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Sound absorption of micro-perforated elastic plates in a cylindrical impedance tube

원통형 임피던스 튜브 내 미세천공 탄성 판의 흡음

  • 김현실 (한국기계연구원 음향소음팀) ;
  • 김봉기 (한국기계연구원 음향소음팀) ;
  • 김상렬 (한국기계연구원 음향소음팀) ;
  • 이성현 (한국기계연구원 음향소음팀) ;
  • 마평식 (한국기계연구원 음향소음팀)
  • Received : 2018.05.23
  • Accepted : 2018.07.19
  • Published : 2018.07.31

Abstract

In this paper, sound absorption of micro-perforated elastic plates installed in an impedance tube of a circular cross-section is discussed using an analytic method. Vibration of the plates and sound pressure fields inside the duct are expressed in terms of an infinite series of modal functions, where modal functions in the radial direction is given in terms of the Bessel functions. Under the plane wave assumption, a low frequency approximation is derived by including the first few plate modes, and the sound absorption coefficient is given in terms of an equivalent impedance of a single surface. The sound absorption coefficient using the proposed formula is in excellent agreement with the result by the FEM (Finite Element Method), and shows dips and peaks at the natural frequencies of the plate. When the perforation ratio is very small, the sound absorption coefficient is dominated by the vibration effect. However, when the perforation ratio reaches a certain value, the sound absorption is mainly governed by the rigid MPP (Micro-Perforated Plate), while the vibration effect becomes very small.

Acknowledgement

Grant : 저주파 흡/차음용 극한 물성 시스템 융합기술 개발, 인공지능 기반 기계시스템 예측진단 및 사고대응 기술

Supported by : 한국기계연구원

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