INSITU ESTIMATION OF AN ACOUSTIC SOURCE IN AN ENCLOSURE AND PREDICTION OF INTERIOR NOISE BY USING THE PRINCIPLE OF VIBROACOUSTIC RECIPROCITY

The volume velocity of an acoustic source can be widely used in determ ining the vibroacoustic transfer functions, in measuring the acoustic transfer impedances, and in finding the generated power of an acoustic source. Several techniques utilizing special experimental devices hav e been proposed for this purpose, including the laser velocimetry, the internal pressure measurement, and the face-to-face electroacoustic m easurement. However, for a source in an enclosure with flexible walls, the vibroacoustic coupling should be considered, especially in the ca se of a loudspeaker source that has low internal mechanical impedance. The present method, which uses the principle of vibroacoustic recipro city, can give a reasonable estimation of the transfer functions and c an be used in determining the volume velocity of a source in situ. Bec ause the present method does not require a special facility or the inf ormation on the source surface vibration, the method can be applied to any irregularly shaped source in a flexible enclosure. With the obtai ned vibroacoustic transfer functions, the interior noise field in an e nclosure can be predicted by vectorial summation when the boundary poi nts are excited by uncorrelated dynamic forces. The predicted internal pressure in an enclosure is in good agreement with the measured inter nal pressure even in the presence of sound absorbers inside the enclos ure.