Aircraft cabin noise barrier design and test

Abstract

The cockpit and cabin of contemporary propeller driven lightplanes continue to suffer high ambient noise levels in flight. These noise levels are typically 85–95 dBA. It was sought to typify and test lightweight barrier configurations in an attempt to achieve the 30 dB predicted performance [J. T. Howlett and D. A. Morales, J. Acoust. Soc. Am. 59, S64 (A) (1976)]. Several structural arrangements were tested as 12 in. (30 cm) square samples. Broadband transmission loss values of 20–25 dB were easily achieved, as opposed to considerably smaller values for thin aluminum panels. The barrier performance due to stiffness over and above that due to the mass law is clearly evident at lower frequencies. The achievable TL values are compared with known aircraft noise spectra, both inside the outside the cabin, to predict cabin quieting achievable with practical weight and cost constraints.