EFFECT OF GRAZING–BIAS FLOW INTERACTION ON ACOUSTIC IMPEDANCE OF PERFORATED PLATES

2002 ◽  
Vol 254 (3) ◽  
pp. 557-573 ◽  
Author(s):  
X. SUN ◽  
X. JING ◽  
H. ZHANG ◽  
Y. SHI
Keyword(s):  
Acoustic Impedance ◽  
Perforated Plates ◽  
Flow Interaction ◽  
Bias Flow

Acoustic impedance of perforated plates in the presence of bias flow

2019 ◽  
Vol 446 ◽  
pp. 159-175 ◽  
Author(s):  
Zhixiang Chen ◽  
Zhenlin Ji ◽  
Hongpu Huang
Keyword(s):  
Acoustic Impedance ◽  
Perforated Plates ◽  
Bias Flow

A New Type of Muffler Based on Microperforated Tubes

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
S. Allam ◽  
M. Åbom
Keyword(s):  
Acoustic Impedance ◽  
Noise Control ◽  
Wave Impedance ◽  
Sound Waves ◽  
Submillimeter Range ◽  
Perforated Plates ◽  
Characteristic Wave ◽  
Standard Temperature ◽  
New Type ◽  
Temperature And Pressure

Microperforated plate (MPP) absorbers are perforated plates with holes typically in the submillimeter range and perforation ratios around 1%. The values are typical for applications in air at standard temperature and pressure (STP). The underlying acoustic principle is simple: It is to create a surface with a built in damping, which effectively absorbs sound waves. To achieve this, the specific acoustic impedance of a MPP absorber is normally tuned to be of the order of the characteristic wave impedance in the medium (∼400 Pa s/m in air at STP). The traditional application for MPP absorbers has been building acoustics often combined with a so called panel absorber to create an absorption peak at a selected frequency. However, MPP absorbers made of metal could also be used for noise control close to or at the source for noise control in ducts. In this paper, the possibility to build dissipative silencers, e.g., for use in automotive exhaust or ventilation systems, is investigated.

A Novel Design Method for Robust Acoustic Dampers With Perforated Plates Backed by a Cavity Operating at Low and High Strouhal Numbers

2012 ◽  
Author(s):  
A. Scarpato ◽  
S. Ducruix ◽  
T. Schuller
Keyword(s):  
Flow Velocity ◽  
Design Method ◽  
Resonant Cavity ◽  
Plate Thickness ◽  
Optimization Procedure ◽  
Absorption Frequency ◽  
Perforated Plates ◽  
Peak Absorption ◽  
Bias Flow ◽  
Optimal Bias

It is known that the frequency of thermo-acoustic instabilities may vary according to various parameters during operation. The design of passive acoustic dampers tuned to damp specific unstable frequencies must then include this aspect to offer robust properties. This problem is tackled here for perforated plates backed by a resonant cavity in the absence of grazing flow. Their current design relies on a relatively complex optimization procedure with a large number of parameters to examine. A new methodology is proposed to reduce this number by finding the optimal parameters maximizing absorption in two limit regimes, where the choice of the optimal bias flow velocity and size of the back cavity can be decoupled. The former is only controlled by the plate porosity while the latter fixes the peak absorption frequency. The analysis also includes effects of the plate thickness. In both regimes, the optimal bias flow velocity is analytically determined. A Helmholtz resonance and a narrow absorption peak in the frequency space characterize the first absorption regime reached at high Strouhal numbers. This regime minimizes the size of the resonant back cavity, but the absorption frequency bandwidth narrows with increasing Strouhal numbers. The second absorption regime reached at low Strouhal numbers operates with a quarter-wave resonator. This regime requires larger cavity depths but offers a wider absorption bandwidth around the peak absorption frequency well suited for low frequency dampers when the bias flow velocity or the unstable frequency may vary within the system. Theoretical predictions are validated against experimental data obtained in the two regimes identified. The expressions derived in this study can be used to improve the design of robust acoustic dampers.

A New Method for Measuring Acoustic Impedance of Perforated Plates with Grazing Flow

2018 ◽  
Vol 2018.56 (0) ◽  
pp. 703
Author(s):  
Daisuke SHIRAGA ◽  
Shunsuke NAKAMURA ◽  
Shotaro YAMAZAKI ◽  
Shinji AKAMATSU ◽  
Yuki MITSUI ◽  
...  
Keyword(s):  
Acoustic Impedance ◽  
New Method ◽  
Perforated Plates ◽  
Grazing Flow

Research on the Absorption Characteristic of Three-Layer Microperforate Plate of the Automotive Body

2011 ◽  
Vol 201-203 ◽  
pp. 2160-2166
Author(s):  
Cong Yun Zhu
Keyword(s):  
Absorption Coefficient ◽  
Equivalent Circuit ◽  
Acoustic Impedance ◽  
Perforated Plate ◽  
Absorption Characteristic ◽  
Perforated Plates ◽  
Automotive Body ◽  
Different Thickness

Three-layer micro perforated plate of the automotive body is researched. Acoustic impedance of the three-layer microperforated plate of the automotive body is attained according to the equivalent circuit, thus absorption coefficient is attained. Different microperforated plate with different porosity, different diameter, different thickness, different depth of cavity of the automotive body is analyzed and some conclusion is drawn to applied some theory to design these types of the micro perforated plates of the automotive body.

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