+ANSI+S1.4a-1985+(R2006).jpg)
Historical
ANSI S1.4-1983 (R2006)/ANSI S1.4a-1985 (R2006)
American National Standard Specification for Sound Level Meters
Conforms as closely as possible to the IEC Standard for Sound Level Meters, Publication 651, First Edition issued in 1979. This revision represents a significant improvement over ANSI S1.4-1971, particularly in its specifictions relating to measurement of transient sound signals. It also permits the use of digital techniques and displays. The principal changes from ANSI S1.4-1971 are: inclusion of an optional impulse exponential-time averaging characteristec; inclusion of an optional peak characteristic; more rigorous definition of the dynamic characteristics for the Fast and Slow exponential-time-averaging; increase in the crest factor requirement to ten for type 1 instuments; specification of a type 0 laboratory instrument with generally smaller tolerance limits than those previously specified for type 1; and deletion of the type 3 survey instrument.
Acoustical Society of America [asa]