| logarithm of the ratio of a given sound pressure to the reference sound pressure of 20 µPa, the sound pressure being obtained with a standard frequency weighting and with a standard exponential time weighting.
NOTE 1 – Sound level in decibels is twenty times the logarithm to the base ten of that ratio.
NOTE 2 – Standard frequency weightings A and B used in IEC 61400-11 are given in IEC 60651 (1979): Sound level meters.
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