Reverberation Chamber Sound Power Measurement of Sources with Discrete-frequency Noise Emissions

摘要

Reverberation room has been designed to generate diffuse sound field, so that the sound power radiatedfrom a sound source can be measured using less number of microphones. Also reverberation room providesmuch higher signal-to-noise ratio due to reverberation effect, which is very important for acousticmeasurement of very quiet noise sources such as hard disk drives with latest fluid dynamic bearingtechnology. However, the sound power calculation involves reverberation time for characterizing the soundabsorbing properties of the chamber. Existing reverberation time measurement methods have been limitedto 1/nth octave band, so does the corresponding sound power measurement. In this paper, an envelopeaveraging approach is proposed for reverberation time measurement at discrete frequencies. Measurementresults show that reverberation time of a reverberation room can vary significantly at different frequencies,even within certain 1/3 octave band. It concludes that, in order to accurately measure sound power ofsources with strong discrete-frequency noise emission in a reverberation room, the reverberation timeshould be compensated at corresponding discrete-frequencies in sound power calculation.