Abstract
Locally resonant metamaterial flat panels have proved to potentially exhibit extraordinary sound transmission loss properties when the resonance frequency of the resonators is tuned to the coincidence frequency region. Whether this technique is also effective to address the ring frequency effect for curved panels is investigated in this paper. For this purpose, a cylindrical shell, as a representation of curved panels, is studied from a theoretical and numerical point of view, with a specific focus on the transmission loss behaviour around the ring frequency region when the shell is mounted with local resonators. The influence from the resonators is presented and compared with that for a flat panel. An inverse effect of the resonators is observed on the sound transmission loss between the metamaterial cylindrical shell and the metamaterial flat panel when the resonance frequency of the resonators is tuned to be below or above the ring or coincidence frequency, respectively. Rather than the extraordinary improvement observed for the metamaterial flat panel, tuning such conventional resonators to the ring frequency of curved panels generates two side dips despite a sharp improvement at the ring frequency itself. This phenomenon is explained from an effective impedance point of view developed in this paper. The approach proposed and the conclusions provided may subsequently allow for the design of suitable resonators in order to resolve the ring frequency effect for curved panels.
Highlights
Acoustic metamaterials have been studied extensively due to their nontrivial acoustic behaviour.1–15 The concept of acoustic metamaterials has been adapted in order to design novel acoustic panels for sound insulation purposes.2–7,12–15 A metamaterial acoustic panel normally consists of a host panel and resonators that may be composed of, e.g., mass-spring systems
It was shown that an extraordinary sound transmission loss may be achieved if the resonance frequency of the resonators is tuned to the coincidence frequency region of the host panel, by successfully overcoming the coincidence effect
The results provided by the impedance approach offer both satisfying accuracy and great efficiency for the scope of the current study
Summary
Acoustic metamaterials have been studied extensively due to their nontrivial acoustic behaviour. The concept of acoustic metamaterials has been adapted in order to design novel acoustic panels for sound insulation purposes. A metamaterial acoustic panel normally consists of a host panel and resonators that may be composed of, e.g., mass-spring systems. In order to support the explanations associated with the sound transmission loss behaviour of the metamaterial cylindrical shell, a flat panel, whose coincidence frequency is on purpose set to be about the same as the ring frequency of the cylindrical shell, is presented. This latter test case serves as a reference in order to highlight the effect of the resonators when associated with the cylindrical shell.
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