This paper presents a project for the development of an impedance tube for measuring the sound absorption coefficient using a transfer function. The tube was developed using the ISO 10534-2 standard to measure the frequency range between 250 and 5000 Hz. To verify the results, a comparison was made with the method described in ISO 10534-1. To make the tube, cheaper and more accessible materials were used, which were processed by classical processing methods. Some elements of the tube were also made with the help of additive technology, which has been developing rapidly in recent times. To be able to achieve accurate measurements in such a wide frequency spectrum, the method described in the standard has been adapted for use with three microphones. For the purposes of the measurements, a software code was developed for the calibration of the microphones and for the calculation of the value of the sound absorption coefficient on the basis of three different combinations of microphone placement. Measurements were performed on ten different porous materials of different thickness. A change in the sound absorption coefficient has been observed with the addition of a larger number of layers of material. The results show that the developed method allows us to make accurate measurements and change samples faster. To determine the flow resistivity σ, a program code based on the empirical Delany - Bazley model was developed.
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