absorber – An acoustical device that reduces the level of sound waves by converting sound energy into heat. The most common absorbers are porous absorbers, panel absorbers, membrane absorbers and Helmholtz absorbers.
absorption – In acoustics, the changing of sound energy to heat. This involves the use of acoustic surface materials and designs that can absorb unwanted sounds.
absorption coefficient – That fraction of sound energy absorbed at a given surface. It has a value between 0 and 1 and varies with the frequency and angle of incidence. If we say that a surface material has an absorption coefficient of .25, this means that the material absorbs 25% of the original acoustic energy and reflects 75% of the total sound energy at that frequency.
acoustics – The science that deals with the production, control, transmission, reception, and the effects or behavior of sound within an enclosed space.
acoustic foam – A special type of open cell foam designed to absorb sound waves.
acoustic treatment – Acoustic devices and materials installed in a space to control the behavior of sound. There are three types: absorbers, reflectors, and diffusers.
A to D – Analog to Digital converter.
AES – Audio Engineering Society
ambiance – The distinctive acoustical character of a given space.
amplifier (amp) – Any device that changes the amplitude of a signal, generally increasing the signal level.
amplitude – The instantaneous magnitude of an oscillating quantity such as sound pressure. The strength or sound pressure level of a signal measured in decibels. The peak value is the maximum value.
analog – A signal whose frequency and level vary continuously in direct relationship to the original electrical or acoustical signal.
anechoic – A space that is totally dead that supports no reflection of sound waves or echos.
anechoic chamber – A room designed to suppress internal sound reflections. Anechoic chambers are used for testing acoustical measurements, not for recording or listening to music.
articulation – A quantitative measure of the intelligibility of speech; the percentage of speech items correctly perceived and recorded.
artificial reverberation – Reverberation generated by electrical or acoustical means to simulate that of concert halls, etc. It is added to a signal to make it sound more lifelike.
ASA – Acoustical Society of America
attack – The beginning portion of a sound, the initial transient of a musical note.
attack time – The time it takes for a signal to go from silence to maximum level. The character and amount of reverb can be influenced by the attack time.
attenuate – To reduce the level of and electrical or acoustical signal.
attenuator – Usually a variable resistance device used to control the level of an electrical signal.
audio – Sound or the electrical signal representing sound.
audio frequency or spectrum – An acoustical or electrical signal of a frequency that that falls within the audible range of the human ear, usually taken as 20Hz to 20kHz.
auditory area – The sensory area lying between the threshold of hearing and the threshold of feeling or pain.
auditory system – The human hearing system made up of the external ear, the middle ear, the inner ear, the nerve pathways and the brain.
aural – Having to do with the auditory mechanism.
axial mode – The room resonances caused by sound reflecting between two parallel surfaces as in a rectangular room.
A-weighting – A frequency-response adjustment of a sound-level meter that makes its reading conform, roughly to human response.
baffle – A movable barrier used in the recording studio to improve separation of signals from different sources. The surface of board upon which a loudspeaker is mounted.
bandwidth – The frequency range passed by a given device or structure.
bass – The lower range of audible frequencies.
bass trap – An acoustic device designed to absorb low-frequency sound waves.
Bel. – A unit of measure expressing the amount a signal drops in level over a mile of telephone wire, named for Alexander Graham Bell.
binaural – Listening with two ears.
bleed – Sound waves “leaking” from one space or another, or into a microphone not intended for the sound source that creates them.
boomy – A colloquial expression for excessive bass response.
broadband – Effective over a wide range of frequencies.
broadband absorber – An acoustic device designed to absorb sound waves across a wide range of frequencies.
byte – A term used in digital systems. One byte is equal to eight bytes of data. A bit is the elemental “low” or “high” state of a binary system.
capacitor – An electric component that passes alternating currents but blocks direct currents, also called a condenser, it is capable of storing electrical current.
clipping – An electrical signal clipped by electronic circuits or by overloading an electronic device. It is an distortion of the signal.
cloud – An acoustical device suspended from the ceiling over the listening position.
coloration – The distortion of a signal detectable by the ear.
comb filtering – A series of deep notches and peaks in frequency response, usually due to phase differences between sound waves. Results in significant coloration of the sound.
compression – Reducing the dynamic range of a signal by electrical circuits that reduce the level of loud passages.
correlogram – A graph shoeing the correlation of one signal with another.
crossover frequency – In a loudspeaker with multiple radiators, the crossover frequency is the -3 dB point of the network dividing the signal energy.
crosstalk – The signal of one channel, track, or circuit interfering with another.
cycles per second – Number of peak/trough cycles in a sound wave that occur in a second.
Also known as “frequency” and “Hertz”.
DAW – Digital Audio Workstation
dead – All or most reflections absorbed.
decade – Ten times any quantity or frequency range, the range of the human is three decades.
decay – The manner in which sound falls to silence.
decay rate – A measure of the decay of acoustical signals, expressed as a slope in dB/second.
decibel (dB) – The human ear responds logarithmically and it is convenient to deal in logarithmic units in audio systems. The Bel. is the logarithm of the ratio of two powers, and the decibel is 1/10th of a Bel.
dB(A) – A sound level meter reading with a A-weighting network simulating the human ear at a loudness level of 40 phons.
dB(B) – The sound level meter reading with a B-weighting network simulating the human ear response to a loudness level of 70 phons.
dB(C) – The sound level meter reading with no weighting network in the circuit, i.e., flat. The reference level is 20 micropascals.
decoupling – Isolating an object, such a a speaker cabinet, monitor, or even a room’s floor or wall, from it’s surroundings.
diaphragm – Any surface that vibrates in response to sound or is vibrated to emit sound,m such as in microphones and loudspeakers. Also applied to the wall and floor surfaces vibrating in response to sound.
dielectric – An insulating material. The material between the plates of a capacitor.
diffraction – In acoustics, sound waves with long wave-lengths bend around objects (diffract).
diffuse – Scattered or spread out.
diffusion – Breaking a single reflection into many smaller, lower-level reflections scattering in different directions.
diffusion coefficient – The ratio of scattered intensity at + 45 degrees to the specular intensity.
diffuser – An acoustical device that scatters sound waves.
digital – A numerical presentation of an analog signal. Pertaining to the application of digital techniques to common tasks.
dip – An area where cancellation of sound waves causes a decrease in level at a particular frequency or range of frequencies.
direct field – Speakers or a sound source set up so that the listener primarily hears the direct sound, with few or no reflections. See also “near field”.
direct sound – Sound from a source that arrives at the listener’s ears without reflecting of any surfaces.
directional – Moving in a single direction.
dispersion – The scattering or distribution of sound waves as they travel from a sound source, such as a speaker, and, the angle or coverage a speaker can produce.
distortion – Any change in waveform or harmonic content of an original signal as it passes through a device. The result of nonlinearity within a device.
driver – Element of a speaker or monitor that creates sound waves.
dropouts – In multi-channel recording on narrow tracks, the signal can be momentarily lost because the magnetic particles in a short section of tape are not well aligned
dynamic range – The ratio (in decibels) of the loudest to softest signals a system can handle without distortion.
dyne – The force that will accelerate a one-gram mass at the rate of 1cm/sec. The old standard reference level for sound pressure was 0.0002 dyne/cm2. The same level today is expressed as 20 micro-pascals.
early sound – Direct and reflected components that arrive at the ear from a source during the first 50ms or so. Such components are replicas of the original sound and arrive at different times producing comb-filter distortion.
echo – A delayed sound that is perceived by the ear as a discrete sound image.
EFC – Energy-frequency curve.
EFTC – Energy-frequency-time curve.
ensemble – Musicians must hear each other to function properly; in other words, the ensemble must prevail. Diffusing elements surrounding the stage area contribute to the ensemble.
equalization – The process of adjusting the frequency response of a device or system to achieve a flat or other desired response.
equalizer (EQ) – A device for adjusting the frequency response of a device or system.
equal loudness contour – A contour representing a constant loudness for all audible frequencies. The contour having a sound pressure level of 40dB at 1,000 Hz s arbitrarily defined as the 40-phon contour.
ETC – Energy-time curve.
fader – Controls the level of the input module signal that is sent on to the output bus.
far field – Speakers or a sound source placed beyond the “near field” range (more than three or four feet or so from the listener).
Fast Fourier Transform (FFT) – A mathematical method for analyzing a waveform that allow for the transfer between time and frequency domains. Baron Fourier figured out that audio waveforms could be represented as the sum of many component single-frequency waves (sine waves). A Fourier Transform is both the graph showing the frequency content of a waveform and the mathematical equation that can be used to represent it.
feedback, acoustic – Unwanted interaction between the output and the input of an acoustical system, e,g., between the loud-speaker and the microphone of a system.
fidelity – As applied to sound quality, the faithfulness to the original.
filter – Audio processor that removes a particular frequency or range of frequencies from a signal.
filter, bandpass – A filter that passes all energy between a low-frequency cutoff point and a high-frequency cutoff point.
filter, high pass – A filter that passes all energy above a cutoff frequency.
filter, low pass – A filter that passes all energy below a cutoff frequency.
first reflection – Sound waves that reach the listener’s ears after one bounce from a surface, less than 20 milliseconds after the direct sound from the source.
flanking sound – Sound traveling by circuitous paths which reduces the effectiveness of a barrier.
flat – a. Having an even frequency response without dips or peaks due to electronic or physical characteristics. b. A device or room in which all frequencies are outputted at unity gain – that is, at the same output level as they came in. Because a flat device or room doesn’t emphasize or de-emphasize any frequencies, it provides a true picture of the signal that will translate well to other systems and rooms.
float – To suspend the floor of a studio on hard rubber “pucks” to isolate it from the rest of the structure.
floating floor – Floor that is isolated from the surrounding structure.
flutter – A repetitive echo set up by parallel reflecting surfaces.
frequency – The measure of the rapidity of alternations of a periodic signal, expressed in cycles per second or Hz.
frequency response – The changes of the sensitivity of a circuit or device with frequency.
FTC – Frequency-time curve.
fundamental – The basic pitch of a music note.
fusion zone – All reflections arriving at the observer’s ears within 20-40 ms 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’.
gain – The increase in power level of a signal produced by an amplifier. graphic EQ – Type of audio equalizer with a separate level control for each dedicated number of frequencies.
graphic-level recorder – A device for recording of signal level in dB vs. time on a tape.
Haas Effect – Delayed sounds are integrated by the auditory apparatus id they fall n the ear with 20-40 ms of the direct sound. The level of the delayed components contributes to the apparent level of the sound. It is accompanied by a pleasant change in character.
harmonic – A tone occurring at an integer multiple of the fundamentals frequency.
headroom – The ability to withstand higher amounts of signal without distorting.
Helmholtz absorber (also device or resonator) – A reactive, tuned sound absorber. In practice, a Helmholtz absorber is a box enclosing a volume of air, with a series of slits or holes in one surface. Air motion due to sound waves causes the absorber to resonate in much the same way as blowing across the opening of a soda bottle creates a tone.
Hertz (Hz) – Number of vibrations or complete cycles of a sound wave occurring within a second. Named for Henrich Hertz, a 19th century physicist who first investigated and artificially produced radio waves.
hot spot – Position in a room where there is a boost at a particular frequency or range of frequencies.
IEEE – Institute of Electrical and Electronic Engineers.
imaging – The ability to localize or pinpoint the position of a sound in a stereo or surround mix when listening.
impedance matching – Maximum power is transferred from one circuit to another when the output impedance of the one is matched to the input impedance of the other. Maximum power transfer may be less important in may electronic circuits than low noise or voltage gain.
impulse – A “spike” of sound of a very short duration used to perform acoustical measurements.
impulse response – Literally, how a device or space response to an impulse. By capturing the response of a room to an impulse, FFT (Fast Fourier Transform) analysis can be performed to obtain frequency-related response information.
infrasonic – Frequencies below the range of human hearing.
inductance – An electrical characteristic of circuits, especially of coils, that introduces inertial lag because of the presence of a magnetic field.
initial time-delay gap – The time gap between the arrival of the direct sound and the first sound reflected from the surfaces of the room.
in phase – Two periodic waves reaching peaks and going through zero at the same time are said to be “in phase”.
insulation – As referred to sound barriers, insulation is applied to the sound transmission loss of a particular wall, etc.
intensity – Acoustic intensity is sound energy flux per unit area. The average rate of sound energy transmitted through a unit area normal to the direction of sound transmission.
interference – The combining of two or more signals results in an interaction called interference. This can be constructive or destructive, aka “undesired signals”.
inverse square law – Physical law that says that intensity is inversely proportional to the square of distance. In acoustic terms, this results in a 6 dB drop every time you double the distance; 10 times the distance reduces the loudness by 20 dB.
isolation – Keeping sound from entering or escaping from a space.
isolation booth – Small room designed to contain, or isolate, the sound of a source so that it can be recorded without bleed to or from other sound sources.
ITD – Initial time-delay gap.
JAES – Journal of the Audio Engineering Society.
JASA – Journal of the Acoustical Society of America.
kilohertz (kHz) – 1,000 Hertz or cycles per second.level – A sound pressure level in dB means that it is calculated with respect to the standard reference level of 20 micropascals. The word “level” associates that figure with the appropriate standard reference level.
linear – A device or circuit with a linear characteristic means that a signal passing through is not distorted.
listening position – Where the listener is ideally located when monitoring audio.
live – Reflective, without absorption.
live end/dead end – An acoustical treatment plan for rooms, in which one end is highly absorbent and the other end is reflective and diffusive.
localization – The ability to discern where in a space of sound is coming from.
logarithm – An exponent of 10 in the common logarithms to the base 10. For example, 10 to the exponent 2 = 100; the log of 100 = 2.
loudness – A subjective term for the sensation of the magnitude of sound.
loudspeaker – An electro-acoustical transducer that changes electrical energy to acoustical energy.
machine room – Dedicated room in a studio designed to isolate devices (such as computers, hard drives, and tape machines) that might contribute to an increased ambient noise floor.
masking – The amount (or the process) by which the threshold of audibility for one sound is raised by the presence of another (masking) sound.
mass-air-mass resonance – A resonating system composed of the mass of two spaced glass panes, for example, and the air between them. At the frequency at which this system is resonant there is usually dip in the transmission-loss curve.
MDF – Stands for medium-density fiberboard, a wood product made from processed wood fibers combined with resin and used wherever real wood might be used.
mean free path – For sound waves in an enclosure, it is the average distance traveled between successive reflections.
membrane trap – Type of bass trap that features a thin “membrane,” panel, diaphragm, or surface that vibrates in response to low-frequency sound waves.
microphone (mic) – An acoustical-electrical transducer by which sound waves in air can be converted to electrical signals.
MIDI – Stands for Musical Instrument Digital Interface. MIDI is an industry standard protocol that enables multiple elctronic instruments, performance controllers, computers and other related devices, from different manufacturers, to communicate with each other throughout a connected network.
midrange – Literally, the middle part of a frequency range. There is no exact range of frequencies defined within the range of human hearing as the “midrange”; it falls somewhere between the low frequencies and the high frequencies.
millisecond (ms) – 1/1,000 of a second.
mixer – A resistive device, sometimes very elaborate, used for combining signals from many sources.
modal – Pertaining to room modes
modal distribution – Ho modes are spaced across the frequency response.
mode – A room resonance. There are axial, tangential, and oblique modes.
monitor – Loudspeaker used in the control room of a recording studio.
monophonic – One audio channel.
multitrack – A system of recording multiple tracks on magnetic tape or other media. The signals recorded on the various tracks are then “mixed down” to obtain the final recording.
music – Organized sound.
NAB – National Association of Broadcasters
near field (TM) – A sound source positioned near the listener, often defined as less than one wavelength, but usually accepted to be within three or four feet. Though commonly used, “near field” is a trademarked term.
near field monitor – Studio speaker designed to be used in close proximity to the listener. Near field monitors take advantage in the inverse square law which says that sound level decreases by the square of the distance. The idea is that the monitors are close to the listener, who will hear primarily direct sound, with any reflections being much lower in level (and therefore much less destructive).
node – A position along a wavelength at which there is no motion. Nodes are spaced 1/2-wavelength apart.
noise – Undesired sound that isn’t related to any desired sound.
noise floor – Level of ambient noise in a room or self-generated noise in a device. Reducing the noise floor increases the dynamic range.
noise criteria – Standard spectrum curves by which a given measured noise may be described by a single NC or NCB number.
nonlinear – A device or circuit is noninear if a signal passing through it is distorted.
normal mode – A room resonance.
NRC – Abbreviation for noise reduction coefficient. An overall performance rating for an acoustical material derived by averaging the absorption coefficient across a range of octave bands.
null – A low or minimum point on a graph. A minimum pressure region of a room.
Nyquist frequency – The maximum audio frequency that the system can accurately represent and reproduce. The selected sample rate must be at least twice as high as the highest frequency to be recorded. In simpler terms: sample rate > 2 X highest frequency.
oblique mode – Mode created by sound reflecting across all six surfaces (four walls, floor, and ceiling) in a room. Oblique modes are roughly half as strong as tangential modes, and one-fourth as strong as axial modes.
octave – The distance between two frequencies having a ratio of 2:1.
omnidirectional – In all directions at once. Omnidirectional microphones pick up sound in a spherical pattern, equally well from all directions. Low frequency speakers tend to be omnidirectional in their dispersion pattern.
oscilloscope – A cathode-ray type of indicating instrument.
out of phase – The offset in time of two related signals.
overdrive indicator – A warning lamp on a channel of the audio console that indicates when transient peaks overdrive amplifiers causing distortion.
overtone – A component of a complex tone having a frequency higher than the fundamental.
panel absorber – A panel mounted with an airspace behind vibrates and absorbs sound energy. A frequency higher than the fundamental.
panpot (panoramic potentiometer) – An adjustable resistance network in an electric circuit by which the signal on a given channel may be positioned in the stereo or quad playback sound field.
parametric equalizer – Type of audio equalizer inverted by producer/engineer George Massenburg that features separate controls for gain, bandwidth, and frequency for each EQ band.
passive absorber – A sound absorber that dissipates sound energy as heat.
passive monitor – Type of studio speaker that requires an external amplifier.
peak – An area where reinforcement of sound waves causes a boost in level at a particular frequency, literally, the highest point.
perforated absorber – A panel absorber with an air space becomes a Helmholtz absorber if holes perforate the panel.
phase – The time relationship between two signals.
phase cancellation – Destructive interaction of two identical out of phase sound waves results in a reduction, increase or cancellation of a sound.
phase distortion – Changing the phase relationship of frequencies within a waveform.
phon – The unit of loudness level of a tone.
pink noise – A signal whose spectrum level decreases at a 3 dB-per-octave rate. This give noise equal energy per octave.
pitch – A subjective term for the perceived frequency of a tone.
polar pattern – A graph of the directional characteristics of a microphone or a loudspeaker.
polarity – The relative position of the high (+) and the low (-) signal leads in an audio system.
preamplifier (preamp) – Electronic device used to raise the level of a signal before the main stage of amplification occurs.
precedence effect – For delay time, less than 50 ms, echos are no longer a noise even if the echo is stronger than the primary sound. This is called the (Haas) effect.
Pro Tools – Computer based DAW hardware and software system manufactured by Digidesign.
psychoacoustics – The study of how we perceive sound and extract information from acoustics.
pure tone – A tone with no harmonics. All energy is concentrated on a single frequency.
Q-factor – Quality factor. A measure of the losses in a resonance system. The sharper the resonance curve, the higher the Q.
quadratic residue diffuser – An acoustical device designed with a random surface pattern using mathematical formulas.
random noise – A noise signal, commonly used in measurements, which has constantly shifting amplitude, phase, and frequency, and a uniform spectral distribution of energy.
range of human hearing – Generally accepted asd 20Hz to 20,000 Hz.
rarefraction – Area of decreased pressure caused by a sound wave. The opposite of a compression.
reactive absorber – A sound absorber, such as the Helmholtz resonator, which involves the effects of mass and compliance as well as resistance.
reactive silencer – A silencer in air-conditioning systems that uses reflection losses for its action.
reflect – To bounce off a surface.
Reflection-Free Zone – Absorbent area in a studio around the main listening position.
reflection-phase grating – A diffuser of sound energy using the principle of the diffraction grating.
reflector – Acoustical device used to redirect sound waves.
refraction – The bending of sound waves traveling through layered media with different sound velocities.
resistance – The quality of electrical or acoustical circuits that results in dissipation of energy through heat.
resonance – A tendency to vibrate at a particular frequency. In acoustics, a boost in a particular frequency due to a room mode or standing wave.
resonant frequency – Frequency at which resonance occurs. Every object and every material has a resonant frequency.
resonator – Acoustical device that vibrates sympathetically in response to a sound wave.
resonator silencer – An air-conditioning silencer employing stubs and their resonating effect for its action.
reverberant decay – Time it takes for the reverb in a room to stop ringing.
reverberation – The tailing off of sound in an enclosure after the source has stopped. Caused by multiple reflections from boundaries of room.
reverberation time (RT60) – The time required for the sound in an enclosure to decay 60dB.
room mode – A low-frequency standing wave in a room. An acoustic resonance at a particular frequency in a room. Room modes occur when sound reflects between parallel surfaces and cause anomalies in the room’s response.
room within a room – Type of studio construction in which a floating floor is constructed, then walls and ceiling are built on top of that floor, resulting in a room that is isolated from the surrounding structure.
sabin – The unit of sound absorption. One square foot of open window has an absorption of 1 sabin.
sequence, maximum length – A mathematical sequence used in determining the well depth of diffusers.
sequence, primitive root – A mathematical sequency used in determining the well depth of diffusers.
sequence, quadratic residue – A mathematical sequency used in determining the well depth of diffusers.
signal – Usually a voltage or current.
signal path – The route a signal takes through a series of pieces of equipment, the devices an audio signal passes through while being recorded, mixed, or processed in a studio.
signal-to-noise ratio – The difference between the nominal or maximum operating level and the noise floor in dB.
sine wave – A type of waveform containing a single frequency – the fundamental – with no harmonics or overtones, similar to the tone produced by a flute.
slap-back – An echo resulting from a sound wave reflecting between parallel surfaces. You can test for slap-back (or slap echo) by clapping your hands and listening for a discrete echo.
solid-state – A branch physics having to do with transistors, etc.
sine – The unit of measurement for subjective loudness.
sound – Vibrations in the range of human hearing.
sound absorption coefficient – The practical unit between 0 and 1 expressing the absorbing efficiency of a material. It is determined experimentally.
sound barrier – Material designed to stop the transmission of sound waves.
sound isolation – A more technically correct way of saying “soundproof”.
sound level meter – A microphone-amplifier-meter arrangement calibrated to read sound-pressure level above the reference level of 20 micropascals.
sound power level – A power expressed in dB above the standard reference level of 1 picowatt.
sound pressure level (SPL) – The volume or loudness of a sound expressed in decibels.
SPL meter – Device that measures sound pressure level.
sound spectrograph – An instrument that displays the time, level, and frequency of a signal.
sound transmission class (STC) – A rating that can be used to compare the acoustical isolation provided by different materials.
sound transmission loss (STL) – A frequency-dependent rating of the amount of isolation from sound transmission a particular material provides.
soundproof – Impervious to sound waves.
sound wave – Wave motion created in the air (or other material) as a result of vibration of a material in the human hearing range.
speaker – Transducer that converts electrical signals into sound waves.
spectrum – The distribution of the energy of a signal with frequency.
spectrum analyzer – An instrument for measuring (and usually recording) the spectrum of a signal.
specularity – A term devised to express the efficiency of diffraction-grating types of diffusers.
speed of sound – Through air, 1,230 feet per second, or 343 meters per second.
spherical divergence – Sound diverges spherically from a point source in free space.
splaying – Walls are splayed when they are constructed somewhat “off square”, i.e., a few degrees from the rectilinear form.
standing wave – Sound waves reflecting between two parallel surfaces in a room. Standing waves always negatively impact the response of the room and are controlled using acoustic treatments.
STC – Sound transmission class: a single-number system of designating sound transmission loss of partitions, etc.
steady-state – A condition devoid of transient effects.
stereo – A stereophonic systems of two channels.
subwoofer – Speaker dedicated to producing low-frequency sound eaves, usually below 120 Hz.
superposition – Many sound waves may traverse the same point in space, the air molecules responding to the vector sum of the demands of the different waves.
supersonic – Technically, traveling at speeds faster than the speed of sound.
surround sound – Sound reproduction system with more than two channels of related audio material.
sweet spot – The location in a listening room with the best response and imaging. For stereo, normally the third point in an equilateral triangle with the two monitors.
tangential mode – A room mode produced by reflection off four of the six surfaces of the room.
test tone – A tone of a certain frequency and timbre played back in a room or through a device to help analyze performance or measure response.
threshold of feel (pain) – The sound pressure level that makes ears tickle, located about 120dB above the threshold of hearing.
threshold of hearing – The lowest sound level that can be perceived by the human auditory system. This is close to the standard reference level of sound pressure, 20 micropascals.
timbre – The tonal quality of a sound.
tone – A distinct musical pitch, the timbrel character of a sound. In musical terms, a whole step.
tone control – An electrical circuit to allow adjustment of frequency response.
transducer – Device that converts one type of energy into another.
transient – A short-lived aspect of a signal, such asd the attack and decay of musical tones.
translate – How consistently an audio mix holds up when heard on different playback systems.
treble – The higher frequencies of the audible spectrum.
tuned absorber – Acoustic device designed and optimized for absorbing sound waves at a particular frequency or range of frequencies.
tweeter – High-frequency transducer in a multi-driver speaker system.
ultrasonic – Frequencies above the range of human hearing.
volume – The loudness of a signal, subject to the perception of the listener.
watt – The unit of electrical or acoustical power.
wave – A regular variation of an electrical signal or acoustical pressure.
waveform – Technically, a graph of the voltages of a periodic signal plotted versus time. The “shape” of a sound wave; the waveform defines the timbre of a sound.
wavelength – Technically, the distance between one peak of sine wave and the next peak. The result of dividing the speed of sound by the frequency of a sine wave. The physical length of a sound wave.
weighting – Adjustment of sound-level meter response to achieve a desired measurement.
wet – A signal with processing, usually artificial reverb.
white noise – Random noise having uniform distribution of energy with frequency.
woofer – Low frequency transducer in a multi-driver speaker system.