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Random incidence transmission loss of miniature Helmholtz resonator embedded acoustic meta-material
Published in International Commission for Acoustics (ICA)
Volume: 2019-September
Pages: 2083 - 2090
An array of light-weight miniature Helmholtz resonators (HRs), was shown to significantly enhance the low frequency absorption, when embedded in a PU foam material; this test was carried out in an impedance tube. This concept was then used to study the sound absorption in a cylindrical cavity. A series of tests were carried out by changing number of HRs, embedded circumferentially into foam, at various radial distances on top of the cavity, with a noise source at the bottom. About 8-14 dB reduction in noise levels was observed at lower frequencies. In this paper, the idea is now extended to examine the random incidence transmission loss (TL) of such an array of embedded HRs. Towards this purpose, a twin room reverberation chamber with a 300 mm x 300 mm panel in between is used; random incidence is carried out using first a 45 mm foam alone followed by the foam embedded with a periodic array of HRs. The effectiveness of this concept to increase TL at lower frequencies will be demonstrated. Also, by adjusting the resonator frequencies, by intruding the neck into resonator cavity, is shown to increase the TL over a broader range of frequencies. © 2019 Proceedings of the International Congress on Acoustics. All rights reserved.
About the journal
JournalProceedings of the International Congress on Acoustics
PublisherInternational Commission for Acoustics (ICA)
Open AccessNo