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Abstract

A method for determining the acoustic absorption coefficient and/or the transmission coefficient at a chosen position in a space in which a certain sound field prevails as a result of the operation of a sound-emitting source, and/or the acoustic power emitted by the source comprises the following steps of:

(a) measuring the sound pressure p(t) and the particle velocity v(t) at the chosen position in the space;(b) calculating the Fourier transforms P(f), V(f) of p(t), v(t);(c) calculating on the basis of P(f) and V(f) the time-averaged active intensity Iac(f) in the direction indicated with the vector n, being the normal vector on the relevant surface, and the time-averaged total intensity Itot(f), in the direction indicated with the vector n;(d) determining the time-averaged incident sound intensity in the direction n:Iin(f)=½(Iac(f)+Itot(f));and the step of:(e) determining the time-averaged absorption coefficient in the direction n:α=Iac(f)/Iin(f);and/or the step of:(f) determining the transmission coefficient θ=Iac(f)/Iin(f) in the direction n for barriers wherein the mechanical absorption can be disregarded; and/or the steps of:(q) defining an enveloping surface around the sound-emitting source; and(r) determining the emitted acoustic power by integrating Iin(f) over the enveloping surface.

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