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TRG-TRC007-EN 11
period one
Fundamentals of Sound
notes
Sounds encompass a wide range of volumes, or levels. The loudest sound the
human ear can hear without damage due to prolonged exposure is about
1,000,000,000 times greater than the quietest perceptible sound. A range of this
magnitude makes using an arithmetic scale cumbersome, so a logarithmic
scale is used instead.
The measurement of sound level is expressed in terms of decibels (dB), a
dimensionless quantity. A decibel is a calculated value based on the ratio of two
quantities. It is defined as ten times the logarithm to the base ten (log
10
) of the
measured quantity divided by the reference quantity. The reference quantity
must be specified to prevent confusion regarding the magnitude of the ratio.
Decibel
measured value
reference value
dB = 10 log
10
Figure 13
dB 10log
10
measured value
reference value
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