Developing an indirect vibration-based sound power method to determine the sound power radiated from acoustic sources

An indirect vibration-based sound power (I-VBSP) method is in development to be used to measure noise from the numerous sources that radiate energy that cannot be captured effectively using surface vibration measurements. These sources are placed inside a rectangular enclosure with four high impedance sides, a single rigid side, and a single mylar side, inducing a vibration on the mylar membrane. A scanning laser Doppler vibrometer (SLDV) is used to scan the vibrating mylar to determine the sound power radiated through the mylar and this sound power result is then calibrated to obtain the free-field radiated sound power. A boundary element method (BEM) model showed that using the baffled flat plate form of the radiation resistance matrix approximates well the energy radiated from the enclosure above the 630 Hz one-third octave (OTO) band, enabling the indirect method to work above that frequency for this enclosure. The experimental sound power measurement of a blender obtained from the I-VBSP method agreed with the free-field sound power obtained in a reverberation chamber using the ISO 3741 standard within +/− 1 to 2 dB from 1.63-10 kHz. Other challenges are discussed that will be addressed in future research.