Measurement of incident sound power using near field acoustic holography

The conventional method of measuring the insertion loss of a partition relies on an assumption of the sound field in the source room being diffuse and the classical relation between the spatial average of the mean square pressure in the source room and the incident sound power per unit area; and it has always been regarded as impossible to measure the sound power that is incident on a wall directly.

This paper examines a new method of determining this quantity from sound pressure measurements at positions on the wall using ‘statistically optimised near field acoustic holography’ (SONAH). The purpose is to examine whether one should use a correction similar to the well-known ‘Waterhouse correction’ when the incident sound power is deduced from the sound pressure in the source room.