Evaluation of the Delany-Bazley-Miki model for the calculation of the sound absorption coefficient of aerogel granules

Abstract

The Delany-Bazley model is a widely used calculation method for the prediction of the sound absorption coefficient of porous materials. It is an empirical model, which provides reasonable values for the characteristic impedance and the wave number for fibrous absorbent materials having a porosity near unity. The biggest strength of the Delany-Bazley model is, that it requires only one material parameter, the flow resistivity, which can be easily measured. Even though this model finds widespread application, however, since the estimation of the characteristic impedance and the wave number is based on quite simple power-law relations, it may not be expected that the model is valid for all the porous materials. Hence for other than fibrous materials an adjustment of the power-law relations might be necessary. In this paper an evaluation of the Delany-Bazley-Miki model, which furthermore satisfies the impedance function positive real part property, for the prediction of the sound absorption coefficient of aerogel granules is discussed. The core question is, if and how the power-law relations, suggested by Delany and Bazley, should be adjusted to provide a good approximation of the characteristic impedance and the wave number with impedance tube measured data for aerogel granules of different particle sizes.

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ORCID for Felix Langfeldt: orcid.org/0000-0003-2380-2746

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