Passive Vibroacoustic Isolation for Payload Containers

Abstract

This paper presents analysis and experimental results which examine key issues related to passive vibroacoustic isolation for container type structures. The key noise reduction principle examined is the passive application of a characteristic impedance mismatch in conjunction with a vibration isolation suspension system to limit structural transmission. The characteristic impedance mismatch is created by imposing a near vacuum condition between partitions of a container structure. Unlike active boundary control techniques, this approach is insensitive to the grazing angle of the source acoustics, is simple, and avoids technology challenges such as the need to develop efficient large stroke actuators. The analysis for this problem is performed by extending Fahy's double-leaf partition model. Using the extended model, numerical simulations are conducted to study the effect of various design parameters on acoustic transmission. Guidelines developed from this study are then used to construct an experiment to show the viability of the concept. The experiment demonstrates that at least a 19 dB reduction in sound pressure level (SPL) may be achieved, with a modest level of vacuum.