Sound Level Definition IEC 801-22-14, 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. Sound level in decibels is twenty times the logarithm to the base ten of that ratio
● Note 1 : standard frequency weightings A, B and C and standard exponential time weightings fast (F), slow (S) and impulse (I) are given in IEC 651 Sound level meters.
● Note 2 : time and frequency weightings employed should be specified, but if not stated explicitly, Fast (F) exponential time weighting and A-frequency weighting are understood.
Sound Level is also known the weighted sound pressure level
● Note 1 : If a frequency weighting is not specified, the A-frequency weighting is understood
● Note 2 : In principle, exponential time weighting is not involved
Not be confused with the Time-average Sound Pressure Level Definition, IEC 801-22-11. To compare these definitions directly click here
With the advent of digital techniques it was possible to integrate the sound levels over a wide dynamic range, use linear averaging circuits over long measurement periods and the integrating averaging sound level meter was born, now commonly known as the Leq or equivalent continuous sound level meter
Integrating circuits also greatly enhance the accuracy and dynamic range of L10, L90, Ln etc., statistical noise measurements.
Sound Level Meter Classes : sound level meters are graded into classes, originally known as 'types'.
Sound Level Meter Class 0 : the requirement for laboratory measurements
Sound Level Meter Class 1 : precision instruments with stricter tolerances than -
Sound Level Meter Class 2 : sometimes referred to as Industrial Grade Meters.
There are also many cheap sound level meters for sale, that do not meet even the Class 2 requirements - buyers beware.
See also noise dose • sound exposure • sound intensity • sound power