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Prediction of acoustic absorption Performance of a Perforated Plate with Air Jets

Journal of Thermal Science 2017年第4期26卷 378-384页

作者： Hiromitsu Hamakawa Masanori Miyazaki Yuta Asai Eru Kurihara Eiichi Nishida Hidechito Hayashi Department of Mechanical Engineering Oita University700 DannoharuOita 870-1192Japan Graduate Student Oita University700 DannoharuOita 870-1192Japan Department of Mechanical Systems Engineering Shonan Institute of Technology1-1-25 Tsujido-NishikaiganFuji-sawaKanagawa 251-8511Japan Department of Mechanical Engineering Nagasaki University1-14 Bunkyo machiNagasaki852-8521Japan

The present study focuses on the prediction of acoustic absorption performance of a perforated plate with air jets by theoretical calculations. In addition, we experimentally measured the flow rate, internal pressure, acoustic pressure, and transfer function using an acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. We investigated the influences of background air space, flow velocity, thickness, aperture rate, and aperture diameter of a perforated plate on the acoustic absorption characteristics. The frequency characteristics of the acoustic absorption coefficient showed a maximum value at a local frequency. As the background air space increased, the peak frequency of acoustic absorption characteristics decreased. As the flow velocity passing through the apertures increased, the peak level of the acoustic absorption coefficient also increased. The theoretical results agreed well with the experimental ones qualitatively.

关键词： acoustic absorption perforated plate theoretical prediction acoustic impedance tube air jets

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Broadband impedance modulation via non-local acoustic metamaterials

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National Science Review 2022年第8期9卷 47-54页

作者： Zhiling Zhou Sibo Huang Dongting Li Jie Zhu Yong Li Institute of acoustics School of Physics Science and EngineeringTongji University Department of Mechanical Engineering The Hong Kong Polytechnic University The Hong Kong Polytechnic University Shenzhen Research Institute

Causality of linear time-invariant systems inherently defines the wave-matter interaction process in wave physics. This principle imposes strict constraints on the interfacial response of materials on various physical platforms. A typical consequence is that a delicate balance has to be struck between the conflicting bandwidth and geometric thickness when constructing a medium with desired impedance, which makes it challenging to realize broadband impedance modulation with compact structures. In pursuit of improvement, the over-damped recipe and the reduced excessive response recipe are creatively presented in this work. As a proof-of-concept demonstration, we construct a metamaterial with intensive mode density that supports strong non-locality over a frequency band from 320 Hz to 6400 Hz. Under the guidelines of the over-damped recipe and the reduced excessive response recipe, the metamaterial realizes impedance matching to air and exhibits broadband near-perfect absorption without evident impedance oscillation and absorption dips in the working frequency band. We further present a dual-functional design capable of frequency-selective absorption and reflection by concentrating the resonance modes in three frequency bands. Our research reveals the significance of over-damped recipe and the strong non-local effect in broadband impedance modulation, which may open up avenues for constructing efficient artificial impedance boundaries for energy absorption and other wave manipulation.

关键词： impedance modulation acoustic absorption non-local metamaterials

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An experimental method to design porous asphalts to account for surface requirements

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Journal of Traffic and Transportation Engineering(English Edition) 2021年第3期8卷 439-452页

作者： Filippo G.Pratico Paolo G.Briante Giuseppe Colicchio Rosario Fedele DIIES Department University“Mediterranea”of Reggio CalabriaReggio Calabria89100Italy

Porous asphalts have supplementary surface and volumetric properties(e.g., acoustic absorption, drain ability, texture, and friction). These properties are linked to intrinsic factors(e.g., gradation and bitumen content) and extrinsic factors(e.g., traffic load), while their evolution over time depends on complex phenomena and processes that cause their deterioration and therefore affect safety, noise, and budget. Despite the decay of so many and complex properties over time, there is a lack of criteria to synergistically optimize the pavement system. Consequently, the objective of this study is to set up and validate a design method that synergistically addresses the most relevant properties of friction courses as a part of a pavement structure. The abovementioned method is based on indepth analyses of the literature and on laboratory and on-site tests carried for several years in order to evaluate the decay over time of the main surface and volumetric *** show that (1) the level of fulfilment of single requirements varies over time and among the characteristics;(2) a sound optimization of the design of the mix in order to balance the different characteristics is needed;(3) further studies are needed because of uncertainty in predicting the main surface properties.

关键词： Road engineering Surface property acoustic absorption Macrotexture Friction Porous asphalt

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Modeling and Measurement of a Tunable Acoustoelastic System

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Sound & Vibration 2018年第3期52卷 12-17页

作者： Deborah Fowler Garrett Lopp Dhiraj Bansal Ryan Schultz Matthew Brake Micah Shepherd Undergraduate Student University of MassachusettsLowell01854 Graduate Research Assistant University of Central FloridaOrlandoFL32816 Graduate Student University of Colorado BoulderBoulderCO 80309 Sandia National Laboratories PO Box 5800-MS0557AlbuquerqueNM87123 Assistant Professor William Marsh Rice University6100 Main StMS 321HoustonTX 77005 Assistant Research Professor The Pennsylvania State UniversityPO Box 30State CollegePA 16804

Acoustoelastic coupling occurs when a hollow structure’s in-vacuo mode aligns with an acoustic mode of the internal *** impact of this coupling on the total dynamic response of the structure can be quite severe depending on the similarity of the modal frequencies and ***,acoustoelastic coupling is not a design feature,but rather an unintended result that must be remedied as modal tests of structures are often used to correlate or validate finite element models of the uncoupled ***,however,a test structure is intentionally designed such that multiple structural and acoustic modes are well-aligned,resulting in a coupled system that allows for an experimental ***,coupling in the system is identified using a measure termed the magnification ***,the structural-acoustic interaction is *** to the system demonstrate the dependency of the coupling on changes in the mode shape and frequency *** includes an investigation of several practical techniques used to decouple the system by altering the internal acoustic cavity,as well as the structure *** results show that acoustic absorption material effectively decoupled the structure while structural modifications,in their current form,proved *** available acoustic absorptive material was effective in reducing the coupled effects while presumably adding negligible mass or stiffness to the structure.

关键词： Structural-acoustic interaction coupled modes acoustic absorption acoustic modes modal testing

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