Acoustic Glossary


 

B : Sound and Vibration Definitions, Terms, Units, Measurements ...


B-weighting


Background Noise

the noise at a given location and time, measured in the absence of any alleged noise nuisance sources, also known as Residual Noise.
 

Background Noise Definition IEC 801-21-13,

total of interference from all sources in a system used for the production, transmission, detection, measurement, or recording of a signal

We have a full page on Background Noise

LA90, the level just exceeded for 90% of the measured time, is commonly used to quantify background noise.

See also statistical noise levels

Other noise descriptors : ambient noisebackground noisebroadband noisenarrowband noiseperiodicpink noisepseudo random noiserandom noisespecific noisewhite noisewideband noise


Backward Curve Integration

method for calculating reverberation time from the impulse noise decay curve. Also known as the Schroeder method.

Balanced Noise Criteria is a refinement of NC : Noise Criteria. The rating is determined by the SIL Speech Interference Level and gets the Classification (R) for Rumble if the spectrum is rich in low frequency sound, the Classification H for Hiss if the spectrum is rich in high frequency sound, or Classification (RV) for Rattle and Vibration and Rattle if the low frequency spectra is likely to produce audible rattling in lightweight building elements.

See also noise criteria


Band

a continuous range of frequencies between two limiting frequencies.

See also octaveone-third octave


Band Pass Filter

a filter covering a band of frequencies from a lower cut-off frequency to an upper cut-off frequency. Outside the filter bandwidth, the signal is attenuated.

Bandwidth

range of frequencies, usually of standard size in acoustics, for example octave or one-third octave bands. The lower and upper frequencies are also known as the -3 dB or half-power points. See also constant percentage bandwidth

Bar

unit of atmospheric pressure, equal to 1000 millibars, one million dynes per square centimetre, 100 kilopascal or 29.53 inches of mercury.

Bark

the human ear combines sounds of similar frequency into frequency bands, called critical bands. Dr Zwicker divided the audio spectrum into 24 critical bands and named the units 'barks'. See also loudness.

Beat Definition IEC 801-23-14,

phenomenon that results from the linear or non-linear superposition of two or more waves of the same kind but of different frequencies.

Beat Frequency

if two vibration components are quite close together in frequency and if they are present at the same time at the same place, they will combine in such a way that their sum will vary in level up and down at a rate equal to the difference in frequency between the two components. This phenomenon is known as beating, and its frequency is the beat frequency.

Bel

a bel is equal to 10 decibels (dB) and because it is a ratio of two quantities it is dimensionless.

The decibel (dB) is used extensively to 'describe' acoustic levels.

Bel Definition IEC 801-22-02,

unit of level of a quantity proportional to power when the base of the logarithm is ten. Also, the unit of level of a field quantity when the base of the logarithm is the square root of ten
Note 1 examples of power-like quantities are sound power and sound energy.
Note 2 examples of field quantities are sound pressure and voltage.

Bending Wave

Binaural hearing involving both ears

Binaural Recording

sound recorded using two microphones spaced to simulate the listeners ears and usually transmitted separately to each ear of the listener. The results, using good quality headphones, can be very realistic.

See also localisation and our head and torso simulator - HATS


Boundary Effect


Bow-tie Correction

multispectral measurements for correlation functions are performed using spectrum averaging. Half of the normal time record is set to zero. Accordingly, correlation functions for continuous signals will decrease with the delay. The bow-tie correction compensates for this.

Broadband Noise

also called wideband Noise - noise whose energy is distributed over a wide section of the audible range as opposed to narrowband noise.
 

Other noise descriptors : ambient noisebackground noisebroadband noisenarrowband noiseperiodicpink noisepseudo random noiserandom noisespecific noisewhite noisewideband noise

 
See also constant bandwidthconstant percentage bandwidthsoctave bandsFFT- fast fourier transform

Buffer a memory location in a computer or digital instrument that is set aside for temporary storage of digital information while it is waiting to be processed.


Building Acoustics see flankingreverberationsound insulation

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