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Design of the test facility for the measurement of noise silencers

Bolejko Romuald, Plaskota Przemysław, Dobrucki Andrzej B., Pruc Krzysztof

Vibrations in Physical Systems

2022

Vol. 33, nr 3

art. no. 2022309

In the paper, a description of the test facility designed and implemented for noise silencers according to the methodology specified in the PN-EN ISO 7235 standard is presented. It is possible to measure the insertion loss, flow noise, and pressure loss on the test stand. In particular, the following issues were presented: noise protection in the low frequency range, the design of the anechoic termination, and measurements of the sound pressure level in the flow. To obtain a sufficiently high level of noise protection, three noise transmission paths were considered: direct, indirect, and flanking. The design of the anechoic termination was based on the profile of the catenoid tube, which made it possible to obtain strong sound absorption in the low-frequency range while maintaining a limited length of a terminator. A specially designed microphone cap was used to measure the sound pressure level in the flow field. The paper also presents results of selected measurements that illustrate the possibilities of the designed test stand.

Research of acoustical impedance of human skin

Plaskota Przemysław

Vibrations in Physical Systems

2019

Vol. 30, nr 1

art. no. 2019143

This paper presents the methodology of measuring acoustic impedance of human skin and discusses the results of the tests. Measurement of the acoustic impedance of human skin is a complex issue. The most difficult thing is related to the nature of the object of research. Cooperation of volunteer participating in the experiment is crucial in collecting accurate data. Appropriate measuring conditions must be provided because of the length of time required to conduct measurement. The Kundt tube method has been used as a research technique applied for evaluation of the material impedance. It was assumed that the results would differ with regard to different points chosen for measurement, located on the body of volunteer as well as with regard to the features of the skin structure of the volunteers participating in this experiment. Results have revealed that for different people similar parameters have been obtained. Moreover, results are alike for various measured points localized on person’s body.