
period one
Fundamentals of Sound
notes
Decibel
dB = 10 log10 |
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Figure 13
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 (log10) of the measured quantity divided by the reference quantity. The reference quantity must be specified to prevent confusion regarding the magnitude of the ratio.
dB = 10 log10
measured value
reference value
11 |