Precision of reverberant sound power measurements
David M. Lubman · The Journal of the Acoustical Society of America · 1974
Determinations of sound power in a reverberation room are subject to random error whose size can be estimated and controlled by the knowledgeable laboratory manager. According to ANSI SI.21-1972, the chief sources of error are the variance of power output with source position and the variance of estimated room-averaged squared pressure. The latter can be expressed in terms of three factors. First, a frequency averaging factor (spatial variance) governed at midfrequencies by the spectrum shape and room reverberation time, at low frequencies by bandwidth and room volume, and at high frequencies by the direct field; second, a spatial averaging factor determined by the number and separation of fixed microphones or the path shape and size for a traversing microphone; and third, a rotating diffuser factor governed by the size and shape of the rotating diffuser in relation to room size and reverberation time.