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2018 Vol.37, Issue 4 Preview Page

Research Article

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

원통형 임피던스 튜브 내 미세천공 탄성 판의 흡음

Hyun-Sil Kim1∗
,
Bong-Ki Kim1
,
Sang-Ryul Kim1
,
Seong-Hyun Lee1
,
Pyung-Sik Ma1
김 현실1∗
,
김 봉기1
,
김 상렬1
,
이 성현1
,
마 평식1
1한국기계연구원 음향소음팀
∗Corresponding Author
31 July 2018. pp. 181-187
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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.

Keywords
Sound absorption
MPP (Micro-Perforated Plate)
Cylindrical impedance tube
Elastic plate

본 논문은 원형 단면 임피던스 튜브내에 고정된 미세천공 탄성판의 흡음을 해석적으로 구하는 방법을 다루었다. 판의 진동과 덕트 내부 음장을 모드 함수의 무한 급수의 합으로 전개하였는데 반경방향으로는 Bessel 함수를 포함한다. 평면파 가정하에서 저주파수 대역의 근사식을 판의 처음 몇 개의 모드만 고려하여 흡음율을 유도하였으며 등가 임피던스를 갖는 단일 표면의 형태로 제시하였다. 본 논문에서 제안한 공식과 FEM(Finite Element Method)을 이용한 결과는 잘 일치 하였는데 탄성의 효과는 판의 고유진동수에 해당하는 골 또는 피크의 형태로 나타난다. 천공율이 매우 작으면 진동의 영향이 지배적이나 천공율이 어느 한계이상 되면 박판의 탄성거동은 매우 작게 나타나고 강체 MPP (Micro-Perforated Plate)의 흡음 특성이 지배적이 된다.

키워드
흡음
미세천공판
원통형 임피던스 튜브
탄성판
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Information
  • Publisher :The Acoustical Society of Korea
  • Publisher(Ko) :한국음향학회
  • Journal Title :The Journal of the Acoustical Society of Korea
  • Journal Title(Ko) :한국음향학회지
  • Volume : 37
  • No :4
  • Pages :181-187
  • Received Date : 2018-05-23
  • Accepted Date : 2018-07-19
  • DOI :https://doi.org/10.7776/ASK.2018.37.4.181
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