Investigation of the radiated sound energy from noise sources using an indirect vibration-based sound power approach

An indirect vibration-based sound power (I-VBSP) method is being developed for acoustic sources radiating energy that cannot be captured using surface vibration measurements. This method involves placing this type of source into a small enclosure that has a single flexible side which the noise source will excite. The vibration-induced side can then be scanned using a scanning laser Doppler vibrometer (SLDV) and calibrated to obtain the free-field energy of each source. Several challenges have been identified during the development of this method, many of which have been addressed to improve the accuracy of calibrating out the effects of the enclosure on the radiation from these noise sources and improve the SLDV measurements. A box-in-box structure was fabricated with a flexible panel to investigate the acoustic response of this new enclosure versus the previous mylar membrane enclosure. Results for the sound power of a source obtained through the mylar and panel structures using the I-VBSP method will be compared with the free-field sound power of the source determined in a reverberation chamber using the ISO 3741 standard. [Funding for this work was provided by the National Science Foundation (NSF).]