Persisting Questions in Steady-State Measurement of Noise Power and Sound Absorption

Abstract

Most steady-state methods for measuring the noise power of equipment and the sound absorption in a room depend on knowing the sound power output of the standard source. But the output of any sound source depends in principle on the radiation impedance presented to it, and this impedance is likely to change with the location of the source, as well as with changes in the amount and distribution of absorptive material in the room. Moreover, no generally accepted method is available for measuring the sound-power output directly. For these reasons, the validity of steady-state methods has been under suspicion for some time. This paper summarizes recent progress in making steady-state methods respectable but calls attention to some remaining problems.