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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.

Methods of ducted fan aircraft propulsion unit noise prediction

Hlaváček D.

Czasopismo Techniczne. Mechanika

2013

R. 110, z. 1-M

155--165

The UL-39 ultra-light aircraft which is being developed by the Department of Aerospace Engineering, Faculty of Mechanical Engineering, Czech Technical University in Prague, is equipped with an unconventional ducted fan propulsion unit. This paper deals with identifying noise sources of this propulsion unit and easily applicable ways of predicting its noise level. At the end, a few potential noise-suppressing design improvements are presented.

UL-39 to ultra lekki samolot, który został skonstruowany w Instytucie Inżynierii Lotnictwa, na Wydziale Mechanicznym Czeskiego Uniwersytetu Technicznego w Pradze. Został on wyposażony w niekonwencjonalny wentylator kanałowy jednostki napędowej. W artykule autor zaprezentował metody identyfikacji źródeł hałasu badanej jednostki napędowej oraz łatwe w zastosowaniu metody przewidywania poziomu generowanego hałasu. Zostały również przedstawione propozycje zmian konstrukcyjnych redukujących hałas.