Glossary

Radiation curve, or characteristic (11)

A graph showing what portion of the internal sound is radiated by the bell or other part of the instrument.

Radius of gyration (13)

A measure of the difficulty of rotating a body of a given mass.

Random-access memory (RAM) (21)

A type of volatile computer memory in which any storage location can be addressed for read or write operations. It typically needs to be refreshed every 3-5 milliseconds.

Rapid eye movement (REM) state (31)

A stage of sleep during which a person can be awakened quite easily by noise (also the stage in which dreaming occurs).

R-DAT (22)

Rotary-head digital audio tape recorder.

Read-only memory (ROM) (21)

A type of computer memory that stores information permantly.

Real time (29)

The operation of a device or system in such a way that it responds to inputs without perceptually significant delay.

Real-time spectrum analyzer (16)

An instrument that rapidly creates a graph of the spectrum of a sound.

Rectifier (18)

A diode that is used to change ac into pulsating dc.

Reflection (03)

An abrupt change in direction of wave propagation at a change of medium (by waves that remain in the first medium).

Refraction (03)

A bending of waves when the speed of propagation changes, either abruptly (at a change of medium) or gradually (e.g., sound waves in a wind of varying speed).

Refraction (30)

The bending of waves when the velocity changes (due to temperature and wind gradients).

Register (12)

A group of related notes on a musical instrument; one register, for example, may include all notes whose pitches correspond to the lowest resonance of an air column.

Reissner’s membrane (05)

A membrane in the cochlea that separates the cochlear duct from the scala vestibuli.

Remanence (magnetic) (22)

The net magnetization that remains after the magnetic material has been saturated and the field has been removed.

Repetition pitch (07)

Pitch sensation created by the interference of a sound with a time-delayed repetition.

Resampling (29)

The operation of changing the sampling rate of a digital signal by an arbitrary amount, which is necessary in pitch-shifting.

Residue theory of pitch (07)

A view that components of a tone that cannot be resolved by the basilar membrane (the residue) are analyzed in time by the central nervous system.

Resister hole (12)

A hole that can be opened in order to cause an instrument to play in a higher register.

Resistor (18)

A device that converts electrical energy into heat.

Resonance (04)

When a vibrator is driven by a force that oscillates at a frequency at or near the natural frequency of the vibrator; a relatively large amplitude results.

Resonance (18)

The natural frequency of a system, at which its response to a mechanical or electrical force reaches a maximum.

Reverberant field (24)

That part of the sound field in which sound level is independent of distance from the source.

Reverberant sound (23)

Sound that builds up and decays gradually and can be "stored in a room for an appreciable time.

Reverberant sound (25)

Sound that reaches the listener after large number of reflections; as one moves away from a sound source, the sound level reaches a steady value called the reverberant level.

Reverberation time (23)

The time required for the stored or reverberant sound to decrease by 60 dB.

Ring modulator (27)

A circuit that multiplies two input signals, thereby forming an output signal containing the sums and differences of all pairs of frequencies present in the two input signals.

Room constant (24)

A quantity that describes the absorption in a room; it is slightly greater than the total absorption A used to calculate reverberation time.

Sabin, metric sabin (23)

Units for measuring absorption of sound; the sabin is equivalent to one square foot of open window, the metric sabin to one square meter.

Saddle (10)

The strip of hard material (ivory or bone) that supports the string at the bridge of a guitar.

Sample (21)

A measurement of the instantaneous value of the amplitude of an analog signal.

Sampler (29)

A device designed to create musical sounds by digitally manipulating the pitches and durations of recorded sounds stored in a waveform memory.

Sampling (Nyquist) theorem (21)

A theorem stating that a band-limited signal containing frequencies of up to F hertz must be sampled at least 2F times per second in order to avoid aliasing.

Sampling (Nyquist) theorem (28)

A theorem stating that a band limited signal containing frequencies up to F hertz must be sampled at least 2F times per second in order to avoid aliasing.

Saturation (magnetic) (22)

State of maximum magnetization when the magnetic domains are aligned as well as possible.

Scala vestibule (05)

A canal in the ear that transmits pressure variations from the oval window to the cochlear duct.

Scale (09)

Succession of notes arranged in ascending or descending order.

Score file (29)

The name given to the input file of an acoustic compiler; a score file typically consists of instrument and stored function definitions, followed by a list of notes to be played on the defined instruments.

S-DAT (22)

Stationary-head digital audio tape recorder.

Second-order beats (08)

Beats between two tones whose frequencies are nearly but not quite in a simple ratio; also called beats between mistuned consonances.

Semitone (07)

One step on a chromatic scale. Normally 1/12 of an octave.

Semitone (09)

A half step; in equal temperament, a semitone corresponds to 100 cents or to a frequency ration of 1.059.

Semivowels (15)

Consonants for which the vocal tract is formed in a configuration generally used for vowels (w, y).

Sensitivity (microphone) (20)

Voltage or power generated in a microphone at a given sound pressure level.

Sequencer (27)

A circuit that switches through a predetermined sequence of control signals.

Serial copy management system (SCMS) (22)

Device that prevents making ("cloning) multiple copies with a digital recorder.

Sidebands (08)

Sum and difference tones generated during modulation.

Sidebands (20)

Sum and difference frequencies created in the modulation process.

Signal-to-noise ratio (22)

The ratio (usually express in dB) of the average recorded signal to the background noise.

Sign-magnitude (21)

The technique of representing negative integers using 1 bit to represent the sign and the rest of the bits to represent the magnitude of a number.

Simple harmonic motion (02)

Smooth regular vibrational motion at a single frequency such as that of a mass supported by a string.

Sinc function (29)

The impulse response of an ideal low-pass filter.

Sine wave (08)

A waveform that is characteristic of a pure tone (that is, a tone without harmonics or overtones) and also simple harmonic motion.

Singer’s formant (17)

A resonance around 2500 to 3000 Hz in Male (and low female) voices that adds brilliance to the tone.

Sinusoidal (12)

Pertaining to a sine wave; thus a pure tone or single frequency of vibration.

Sinusoidal force (10)

A smoothly varying force with a single frequency; the waveform is described as a sine wave.

Sones (06)

A unit used to express subjective loudness; doubling the number of sones should describe a sound twice as loud.

Sonic boom (32)

Pressure transient that occurs during the flyover of an aircraft faster than the speed of sound.

Sound encoding (lossless) (29)

The body of techniques typically used to reduce the number of bits needed to represent a sound signal in such a manner that the original signal can be recovered perfectly.

Sound encoding (lossy) (29)

The body of techniques typically used to reduce the number of bits needed to represent a sound signal by discarding its perceptually irrelevant or unnecessary features. Because some information is discarded, the original signal cannot be perfectly reconstructed from its encoded form.

Sound hole (rose hole) (10)

The round hole in the top plate of a guitar that plays an important role in determining the lower resonances of the body.

Sound post (10)

The short round stick (of spruce) connecting the top and back plates of a violin or other string instruments.

Sound power level (06)

Lw=10logW/W0, where W is sound power and W0 =10^-12W.

Sound power level (LW)(24)

10 log W/Wo (see Chapter 6).

Sound pressure level (06)

Lp=20logp/p0, where p is sound pressure and p0 = 2X10^-5 N/m^2 (or 20 micropascals).

Sound pressure level (Lp) (24)

10 log p/po (see Chapter 6).

Sound spatialization (29)

The use of technological means to create the impression that one or more sounds come from specified, possibly time-varying locations in a "virtual acoustic space surrounding the listener.

Sound spectrograph (16)

An instrument that displays sound level as a function of frequency and time for a brief sample of speech.

Soundboard (04)

A sheet of wood or other material that radiates a substantial amount of sound when it is driven in sympathetic vibration by a vibrating string or in some other manner.

Soundboard (14)

The wooden plate that radiates much of the sound in string instruments.

Speaker’s formant (17)

A prominent fourth formant in the speaking and singing of country singers.

Spectral dominance (07)

A view that certain partials dominate in the determination of the pitch of a complex tone.

Spectrogram (16)

A graph of sound level versus frequency and time as recorded on a sound spectrograph or similar instrument.

Spectrum (02)

A “recipe” that gives the frequency and amplitude of each component of a complex vibration.

Spectrum (07)

The “recipe” for a complex tone that gives the amplitude and frequency of the various partials.

Spectrum analysis (07)

The determination of the component tones that make up a complex tone or waveform.

Speech cues (31)

Particular combinations of sounds or dynamic changes in sound by which a listener identifies phonemes (speech sounds).

Speech interference level (SIL) (31)

The average of sound levels in the 500-, 1000-, and 2000-Hz octave bands.

Speech synthesis (16)

Creating speech-like sounds artificially.

Speed (01)

The rate at which distance is covered; equal to distance divided by time.

Spring constant (02)

The strength or stiffness of a spring; restoring force divided by displacement.

SQNR (signal-to-quantization error noise ration) (21)

Ratio of the amplitude of the signal to the amplitude of the quantization error noise, expressed in dB.

SRAM (static random-access memory

A type of computer memory that holds information as long as power is applied. It is generally faster than DRAM and does not require refreshing.

Standing wave (03)

A wavelike pattern that results from the interference of two or more waves; a standing wave has regions of minimum and maximum amplitude called nodes and antinodes.

STC (sound transmission class) (32)

A number that describes the effectiveness of a wall structure in attenuating airborne noise.

Stereocilia (05)

The tiny fibers attached to hair cells that bend and cause electrical signals to be transmitted on the auditory nerve fibers.

Stereophonic (25)

Sound reproduction using two microphones to feed two loudspeakers.

Stored functions (29)

The name given to data tables used to hold control and/or waveform data in an acoustic compiler.

Stretch tuning (14)

Tuning octaves slightly larger than a 2:1 ratio.

Strike note (07)

Note heard when a bell or chime is struck.

Strike tone (13)

The subjective tone that determines the pitch of a bell or chime; in most tuned bells it corresponds closely to one of the partials, but in chimes it does not.

Stroboscope (01)

A light that flashes at a regular rate, making possible a photographic record of motion.

Stroboscopic (09) (09)tuner

A tuning device that makes use of a rotating pattern illuminated by flashing lights.

Strohbass (vocal fry) register (17)

Register used for very low bass notes; makes use of a loose glottal closure termed vocal fry.

Subglottal pressure (17)

Amount by which the air pressure in the lungs exceeds atmospheric pressure.

Subjective pitch (07)

Pitch determined to have a frequency that does not correspond to that of any partial.

Subtractive synthesis (26)

Sound synthesis based on the controlled attenuation or removal (by filtering) of components from a multi-component waveform, such as a sawtooth or triangular waveform.

Subtractive synthesis (29)

The process of synthesizing sounds by passing time varying complex sounds through filters with time-varying characteristics.

Subwoofer (19)

A loudspeaker designed to produce extra-low-frequency sound, below the woofer.

Sul ponticello (10)

Bowing near the bridge.

Sul tasto (10)

Bowing near the fingerboard.

Superposition (03)

The motion at one point in a medium is the sum of the individual motions that would occur if each wave were present by itself without the others.

Supersonic (32)

Having a speed greater than that of sound (approximately 340 m/s or 770 mi/h).

Surround sound (20)

A multi-channel loudspeaker system used in home theaters.

Surround sound (25)

A system using multiple channels of sound and multiple loudspeakers to envelop the listener and create a feeling of spaciousness.

Sustaining pedal (14)

Right hand pedal of a piano, which raises all dampers, allowing the strings to continue vibrating after the keys are released.

Sweet spot (25)

The listening area in a room where the best spatial imaging takes place.

Synthesizer (27)

An instrument that creates complex sounds by generating, altering, and combining various electrical waveforms, typically by means of voltage-controlled modules.

Synthetic (holistic) listening (07)

Listening to a complex tone in a way that focuses on the whole sound rather than the individual components.

Syntonic comma

The small difference between a major or minor chord in the Pythagorean and just tunings.

Table lookup oscillator (29)

The primary synthetic signal source in an acoustic compiler: it can typically output an arbitrary waveform (specified in a stored function) at an arbitrary amplitude, frequency, and phase.

Tangent (14)

The small metal square that strikes the string of the clavichord

Temperament (09)

System of tuning in which intervals deviate from acoustically “pure” (Pythagorean” intervals.

Temporary threshold shift (TTS) (31)

A reversible increase in the threshold of hearing that disappears in hours, days, or weeks depending on its severity (also called auditory fatigue).

Tension (13)

The force applied to the two ends of a string, or around the periphery of a membrane, that provides a restoring force during vibration.

Thyroarytenoids (vocalis muscles) (17)

The muscles that form part of the vocal folds.

Thyroid (17)

The upper cartilage of the larynx.

Tidal volume (17)

The volume of air moved in and out of the lungs during a normal breath.

Timbre (07)

An attribute of the auditory sensation by which8 two sounds with the same loudness and pitch can be judged dissimilar.

Time domain (28)

The representation of a signal as a function of time, such as time-dependent amplitude of a sound waveform.

TL (transmission loss) (32)

A number that describes the reduction in the sound transmitted through a wall relative to the incident sound.

Tone hole (12)

A hole that can be opened to raise the pitch of an instrument.

Torsional mode (13)

An oscillatory motion that involves twisting of the vibrating member.

Transducer (19)

A device that converts one form of energy into another.

Transducer (20)

A device that converts one form of energy into another; in this chapter, the conversion of acoustics energy to electrical energy by a microphone was discussed.

Transfer function (28)

A function that represents how the input of a filter is transferred to its output, usually by multiplication in the frequency domain.

Transformer (18)

A device that changes ac at one voltage into ac at a higher or lower voltage.

Transient (07)

A sound that does not reoccur, at least on a regular basis.

Transient distortion (20)

Overshoot, or other un-programmed response, that results from the inability of some component to follow a very rapid change in signal.

Transistor (18)

A solid-state amplifying device consisting of a crystal of germanium or silicon with carefully selected impurities.

Transistor (26)

A device fabricated from semiconductor material (such as silicon) in which a base element controls the flow of current from an emitter element to a collector element.

Transmission curve (25)

A frequency-dependent curve showing how well sound is transmitted through a barrier.

Transverse vibration (02)

Vibration in which the principal motion is at right angles to the longest dimension.

Transverse wave (03)

A wave in which the vibrations are at right angles to the direction of propagation of the wave; example: waves on a rope.

Tremolo (14)

A device on an organ that produces a vibrato, usually by varying the air pressure.

Tremulant (14)

A device on an organ that produces a vibrato, usually by varying the air pressure.

Triad (09)

A chord of three notes; in the just tuning, a major triad has frequency ratios of 4:5:6, and a minor triad has ratios of 10:12:15.

Tristimulus diagram (07)

A way of representing timbre graphically in terms of the relative loudness of three different parts of the spectrum.

Tuning (09)

An adjustment of pitch in any instrument so that it corresponds to an accepted norm.

Turbofan engine (32)

A type of jet aircraft engine that uses a large fan to drive air into or through the engine.

Turbulent flow (14)

Fluid flow characterized by eddies and vortices; the flow velocity tends to vary randomly.

Turning point (11)

The point at which reflection of a wave occurs at the open end of the bell or tubing.

Turning point (12)

The point in a musical instrument at which most of the sound wave is reflected back toward the mouthpiece.

Tweeter (19)

A loudspeaker designed to produce high-frequency sound.

Two’s complement (21)

The technique of representing negative integers as a 1 plus the bit-complement of the corresponding positive integer.

Ultrasonic (32)

Having a frequency above the audible range.

Una corda pedal (14)

Pedal on grand pianos which shifts the entire action sideways, causing treble hammers to strike only two of the three unison strings.

UNICODE (21)

A coding standard that assign 16-bit codes to commonly used symbols used in many language.

Unit generator (29)

The name given to subprograms that implement specific signal-processing functions (such as oscillating, filtering, or adding) in an acoustic compiler.

Unsigned (21)

An ordered collection of bits that represents a numerical magnitude.

Upsampling (21)

The process of increasing the sampling rate of a digital signal by inserting samples: a factor-L upsampler would insert L-1 zeros between each sample of a digital signal (this signal would typically then be digitally filtered).