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Absolute Pitch: The exact pitch value of a musical note (for example, middle C)
Acoustic Cavity: The acoustics of enclosed volumes are important when considering sound propagation within the volume.
Acoustic Centre: The point in space of the origin of sound.
Acoustic Feedback: Acoustic feedback is the return of acoustic energy from the output of a sound reproducing equipment.
Action Level: An action level is basically a noise exposure level at which employers are required to take certain steps to reduce the harmful effects of noise on hearing.
Adaptive Differential Pulse Code Modulation: A compression technique which encodes the predictive residual instead of the original waveform signal so that the compression efficiency is improved by a predictive gain.
Adaptive Transform Acoustic Coding: A lossy audio coding system based on psychoacoustic principles.
ADC: Abbreviation of Analogue to Digital converter.
ADPCM: A compression technique which encodes the predictive residual instead of the original waveform signal so that the compression efficiency is improved by a predictive gain.
ALCONS: The measured percentage of Articulation Loss of Consonants by a listener.
Allusive Listening: Allusive listening is a presumed listening mode that may be said to occur where a listener relates moments or features of the music to similar moments or features in other musical works.
Ambience: The acoustic characteristics of a space with regard to reverberation.
Amplitude Distortion: A distortion of the wave shape of a signal.
Anomia: A neurological disorder which causes a marked inability to name otherwise familiar stimuli.
Apical Turn: The final turn in the spiral of the cochlea furthest from the oval and round windows.
Apparent Source Width: Discovered and developed by A. H. Marshall, ASW is a subjective parameter of spaciousness in concert halls, and is related to the level, at the listener's ears, of lateral reflections in the first 50 to 80 milliseconds after the arrival of the direct sound.
Arithmetic Coding: Arithmetic coding removes this restriction by representing messages as intervals of the real numbers between 0 and 1.
Articulation Loss of Consonants: The measured percentage of Articulation Loss of Consonants by a listener.
ATRAC: A lossy audio coding system based on psychoacoustic principles.
Attack: The beginning of a sound; the initial transient of a musical note.
Audio Amplifier: An amplifier designed specifically for amplifying audio signals in the frequency range 20Hz to 20kHz.
Audio Frequency: Generally in the range 20Hz to 20KHz.
Audiogram: Graph of hearing threshold level as a function of frequency.
Audiometer: An instrument for measuring hearing acuity.
Auditory Anomia: A neurological disorder which causes a marked inability to name otherwise familiar acoustic stimuli such as a door bell or motor vehicle.
Auditory Cortex: Region of the cortex devoted to the analysis of sound information.
Auditory Nerve: Bundle of nerve fibers that carry information from the cochlea to the higher stages of the auditory system.
Auralization: The technique of using computer-based mathematical models of an acoustic environment and 3D sound processing methods to make audible the sound field of a source in the modeled space.
A Weighting: This is the most generally used filter when making overall noise measurements.
Axial Mode: The room resonances associated with each pair of parallel walls.
Backward Recognition Masking: The reduction in the ability to recognize a sound pattern due to the subsequent presentation of another sound pattern with similar information content.
Baffle: A movable barrier used to achieve separation of signals from different sources.
Band Reject Frequencies: A tuned circuit that does not pass a specified band of frequencies.
Barany Box: Clockwork noise generator used when necessary as a masker in tuning fork or clinical speech tests.
Bark: The Bark is the standard unit corresponding to one critical band width of human hearing.
Bass: The lower range of audible frequencies.
Block Companding: Normalising of the digital representation of an audio signal within a certain time period.
Brilliance: In concert hall acoustics, a bright, clear, ringing sound, rich in harmonics, is called brilliant.
B Weighting: The B-weigthing curve approximately follows the 70 phon curve.
CD: Abbreviation of Compact Disc, an optical disc designed to store digitally 74 minutes of stereo audio data.
cdrom: Abbreviation that stands for Compact Disc Read Only Memory.
Chirp: A chirp is a sound that has a rapid increase in frequency.
Chord: A line segment that connects two points of a curve or circle.
Circular Frequency: The frequency of a steady recurring phenomenum in radians per second.
Clarity: In concert hall acoustics, the ratio, expressed in decibels, of the energy in the first 80 milliseconds of an impulse sound arriving at a listener's position divided by the energy in the sound after 80 milliseconds.
Class A Amplifier Operation: The type of operation in which the amplifier is biased so that variations in input signal polarities occur within the limits of cutoff and saturation.
Class AB Amplifier Operation: The type of operation in which the amplifier is biased so that collector current is cut off for a portion of the alternation of the input signal.
Class B Amplifier Operation: The type of operation in which the amplifier is biased so that collector current is cut off for one-half of the input signal.
Class C Amplifier Operation: The type of operation in which the amplifier is biased so that collector current is cut off for more than one-half of the input signal.
Click: When the duration of a sound is less than a time threshold required for pitch recognition, the sound is heard as a click rather than a tone.
CNEL: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Codec: Acronym for compressor/decompressor.
Community Noise Criteria: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Community Noise Equivalent Level: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Compact Disc: An optical disc designed to store digitally 74 minutes of stereo audio data.
Concert Pitch: Established by the International Organisation for Standardisation in 1955, the agreed reference frequency of 440 Hz. for the note called middle A.
Conductive Hearing Loss: Hearing loss due to the impairment of sound transmission before it reaches the inner ear.
Consonance: Two or more sounds that, when heard together, sound pleasant.
Convolution: Convolution meaning ..intertwined, coiled�
Critical Band: In human hearing, only those frequency components within a narrow band, called the critical band, will mask a given tone.
C Weighting: The C-weighting curve approximately follows the 100 phon curve.
DAB: Abbreviation of Digital Audio Broadcasting.
dB: Short for decibel.
dBA: A sound-level meter reading with an A-weighting network simulating the human-ear response at a loudness level of 40 phons.
dBB: A sound-level meter reading with a B-weighting network simulating the human-ear response at a loudness level of 70 phons.
Dead Room: Room characterized by a relatively large amount of sound absorption and a relatively short reverberation time.
Decade: Ten times any quantity or frequency range. The range of the human ear is about 3 decades.
Decibel: The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems.
De-Emphasis: Filtering applied to an audio signal after storage or transmission to undo a linear distortion due to emphasis.
Diagnostic Acceptability Measure: Scores are based on results of test methods evaluating the quality of a communication system based on the acceptability of speech as perceived by a trained normative listener.
Diagnostic Rhyme Test: An intelligibility measure where the subject′s task is to recognize one of two possible words in a set of rhyming pairs.
Dichotic: Listening condition in which different signals are applied to the two ears.
Diffusion: The mixing of two substances caused by random molecular motions.
Digital Audio Broadcasting: The transmission of radio signals using digital rather than analogue methods.
Digital Versatile Disc: Optical disc used for data, video and audio storage.
Diotically: The same signal at both ears.
Directivity Factor: The ratio of the sound pressure squared, radiated directly ahead of a sound source, to the sound pressure squared radiated in all directions.
Discrete Tone: A prominent single frequency component within a broadband noise signal.
Distance Double Law: In pure spherical divergence of sound from a point source in free space, the sound pressure level decreases 6 dB for each doubling of the distance.
Dolby Prologic: This is a four-channel sound reproduction system consisting of left, center, right and rear channel, (the single rear channel is usually played through two speakers).
Drumming Noise: Often used to describe noise in the frequency range 30 to 60Hz.
Duct Acoustics: Ducts with acoustic waves propagating through them exist in many forms.
Duplex Theory of Localization: This is the combination of the two methods that describe human binaural sound localization first proposed by Lord Rayleigh around 1900.
DVD: Digital Versatile Disc, optical disc used for data, video and audio storage.
Dynamic Headroom: The ability of an audio device to respond to musical peaks.
Dynamic Microphone: A device in which sound waves move a coil of fine wire that is mounted on the back of a diaphragm and located in the magnetic field of a permanent magnet.
Ear: The human ear, as a sound receiver, has to operate under a wide range of conditions.
Ear Canal: The external auditory meatus; the canal between the pinna and the eardrum.
Earplug: Hearing protector that is inserted into the ear canal.
Echo: A delayed return of sound that is perceived by the ear as a discrete sound image.
Echo Location: Determining the location of a target relative to the sensor face by means of measuring the time it takes for a sound wave to travel to the target and be reflected back to the sensor
Echograms: A record of the very early reverberatory decay of sound in a room.
Effective Perceived Noise Level: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Emphasis: Filtering applied to an audio signal before storage or transmission to improve the signal-to-noise ratio at high frequencies.
Entropy Coding: Variable length lossless coding of the digital representation of a signal to reduce statistical redundancy.
Equal Loudness Contour: A contour representing a constant loudness for all audible frequencies.
Equivalent Continuous Sound Level: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Eustachian Tube: The tube running from the middle ear into the pharynx that equalizes middle-ear and atmospheric pressure.
Fidelity: As applied to sound quality, the faithfulness to the original.
Field Sound Transmission Class: The same as STC rating except as measured in the field in accordance with standard methods.
Free Vibration: Free vibration occurs without forcing, the vibration of a string after it has been plucked.
Frequency Range: The bandwidth of a filter or signal.
Fusion Zone: All reflections arriving at the observer's ear within 20 to 40 msec of the direct sound are integrated, or fused together, with a resulting apparent increase in level and a pleasant change of character. This is the Haas effect.
G Weighted Overall Level: This purportedly reflects human response to infrasound.
Haas Effect: Delayed sounds are integrated by the auditory system if they arrive at the ear within 20 to 40 msec of the direct sound.
Habituation: The process by which an organism ceases to respond to some recurring or familiar stimulus.
Harmonic Distortion: Distortion of a signal by adding content that is harmonically related to the original signal. Clipping overload of an amplifier adds odd-order harmonics to the signal.
Harshness: A typical transient interdisciplinary phenomenon of noise and vibration.
HDMI: Abbreviation of High-Definition Multimedia Interface.
Headroom: A term related to dynamic range, used to express in dB, the level between the typical operating level and the maximum operating level above which the signal will be clipped.
Hearing Damage: A person exposed to high noise levels can suffer hearing damage. The damage may be gradual or traumatic.
Hearing Range in Animals: Many animals hear a much wider range of frequencies than is possible for humans.
Hertz: The SI unit of frequency indicating the number of cycles per second (symbol Hz).
High-Definition Multimedia Interface: A compact audio visual interface for transmitting uncompressed digital data.
Huffman Coding: For a given character distribution, by assigning short codes to frequently occurring characters and longer codes to infrequently occurring characters, Huffman's minimum redundancy encoding minimizes the average number of bytes required to represent the characters in a text.
Hydrophone: A hydrophone converts acoustic energy into electrical energy and is used in underwater passive systems for listening only.
Hz: An abbreviation of hertz. The SI unit of frequency.
Impact Isolation Class: A measure or specification of isolation effectiveness of building structures from impact noises such as slammed doors, dropped objects, footfalls, shuffled furniture, etc. The higher the IIC rating, the better such isolation.
Inner Ear: The inner ear is a labyrinth of twisting fluid-filled passages associated with hearing and balance.
Intensity Stereo: A method of exploiting stereo irrelevance or redundancy in stereophonic audio programmes.
Interaural Level Difference: In binaural hearing the interaural level difference has an impact on lateralization throughout the frequency spectrum.
Interaural Phase Difference: Coincident with the interaural time delay, varies systematically with source azimuth and wavelength due to distance from source and refraction around the head.
Knudson′s Law: The difference in frequency between pure tones of equal strength and of which the difference in pitch is just perceptible is defined by Knudson′s law.
L_AeqT: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
L_dn: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
L_EPN: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Live Room: Room characterized by a relatively small amount of sound absorption.
L_N: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
L_NP: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Localization Accuracy: Our ability to detect changes in localization or lateralization is not absolute.
Lombard Effect: As noise levels increase, talkers increase their voice levels to compensate and to maintain adequate conditions for verbal communication.
Loudness: A subjective term for the sensation of the magnitude of sound.
Low Frequency Sound: Acoustic waves below 20Hz are normally inaudible, but may be experienced as being in a region of high pressure.
Macrosonics: The technology of sound at signal amplitudes so large that linear approximations are not valid.
Masking: A property of the human auditory system by which an audio signal cannot be perceived in the presence of another audio signal.
Masking Threshold: A function in frequency and time below which an audio signal cannot be perceived by the human auditory system.
Mel: A proportional scale, in which equal intervals correspond to equal perceived interval sizes.
Middle Ear: The cavity between the eardrum and the cochlea housing the ossicles connecting the eardrum to the oval window of the cochlea.
Missing Fundamental: The phenomenon by which an observer, presented with a harmonic tone in which the fundamental is absent, hears the same pitch as would be heard if the fundamental had been present.
M/S Stereo: A method of removing imaging artefacts as well as exploiting stereo irrelevance or redundancy in stereophonic audio programmes based on coding the sum and difference signal instead of the left and right channels.
Muddy: A listening term, a sound that is poorly defined, sloppy or vague. For example, a "muddy" bass is often boomy with all the notes tending to run together.
NEF: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Noise Exposure Forecast: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Noise Exposure Limits: The amount of hearing loss is dependent on the noise level and duration.
Noise Pollution Level: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Noise Reduction Rating: Indicates a hearing protectors noise reduction capability.
NVH: Commonly used abbreviation for Noise, Vibration and Harshness
Otologist: A physician who specializes in the ear and its diseases.
Overtone: A harmonic frequency related to the fundamental.
Permanent Magnet Speaker: A speaker with a permanent magnet mounted on soft iron pole pieces.
Pinna: The exterior part of the ear.
Pop: An undesirable short duration microphone output, often caused by explosive exhalation of air during the formation of certain vocal sounds.
Power Amplifier: An amplifier in which the output-signal power is greater than the input-signal power.
Precedence Effect: Delayed sounds are integrated by the auditory system if they arrive at the ear within 20 to 40 msec of the direct sound.
Presbycusis: Gradual and biologically normal loss of acute hearing with advancing age.
Privacy Index: A measure for rating the speech privacy performance of an architectural space.
Psychoacoustics: The study of the interaction of the auditory system and acoustics.
Pulse Code Modulation: Coding where the input signal is represented by a given number of fixed-width samples per second.
Pure Tone: A tone with a sinusoidal waveform.
Quarter Wave Tube: A resonator used most commonly on automotive air intake systems to reduce resonance.
Rapid Speech Transmission Index: Abbreviated as RASTI and expressed in a decimal range of 0.2 for "bad" to 1.00 for "Excellent".
Rasp: A sort of blowing noise emitted often from the exhaust pipes of internal combustion engines, usually, it is dominated by a mixture of 4E, 6E and 8E engine orders on 4 cylinder engines.
RASTI: Rapid Speech Transmission Index, expressed in a decimal range of 0.2 for "bad" to 1.00 for "Excellent".
Rayl: The Rayl is the SI derived unit of specific acoustic impedance.
Reactive Sound Field: A sound field in which the particle velocity is 90� out of phase with the pressure.
Reactivity Index: The reactivity index in a given direction at a point is defined as the difference between the sound intensity level and the sound pressure level measured in the given direction at that point.
Room Acoustics: The general acoustic requirements of a room depend on the use.
SCART Connector: French-originated standard and associated 21-pin connector for connecting audio-visual equipment together.
SEL: There are a number of different noise criteria measurements used by local authorities to determine noise levels in the community.
Sibilance: A hissing sound produced when pronouncing S and Z.
Significant Threshold Shift: A shift in hearing threshold, outside the range of audiometric testing variability.
Single Event Noise Exposure Level: The dB(A) level which, if it lasted for one second, would produce the same A-weighted sound energy as the actual event.
Sound Definition: This compares �useful� sound with total sound.
Sound Focusing: Focusing of sound can be caused by reflection from large concave surfaces.
Sound Growth: The growth of sound in the room.
Sound Quality: Pertaining to the quality or other aspects of the machine that might be inferred from the sound it makes.
Sound Transmission Class: In acoustics, a single number rating for describing sound transmission loss of a wall or partition.
Sound Waves: Sound waves can be thought of like the waves in water.
Source: The object that produces the wave or disturbance.
Spectrum Analyser: An instrument for measuring, and usually recording, the spectrum of a signal.
Speech Coding: Excellent speech quality implies that coded speech is indistinguishable from the original and without perceptible noise.
Speed of Sound: Depends on the elastic and inertial properties of the particular medium.
Stereo: From the Greek meaning solid.
Stereo Irrelevance: A portion of a stereo audio signal which does not contribute to spatial perception.
Subwoofer: A speaker designed exclusively for low-frequency reproduction.
Tangential Mode: A room mode produced by reflections off four of the six surfaces of the room.
Tempo: The speed of occurrence of the beats for a given metric structure.
Threshold of Hearing: The equation defining the threshold of hearing.
Time History: A continuous record of the variation of a physical quantity (e.g. displacement, acceleration, force, etc.) with time.
Time Weighted Average: The yardstick used by the Occupational Safety and Health Administration to measure noise levels in the workplace.
Toe-In: Setting the front wheels to toe in will mean that when driven the wheels will tend to be aligned.
Treble: The higher frequencies of the audible spectrum.
Tuning Fork: A small two-pronged steel instrument which when struck produces a fixed tone.
Warmth: A term that is used to describe a listening term in terms of frequency, generally considered the range from approximately 150Hz-400Hz.
XLR Connector: A three pin connector widely used in the audio industry.