Broadband low-frequency noise reduction using Helmholtz resonator-based metamaterial
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Jhalu Gorain [1] ; Chandramouli Padmanabhan [1]
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[1] Indian Institute of Technology Madras
Indian Institute of Technology Madras
India
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- Localización: Noise Control Engineering Journal, ISSN 0736-2501, Vol. 69, Nº. 4, 2021, págs. 351-363
- Idioma: inglés
- Texto completo no disponible (Saber más ...)
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Resumen
Achieving broadband noise attenuation at low frequencies is still a significant challenge. Helmholtz resonators offer good low-frequency noise attenuation but are effective only over a narrow band; the cavity volume required at these frequencies is also larger. This article proposes a new broadband acoustic metamaterial (AMM) absorber, which uses polyurethane (PU) foam embedded with small-size resonators tuned to different frequencies. The AMM design is achieved in three phases: (1) develop a transfer-matrix-based one-dimensional model for a resonator with intruded neck; (2) use this model to develop a novel band broadening method, to select appropriate resonators tuned to different frequencies; and (3) construct a unit cell metamaterial embedded with an array of resonators into PU foam. A small-size resonator tuned to 415 Hz is modified, by varying the intrusion lengths of the neck, to achieve natural frequencies ranging from 210 to 415 Hz. Using the band broadening methodology, 1 unit cell metamaterial is constructed; its effectiveness is demonstrated by testing in an acoustic impedance tube. The broadband attenuation characteristics of the constructed unit cell metamaterial are shown to match well with the predicted results. To demonstrate further the effectiveness of the idea, a metamaterial is formed using 4 periodic unit cells and is tested in a twin room reverberation chamber. The transmission loss is shown to improve significantly, at low frequencies, due to the inclusion of the resonators.
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