| logarithm of the ratio of a given sound pressure to the reference sound pressure. Sound pressure level in decibels is 20 times the logarithm to the base ten of the ratio
NOTE 1 – Unless otherwise specified, the reference sound pressure is 20 μPа for airborne sound and 1 μPa for sound in media other than air.
NOTE 2 – Unless otherwise specified, the sound pressures are understood to be expressed in root-mean-square values.
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