Abstract
Besides generating their own perfect absorption bands, the primary hybrid resonances of a hybrid membrane resonator (HMR) consisting of a decorated membrane resonator (DMR) backed by a cavity can also provide strong assistance for weak resonances to create secondary hybrid resonances and multiple-frequency perfect absorption by forming a low impedance region between the primary hybrid resonances. The weak resonances can be introduced by placing another DMR in front of a HMR or by using a DMR with an off-centered platelet in an HMR. In one such sample, five perfect absorption bands within the range of 200–1000 Hz are experimentally observed with minimum reflection values ranging from 1.2% to 7%.
Highlights
A modified version of the hybrid membrane resonator (HMR), where the membrane is replaced by a rigid platelet, achieved perfect absorption when a porous plate is added.[4]
Critical couplings can be realized by various forms of Helmholtz resonators (HRs), such as the HRs coupled via a narrow channel,[5] the HRs with embedded apertures which operate in virtually the same mechanism as the coupled HRs,[6] the HRs coupled to the narrow slits where the strong interaction between them result in the impedance match to air,[7] or the HRs with small holes to enhance the thermal acoustic effect for dual-frequency perfect absorption.[8]
Besides decorated membrane resonator (DMR), resonators such as HRs or a viscoelastic porous plate backed by a cavity can achieve perfect absorption.[9]
Summary
This version is available at HKUST SPD - Institutional Repository (https://repository.ust.hk). If it is the author's pre-published version, changes introduced as a result of publishing processes such as copy-editing and formatting may not be reflected in this document. For a definitive version of this work, please refer to the published version.
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