Über ein Gesetz der räumlichen Zufallsschwankung von Rauschpegeln in Räumen und seine Anwendung auf Schalleistungsmessungen

The spatial and time fluctuations of the noise pressure level in closed rooms determine the measuring accuracy in architectural acoustics. These fluctuations are discussed and simple laws are derived for the magnitude of the fluctuations. The laws are valid in any room under almost unrestricted conditions. Especially it is shown how the spatial standard deviation of the noise pressure level depends on the reverberation time and the band-width of the noise. The starting point for the theory of stochastic processes used here is a statement of the superposition of normal modes in rooms of arbitrary shape.

Numerous experimental results are shown, which verify the derived laws. An influence of regression between the sound pressure level and the microphone position in the room is observed in some measurements and it is also investigated.

The practical use of the standard deviation laws is illustrated in the measurements of the sound pressure level in reverberation rooms. It is shown how the number of samples can be determined for a desired measuring accuracy.