Design of large reactive silencers for industrial applications

© INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering. All rights reserved. It is common for large internal combustion engines to generate high levels of noise in harmonic tones below 100 Hz. The attenuation of low frequency tonal noise is challenging because if one wishes to rely on passive techniques then it is normally necessary to use large reactive chambers, as dissipative elements are ineffective at such low frequencies. However, it is common for the physical space available for the silencer to be limited and so one is often faced with the challenge of delivering high levels of sound attenuation in a relatively confined space. This paper reviews some different approaches to addressing this design challenge, and examines the trade-off between levels of attenuation and the frequency bandwidth over which the silencers are effective. This investigation includes the analysis of different reactive straight-through muffler configurations having elliptical and circular cross-section, and the use of airways that are offset from the geometrical center of the chamber. Predictions are generated using an optimized two-dimensional finite element (FE) and mode-matching approach, and it is shown that through careful design considerations, one can achieve relatively high levels of attenuation in the low-frequency range