B&K 2250 Light, Руководство пользователя

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175
Appendix E
Glossary
A-weighting Filter: Frequency weighting corresponding approximately to the 40 dB equal
loudness curve, that is to say, the human ear’s response at low to medium
sound levels. It is by far the most commonly applied frequency weighting
and is used for all levels of sound.
B-weighting Filter: Frequency weighting corresponding approximately to the 70 dB equal
loudness curve, that is to say, the human ear’s response at medium sound
levels.
C-weighting Filter: Frequency weighting corresponding to the 100 dB equal loudness curve, that
is to say, the human ear’s response at fairly high sound levels. Mainly used
when assessing peak values of high sound pressure levels.
Criterion Level: Criterion Level is the maximum averaged sound level allowed for an 8-hour
period. Used for calculation of Dose, ProjDose, DoseUQ and ProjDoseUQ,
where U = F or S and Q = 4, 5 or 6 dB.
Decibel (dB): The measurement unit for expressing the relative intensity of sound. A direct
application of linear scales (in Pa) to the measurement of sound pressure
leads to large and unwieldy numbers. As the ear responds logarithmically
rather than linearly to stimuli, it is more practical to express acoustic
parameters as a logarithmic ratio of the measured value to a reference value.
This logarithmic ratio is called a decibel or dB. The advantage of using dB
can be clearly seen in the below illustration. Here, the linear scale with its
large numbers is converted into a manageable scale from 0 dB at the
threshold of hearing (20

Pa) to 130 dB at the threshold of pain (

100 Pa).