scope:

This standard specifies requirements and procedures for the measurement of sound pressure levels in air. These requirements and procedures apply primarily to measurements performed under normal, relatively quiescent meteorological conditions. Nearly all measurements made indoors will fall under such conditions, but outdoor measurements may also be made, and may remain in conformance with this standard provided the ranges of certain environmental variables are restricted, as described herein.

The type of sounds measured using methods described in this standard may differ widely in temporal and spectral characteristics but do not include impulsive sounds, those whose duration is less than 1 second. The sound to be measured may be continuous or intermittent; it may be steady or fluctuating; and it may be essentially broad band or contain discrete tones or narrow bands of noise.

The frequency range covered by the requirements of this standard depends on the specific type of sound level meter or instrumentation being used, but, in general, the frequency content of the sound being measured should be contained within the range from 20 Hz to 20 kHz. The sound pressure levels of sounds whose energy is concentrated outside of this range may not be measured accurately according to the procedures of this standard.

In some cases, the sound of interest being measured may also be classified according to its spatial characteristics, that is, how the level varies from one point to another in the sound field. This standard, however, does not address the measurement of the spatial characteristics of the sound field.

This standard does not address the measurement of sound pressure levels in environments other than air (such as other gases, liquids, or solids), the measurement of infrasonic or ultrasonic sounds, the measurement of impulsive sounds (see ANSI S12.7 for methods) whose durations are typically less than 1 second, the measurement of spatial characteristics of sound fields, or (generally) the measurement of sound pressure levels outdoors in nonquiescent conditions.