamship for laying long-distance cables. [AHD]

sigma-delta See delta-sigma modulation.

signal ground The common electrical reference point of a circuit, usually separate from the chassis ground but tied together at the power supply. See the RaneNote Sound System Interconnection.

signal levels Audio signal levels: see levels.

signal present indicator or SIG PRES An indicator found on pro audio signal processing units that lights once the input signal level exceeds a preset point. There is no standard specifying when a SIG PRES light should illuminate, although common practice makes it -20 dBu (77.5 mV), or the pro audio de facto standard line-level of +4 dBu (1.23 volts).

signal-to-noise ratio See S/N.

sihu Musical Instrument. Chinese 4-string huqin.

SIL (speech interference level) The numerical part of the RC noise rating.

silence Meaning without sound, yet "The Sound of Silence," was a mega hit for Simon and Garfunkel -- no zen intended. But the most interesting story about silence is told by David Lister in his article "Big noises at odds over the sound of silence," reproduced here:

'The Sound of Silence' may have prompted engaging harmonies from Simon and Garfunkel -- but a more literal appreciation of the absence of noise has prompted one of the more curious copyright disputes of modern times.

Mike Batt, the man behind the Wombles and Vanessa Mae, has put a silent 60-second track on the album of his latest classical chart-topping protégés, the Planets. This has enraged representatives of the avant-garde, experimentalist composer John Cage, who died in 1992. The silence on his group's album clearly sounds uncannily like 4'33", the silence composed by Cage in his prime.

Batt said last night: "I've received a letter on behalf of John Cage's music publishers. I was in hysterics when I read their letter.

"As my mother said when I told her, 'which part of the silence are they claiming you nicked?'. They say they are claiming copyright on a piece of mine called 'One Minute's Silence' on the Planets' album, which I credit Batt/Cage just for a laugh. But my silence is original silence, not a quotation from his silence."

silent disco Term coined by the organizers for Britain's famed Glastonbury music festival, where to meet noise restriction requirements everyone was given wireless headphones for listening and wearing while dancing. Apparently it is quite a sight to see all these wriggling bodies synchronized to silence.

silicon carbide See: SiC.

Silicon Dust™ Nickname for microchips. Trademarked name first coined by National Semiconductor to describe the world's smallest op amp (as of May 5, 1999), the LMV921. Used in surface mount technology (SMT), they are about the size of a single letter on this page.

silver One of the English language words without a rhyme -- others are "month," "orange" & "purple."

simplex power Old telephone term for phantom power.

SIN (signal induced noise) Tongue-in-cheek term created by John K. Chester for cable shield induced noise found when the analog audio cable shield is grounded at one end only.

SINAD (pronounced "sin-add") or S/N+D (signal-to-noise and distortion) Acronym for the ratio: (signal + noise + distortion) / (noise + distortion).

Or, as Metzler explains, it is the reciprocal of THD+N stated in decibels (dB). Originally developed for measuring FM receivers, it now also appears on A/D data sheets. Generally, the term "SINAD" is favored by the communication industry, while the audio industry used "S/N+D," but they both mean the same thing. It is the preferred way to specify the dynamic range, or maximum S/N, since the noise and distortion products are measured in the presence of a signal. (A signal is applied to the input, the output is passed through a notch filter to remove the signal and what remains is measured. Then the ratio of the rms value of the measured output signal to the rms value of everything else coming out [i.e., noise + distortion] is expressed in decibels.) This gives a more accurate picture of real dynamic performance. Sometimes the measurement is stated for three reference levels of 0 dBFS, -20 dBFS, and -60 dBFS.

sinc function Mathematics. The unnormalized definition is sin (x)/x; normalizing adds pi to each x-term. In pro audio it is used in aliasing to design sinc filters.

sine Abbr. sin Mathematics. 1. The ordinate of the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from the point (1, 0) if x is positive or clockwise if x is negative. 2. In a right triangle, the ratio of the length of the side opposite an acute angle to the length of the hypotenuse. [AHD]

sine curve Mathematics. The graph of the equation y = sin x. Also called sinusoid. [AHD]

sine wave Physics. A waveform with deviation that can be graphically expressed as the sine curve. [AHD]

sine wave speech A term coined by psychologists Robert Remez and David Pisoni to describe their experiment consisting of synthesizing three simultaneous wavering sine wave tones. The sound was nothing like speech, yet participants could hear words thus suggesting that the brain can hear speech content in sounds that do not even resemble speech. [Pinker]

sinusoid Mathematics. See sine curve.

sitar Musical Instrument. A stringed instrument of India made of seasoned gourds and teak and having a track of 20 movable frets with 6 or 7 metal playing strings above and usually 13 sympathetic resonating strings below. [AHD]

sitzprobe Musical Theater. The first rehearsal of a performance where the singers and orchestra perform together.

Six Sigma Abbr. 6s and 6 Sigma In 1986, Bill Smith, a senior engineer and scientist at Motorola, introduced the concept of Six Sigma (a registered trademark of Motorola, Inc.) to standardize the way defects are counted. Simply put, it is a statistical methodology for improving quality control. The Greek letter "sigma" is used in statistics to represent one standard deviation. This measures how far a given process deviates from perfection. Six sigma refers to six standard deviations, which equals 99.99985% of the total (1.5 defects per million). The central idea behind Six Sigma is that if you can measure how many defects you have in a process, you can systematically figure out how to eliminate them and get as close to zero defects as possible. However, today six sigma methods foster a huge business in and of itself.

ska Music. Popular music originating in Jamaica in the 1960s, having elements of rhythm and blues, jazz, and calypso and marked by a fast tempo and a strongly accented offbeat. [From the phrase (Love) Ska (voovie), greeting used by Jamaican bassist Cluet Johnson, one of the early creators of ska, or imitative of the sound of a guitar in tandem with a rim click on a snare drum.] [AHD

skin effect 1. Electrical cable. The tendency of high frequency (RF and higher) current to be concentrated at the surface of the conductor. [Long answer: Electrical current seeks the path of lowest impedance, which for low frequencies equals the path of least resistance. This means that at DC and low frequencies the current fills the entire conductor. However for higher frequencies above a few MHz the path of lowest impedance becomes the path of least inductance. The magnetic fields created by AC signals are strongest at the center of the conductor. This produces a higher inductance at the center than on the surface. Therefore the current bunches on the surface or 'skin' of the conductor. ] 2. Induction heating. Tendency of an alternating current to concentrate in the areas of lowest impedance.

slack-key Music. Of or being a style of Hawaiian popular music played by fingerpicking an acoustic guitar that has been tuned to any of various open chords. [AHD]

slapback See slap echo below.

slap echo also called slapback 1. Acoustics. A single echo resulting from parallel non-absorbing (i.e., reflective) walls, characterized by lots of high frequency content. So-called because you can test for slap echo by sharply clapping your hands and listening for the characteristic sound of the echo in the mid-range. Slap echo smears a stereo sound field by destroying the critical phase relationships necessary to form an accurate sound stage. 2. Recording. Devices that simulate slap echo are popular in recording. One distinct repeat echo is added to an instrument sound resulting in a very live sound similar to what you would hear in an auditorium.

slew rate 1. The term used to define the maximum rate of change of an amplifier's output voltage with respect to its input voltage. In essence, slew rate is a measure of an amplifier's ability to follow its input signal. It is measured by applying a large amplitude step function (a signal starting at 0 volts and "instantaneously" jumping to some large level [without overshoot or ringing], creating a step-like look on an oscilloscope) to the amplifier under test and measuring the slope of the output waveform. For a "perfect" step input (i.e., one with a rise time at least 100 times faster than the amplifier under test), the output will not be vertical; it will exhibit a pronounced slope. The slope is caused by the amplifier having a finite amount of current available to charge and discharge its internal compensation capacitor. 2. Mathematics. Slew rate is defined to be the maximum derivative of the output voltage with respect to time. That is, it is a measure of the worst case delta change of voltage over a delta change in time, or the rate-of-change of the voltage vs. time. For sinusoidal signals (audio), this equals 2 pi times the maximum frequency, times the maximum peak output voltage: SR = (2 pi) (Fmax) (Vpeak).

SLS (scalable lossless coding) Popular name for the MPEG-4 standard, ISO/IEC 14496-3, for lossless audio coding. This technology combines lossy audio coding, lossless audio coding and scalable audio coding in a single framework. [Now the question the begs to be asked is why "SLS" as opposed to, oh, I don't know, say, "SLC"? No one seems to know. I'm betting it is a French language thing. If you know and can document it, write me.]

slush pump A trombone. [Decharne]

smoke From the phlogiston theory of electronics, it is smoke that makes ICs and transistors work. The proof of this is self-evident because every time you let the smoke out of an IC or transistor it stops working -- elementary. This has been verified through exhaustive testing, particularly regarding power amplifier ICs and transistors. (Incidentally, wires carry smoke from one device to another.) [Origin unknown but classic.]

smoothing filter See anti-imaging filter.

SMPS (switch-mode, or switchmode, power supply) Electronics. An electronic power supply characterized by switching a power transistor on and off with a variable duty cycle whose average is the desired output voltage. Also known as a chopper. See Billings for an excellent design handbook.

SMPTE (pronounced "simty") (Society of Motion Picture and Television Engineers) A professional engineering society that establishes standards, including a time code standard used for synchronization.

SMT (surface mounting technology) The science of attaching and interconnecting electronic devices, whose entire body projects in front of the mounting surface, as opposed to through-hole devices found on the earliest printed circuit boards. With surface mount technology all components sit on the surface of printed circuit boards and are soldered to conductive pads. With through-hole parts, component leads are placed through holes in the boards and then soldered from the back side. SMT is more cost-effective and allows far greater density of parts.

S/MUX Abbreviation used for several different things: 1. Sample Multiplexing. Proprietary technology licensed by Sonorus used to transmit high bandwidth digital audio using existing lower bandwidth technology. 2. Serial Multiplexer manufactured by MicroRidge. 3. Subtitle Multiplexer manufactured by Cavena.

S/N or SNR (signal-to-noise ratio) An audio measurement of the residual noise of a unit, stated as the ratio of signal level (or power) to noise level (or power), normally expressed in decibels. The "signal" reference level must be stated. Typically this is either the expected nominal operating level, say, +4 dBu for professional audio, or the maximum output level, usually around +20 dBu. The noise is measured using a true rms type voltmeter over a specified bandwidth, and sometimes using weighting filters. All these thing must be stated for a S/N spec to have meaning. Simply saying a unit has a SNR of 90 dB means nothing, without giving the reference level, measurement bandwidth, and any weighting filers. A system's maximum S/N is called the dynamic range. See the RaneNote Audio Specifications.

snake or audio snake Live Sound. The nickname for the cable running from the stage of a live performance to the main mixing console, which is usually set-up in the middle or rear of the audience (in spite of being called FOH). It typically contains one shielded pair (STP) of wires for each of the stage microphones. The name comes from the multiconductor cable looking sort of snake-like.

snapshot A term coined by British hunters to describe a quick shot with a gun. First applied to cameras at the Chicago World's Fair in 1893 where Kodak rented and popularized the first point-and-shoot camera. So called because the photographs taken were fast.

S/N+D or S/(N+D) See SINAD.

Snell's Law States the relationship between the angles of incidence and refraction and the indices of refraction of any two mediums.

SNMP (Simple Network Management Protocol) The most common method by which network management applications can query a management agent using a supported MIB (Management Information Base). SNMP operates at the OSI Application layer. The IP (Internet Protocol)-based SNMP is the basis of most network management software, to the extent that today the phrase "managed device" implies SNMP compliance.

snollygoster Defined in 1895 as "a fellow who wants office, regardless of party, platform or principles and who ... gets there by the sheer force of monumental talknophical assumancy". [McQuain, Never Enough Words]

snoring Doesn't happen in space because there is less airway obstruction in space according to flight surgeon Dr. J.D. Polk: "Earthly snoring occurs when gravity pulls the tongue and soft tissues in the rear of your mouth backward," he said. "If your airway is partially obstructed you get these tissues flapping. In microgravity, the tongue and the jaw do not fall back in the throat, so there is less airway obstruction in space."

Snow, William B. (1903-1968) American engineer best remembered for his foundation work for stereophonic reproduction in large rooms. See U.S. Patent 2,137,032 Sound Reproducing System. His paper titled "Basic Principles of Stereophonic Sound," Stereophonic Techniques: An Anthology, edited by John Eargle (Audio Engineering Society, ISBN 0-937803-08-1, NY, 1986, pp. 9-31) is considered the best introduction to this subject. Other papers of interest by Snow are collected in Sound Reinforcement: An Anthology, edited by David L. Klepper (Audio Engineering Society, NY, 1978). His grandson, John Snow, tells the story of how William used to play binaural wire recordings for them when they were kids, which he describes as "lots of surreal, cool stuff." Also see: Steinberg.

SNS (sudden noise syndrome) Term coined by Karl Brunvoll of Renkus-Heinz to describe high-level intermittent noise (oscillation).

Soca (soul calypso) Music. First named for a dance in Trinidad derived from calypso.

sodar (sonic detection and ranging) "A meteorological instrument also known as a wind profiler which measures the scattering of sound waves by atmospheric turbulence." From link. Compare with sonar and radar.

soft clipping See clipping.

software driver See: driver.

sol Music. The fifth tone of the diatonic scale in solfeggio. [AHD]

sol-fa Music. The set of syllables do, re, mi, fa, sol, la, and ti, used to represent the tones of the scale. [AHD]

solfeggio Music. 1. Use of the sol-fa syllables to note the tones of the scale; solmization. 2. A singing exercise in which the sol-fa syllables are used instead of text. [AHD]

solidus Printing. A virgule; a slash.

solo A term used in recording and live-sound mixing to describe monitoring (via headphones) a single channel without affecting the main outputs (see PFL) -- same as cueing; however, it can also refer to certain console designs where it replaces the main mix with the soloed channel (called destructive solo).

sonar (sound navigation and ranging) 1. A system using transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distance to the floor of a body of water. 2. An apparatus, as one in a submarine, using sonar. 3. Echolocation. [AHD] Compare with sodar and radar.

sone A subjective unit of loudness, as perceived by a person with normal hearing, equal to the loudness of a pure tone having a frequency of 1,000 hertz at 40 decibels sound pressure level. [AHD]

songworm That song going round and round in your head that you can't get rid of.

sonification The design of sounds to provide useful information (Stephen Barrass, JAES, September 2012, p. 709). An early example is the Geiger counter.

sonofusion Name given by inventor Dr. Rusi P. Taleyarkhan, Purdue University physicist, for his cold fusion experiments combining bursts of ultrasonic high-frequency sound waves with neutron pulses.

sonorous 1. Having or producing sound. 2. Having or producing a full, deep, or rich sound. [AHD]

soss 1. A sound made by the impact of a body on water; a splash. 2. A muffled sound (as) made by the impact of a heavy soft body; a thud; a heavy fall. Chiefly in with a soss. [OED]

sound 1.a. Vibrations transmitted through an elastic material or a solid, liquid, or gas, with frequencies in the approximate range of 20 to 20,000 hertz, capable of being detected by human ears. Sound (in air) at a particular point is a rapid variation in the air pressure around a steady-state value (atmospheric pressure) - that is, sound is a disturbance in the surrounding medium. b. Transmitted vibrations of any frequency. c. The sensation stimulated in the ears by such vibrations in the air or other medium. d. Such sensations considered as a group. 2. Auditory material that is recorded, as for a movie. 3. Meaningless noise. 4. Music. A distinctive style, as of an orchestra or a singer. 5. Oceanography. A long, relatively wide body of water, larger than a strait or a channel, connecting larger bodies of water (as in Puget Sound where I live and work). [AHD] Also see the RaneNote: Signal Processing Fundamentals. See: velocity of sound.

sound absorption See absorption.

sound bath Many definitions but generally a meditative experience resulting from an emersion in sound, either music, chanting, chimes, singing crystal bowls, etc., all said to produce calming effects.

sound card Computers. An accessory card or outboard unit that allows and controls audio in and out from a computer.

Sound City Recording. Perhaps the most famous recording studio ever, having recorded many of the greatest albums in rock and roll history, all using their famous Neve 8028 analog mixing console.

soundfield microphone A specialized microphone array comprised of four cardiod or supercardiod microphones: three to measure left-right, front-back, up-down sound pressure levels and another that measures overall sound pressure level. This arrangement is known as the A-Format, while another one, the B-format, is created by signal processing. This forms the heart of an Ambisonics and other such systems. An organization that "... provides real world advice and support for women working or wishing to enter the field of professional audio." Women make up only five percent of all audio engineers according to their website. See the website for great stories about women in audio as well as vintage photos dating back to the '70s. [ Bet you didn't know there was a woman on the Grateful Dead sound crew.]

sound intensity See: intensity.

sound level meter Acoustics. Electronic instrument for measuring sound pressure levels.

sound masking Acoustics. The science of using one type of sound to cover up (mask) other sounds. See: Chanaud for the best in-depth source on this subject.

sound measurement glossary Great resource compiled by Pat Brown, SynAudCon. Access is restricted to SynAudCon members, which cost very little with big benefits.

sound mirrors Acoustics. Giant parabolic reflector concrete structures used as an early warning system to detect enemy aircraft approaching Great Britain in the 1920s and 1930s before the advent of radar. Great photos here.

sound morphing Combining two sounds to produce a new sound having characteristics of the two originals.

sound occlusion See occlusion effect.

sound off To express one's views vigorously: He was always sounding off about his boss. [AHD]

sound pressure The value of the rapid variation in air pressure due to a sound wave, measured in pascals, microbars, or dynes - all used interchangeable, but pascals is now the preferred term. Instantaneous sound pressure is the peak value of the air pressure, often used in noise control measurements. Effective sound pressure is the rms value of the instantaneous sound pressure taken at a point over a period of time.

sound pressure level or SPL 1. A measure of intensity. The rms sound pressure expressed in dB re 20 microPa (the lowest threshold of hearing for 1 kHz). [As points of reference, 0 dB-SPL equals the threshold of hearing, while 140 dB-SPL equals irreparable hearing damage.] See: inverse square law 2. Blue whales, the largest living animals, said to make the loudest sounds by any living source. Their low-frequency pulses have been measured at 188 dB-SPL and detected 530 miles away according to The Guinness Book of World Records®. [Note: there is no mention of the reference level, so if this is referenced to the normal 20 microPA for gases then it is, in fact, 26 dB less, or 162 dB-SPL due to the reference level for water being 1 microPA (per ANSI S1.1-1994) -- still an impressive number.] 3. In addition to Blue whales Sperm whales are claimed to make impulsive sounds (clicks) up to 235 dB rms (re 1uPa @ 1m) according to Applied Signal Processing by T. Dutoit and F. Marques [Thanks JMF, Spain]

Sound Recording History Fantastic site put together by David Morton.

sound reinforcement See SR.

Sound Shaper® Registered trademark (now expired) of ADC (Audio Dynamics Corporation) for their line of equalizers/analyzers that pioneered use of RTAs and equalization for the home and studio environment.

Sousa, John Philip (1854-1932) American bandmaster and composer who wrote comic operas and marches such as Stars and Stripes Forever (1897). [AHD]

sousaphone Musical Instrument. A large brass wind instrument, similar in range to the tuba, having a flaring bell and a shape adapted to being carried in marching bands. [After John Philip Sousa.] [AHD]

spanning tree protocol See: STP.

SPARS (Society of Professional Audio Recording Services) Founded in 1979, a professional trade organization that unites the manufacturers of audio recording equipment and providers of services with the users. Their goal is worldwide promotion of communication, education and service among all those who make and use recording equipment. Often confused with NARAS.

spatial Of, relating to, involving, or having the nature of space. [AHD]

Spatializer A single-ended spatial enhancement technique developed by Desper Products, Inc., a subsidiary of Spatializer Audio Labs, Inc. Widely licensed in both the consumer audio and multimedia computing markets, the Desper, or Spatializer process is normally used as a postprocessor. The Spatializer technology manipulates the original signal in a way that causes the listener to perceive a stereo image beyond the boundaries of the two loudspeakers. It claims to place sounds in front of the listener in an arc of 180 degrees, with excellent imaging and fidelity.

S/PDIF (Sony/Philips digital interface format, also seen w/o slash as SPDIF) A consumer version of the AES3 (old AES/EBU) digital audio interconnection standard based on coaxial cable and RCA connectors. See the RaneNote Interfacing AES3 and S/PDIF

Speakon® See connectors.

spectra A plural of spectrum. In pro audio use, the distribution of frequency of a sound signal, especially the distribution of sound energy, arranged in order of frequency wavelengths.

spectral band replication See SBR.

spectrogram A graphic or photographic representation of a spectrum. [AHD]

spectrum 1. Physics The distribution of a characteristic of a physical system or phenomenon, especially: a. The distribution of energy emitted by a radiant source, as by an incandescent body, arranged in order of wavelengths. b. The distribution of atomic or subatomic particles in a system, as in a magnetically resolved molecular beam, arranged in order of masses. 2. A graphic or photographic representation of such a distribution. [AHD]

spectrum analyzer Audio Test Equipment. A type of electronic measurement device used to display the amplitude/frequency components of a continuous signal, as opposed to the amplitude/time domain oscilloscope. The formal IEEE definitions are "(1) An instrument generally used to display the power distribution of an incoming signal as a function of frequency. (2) An instrument that measures the power of a complex signal in many bands. The frequency bands can be either constant absolute bandwidth (e.g., FFT analyzer), or constant percentage bandwidth (e.g., RTA analyzer)."

speech intelligibility See STI, RASTI , ALCONS and STIpa. Also Peter Mapp's overview article "Measuring Intelligibility" in S&VC magazine and John Murray's It's The Intelligibility in Live Sound International magazine.

speech interference level (SIL) The numerical part of the RC noise rating.

speed of sound See velocity of sound.

spell checker A software program used by word processors to tell you that the following truism has no spelling errors: "Dew knot trussed yore spell chequer two fined awl mistakes."

spherical wave Acoustics. Sound waves that radiate out from a point source into open space are concentric spheres.

SPICE (simulation program with integrated circuit emphasis) A computer circuit analysis program first developed and written by L. W. Nagel and D. O. Pederson of the EECS (Electrical Engineering and Computer Sciences) Department of UC Berkeley¹. This was not the first simulation program by members of UC Berkeley's EECS Department. SPICE evolved from forerunners BIAS² and CANCER³. The SPICE program was used extensively for classroom instruction and graduate research. As such, each year it was refined and expanded by each new batch of graduate students (yes, even I worked on SPICE, helping develop op amp models during my graduate years at UC Berkeley) until it expanded beyond Berkeley's domain through licensing and the advent of mini and personal computers beginning in 1981. Indeed, PSPICE (Personal SPICE) developed in 1984 by Wolfram Blume (first doing business as Blume Engineering, then MicroSim, acquired by OrCAD, now owned by Cadence), the first version of SPICE for personal computers, is now the industry standard for circuit-simulation.


  1. L.W. Nagel and D.O. Pederson, "Simulation Program with Integrated Circuit Emphasis (SPICE)," presented at the 16th Midwest Symposium on Circuit Theory, Waterloo, Ontario, April 12, 1973.
  2. W.J. McCalla and W.G. Howard, Jr., "BIAS-3 -- A Program for the Nonlinear DC analysis of Bipolar Transistor Circuits," IEEE J. Solid-State Circuits, vol. SC-6, Feb. 1971, PP. 14-19.
  3. L. Nagel and R. Rohrer, "Computer Analysis of Nonlinear Circuits, Excluding Radiation (CANCER)," IEEE J. Solid-State Circuits, vol. SC-6, Aug. 1971, pp. 166-182.

spider Loudspeakers. The assembly which holds the voice coil of a dynamic loudspeaker centered in the magnetic gap. The spider is a corrugated circular piece of specially treated fabric. The name comes from the early days of loudspeakers when it was made of a plastic material that resembled the legs of a spider. [White]

SPIF (sales promotion incentive fund) Same as #3 following:

spiff 1. To make attractive, stylish, or up-to-date: spiffed up the old storefront. 2. Attractiveness or charm in appearance, dress, or manners: "He may need more than spiff to get him through the bad patches ahead" James Wolcott (Possibly from dialectal spiff well-dressed) [AHD] 3. Giveaways (usually in the form of money) by manufacturers as added incentive ("make attractive") to personnel selling their goods. Compare with swag.

spike fiddle Musical Instruments. A type of string instrument in which the neck passes through the sound chest to protrude as a spike at the lower end; the strings are attached to it. The instrument is known in many parts of the Middle East and Central and South-east Asia. [Sadie] Member of the rebab family of musical instruments.

spintronics Electronics. Shorten form for spin-based electronics, it describes technology that makes use of the spin state of electrons.

spiral quad Same as star quad; see cables.

spirant See fricative.

spit harp Slang for a harmonica.

SPL See sound pressure level.

SPL controller See leveler.

splitbox See: splitter.

split cue DJ Mixers. Headphone cueing system utilizing a pan control to choose between what is cued and what is playing. In its normal mode the cued program feeds one ear and the master, or program (what is playing) feeds the other ear. This makes beat matching easy and convenient since you listen to both turntables (or CDs, or MP3 files, or any combination) at the same time. Rotating the pan control fully CW, or CCW, puts a monoed signal into one ear with no signal going to the other, and vice-versa. Rotating the pan control to its center position routes equal amounts of cue signal to one ear and program signal to the other ear. Pioneered in 1986 by Rane with the introduction of the MP 24 DJ Mixer.

splitter (aka splitbox) An audio device used to divide one input signal into two or more outputs. Typically this type of unit has one input with 6-16 (or more) outputs, each with a level control and often is unbalanced. See distribution amplifier.

spooler Comes from the acronym SPOOL derived from simultaneous peripheral operation on-line (also sequential peripheral operations on-line). A program or piece of hardware that controls a buffer of data going to some output device, including a printer or a screen. Spooling temporarily stores programs or program outputs on magnetic tape, RAM or disks for output or processing. [Newton] ... and you thought you were done learning for the day -- Ha!

spring reverb See: Hammond.

spurious signals Test & Measurement. "Any signal(s) in the output of an audio device that are not: the stimulus or program material, harmonic distortion, intermodulation distortion, crosstalk, hum or broadband noise." [David Mathew, Audio Precision, How to write (and read) audio specifications.]

SQ Columbia's (CBS - now Sony Music) name for their quadraphonic sound system using a proprietary matrixing algorithm for encoding four-channel sound down to two-channels. Compare with QS.

SQL (structured query language) Software. A program used to request information from databases.


SQNR (signal to quantization noise ratio A measure of the quality of the quantization, or digital conversion of an analog signal. Defined as normalized signal power divided by normalized quantization noise power. The SQNR in dB is approximately equal to 6 times the number of bits of the ADC, for example, the maximum SQNR for 16 bits is approximately 96 dB.

square wave A periodic waveform characterized by a 50% duty cycle and a Fourier series consisting of odd-ordered, equal phase, sinusoidal harmonic components of its fundamental frequency with amplitudes (coefficients multiplying the magnitude of the fundamental sine wave) equal to 1/n, where n equals the harmonic number. Therefore the first few harmonic amplitudes are 1/3, 1/5, 1/7, 1/9, etc. For a very cool pictorial, see Fourier Series: Square Wave Tool. And if you are missing the math, see Cuthbert Nyack's Fourier Series of Square Wave

SR (sound reinforcement) See Bruce Borgerson excellent S&VC article on P.A. vs. SR.

SRS (Sound Retrieval System) A stereo image enhancement scheme invented by Arnold Klayman in the early '80s while working for Hughes Aircraft, and since 1993, marketed by SRS Labs, Inc. A standalone spatial enhancement scheme, SRS benefits from not requiring encoding of the signal, but thus prevents the audio producer from determining the location of individual sound effects. The results vary, being heavily dependent upon the original stereo mix. The goal is to extend the sound field well beyond the limitations of the loudspeakers, and make the overall sound seem more expansive. The elimination of the sweet spot is claimed.

SSID (Service Set Identifier) Networks. A sequence of letters or numbers that is the name of a WLAN (wireless local area network).

standard component values Electronic Circuit Design. Standard IEC values for resistors and capacitors per IEC 60063.

standing wave See room mode.

Stanley III, Augustus Owsley (1935-2011) A '60s icon known as "Bear," he was instrumental in helping create the famous "Wall of Sound" for the Grateful Dead while he was their live sound engineer.

star quad mic cable See cables.

Star-Spangled Banner The flag of the United States.

star topology 1. A set of three or more branches with one terminal of each connected at a common node. 2. A communications network based on a star pattern where all equipment is connected to a central location with a single path.

star-wired ring See token ring.

state-variable filter An electronic filter based on state-variable techniques, first described by W. J. Kerwin, L. P. Huelsman, and R. W. Newcomb, "State variable synthesis for insensitive integrated circuit transfer functions," IEEE J. Solid Circuits, vol. SC-2, pp. 87-92, Sept. 1967. State-variable filters are also known as KHN filters in their honor. The concept of state-variable is one where a single variable defines one of the characteristics (or states) of a filter (e.g., the gain, or the center/corner frequency, or the Q). The state-variable approach yields independent adjustment of the transfer function pole and zero locations. [The transfer function is a Laplace transform equation of the output divided by the input consisting of the ratio of two polynomials. Poles and zeros are the mathematical names for the solutions of the numerator polynomial -- called zeros because they cause the numerator to have zero value -- and denominator polynomial -- called poles because they cause the denominator to have zero value which makes the ratio infinity.] This desirable independent adjustment feature allows the design of parametric EQs with independent adjustment of all three filter parameters, or constant-Q graphic EQs with amplitude-bandwidth independence (See the RaneNote Constant-Q Graphic Equalizers), or simultaneous low-pass and high-pass active crossovers (See the RaneNote Linkwitz-Riley Crossovers: A Primer). The state-variable topologies also have lower component sensitivities that other designs, thus producing more production-friendly products. Most commonly seen with three op amps, they may be constructed using from one to four op amps.

STC (Sound transmission Class) Noise Measurement. Method of measuring sound through partitions.

St. Croix, Stephen Curtis (1948-2006) American inventor, musician, engineer and producer who founded Marshall Electronic and changed his last name from Marshall to St. Croix because he loved the islands. Along with John Ariosa he developed the Marshall Time Modulator in 1976, one of the earliest audio delay units. He wrote The Fast Lane column, for Mix magazine for 20 years, now available in book form from MIX as Life in the Fast Lane.

steganography The science of communicating in a way that hides the existence of the actual communication. The practice of hiding information in a wider bandwidth carrier. This field covers the techniques used in digital watermarking schemes.

Steinberg, John C. (1895-1988) American engineer who worked with Snow and in 1936 co-patented an improved three channel stereophonic system as U.S. Patent #2,126,929.

Steinmetz, Charles Proteus (1865-1923) A German-American mathematician and engineer who first developed the mathematics (based on complex numbers) describing alternating current.

Steinweiss, Alex (1916- ) The father of the album cover, he designed the first album cover in 1939 for Columbia Records where he worked as their first art director. See: Alex Steinweiss: The Inventor of the Modern Album Cover.

stems 1. Recording. Nickname for the individual tracks used to create the final mix and saved for remixing purposes. Origin is from movie soundtracks where there are three main stems: dialog, music and effects. 2. Music. The vertical line extending from the head of a note found in music notation. Compare with separation mastering.

stereo or stereophonic sound 1. "The word stereophonics was derived by combining two Greek words: stereo, which means solid and implicates the three spatial dimensions (depth, breadth, and height), and phonics, which means the science of sound. Thus, stereophonics denotes the science of 3-dimensional sound" [Streicher & Everest]. 2. Term applied to any system of recording (or transmission) using multiple microphones for capturing and multiple loudspeakers for reproduction the sound. Stereo as the term has become popularly used restricts the number of playback loudspeakers to two, but strictly speaking the term can apply to any number of loudspeakers. Although stereo was first demonstrated at the Paris Opera in 1881 (really) using carbon microphones and earphones, it would not become widespread until the work of Blumlein in the 1930s. Also see William B. Snow.

stereo 2-way or stereo 3-way, etc. See active crossover.

Stereobelt The first portable stereo cassette player, developed by Andreas Pavel in 1972.

stereo disc lathe Phonographs. Invented by Neumann in 1956, the invention that opened the door to the modern stereo LP record.

stereo imaging See: imaging.

stewardesses Longest English word typed using only the left hand.

STI (speech transmission index) "An objective measure to predict the intelligibility of speech transmitted from talker to listener by a transmission channel," thus begins the Introduction to standard IEC 60268-16, Edition 4, 2011-06. From the Abstract: "IEC 60268-16:2011(E) specifies objective methods for rating the transmission quality of speech with respect to intelligibility. It provides a comprehensive manual for all types of users of the STI method in the fields of audio, communications and acoustics. Three methods are presented, which are closely related and are referred to as STI, STIPA, and STITEL. The first two methods are intended for rating speech transmission performance with or without sound systems. The STITEL method has more restricted uses. ... This edition includes the following significant technical changes with respect to the previous edition: development of more comprehensive, complete and unambiguous standardization of the STI methodology; the term STIr is discontinued. A new function for the prediction of auditory masking effects is introduced; the concept of 'speech level' and the setting of the level of the test signal have been introduced; additional information has been included on prediction and measurement procedures." Here is a nice summary of the technique: "In STI testing, speech is modeled by a special test signal with speech-like characteristics. Following on the concept that speech can be described as a fundamental waveform that is modulated by low-frequency signals, STI employs a complex amplitude modulation scheme to generate its test signal. At the receiving end of the communication system, the depth of modulation of the received signal is compared with that of the test signal in each of a number of frequency bands. Reductions in the modulation depth are associated with loss of intelligibility." [Meyer Sound Notes] Contrast with obsolete method, RASTI. Compare with %ALCONS.

Sting Stage name of Gorden Sumner.

STIpa (speech transmission index for public address systems) A speech intelligibility measurement described by developers H. Steeneken, J. Verhave, S. McManus and K. Jacob in their paper "Development of an Accurate, Handheld Simple-to-Use, Meter for the Prediction of Speech Intelligibility," Proc. IOA, Vol. 23, Pt. 8, 2001. Goldline manufactures a model. Equivalent British term is PASTI for public address STI.

Stick®See Chapman Stick®.

stiction Physics. In positioning, the friction that prevents immediate motion when force is first applied to a body or surface at rest.

stochastic resonance Communications. The science behind dither. A phenomenon of nonlinear systems where low-level input signals are amplified and optimized by adding noise, i.e., an increase in the input noise produces an improvement in the output signal-to-noise ratio "The effect requires three basic ingredients: (i) an energetic activation barrier or, more generally, a form of threshold; (ii) a weak coherent input (such as a periodic signal); (iii) a source of noise that is inherent in the system, or that adds to the coherent input. Given these features, the response of the system undergoes resonance-like behavior as a function of the noise level; hence the name stochastic resonance." [From Stochastic Resonance by L Gammaitoni, P Haenggi, P Jung, and F Marchesoni. Thanks S.H.!]

Stockham, Jr., Thomas G. (1934-2004) American electrical engineer best known for his pioneering work in digital audio recording and editing. Known as the father of digital magnetic sound recording, Dr. Stockham earned Grammy, Emmy and Academy awards for his work and was the founder of Soundstream, Inc.

Stockhausen, Karlheinz (1928-2007) German composer renowned for his pioneering work in electronic music. The Beatles featured a photo of him on the cover of their album, "Sgt. Pepper's Lonely Hearts Club Band" (fifth from the left in the back row.)

stompboxes See: effects boxes.

stopband The range of frequencies substantially attenuated by a filter as opposed to the range of frequencies unaffected by the filter. The opposite of passband.

stops Speech. "In phonetics, the class of consonants produced by a complete closure of the flow of air in the vocal tract. Examples are 'p', 'd', and 'k'." [Bregman]

stovepiping 1. Information Technology. Refers to information traveling up and down in an organization with little horizontal sharing or checking. 2. Computer Science. "Retrieval of information from unconnected databases; the situation that exists when it is necessary to climb out of one database in order to climb down into another; sometimes used for protection against wandering hackers." [Word]

STP (shielded twisted-pair) See cables; also Scientifically Treated Petroleum, but that's another story from another time.

STP (spanning tree protocol) A link management protocol providing path redundancy and preventing network loops by defining a tree to span all switches in a network. It forces redundant data paths into a standby (blocked) state. If a path malfunctions, the topology is reconfigured and the link reestablished by activating the standby path. [CTRLink]

strad Musical Instruments. Affectionate nickname for instruments made by Antonio Stradivari, who created more than 1,000 stringed instruments, with estimates of 600 remaining.

Stradivari, Antonio (1644-1737) Italian violin maker who developed the proportions of the modern violin and created instruments of unsurpassed beauty and tone. His sons Francesco (1671-1743) and Omobono (1679-1742) carried on the family tradition of fine artistry. [AHD]

Strawberry Music Festival Big folk and bluegrass music festival held each year over Labor Day weekend at Camp Mather, bordering Yosemite National Park, begun in 1982 by Charlie Cran and others.

streaming media Internet. A process in which audio, video, and other multimedia is delivered "just in time" over the Internet or company intranet. Pioneered and named by Netscape, as a smarter way to deliver data, their browser immediately loaded text and then followed with graphics in real time as it arrived (streamed in), then RealNetworks came along and applied this technology to audio and video.

stripline Electronics. A flat transmission line surrounded by a dielectric between a pair of ground planes. Contrast with microstrip.

strophe 1. a. The first of a pair of stanzas of alternating form on which the structure of a given poem is based. b. A stanza containing irregular lines. 2. The first division of the triad constituting a section of a Pindaric ode. 3. a. The first movement of the chorus in classical Greek drama while turning from one side of the orchestra to the other. b. The part of a choral ode sung while this movement is executed. [AHD]

strophic 1. Relating to or consisting of strophes. 2. Music Having the same melody used for each strophe. [AHD]

structured audio See MPEG-4.

Strutt, John William See: Lord Rayleigh

Studio 54 (1977-1979: dates for the original club) Famous disco club located in an old CBS TV studio located at 254 West 54th Street, Manhattan, NY -- hence, the name.

stutter edit DJ. A popular remixing effect. See Jason Scott Alexander's "Fractal Tendencies" published in Remix magazine for how-to tips.

subcardioid microphone See microphone polar response.

subcode Non-audio digital data encoded on a CD that contains definable information such as track number, times, copy inhibit, copyright, etc.

subgroups See groups.

subharmonic Frequencies that are fractions of the fundamental, i.e., multiples of 1/2, 1/3, 1/4 etc.

submix See groups.

subsonic Having a speed less than that of sound in a designated medium. [AHD] (Use infrasonic if referring to frequencies below human hearing range.)

subtend 1. Mathematics. To be opposite to and delimit: The side of a triangle subtends the opposite angle. 2. To underlie so as to enclose or surround: flowers subtended by leafy bracts. [AHD]

subwoofer A large woofer loudspeaker designed to reproduce audio's very bottom-end, i.e., approximately the last one or two octaves, from 20 Hz to 80-100 Hz. (Actually misnamed since subsonic means slower than audio, while infrasonic means lower than audio, it should be called an "infrawoofer.") See Royal Device for the ultimate subwoofer.

successive approximation Early method of A/D conversion. For a detailed example see the RaneNote Digital Dharma of Audio A/D Converters.

Summerfest Music festival held in Milwaukee, WI, recognized by Guinness World Records as the largest music festival for over 15 years, mostly due to its 11-day duration.

supra-aural Headphones. Literally "on the ear," thus headphones with earpieces resting on the ear. Comfortable to wear but the lack of a tight seal allows lots of ambient noise -- sometimes this is desired; sometimes it is not. Compare with: circumaural.

supercardioid microphone See microphone polar response.

supersonic Having, caused by, or relating to a speed greater than the speed of sound in a given medium, especially air. [AHD] (Use ultrasonic if referring to frequencies above human hearing range.)

suppression also gain suppression In teleconferencing the term used to describe the technique of instantaneous reduction of a sound system's overall gain to control acoustic feedback and thus reduce echoes.

surface transfer impedance See ZT.

surround Loudspeakers. The circular ring mechanism that attaches the cone to the frame ("surrounding" the cone), usually rolled (allows greater throw) and made from foam or rubber material.

surround sound Generic term for sound systems using more than mono (one front channel), or stereo (two left-right channels) loudspeakers to create a two- or three-dimensional experience. For examples see 5.1 surround sound and Ambisonics.

susceptance Electronics. The reciprocal of reactance, i.e., the imaginary part of the admittance . It is measured in siemens. Its mathematical symbol is “B” [confusingly the same symbol as that of magnetic flux density].

sustain Music. A prolonged note, especially the ability to maintain a note beyond its natural decay. Electric guitarists produce this effect by leaning toward their amplifier loudspeaker causing the signal to feed back into the pick-up. In popular music, most famously used by Carlos Santana, Jimi Hendrix and Gabor Szabo.

S-video Also called Y/C video, a two-channel video channel that transmits black and white, or luminance (Y), and color portions, or chrominance (C), separately using multiple wires. This avoids composite video encoding, such as NTSC, thus providing better picture quality. Found mostly on S-VHS and Hi8 products, and some Laserdisc and DVD players.


swag 1. Slang Stolen property; loot. 2. Slang Herbal tea in a plastic sandwich bag sold as marijuana to an unsuspecting customer. 3. Australian To travel about with a pack or swag. [AHD] 4. Slang Acronym for scientific (or silly or sophisticated) wild-ass guess. 5. Slang Giveaways (usually in the form of merchandise "loot") by manufacturers as added incentive to personnel either selling or buying their goods. Compare with spiff.

swamp pop Music. Nickname for south Louisiana sound.

Swanson Sound Service Founded in 1926, in Oakland, California by Art Swanson, the Swanson Sound Service company, along with R.G. Jones (near London) are considered the first sound companies, and both are still going strong.

Sweet Sixteen Loudspeakers. Nickname for a briefly popular loudspeaker design in the early '60s using sixteen 5-inch speakers per channel arranged in a 4 x 4 array on a flat baffle. The idea was for them to combine and act like one huge speaker [well, today we all know how well that works]. Originally published as a DIY article by Jim Kyle in the January 1961 issue of Popular Electronics.

sweet spot Any location in a two-loudspeaker stereo playback system where the listener is positioned equidistant from each loudspeaker. The apex of all possible isosceles (two equal sides) triangles formed by the loudspeakers and the listener. In this sense, the sweet spot lies anywhere on the sweet plane extending forward from the midpoint between the speakers.

swept frequency capacitive sensing See: Touché.

SWG (standard wire gauge) British or Imperial standard. See AWG.

switch-mode power supply See: SMPS

SWLABR Music. Song title from the album Disraeli Gears by Cream. The title is an abbreviation for "She Was Like A Bearded Rainbow." [Hey, it was the 60s -- lighten up.]


SXSW (South by Southwest) Huge annual music, film and technology festival held in Austin, TX since 1987.

symmetrical (reciprocal) response Term used to describe the comparative shapes of the boost/cut curves for variable equalizers. The cut curve exactly mirrors the boost curve.

Syn-Aud-Con (Synergetic Audio Concepts) A private organization conducting audio seminars and workshops, sponsored by several pro audio companies.

synesthesia also synaesthesia Physiology. A condition in which one type of stimulation evokes the sensation of another, as when the hearing of a sound produces the visualization of a color. 2. A sensation felt in one part of the body as a result of stimulus applied to another, as in referred pain. 3. The description of one kind of sense impression by using words that normally describe another. [AHD]

synchronous A transmission process where the bit rate of the signal is fixed and synchronized to a master clock. 

syzygy Astronomy. Very strange word for when the earth, moon and sun align. Technically: a. Either of two points in the orbit of a celestial body where the body is in opposition to or in conjunction with the sun. b. Either of two points in the orbit of the moon when the moon lies in a straight line with the sun and Earth. c. The configuration of the sun, the moon, and Earth lying in a straight line. [AHD].