A RADIATION EFFICIENCY FOR UNBAFFLED PLATES WITH EXPERIMENTAL VALIDATION

摘要

A radiation efficiency is developed for sound radiation from rectangular plates with unbaffled edges below the plate critical frequency. The expression modifies the modal average radiation efficiencies obtained from the simply supported plane-baffled plate by considering the effects of fluid flow around a structure. These flows reduce sound radiation by allowing fluid to escape compression. The unbaffled plate radiation efficiency is assessed by comparison with experimental data of sound radiated by impacts between balls and a plate. The expression is observed to be more accurate than the simply supported plane-baffled plate model and more versatile than a model of sound radiated from a plane-baffled free edge of a plate. Sound radiated by non-propagating plate vibration near ball-plate impacts appears to play a minor role. Improvements in accuracy over the simply supported plane-baffled model typically range from 4-12 dB, with the greatest improvements occurring at low frequencies. A statistical method for bounding radiated sound power with a degree of confidence is also developed and tested against measured data. The results are encouraging but not statistically conclusive due to a limited amount of measured data. (C) 1997 Academic Press Limited. [References: 24]