A general theory of microperforated-panel absorbers is proposed on the basis of equhaleot circuits. The characterizing parameters of the absorber are its relative acoustic resistance γ, the diameter d of the perforat...A general theory of microperforated-panel absorbers is proposed on the basis of equhaleot circuits. The characterizing parameters of the absorber are its relative acoustic resistance γ, the diameter d of the perforations and the resonance frequency fo. The later two form the perforate constaot k = , which, together with γ, decides the structure and characteristics of the microperforated-panel absorber. The maximum value of the absorption band width △f/f0 is (4/π)tan-1(1＋γ), as k approaches zero, and it does not change much as far as k is less than 1, the cavity depth is nearly a quarter wavelength of the resonance frequency For large values of k, the absorption band narrows down significalltly and the cavity depth required becomes a small fraction of the wavelength. The general properties of the microperforated absorber are discussed.展开更多
文摘A general theory of microperforated-panel absorbers is proposed on the basis of equhaleot circuits. The characterizing parameters of the absorber are its relative acoustic resistance γ, the diameter d of the perforations and the resonance frequency fo. The later two form the perforate constaot k = , which, together with γ, decides the structure and characteristics of the microperforated-panel absorber. The maximum value of the absorption band width △f/f0 is (4/π)tan-1(1＋γ), as k approaches zero, and it does not change much as far as k is less than 1, the cavity depth is nearly a quarter wavelength of the resonance frequency For large values of k, the absorption band narrows down significalltly and the cavity depth required becomes a small fraction of the wavelength. The general properties of the microperforated absorber are discussed.
