engleski

Student project of building an impedance tube

This paper describes a project of building an impedance tube for measuring the absorption coefficient using the transfer-function method, in accordance with the standard ISO 10534-2. For the tube, only inexpensive materials and transducers were used. The tube was designed for the frequency range between 90 and 2000 Hz. In order to achieve this range with a single tube, three microphone positions have been used. The resulting absorption coefficient has been calculated using the one-microphone method. The goal of this paper is to compare the two methods for measuring the sound absorption coefficient, the method that uses the standing wave ratio and the transfer-function method, on several different materials using different broadband excitation signals such as MLS, pink noise and sine sweep. Various problems with the design and construction are addressed and the optimal configuration is discussed. The initial measurements were performed without the tested material in the tubes. Additional measurements were made on mineral wool and foam.

impedance tube; absorption; acoustic materials

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