High-frequency silencer concepts

Broad frequency band noise from air exchange systems can cause strong annoyance. Usually, reactive silencer solutions are designed to attenuate noise in low and mid frequency range, whereas resistive materials are used in the silencers in order to absorb sound in the higher frequencies. Wool and fiber based resistive materials have limited lifetime and one major problem with these materials is development of brittleness. In this paper, completely solid structures based on Herschel-Quincke tubes (HQ-tubes) and micro perforated plates (MPPs) are investigated. A HQ-tube dimensioning tool based on optimization algorithms is developed. Commercially available aluminium MPPs are combined with additively manufactured (AM) silencer casing modules and the prototypes are tested in an internal combustion engine (IC-engine) intake system