BRUEL & KJAER HATS 4606, Руководство пользователя

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Appendix B
Glossary
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 illustration that follows. 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).
Our hearing covers a surprisingly wide range of sound pressures – a ratio of over a
million to one. The dB scale makes the numbers manageable
0
10 10
20 20
30 30
40 40
50 50
60 60
70 70
80 80
90 90
100 100
110 110
120 120
130 130
140 140
20 20
100 100
1,000 1,000
10,000 10,000
1,000,000 1,000,000
10,000,000 10,000,000
100,000,000 100,000,000
Sound pressure level (dB) Sound pressure level (dB) Sound pressure (µPa) Sound pressure (µPa)
100,000 100,000
Normal traffic Normal traffic
Library Library
Bedroom Bedroom
Conversation Conversation
Take-off Take-off
(from (from 25 25 m) m)
Rock group Rock group
Firecrackers Firecrackers
Pneumatic hammer Pneumatic hammer
Noisy workplace Noisy workplace
Office Office
Living room Living room
Woods Woods
180066