scope:

This standard describes the instrumentation, measuring methods and test procedures necessary for the determination of a gear unit's sound power and sound pressure levels for acceptance testing.

Sound power level is independent of the environment and the sound power levels of multiple sound sources can be added (energy addition). Sound pressure levels change depending on the environment but are useful for relative comparisons. Sound pressure has been used historically because it is less complex. The current availability of data acquisition equipment and computers, which make calculations trivial, has increased the popularity of sound power. Sound power requires the use of multiple microphones and post processing, whereas sound pressure is a direct measurement.

Other standards refer to this standard without specifying sound pressure or sound power. Historically, if unspecified, sound pressure was the measurement used over sound power. Municipal ordinances, standards, or build specifications may give some direction in the selection of the parameter. This standard provides instruction for using either method, and the user of this standard shall specify whether the measurement is sound power or sound pressure.