Acoustical properties of fibrous absorbent materials

Abstract Results are presented of an investigation into the acoustical properties of a range of fibrous absorbent materials. Measured values of characteristic impedance and propagation coefficient are shown to normalise as a function of frequency divided by flow-resistance and can be represented by simple power-law functions. Absorption coefficients of thin layers of material over a range of flow-resistance values are also shown. Supplementary data provide a basis for estimating the flow-resistance of a material from its bulk density.