Acoustic treatment impedance models for high frequencies

Abstract

The ability to design, build, and test miniaturized acoustic treatment panels on scale model fan rigs representative of the full-scale engine provides not only a cost-saving but an opportunity to optimize the treatment by allowing tests of different designs. To be able to use scale model treatment as a full-scale design tool, it is necessary that the designer be able to reliably translate the scale model design and performance to an equivalent full-scale design. The key to this accomplishment is the acoustic treatment impedance parameter. Current full-scale impedance models for acoustic treatment panels have been validated by measurement only up to about 6000 Hz. It is the purpose of this study to examine implications of high frequencies on the theoretical basis of the acoustic impedance models and to double the upper limit of validated models to around 1213,000 Hz. Ultimately, it will be necessary to extend the models to 40,000 Hz or higher to realize the full potential of scale model treatment as a design tool.