Hybrid membrane resonators for multiple frequency asymmetric absorption and reflection in large waveguide

  • Caixing Fu
    Hong Kong University of Science and Technology Department of Physics, , Clearwater Bay, Kowloon, Hong Kong, China
  • Xiaonan Zhang
    Hong Kong University of Science and Technology Department of Physics, , Clearwater Bay, Kowloon, Hong Kong, China
  • Min Yang
    Hong Kong University of Science and Technology Department of Physics, , Clearwater Bay, Kowloon, Hong Kong, China
  • Songwen Xiao
    Hong Kong University of Science and Technology Department of Physics, , Clearwater Bay, Kowloon, Hong Kong, China
  • Z. Yang
    Hong Kong University of Science and Technology Department of Physics, , Clearwater Bay, Kowloon, Hong Kong, China

抄録

<jats:p>We report that Hybrid membrane resonators (HMRs) made of a decorated membrane resonator backed by a shallow cavity can function as Helmholtz resonators (HRs) when mounted on the sidewall of a clear waveguide for air ventilation. When two single-frequency HMRs are used in the same scheme as two frequency-detuned HRs, asymmetric total absorption/reflection is demonstrated at 286.7 Hz with absorption coefficient over 97% in a waveguide 9 cm × 9 cm in cross section. When two multiple-frequency HMRs are used, absorption in the range of near 60% to above 80% is observed at 403 Hz, 450 Hz, 688 Hz, 863 Hz, and 945 Hz. Theoretical predictions agree well with the experimental data. The HMRs may replace HRs in duct noise reduction applications, in that at a single operation frequency they have stronger strength to cover a much larger cross section area than that of HRs with similar cavity volume, and they can be designed to provide multiple frequency absorption band.</jats:p>

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