Design of the test facility for the measurement of noise silencers

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.