HD 425 S1:1983

Sound Level meters

Scope

This standard describes instruments (sound level meters) for the measurement of certain frequency and time weighted sound pressure levels - This standard specifies sound level meters of four degrees of precision, designated Types 0,1,2 and 3 - The specifications for Types 0,1,2 and 3 sound level meters have the same centre values and differ only in the tolerances allowed - Tolerances generally broaden as the type number increases and differ for the various types to a degree which affects manufacturing costs significantly - This standard specifies the following characteristics of sound level meters: a) directional characteristics b) frequency weighting characteristics c) time weighting detector and indicator characteristics d) sensitivity to various environments - This standard specifies electrical and acoustical tests to verify compliance with the characteristics specified (see subclause 1.4) - It also describes the method for absolute sensitivity calibration