Help Topics - B

B weighting

One of the standard frequency correction curves (or weightings) applied to sounds in a measurement device to simulate the hearing capability of the human hearing mechanism. The B weighting is hardly ever used for noise measurements nowadays. Other frequency weightings include the 'A', 'C' and 'Z' curves.

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Background noise level

The total noise level of all sources other than that caused by the specific noise of interest. The unit called the 90th percentile noise level, L90%, often identifies this.

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Back pressure

The differential pressure drop across a restriction, such as a filter in an air  cassette, normally measured in inches of water.

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Band

Any range of values such as in the frequency spectrum for noise measurements. For example, the band from 20 Hz to 20,000 Hz.

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Band pass filter

A filter for noise measurements that has a single transmission band extending from a lower cutoff frequency greater than zero to some finite upper limit or cutoff frequency.

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Barrier

A physical obstruction to the transmission of a stimulus between a source and a receiver. Such barriers in the case of noise can be placed by the side of roads or rail lines to reduce the levels of unwanted noise exposure to local residents living close to such sources

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Black globe temperature

The temperature within a matt black, hollow sphere. It measures the radiant temperature of the ambient air.

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Breathing zone

The volume within about 8 inches (200 mm) of the operator’s mouth or nose.

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Broadband noise

Noise with components over a wide range of frequencies, the overall noise without any noticeable tonality.

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Broadband noise level

The single number overall measurement of all noise in the audible range (20Hz to 20kHz) measured with one of the standard broadband frequency weightings.  This is typically carried out using the ‘A’ weighting network in a sound level meter.

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BSI

British Standards Institute in the UK.

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Building acoustics

The science of the behavior of sound within enclosed spaces, such as the size, shape and amount of noise that determines the audibility and perception of speech and music within the room.

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