Statistical Parameters of the Frequency Response Curves of Large Rooms
The following statistical quantities of the frequency response curve of "large rooms" are calculated: the rms response fluctuation, the average height of the maximum, the mean spacing of the zeros (i.e., the intersections of the response curve with the mean level), the mean spacing of the maxima, the mean rate of phase rotation per hertz, and finally the so-called frequence irregularity.: These quantities are exclusively dependent on the reverberation time of the room if certain conditions are met, the only substantial one of them being that the mean spacing of the normal modes is small compared to the half-power width of an individual resonance. This is the case with all large auditoriums, which are not reverberation chambers. In quantitative form the condition to be fulfilled is f >4000 -T/V Hz, where f is the frequency, T Sabine's reverberation time, and V the volume of the room in cubic meters.: Some of the more important results are mean height of the maxima=10 dB, mean spacing of the maxima = 7/T Hz, and frequency irregularity = 1.4T db s.:
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