IEC 60651 (2001)
Sound level meters
Deals with sound level meters of four degrees of precision, designated Types 0, 1, 2 and 3. Specifies the following characteristics: directional characteristics, frequency weighting characteristics, time-weighting, detector and indicator characteristics, sensitivity to various environments. Establishes electrical and acoustical tests to verify compliance with characteristics specified and describes the method for absolute sensitivity calibration. This standard supersedes IEC 60123 and IEC 60179.