Sound absorption of a finite flexible micro-perforated panel backed by an air cavity
TL;DR: In this paper, the acoustic absorption of a finite flexible micro-perforated panel backed by an air cavity is studied in detail, and the absorption model is developed based on the modal analysis solution of the classical plate equation coupled with the acoustic wave equation.
About: This article is published in Journal of Sound and Vibration.The article was published on 2005-10-06. It has received 160 citations till now. The article focuses on the topics: Absorption (acoustics) & Normal mode.
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TL;DR: The acoustic properties of a compound micro-perforated panel (MPP) absorber array are investigated and it is shown that although other absorption mechanisms may exist, dissipation by the MPP is dominant in theMPP absorbers array.
Abstract: The acoustic properties of a compound micro-perforated panel (MPP) absorber array are investigated. The absorber array consists of three parallel-arranged MPP absorbers with different cavity depths. A finite element procedure is used to simulate its acoustic behaviors under normal incidence. Experimental studies are carried out to verify the numerical simulations. Due to different reactance matching conditions in the absorber array, strong local resonance occurs and the corresponding local resonance absorption dominates. Compared with single MPP absorber, the absorber array requires lower acoustic resistance for good absorption performance, and the resonance frequencies shift due to inter-resonator interactions. The different acoustic resistance requirement is explained by considering the reduced effective perforation rate of the MPP in the absorber array. The performance of the absorber array varies with the sizes and spatial arrangement of the component absorbers. When the distance between component absorbers is larger than a quarter-wavelength, the above-mentioned parallel absorption mechanism diminishes. In the experimental study, the normal incidence absorption coefficients of a prototype MPP absorber array are tested. The measured results compare well with the numerical predictions. The experimental study also shows that although other absorption mechanisms may exist, dissipation by the MPP is dominant in the MPP absorber array.
176 citations
TL;DR: In this paper, the authors proposed a micro-perforated panel absorber backed by Helmholtz resonators to improve sound absorption in the low-frequency region where conventional MPRs cannot provide sufficient absorption.
112 citations
TL;DR: In the pursuit of more effective noise control devices, the cavity backed micro-perforated panel absorber (CBMPPA) is developed and results show that the shape of the backing cavity can significantly alter the sound absorption mechanisms and frequency distribution of overall sound absorption coefficient of the absorber.
Abstract: In the pursuit of more effective noise control devices, the cavity backed micro-perforated panel absorber (CBMPPA) is developed in this study. A CBMPPA differs from the conventional micro-perforated panel (MPP) absorber in that the MPP is backed by a trapezoidal cavity, which allows more effective vibroacoustic coupling between the MPP and the cavity. A two-dimensional theoretical model is established and tested both numerically and experimentally. Based on the verified theoretical model, sound absorption performance of a trapezoidal CBMPPA is investigated numerically. Results show that the shape of the backing cavity can significantly alter the sound absorption mechanisms and frequency distribution of overall sound absorption coefficient of the absorber. Further analyses show that acoustic modes that are initially decoupled from the MPP in the rectangular configuration are coupled with the air motion in the MPP, which accounts for the change in absorption pattern of the trapezoidal CBMPPA. By the same token, it also provides the flexibility for tuning the effective absorption range of the absorber. Due to the varying impedance matching conditions, the absorption performance of the trapezoidal CBMPPA exhibits obvious local characteristics over the MPP surface, which contrasts with the spatially uniform absorption in the conventional MPP absorber.
111 citations
Cites background or methods from "Sound absorption of a finite flexib..."
...The theoretical model established in Lee et al. 2005 takes into account the full coupling between the cavity acoustics and the panel vibration....
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...In studying the sound absorption of a finite flexible MPP backed by an air cavity, Lee et al. 2005 developed a solution procedure based on the modal analysis approach....
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...Detailed discussion on the panel vibration effect can be found in Lee et al. 2005 ....
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TL;DR: In this article, a perforated plate (PP) was added to the multilayer structure to further enhance the sound absorption in this area, and analyses were accomplished through three PP modeling approaches (Allard, Beranek and Ver, Atalla and Sgard) and Allard Transfer Function (TF) method.
109 citations
TL;DR: The technical feasibility of a transparent, sound-absorbing panel for outdoor antinoise devices is investigated and an optimized three-layer configuration can achieve sound- absorption properties similar to nontransparent products with only a limited loss of visual transparency and appropriate mechanical strength.
Abstract: Sound absorption and optical transparency are among the most useful properties of noise barriers. While the latter is required to reduce visual impact and for aesthetical reasons, the former is required whenever conditions of multiple reflections and presence of close, high receivers occur. The technical feasibility of a transparent, sound-absorbing panel for outdoor antinoise devices is investigated in this paper. An analysis of acoustical performance of multiple perforated plates is performed employing an existing theory for microperforated absorbers under normal incidence and diffused sound field. An optimization of the geometrical parameters is carried out on the basis of the European classification criteria of noise barriers for roadways. An optimized three-layer configuration can achieve sound-absorption properties similar to nontransparent products with only a limited loss of visual transparency and appropriate mechanical strength. Experimental data obtained with an impedance tube on small test sam...
109 citations
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TL;DR: The most important parameter of the microperforated panel (MPP) is found to be the perforate constant k which is proportional to the ratio of the perfusion radius to the viscous boundary layer thickness inside the holes as discussed by the authors, and this, together with the relative (to the characteristic acoustic impedance in air) acoustic resistance r and the frequency f0 of maximum absorption of the MPP absorber, decides the entire structure and its frequency characteristics.
Abstract: Many applications have been found for the microperforated panel (MPP) absorber, on which the perforations are reduced to submillimeter size so that they themselves will provide enough acoustic resistance and also sufficiently low acoustic mass reactance necessary for a wide-band sound absorber. The most important parameter of the MPP is found to be the perforate constant k which is proportional to the ratio of the perforation radius to the viscous boundary layer thickness inside the holes. This, together with the relative (to the characteristic acoustic impedance in air) acoustic resistance r and the frequency f0 of maximum absorption of the MPP absorber, decides the entire structure of the MPP absorber and its frequency characteristics. In other words, the MPP absorber may be designed according to the required absorbing characteristics in terms of the parameters k, r, and f0. Formulas and curves are presented toward this end. It is shown that the MPP absorber has tremendous potential for wide-band absorp...
832 citations
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29 Sep 2003TL;DR: In this paper, the authors describe the human ear's physical properties of the central partition of the Central Partition of Noise Induced Hearing Loss Subjective Response to Sound Pressure Level Instrumentation for Noise Measurement and Analysis Microphones Weighting Networks Sound Level Meters Classes of Sound Level Meter Sound Level meter Calibration Noise Measurements Using Sound Level Measurement Data Loggers Personal Sound Exposure Meter Recording of Noise Spectrum Analysers Intensity Meter Energy Density Sensors Sound Source Localization Criteria Introduction Hearing Loss Hearing Damage Risk Hearing Damage risk Criteria Implementing a Hearing Conservation
Abstract: Fundamentals and Basic Terminology Introduction Noise-Control Strategies Acoustic Field Variables Wave Equations Mean Square Quantities Energy Density Sound Density Sound Power Units Spectra Combining Sound Pressures Impedance Flow Resistance The Human Ear Brief Description of the Ear Mechanical Properties of the Central Partition Noise Induced Hearing Loss Subjective Response to Sound Pressure Level Instrumentation for Noise Measurement and Analysis Microphones Weighting Networks Sound Level Meters Classes of Sound Level Meter Sound Level Meter Calibration Noise Measurements Using Sound Level Meters Time-Varying Sound Noise Level Measurement Data Loggers Personal Sound Exposure Meter Recording of Noise Spectrum Analysers Intensity Meter Energy Density Sensors Sound Source Localization Criteria Introduction Hearing Loss Hearing Damage Risk Hearing Damage Risk Criteria Implementing a Hearing Conservation Program Speech Interference Criteria Psychological Effects of Noise Ambient Noise Level Specification Environmental Noise Level Criteria Environmental Noise Level Surveys Sound Sources and Outdoor Sound Propagation Introduction Simple Source Dipole Source Quadruple Source (Far-Field Approximation) Line Source Piston in an Infinite Baffle Incoherent Plane Radiator Directivity Reflection Effects Reflection and Transmission at a Plane/Two Media Interface Sound Propagation Outdoors, General Concepts Sound Power, its Use and Measurement Introduction Radiation Impedance Relation between Sound Power and Sound Pressure Radiation Field of a Sound Source Determination of Sound Power Using Intensity Measurements Determination of Sound Power Using Surface Vibration Measurements Some Uses of Sound Power Information Sound in Enclosed Spaces Introduction Low Frequencies Bound between Low-Frequency and High-Frequency Behavior High Frequencies, Statistical Analysis Transit Response Porous Sound Absorbers Panel Sound Absorbers Flat and Long Rooms Applications of Sound Absorption Auditorium Design Partitions, Enclosures and Barriers Introduction Sound Transmission through Partitions Noise Reduction vs Transmission Loss Enclosures Barriers Pipe Lagging Muffling Devices Introduction Measures of Performance Diffusers as Muffling Devices Classification of Muffling Devices Acoustic Impedance Lumped Element Devices Reactive Devices Lined Ducts Duct Bends or Elbows Unlined Ducts Effect of Duct End Reflections Duct Break-Out Noise Line Plenum Attenuator Water Injection Directivity of Exhaust Duct Vibration Control Introduction Vibration Isolation Types of Isolators Vibration Absorbers Vibration Neutralizers Vibration Measurement Damping of Vibrating Surfaces Measurement of Damping Sound Power and Sound Pressure Level Estimation Procedures Introduction Fan Noise Air Compressors Compressors for Chillers and Refrigeration Units Cooling Towers Pumps Jets Control Valves Pipe Flow Boilers Turbines Diesel and Gas-Driven Engines Furnace Noise Electric Motors Generators Transformers Gears Transportation Noise Practical Numerical Acoustics Introduction Low-Frequency Region High-Frequency Region: Statistical Energy ANalysis
548 citations
TL;DR: In this paper, a comprehensive theoretical model has been developed for interior sound fields which are created by flexible wall motion resulting from exterior sound fields, and an efficient computational method is used to determine acoustic natural frequencies of multiply connected cavities.
360 citations
352 citations