1.1 This standard specifies the calibration method using free field measurements to determine the random incidence sensitivity level of a sound level meter, and the calibration method using diffuse sound field measurements to determine the diffuse sound field sensitivity level. 1.2 This standard treats diffuse sound field sensitivity levels and random incidence sensitivity levels as equivalent. Either calibration method may be used depending on the equipment available. 1.3 The results calibrated according to this standard depend on the configuration of the sound level meter placed in the sound field. Reference: The sensitivity level required by this standard can vary greatly depending on the dimensions and geometry of the equipment placed in the sound field. For example, a sound level meter with a detachable microphone is placed in the sound field in the same configuration as when it is actually used. 1.4 In this standard, sound level meter refers to all sound measurement systems, including sound level meters.
JIS C 1508:2000 history
2000JIS C 1508:2000 Electroacoustics -- Random incidence and diffuse field calibration of sound level meters