UNE-EN ISO 10534-2:2024

This test method covers the use of an impedance tube, two microphone locations and a frequency

analysis system for the determination of the sound absorption coefficient of sound absorbing materials

for normal sound incidence. It can also be applied for the determination of the acoustical surface

impedance or surface admittance of sound absorbing materials. As an extension, it can also be used to

assess intrinsic properties of homogeneous acoustical materials such as their characteristic impedance,

characteristic wavenumber, dynamic mass density and dynamic bulk modulus.

The test method is similar to the test method specified in ISO 10534-1[1] in that it uses an impedance

tube with a sound source connected to one end and the test sample mounted in the tube at the

other end. However, the measurement technique is different. In this test method, plane waves are

generated in a tube by a noise source, and the decomposition of the interference field is achieved by the

measurement of acoustic pressures at two fixed locations using wall-mounted microphones or an intube

traversing microphone, and subsequent calculation of the complex acoustic transfer function and

quantities reported in the previous paragraph. The test method is intended to provide an alternative,

and generally much faster, measurement technique than that of ISO 10534-1[1].

Normal incidence absorption coefficients coming from impedance tube measurements are not

comparable with random incidence absorption coefficients measured in reverberation rooms according

to ISO 354.[2] The reverberation room method will (under ideal conditions) determine the sound

absorption coefficient for diffuse sound incidence. However, the reverberation room method requires

test specimens which are rather large. The impedance tube method is limited to studies at normal and

plane incidence and requires samples of the test object which are of the same size as the cross-section

of the impedance tube. For materials that are locally reacting only, diffuse incidence sound absorption

coefficients can be estimated from measurement results obtained by the impedance tube method (see

Annex E).

Through the whole document, a e+ jt time convention is used.