International Community for Auditory Display

Commonly used terms in audio related research:

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

Absolute threshold The minimum detectable level of a sound in the abscence of any other external sounds

Amplitude The instantaneous amplitude of an oscillating quantity is its value at any instant, while the peak amplitude is the maximum value that the quantity contains

Audiogram A graph showing absolute threshold for pure tones as a function of frequency. It is usually plotted as hearing loss in dB as a function of frequency, with increasing loss plotted in the downward direction

Aural harmonic A harmonic generated in the auditory system

B

Bandwidth A range of frequencies

Basilar membrane A membrane inside the cochlea which vibrates in response to sound and whose vibrations lead to activity in the auditory pathways

Beats Periodic fluctuations in peak amplitude which occur when to sinusoids with slightly different frequencies are superimposed

Bel A unit for expressing the ratio of two powers. The number of Bels is the logarithm to the base 10 of the power ratio

Best frequency See Characterisitc frequency

Binaural A situation involving listening with two ears

Binaural masking level difference (BMLD or MLD) A measure of the improvement in detectability of a signal which can occur under binaural listenting condidtions. It is the difference in threshold of the signal (in dB) for the case where the signal and the masker have the same phase and level relationships at the two ears and the case where the interaural phase and/or level relationships of the signal and masker are different

C

Categorical perception A type of perception where stimuli can only be distinguished if they are identified as belonging to a different category

Characteristic frequency (CF) The frequency at which the threshold of a given single neuron is lowest (i.e. the frequency at which it is most sensitive)

Combination tone A tone perceived as a component of a complex stimulus which is not present in the sensations produced by the constituent components of the complex when they are presented alone

Complex tone A tone composed of a number of sinusoids of different frequencies

Co-modulation masking release (CMR) The release from masking which can occur when the components of a masker have the same amplitude modulation pattern in different frequency regions

Component One of the sinusoids composing a complex sound, also called a frequency component

Cycle The portion of a periodic function that occurs in one period

D

Decibel One-tenth of a Bel, abbreviated dB. The number of dB is equal to ten times the logarithm of the ratio of two intensities, or 20 times the logarithm of the ratio of two amplitudes or pressures

Dichotic A situation in which the sounds reaching the two ears are not the same

Difference limen (DL) The smallest detectable change in a stimulus, also called the just-noticeable difference (JND), or the difference threshold

Diotic A situation in which the sounds reaching the two ears are the same

Diplacusis Binaural diplacusis describes the case when a tone of fixed frequency evokes different pitches in the left and right ear

E

Envelope The envelope of any function is the smooth curve passing through the peaks of the function

Equal-loudness countours Curves plotted as a function of frequency showing the sound pressure level required to produce a given loudness level

Equivalent rectangular bandwidth (ERB) The bandwidth of a rectangular filter which has the same peak transmission as that filter and which passes the same total power for a white noise input

Excitation pattern A term used to describe the pattern of neural activity evoked by a given sound as a function of the characteristic frequency (CF) of the neurons being excited

F

Filter A device which modifies the frequency spectrum of a signal, usually while it is in electrical form

Formant A resonance in the vocal tract which is usually manifested as a peak in the spectral envelope of a speech sound

Free field A field or system of waves free from the effects of boundaries

Frequency For a sine wave the frequency is the number of periods occuring in one second. The unit is the cycles per second, or Hz. For a complex periodic sound the term 'repetition rate' is used to describe the number of periods per second (p.p.s.)

Frequency threshold curve See Tuning curve

Fundamental frequency The frequency of that sinusoidal component of the sound that has the same period as the periodic sound

G

H

Harmonic A component of a complex tone whose frequency is an integral multiple of the fundamental frequency of the complex

Hertz A unit of frequency equal to one cycle per second (Abrv. Hz)

I

Intensity The sound power transmitted through a given area in a sound field. Units such as watts per square meter are used. The term is also used as a generic name for any quantity relating to amount of sound, such as power or energy, although this is not technically correct

J

K

L

Level The level of a sound is specified in dB in releation to some reference level. See Sensation level and Sound pressure level

Linear A system which satisfies the conditions of superposition and homogeneity

Loudness The intensity attribute of an auditory sensation, in terms of which sounds may be ordered on a scale extending from quiet to loud

Loudness level The sound pressure level in dB of a pure tone frequency 1kHz which is judged by the listener to be equivalent in loudness; measured in phone

M

Masked audiogram See Masking pattern

Masking The amount (or the process) by which the threshold of audibility for one sound is raised by the presence of another (masking) sound

Masking level difference (MLD) See Binaural masking level difference

Masking pattern A graph of the amount of masking (in dB) produced by a given sound as a function of the frequency of the masked sound

Modulation A periodic change in a particular dimension of a stimulus

Monaural A situation in which sounds are presented to one ear only

N

Noise Any unwanted sound. White noise is a sound whose power per unit bandwidth is constant, on average, over the range of audible frequencies. It usually has a normal (Gaussian) distribution of instantaneous amplitudes

O

Octave The interval between two tones when their frequencies are in the ration 2:1

P

Partial Any sinusoidal frequency component in a complex tone. It may or may not be a harmonic

Period The smallest time interval in a periodic function over which the function repeats itself

Periodic sound A sound whose waveform repeats itself regularly as a function of time

Phase The fractional part of a period through which the waveform has advanced, measured from some arbitrary point in time

Phase-locking The tendency for nerve firings to occur at a particular phase of the stimulating waveform on the basilar membrane

Phon The unit of loudness level

Pitch The attribute of auditory sensation in terms of which sounds may be ordered on a musical scale

Psychophysical tuning curve (PTC) A curve showing the level of narrow-band masker needed to mask a fixed sinusoidal signal; plotted as a function of masker frequency

Pure tone A sound wave whose instantaneous pressure variation as a function of time is a sinusoidal function, also called a simple tone

Q

R

Recruitment A more rapid than usual growth of loudness with increase in stimulus level, which occurs in certain types of hearing disorders

Residue pitch The lowest pitch heard when a group of partials is perceived as a coherent whole. Also known as virtual pitch, low pitch, and periodicity pitch

S

Sensation level The level of a sound in decibels relative to the threshold level for that sound for the individual listener

Simple tone See Pure tone

Sine wave, Sinusoidal vibration A waveform whose variation as a function of time is a sine function. This is the function relating the sine of an angle to the size of the angle

Sonification The use of nonspeech audio to convey information; more specifically sonification is the transformation of data relations into perceived relations in an acoustic signal for the purposes of facilitating communication or interpretation

Sound pressure level The level of a sound in decibels relative to an internationally defined reference level. The latter corresponds to an intensity of 10^-12 W/m², which is equivalent to a sound pressure of 20 microPa

Spectrum The distribution in frequency of the magnitudes (and sometimes the phases) of the components of the wave

Spike A single nerve impluse or action potential

T

Timbre The attribute of auditory sensation in terms of which a listener can judge that two sounds similarly presented and have the same loudness and pitch are dissimilar. Put more simply, it relates to the quality of a sound

Tone A sound wave capable of evoking an audiotory sensation having pitch

Tuning curve For a single nerve fiber this is a graph of the lowest sound level at which the fiber will respond, plotted as a function of frequency, also called a frequency threshold curve (FTC)

U

V

Virtual pitch See Residue pitch

W

Waveform The form or shape of a wave. It may be represented graphically by plotting instantaneous amplitude or pressure as a function of time 

X

Y

Z