Sound absorption coefficient measurements can be performed using different methods. They differ from each other according to the required sample sizes, time duration of the measurement, size of the measuring point, necessary supporting equipment, etc. In our example, the transfer functions method in an impedance tube was used to determine the sound absorption coefficient of different materials using two microphones according the SIST ISO 10534-2 standard. Following the standard, we created a support Matlab code for calculating the sound absorption value based on two stereo audio signals and performed measurements for six different sampled materials. The obtained values were compared with the reference values of measurements performed in a second impedance tube with the method from the standing wave ratio. The validation of the transfer function method in the impedance tube has shown to a greater degree the consistency of measurements by both methods within the observed frequency range. The resulting minor deviation of the sound absorption curve can be attributed to a systemic error that depends on the distance of the reference plane of the samples and the distant microphone, and the incomplete equivalence of the samples used in the measurements using both methods.
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