A design method of micro-perforated panel absorber at high sound pressure environment in launcher fairings

A design method of micro-perforated panel absorbers is proposed for the enhancement of acoustic absorption inside the payload fairings of launch vehicles. An empirical acoustic resistance model of a micro-perforated panel absorber in a high sound pressure environment is suggested to this end. The resistance model is especially appropriate for the launcher fairing application, so that the incident pressure to the surface of bare fairings is considered as a main variable. Other design variables, e.g., the minute hole diameter, the perforation ratio and the thickness of the panel, are also considered in the proposed model. The estimated acoustic resistances and corresponding absorption coefficients are verified by comparing them with the measured results for several micro-perforated panel absorbers having a practical range of parameters. The estimated and measured results show good agreement when the perforation ratio is in the range of 1.4% to 53%. The effects of design parameters on the absorption coefficient are discussed. It is demonstrated that the micro-perforated panel absorber with a large hole diameter (about 1.0 mm), which shows a poor sound absorption at low pressure levels, can be a good sound absorber at high incident pressure levels. A set of design charts is provided and this enables one to readily design a micro-perforated panel absorber for the mitigation of acoustic loads in launcher fairings. (C) 2012 Elsevier Ltd. All rights reserved.