Relevant bibliographies by topics / Acoustic absorber

Academic literature on the topic 'Acoustic absorber'

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Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Acoustic absorber"

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Herlina Sari, Nasmi, and Jauhar Fajrin. "Acoustic Properties of Sound Absorber from Modified Polyester with Filler Sodium Bicarbonate." Oriental Journal of Chemistry 34, no. 4 (August 25, 2018): 2187–91. http://dx.doi.org/10.13005/ojc/3404061.

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The combination of low price, ease of manufacturing and waterproofing characteristics has placed polyester resin as a potential sound absorbent material. Previous studies showed that adding filler material to the blending may increase the acoustics properties of a sound absorbent material. This study aims to investigate the potential of sodium bicarbonate (NaHCO3) to be employed as a filler to improve the acoustic properties of the sound absorber made of polyester resin. Two important acoustic parameters were carefully assessed; absorption coefficient and acoustic impedance. The results showed that the sound absorption performance increased significantly at low and medium frequencies in the presence of NaHCO3 filler in polyester resin. Meanwhile, the use of a back cavity on the absorbent material reduced the sound absorption performance of materials at low and medium frequencies. This suggests that sound absorber made of polyester with sodium bicarbonate filler may be used as an alternative for sound absorber materials.
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Xu, Weikai, Yingchun Tang, Meng Zhang, Wuchao Qi, and Wei Wang. "Arbitrary shaped acoustic omnidirectional absorber based on transformation theory." International Journal of Modern Physics B 34, no. 11 (April 30, 2020): 2050111. http://dx.doi.org/10.1142/s0217979220501118.

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In this study, an arbitrary shaped acoustic omnidirectional absorber (AOA) is achieved for absorbing incoming acoustic/elastic waves in the ambient environment. Using the transformation acoustics theory, we present a theoretical framework for two-dimensional acoustic path guidance around arbitrary shapes for which the material parameters in the transformed space can be obtained analytically. Results indicate that the transformed space is distorted rather than compressed; numerical simulations confirm that these absorbers exhibit a remarkably large absorption and that the proposed method can control acoustic absorption for arbitrary geometries of interest. This method can potentially be applied to sound absorption and noise control.
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Putra, Azma, D. Hafizah, M. Y. Yaakob, and Mohd Jailani Mohd Nor. "Study on the Use of Micro-Perforated Panel to Improve Acoustic Performance in Mosque." Applied Mechanics and Materials 393 (September 2013): 971–75. http://dx.doi.org/10.4028/www.scientific.net/amm.393.971.

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Most activities in mosque such as Friday prayer and the sermon by an Imam require clarity of speech. Unfortunately, this speech intelligibility performance is often poor due to initial design of a mosque. This paper presents assessment of the indoor acoustics of a mosque. Acoustical properties such as reverberation time, clarity and early decay time are obtained from simulation data using CATT indoor acoustic software. The study started with an empty mosque with no acoustic treatment. Acoustic green absorbers using micro-perforated panel (MPP) are then introduced to improve the acoustic performance. The application of MPP is still rare for mosque and is expected to replace the typical porous absorber. The effect of the panel size, location and frequency range of sound absorption are simulated and the results are discussed.
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Halama, Jakub, Milan Klapka, and Ivan Mazůrek. "Experimental Methodology for Acoustic Diagnostics of Shock Absorbers." Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 66, no. 5 (2018): 1119–25. http://dx.doi.org/10.11118/actaun201866051119.

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The application of acoustic measurements brings about a new diagnostic method for evaluating the conditions of shock absorbers. In shock absorber diagnostics, it is advantageous to observe and understand what phenomena occur during the working cycle in the inner tube. Using a non‑destructive and non‑contact method can avoid dismantling whole device. For the research of this new acoustic method, a classic sound meter, an automotive and a train shock absorber were used. FFT analysis and concurrent filtration were applied for the measurement evaluation of obtained data. It has been proven that applying acoustic methods can lead to diagnostics of aeration in the shock absorbers. A defective shock absorber changes its damping characteristics as well as noise radiation compared with the properly functioning one; these differences in noise are measurable and quantifiable. The results show that characteristics of acoustic radiation of the aerated shock absorbers relate to the shock construction type.
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Liu, Xingxing, Xiang Li, and Zhiying Ren. "Miniaturized Spiral Metamaterial Array for a Ventilated Broadband Acoustic Absorber." Shock and Vibration 2020 (November 2, 2020): 1–6. http://dx.doi.org/10.1155/2020/8887571.

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The high-efficiency and broadband acoustic reduction performance in a miniaturized free-flow structure remains challenging in acoustic engineering applications due to the contradiction of ventilation and acoustic reduction performance. Traditional acoustic absorbers can sufficiently attenuate acoustic wave, but meanwhile, block fluid flow due to the longitudinal nature of acoustic waves that can transmit among any small holes. Although different types of ventilated metamaterial absorbers (VMAs) with proper reduction and ventilation performance have been demonstrated recently, their insufficiencies lie in small open-area ratios, not efficient-enough reduction performance, bulky structure, and narrow working band. To further solve existing defects, a ventilated broadband absorber with the miniaturized metamaterial structure has been proposed. The designed absorber consists of miniaturized Archimedean spiral units, which can be easily stacked to achieve broadband and ventilated performance. This work opens up possibilities for practical acoustic applications where both noise control and ventilation are required, especially in a small space.
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Lerner, Lawrence, and Stephen P. Diskin. "Portable adjustable acoustic absorber." Journal of the Acoustical Society of America 83, no. 2 (February 1988): 845–46. http://dx.doi.org/10.1121/1.396070.

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Naify, Christina J., Theodore P. Martin, Christopher N. Layman, Michael Nicholas, Abel L. Thangawng, David C. Calvo, and Gregory J. Orris. "Underwater acoustic omnidirectional absorber." Applied Physics Letters 104, no. 7 (February 17, 2014): 073505. http://dx.doi.org/10.1063/1.4865480.

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Wang, Heng, and Qibo Mao. "Development and Investigation of Fully Ventilated Deep Subwavelength Absorbers." Symmetry 13, no. 10 (October 1, 2021): 1835. http://dx.doi.org/10.3390/sym13101835.

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A new type of deep subwavelength acoustic metamaterial (AMM) absorber with 100% ventilation is presented in this study. The proposed ventilation absorber consists of coiled-up half-wave resonators (HWRs) and quarter-wave resonators (QWRs). First, the sound absorption and sound transmission performances for absorbers were analyzed considering the thermal viscosity dissipation. Then, the prototype with ten HWRs and three QWRs composed of acrylic plates was manufactured based on the theoretical model. The acoustic performance of the absorber was tested in an air-filled acoustic impedance tube to determine the sound absorption and transmission loss performances. Good agreement was found between the measured and theoretically predicted results. The experimental results show that the proposed ventilation AMM absorber is able to achieve sound absorption in a range between 330 Hz and 460 Hz with a thickness of only 32 mm (about 3% of the wavelength in the air). Furthermore, the sound transmission loss can achieve 17 dB from 330 Hz to 460 Hz. The main advantage of the proposed absorber is that it can be completely ventilated in duct noise control.
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El-Raheb, M., and P. Wagner. "Damped Response of Shells by a Constrained Viscoelastic Layer." Journal of Applied Mechanics 53, no. 4 (December 1, 1986): 902–8. http://dx.doi.org/10.1115/1.3171879.

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Vibration absorbers are introduced into an asymmetric configuration of thin cylinders and tori enclosing an acoustic medium. The absorbers consist of thin axial strips bonded to the cylinder with a thin viscoelastic layer. The constrained layer dissipates the energy of relative motions between strip and cylinder. The absorber is most effective on response modes with two or more circumferential waves. The use of transfer matrices is extended to the coupled cylinder-absorber system.
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Ng, C. F., and Qin Hao-Ming. "Double Perforated Honeycomb Panel as a Low Frequency Acoustic Absorber." Building Acoustics 4, no. 1 (March 1997): 21–37. http://dx.doi.org/10.1177/1351010x9700400102.

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This report deals with a theoretical and experimental study of the low frequency sound absorption characteristics of perforated honeycomb sandwich panels. The derivations of formulae for absorption in terms of double perforation ratio and air gap are presented. Results show that the honeycomb absorber, with double perforated sheets, can be an effective low frequency absorber for frequencies down to 63 Hz. In addition, honeycomb panels have advantages over other low frequency absorbers in that they are light weight and strong.
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Dissertations / Theses on the topic "Acoustic absorber"

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Parkinson, Jerome P. "Acoustic absorber design." Thesis, University of Canterbury. Mechanical Engineering, 1999. http://hdl.handle.net/10092/6414.

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The aim of the Acoustic Absorber Project was to investigate the performance of a range of materials as acoustic absorbers. A literature search on acoustic absorbers was carried out first and is presented with a summary of commercially available absorbers in the Absorber Survey. Modifications were made to the Reverberation Room in the Department of Mechanical Engineering, University of Canterbury. Tests showed that the Room modifications and diffuser installation improved its sound field diffusivity and uniformity, ensuring reliable absorption measurements. Apparatus was then built and used to measure the flow resistance of porous materials. This equipment was pivotal to the successful specification of materials used as acoustic absorbers. More than fifty different absorbers were tested in the refurbished Reverberation Room to determine their absorption coefficients. Subsequent analysis was carried out to compare the different materials, thicknesses and systems used as absorbers. Various models were used and developed to predict the measured results. The models produced similar trends to the measured data but with lower absorption coefficients. It was found that tuned absorbers could be produced from CMSG foam with impervious films, giving high absorption in selected frequencies. Wideband absorbers could be made at low cost from low density foam, polyester or fibreglass with fabric coverings, each optimised for flow resistance. Contoured foams were also found to be very effective wideband absorbers. Optimal acoustic absorbers can now be designed and produced to satisfy different absorption requirements.
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Onen, Onursal. "Development Of An Effective Single Layer Micro-perforated Sound Absorber." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610064/index.pdf.

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Micro-perforated sound absorbers with sub-millimeter size holes can provide high absorption coefficients. Various types of micro-perforated absorbers are now available in literature for different applications. This thesis presents results of work on the development of an effective single layer micro-perforated sound absorber from the commercial composite material Parabeam with micro diameter holes drilled on one side. Parabeam is used as a structural material made from a fabric woven out of a E-glass yarn and consists of two decklayers bonded together by vertical piles in a sandwich structure with piles (thick fibers) woven into the decklayers. The thesis includes, the analytical model developed for prediction of absorption coefficients, finite element solution using commercial software MSC.ACTRAN and experimental results obtained from impedance tube measurements. Different absorption characteristics can be achieved by variations in hole diameter and hole spacing. Based on the developed models, an optimization is performed to obtain an efficient absorber configuration. It has been anticipated that several different and interesting applications can be deduced by combining structural and sound absorption properties of this new micro-perforated absorber along with conventional fibrous absorbers.
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Estève, Simon J. "Control of sound transmission into payload fairings using distributed vibration absorbers and Helmholtz resonators." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11183.

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A new passive treatment to reduce sound transmission into payload fairing at low frequency is investigated. This new solution is composed of optimally damped vibration absorbers (DVA) and optimally damped Helmholtz resonators (HR). A fully coupled structural-acoustic model of a composite cylinder excited by an external plane wave is developed as a first approximation of the system. A modal expansion method is used to describe the behavior of the cylindrical shell and the acoustic cavity; the noise reduction devices are modeled as surface impedances. All the elements are then fully coupled using an impedance matching method. This model is then refined using the digitized mode shapes and natural frequencies obtained from a fairing finite element model. For both models, the noise transmission mechanisms are highlighted and the noise reduction mechanisms are explained. Procedures to design the structural and acoustic absorbers based on single degree of freedom system are modified for the multi-mode framework. The optimization of the overall treatment parameters namely location, tuning frequency, and damping of each device is also investigated using genetic algorithm. Noise reduction of up to 9dB from 50Hz to 160Hz using 4% of the cylinder mass for the DVA and 5% of the cavity volume for the HR can be achieved. The robustness of the treatment performance to changes in the excitation, system and devices characteristics is also addressed. The model is validated by experiments done outdoors on a 10-foot long, 8-foot diameter composite cylinder. The excitation level reached 136dB at the cylinder surface comparable to real launch acoustic environment. With HRs representing 2% of the cylinder volume, the noise transmission from 50Hz to160Hz is reduced by 3dB and the addition of DVAs representing 6.5% of the cylinder mass enhances this performance to 4.3dB. Using the fairing model, a HR+DVA treatment is designed under flight constraints and is implemented in a real Boeing fairing. The treatment is composed of 220 HRs and 60 DVAs representing 1.1% and 2.5% of the fairing volume and mass respectively. Noise reduction of 3.2dB from 30Hz to 90Hz is obtained experimentally. As a natural extension, a new type of adaptive Helmholtz resonator is developed. A tuning law commonly used to track single frequency disturbance is newly applied to track modes driven by broadband excitation. This tuning law only requires information local to the resonator simplifying greatly its implementation in a fairing where it can adapt to shifts in acoustic natural frequencies caused by varying payload fills. A time domain model of adaptive resonators coupled to a cylinder is developed. Simulations demonstrate that multiple adaptive HRs lead to broadband noise reductions similar to the ones obtained with genetic optimization. Experiments conducted on the cylinder confirmed the ability of adaptive HRs to converge to a near optimal solution in a frequency band including multiple resonances.
Ph. D.
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Halama, Jakub. "Metodika pro bezkontaktní diagnostiku automobilových tlumičů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-377521.

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The diploma thesis deals with the application of acoustic methods for evaluating the technical condition of the shock absorbers. Analysis of acoustic radiation during damping operation leads to the definition of a new non-contact diagnostic methodology that can determine the condition of the shock absorbers. The first part of the thesis focuses on the noise radiation of the shock absorbers, which is caused by discontinuous dumping. Further, the methods for the noise source localization available at The Institute of Machine and Industrial Design are described – with their functionalities, advantages and limitations. Based on all the information, an appropriate method is selected and used in the experimental part of this work. Then, aeration and removing the full volume of oil with damage of the shock absorber tube are caused (induced) on several types of the shocks. Noise radiation is measured by a microphone array and by a sound meter; the acoustic maps, frequency spectra and the synchronous filtration graphs are calculated from the measured data. From the differences in the acoustic radiations of each shock condition, a suitable diagnostic criterion for a specific shock absorber is defined. The final part discusses obtained results. Based on these results, a general diagnostic methodology, applicable to any type of shock absorber, is formulated.
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Iurasov, Volodymyr. "Contrôle passif en vibroacoustique avec absorbeur dynamique bistable." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0034.

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Le travail présenté dans cette thèse est dédié à l’étude d’un absorbeur bistable continu basé sur le principe du "Nonlinear Energy Sink" (NES) et son utilisation pour l’atténuation des vibrations d’un système mécanique à plusieurs degrés de liberté sous excitation acoustique. Le modèle analytique du comportement linéaire de l’absorbeur ainsi que le modèle numérique complet ont été présentés, analysés et validés par des séries d’expériences. Le complexité du transfert énergétique ciblé ("Targeted Energy Transfer" ou TET) entre l'absorbeur et le système primaire à contrôler n’a pas permis une description analytique simple. Nous avons donc choisi de concentrer cette étude sur l’exploration expérimentale et numérique de l’absorbeur couplé à des systèmes mécaniques sous excitations harmonique et aléatoire ainsi que sur l’identification des mécanismes de transfert d’énergie. Le système couplé a montré une dynamique très riche du fait de différents régimes de TET qui ont été décrits dans la littérature pour d’autres types de NES. Ce projet a été financé par Saint-Gobain. L’absorbeur a été adapté pour l’application prévue par la direction industrielle de la thèse: contrôle des vibrations de la double paroi sous excitation acoustique afin d’améliorer l’isolation acoustique fournie par le système.Les connaissances qualitatives sur la dynamique de l’absorbeur obtenues à partir des résultats expérimentaux et numériques, ainsi que l’analogie avec les autres types de NES, ont permis la création d’un absorbeur qui répond à la problématique posée. Les moyens pour l’optimisation et le développement de l’absorbeur ont été identifiés et les simulations préliminaires ont été fournies
The work presented in this thesis is dedicated to the study of a continuous bistable absorber based on the principle of Nonlinear Energy Sink (NES) and its use for the vibration mitigation of a many-degree-offreedom mechanical systems under acoustic excitation. The analytical model of the linear behavior of the absorber and its complete numerical model were presented, analyzed and validated by series of experiments. The complexity of the Targeted Energy Transfer (TET) between the absorber and the primary system did not allow a simple analytical description. We have chosen to concentrate this study on the experimental and numerical exploration of the absorber coupled to mechanical systems under harmonic and random excitations, as well as on the identification of the mechanisms of energy transfer. The coupled system have shown very rich dynamics as it possessed different regimes of TET, which were earlier described in literature for other types of NES. This project was funded by Saint-Gobain. The absorber was adapted for the application foreseen by the industrial supervisors of the PhD: the vibration control of partitioning double walls under acoustic excitation so that to improve the acoustic isolation provided by the system. The qualitative knowledge on the absorber dynamics obtained from the experimental and numerical results, as well as the analogy with the other types of NES, permitted the creation of an absorber which corresponds to the problematic. The ways for the further optimization and development of the absorber were identified and preliminary simulations were provided
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Proctor, Martin J. "Ultrasound power measurement : a microprocessor based device utilising thermal expansion of a total absorber." Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU009820.

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A new type of ultrasound power meter is described which is robust, portable, easy to operate and therefore suitable for use in the work place by non-specialist personnel. The device should be of particular value in the field of ultrasonic therapy, where a lack of suitable instrumentation has discouraged performance monitoring of ultrasound machines in the past although numerous surveys have found the calibration of such equipment generally to be poor. The mode of operation is based on absorption of the ultrasound beam within a liquid, which expands as the energy becomes degraded to heat. The rate of this thermal expansion is monitored by means of a capacitative liquid level sensor, the output signal being suitably processsed and passed to a microcomputer for analysis. Correction for interchange of heat with the surroundings is carried out automatically by the micro, by recording the 'background drift' in liquid volume for a few seconds prior to insonation and subtracting this from the expansion rate observed during input of ultrasound. Calibration is achieved by measuring the (corrected) expansion rates brought about by known powers supplied from an electrical heating coil. When using the new power meter for measurements of therapeutic ultrasound the performance compares favourably with that of other techniques: the reproducibility is on the order of 5% above about 0.5W, becoming less good below this (reaching about 20% at the minimum measurable power of 25-50mW). Design modifications which may improve performance at low power levels and possibly allow measurement of dignostic ultrasound are suggested.
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Leng, Julien. "Controlling flexural waves using subwavelength perfect absorbers : application to Acoustic Black Holes." Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1027/document.

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Le contrôle des vibrations à basse fréquence adapté aux structures légères est un défi scientifique ettechnologique en raison de contraintes économiques et écologiques de plus en plus strictes. De récentes études enacoustique ont portées sur l’absorption totale d’ondes basses fréquences à l’aide d’absorbeurs parfaits sublongueursd’onde. Ces métamatériaux sont obtenus en exploitant la condition de couplage critique. Unegénéralisation de cette méthode pour le domaine élastodynamique serait d’un grand intérêt pour répondre auxexigences du contrôle des vibrations de structures légères à basse fréquence.Cette thèse vise à adapter le problème d’absorption parfaite des ondes de flexion dans des systèmes 1D et 2D avecdes résonateurs locaux en utilisant la condition de couplage critique. Une étude préliminaire sur des systèmes 1D àgéométries simples sont d’abord proposée. Celle-ci propose une méthode de conception de résonateurs simplespour une absorption efficace des ondes de flexion. Une complexification du système 1D est ensuite considérée avecl’étude du couplage critique de Trou Noir Acoustique (TNA) 1D. Ceci a motivé l’interprétation de l’effet TNA à l’aidedu concept de couplage critique afin de présenter des outils clés à de futures procédures d’optimisation pour ce typede terminaisons. La condition de couplage critique est ensuite étendue aux systèmes 2D. L’absorption parfaite parle premier mode axisymétrique d’un résonateur circulaire inséré dans une plaque mince infinie est analysée. Ladiffusion multiple par une ligne de résonateurs circulaires insérés dans une plaque mince 2D infinie ou semi-infinie,appelée métaplaque, est aussi considérée dans l’optique de se rapprocher d’une application industrielle. A traverscette thèse, des modèles analytiques, des simulations numériques et des expériences sont présentés pour valider lecomportement physique des systèmes présentés
The vibration control adapted to light structures is a scientific and technological challenge due toincreasingly stringent economic and ecological standards. Meanwhile, recent studies in audible acoustics havefocused on broadband wave absorption at low frequencies by means of subwavelength perfect absorbers. Suchmetamaterials can totally absorb the energy of an incident wave. The generalisation of this method for applicationsin elastodynamics could be of great interest for the vibration control of light structures.This thesis aims at adapting the perfect absorption problem for flexural waves in 1D and 2D systems with localresonators using the critical coupling condition. A study of 1D systems with simple geometries is first proposed. Thisprovides methods to design simple resonators for an effective absorption of flexural waves. The 1D systems thenbecome more complex by studying the critical coupling of 1D Acoustic Black Holes (ABH). The ABH effect is theninterpreted using the concept of critical coupling, and key features for future optimisation procedures of ABHs arepresented. The critical coupling condition is then extended to 2D systems. The perfect absorption by the firstaxisymmetric mode of a circular resonator inserted in a thin plate is analysed. Multiple scattering by an array ofcircular resonators inserted in an infinite or semi-infinite 2D thin plate, called metaplate, is also considered to getclose to practical applications. Through this thesis, analytical models, numerical simulations and experiments areshown to validate the physical behaviour of the systems presented
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Nash, Grant. "Utilizing Distributed Vibration Absorbers to Reduce Noise Transmission Through the Windshield of a Cessna 150." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/34508.

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High levels of noise have historically been present in the interior of aircrafts. This causes passenger, pilot, and other aircraft employee fatigue as well as speech interference and discomfort issues. In general aviation aircraft, little has been done to reduce the noise in the interior of fuselages. Noise transmitting into the cabin of a single engine aircraft is complex. Researchers have identified areas of noise transmission in general aviation aircraft to include the windshield, exhaust, side windows, and little through the engine firewall. Sources originally noted that structure-borne and airborne noise transmission paths were equal contributors to interior energy penetration of single-engine aircraft. However, additional studies found that airborne noise transmission paths dominate interior energy transmission for single-engine aircraft. Energy transmits mostly through the front of the aircraft via the windshield. Little goes through the engine firewall, which contradicts the original assumption that engine vibration contributed to large noise transmission into the cabin of the aircraft via the firewall. Airborne noise and some exhaust noise transmit through the firewall, but not near as much as noise that transmits through the windshield.

Reducing interior aircraft noise levels is a complicated joint effort, combining propeller radiation control; fuselage wall reduction methods; exhaust emission regulation, management of air turbulence; some propeller, wake-induced vibration control; and a little engine vibration restraint. For minimum propeller acoustic propagation, it is important to control propeller radiation by using techniques such as increasing the number of blades, altering blade airfoil (especially using a felix or grooved design); applying small angle of attack; utilizing swept blades; decreasing blade diameter; lowering tip speed; and reducing the load on a propeller (i.e. by controlling the blade thickness, tip volume, and blade shape). Controlling the vibration in the fuselage skin can also help to reduce interior noise. Some early attempts were made using ribs/stiffeners, tuned dampers, and a limp mass double wall. More recently, dynamic vibration absorbers have been utilized, quite successfully, to reduce fuselage skin vibration and thus, interior noise levels. Attempting to control the exhaust emission and induced vibration from air turbulence has contributed to lower airplane cabin noise levels as well. For large aircrafts, the strategic location of luggage compartments and bathrooms help in keeping the interior quiet. Most importantly for small single-engine aircraft, the windshield has been found to contribute heavily to aircraft interior noise levels.

Currently, the use of active control methods (especially the active structural acoustic control methods) and the utilization of dynamic vibration absorbers (a form of passive noise control) are the most popular techniques to reduce interior aircraft noise levels. In small general aviation aircraft, the blade passage frequency (bpf) and the first few harmonics have been found to be the largest contributor to noise transmitting into the fuselage. This project analyzes a two degree-of-freedom (DOF) dynamic vibration absorber in hopes of reducing windshield vibration of a Cessna 150 fuselage at the fundamental blade passage frequency of approximately 87 Hz and thus, reducing noise transmitting into the interior of the aircraft.

This research project is unique in several ways. First, numerous passive noise control techniques have been utilized to control vibration and acoustics on an aircraft, but none have used the two degree of freedom Distributed Vibration Absorbers (DVA) employed in this project, as a noise reduction method on the windshield of an aircraft. Secondly, little research has been done on analyzing noise transmission into small, single engine general aviation aircraft, which is conducted in the work here. Third, little work has been done on analyzing and reducing noise propagation through the windshield of a small engine aircraft, which is also analyzed in this project. Finally, the modal analysis conducted on the windshield of the small engine plane is one of the few modal decompositions that has been conducted on a small general aircraft windshield.
Master of Science

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Bryk, Pierre-Yvon. "Pompage énergétique en acoustique par absorbeur dynamique non-linéaire hybride passif-actif." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0114.

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Ce mémoire est consacré à l'étude d'un absorbeur dynamique non linéaire hybride passif-actif (ADNLH) pour la réduction du bruit en basses-fréquences. La partie passive de l'ADNLH est une membrane en latex à déformée non linéaire dont la face avant est couplée au champ acoustique que l'on souhaite réduire. Cette membrane se comporte comme un oscillateur non linéaire et fait partie de la famille des absorbeurs non linéaires connus sous le nom de Nonlinear Energy Sink (NES). La face arrière de la membrane est encoffrée et un dispositif de contrôle actif est inclus dans le volume d'encoffrement. Ce dispositif est conçu pour modifier la raideur linéaire et l'amortissement de la membrane. Des précédents travaux ont été réalisés uniquement sur la partie passive (la membrane) et ont permis de valider le principe de pompage énergétique dans le domaine acoustique. Cependant la membrane seule possède des limitations (notamment le seuil de déclenchement du pompage) qui restreignent les applications possibles. L'objectif de l'ADNLH est d'améliorer les performances du pompage énergétique acoustique en modifiant les propriétés linéaires de la membrane grâce à la boucle d'asservissement. Dans un premier temps une étude théorique et expérimentale est réalisée sur l'ADNLH. L'ADNLH est ensuite couplé à un tube résonant avec une excitation sinusoïdale et en bruit blanc. Il permet bien d'écrêter le premier pic de résonance du tube avec de meilleures performances que la version passive. Enfin l'ADNLH est installé dans une salle peu amortie. Il permet d'atténuer la première résonance acoustique de la salle dans le cas d'une excitation sinusoïdale
This thesis is devoted to the study of a hybrid passive-active nonlinear dynamic absorber for the reduction of noise in low frequencies. The passive part of the ADNLH is a membrane in latex with a nonlinear deformation and its front face coupled to the acoustic field to be reduced. This membrane is acting as a nonlinear oscillator and is part of the family of absorbers known as Nonlinear Sink Energy (NES). The rear face is enclosed and a active device is included inside this enclosure. This device is designed in order to modify the linear stiffness and the damping of the membrane. Previous work has been done only on the passive part (the membrane) and has validated the principle of energy pumping for Acoustics. However the membrane has some limitations (like the threshold of energy pumping) that restrain the practical applications. The goal of the ADNLH is to improve the performance of the energy pumping by modifying the linear properties of the membrane with the help of the active device. In a first time an experimental and theoretical study of the ADNLH is done. Then the ADNLH is coupled to a tube of air thanks to an academic assembly under a sinusoidal excitation or broadband. It allows to cut the top off the first acoustic resonance of the tube with better performances than the membrane alone. At last the ADNLH is set inside a weakly damped room. The ADNLH allows to attenuate the first resonance of the room in the case of a sinusoidal excitation. One also shows that the control of the damping of the membrane is the key parameter for the performance of the ADNLH
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Hua, Xin. "ADVANCED STUDIES ON TRANSFER IMPEDANCE WITH APPLICATION TO AFTER-TREATMENT DEVICES AND MICRO-PERFORATED PANEL ABSORBERS." UKnowledge, 2013. http://uknowledge.uky.edu/me_etds/30.

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This work is primarily comprised of five self-contained papers. Three papers are applications oriented. A common element in the first three papers is that micro-perforated panels (MPP), the permeable membranes in diesel particulate filters, and a source impedance are all modeled as a transfer impedance. The first paper deals with enhancing the performance of micro-perforated panels by partitioning the backing cavity. Several different backing schemes are considered which enhance the performance without increasing the total volume of the MPP and backing. In the second paper, a finite element modeling approach is used to model diesel particulate filters below and above the plane wave cutoff frequency. The filter itself is modeled using a symmetric finite element model and results are compared to plane wave theory. After the transfer matrix of the filters is known, it is used in three-dimensional finite and boundary element models. The third paper is a tutorial that shows how a source impedance can be modeled using transfer impedance approaches in finite element analysis. The approach used is useful for better understanding the resonance effects caused by pipes upstream and downstream of the exhaust. The fourth paper examines the best practice for the two-load transmission loss measurement. This method was integral to obtaining the measurements for validating the diesel particulate filter models. The fifth paper proposes transmission and insertion loss metrics for multi-inlet mufflers. It is shown that the transmission loss depends on the amplitude and phase relationship between sources (at the inlets) whereas insertion loss depends on both the source strength and impedance for each inlet.
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Books on the topic "Acoustic absorber"

1

Cox, Trevor J. Acoustic Absorbers and Diffusers. London: Taylor & Francis Group Plc, 2004.

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Fuchs, Helmut V. Applied Acoustics: Concepts, Absorbers, and Silencers for Acoustical Comfort and Noise Control. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-29367-2.

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Peter, D'Antonio, ed. Acoustic absorbers and diffusers: Theory, design, and application. New York, NY: Spon Press, 2006.

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Cox, Trevor J. Acoustic absorbers and diffusers: Theory, design, and application. London: Spon Press, 2004.

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Peter, D'Antonio, ed. Acoustic absorbers and diffusers: Theory, design, and application. 2nd ed. London: Taylor & Francis, 2009.

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Fuchs, Helmut V. Applied Acoustics: Concepts, Absorbers, and Silencers for Acoustical Comfort and Noise Control: Alternative Solutions - Innovative Tools - Practical Examples. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013.

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Vance, Mary A. Sound absorbent materials: A revision of A 662. Monticello, Ill., USA: Vance Bibliographies, 1988.

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Cox, Trevor J. Acoustic Absorbers and Diffusers. CRC Press, 2002. http://dx.doi.org/10.1201/9781482288254.

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Acoustic Absorbers and Diffusers. Routledge, 2009. http://dx.doi.org/10.4324/9780203893050.

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Acoustic Absorbers and Diffusers. Routledge, 2004. http://dx.doi.org/10.4324/9780203492994.

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Book chapters on the topic "Acoustic absorber"

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Putra, Azma, Iwan Prasetiyo, and Zulkefli Selamat. "Green Acoustic Absorber from Pineapple Leaf Fibers." In Pineapple Leaf Fibers, 143–65. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-1416-6_8.

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Mustafa, Mohd Syafiq Syazwan, Mohammad Amin Nurasyid, Kamarul Aini Mohd Sari, Fatimah Yusop, Mariah Awang, M. A. A. Rahman, Nuramidah Hamidon, Mohd Kamaruzaman Musa, and Faridahanim Ahmad. "Utilizing Natural Fibre as a Sustainable Acoustic Absorber." In Lecture Notes in Mechanical Engineering, 243–56. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-0742-4_17.

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Yahya, K., Z. Haron, S. N. Shaikh Abdul Hamid, N. Mohd Fasli, and E. M. Taiwo. "The Potential of Pineapple Leaf Fibre as an Acoustic Absorber." In Proceedings of AICCE'19, 919–31. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-32816-0_68.

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Makni, Amine, Marwa Kani, Mohamed Taktak, and Mohamed Haddar. "Evaluation of the Acoustic Performance of Perforated Multilayer Absorber Materials." In Applied Condition Monitoring, 155–70. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-76517-0_18.

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Kamal, Tafzeelul, Issam Wajih, Vikas Sharma, Yasser Rafat, and M. A. Siddiqui. "Evaluation of Agricultural Waste Natural Fiber as an Acoustic Absorber for Reduction of Industrial Noise." In Design Science and Innovation, 335–41. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-9054-2_38.

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Möser, Michael. "Sound Absorbers." In Engineering Acoustics, 119–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-05391-1_6.

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Möser, Michael. "Sound absorbers." In Engineering Acoustics, 171–215. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-92723-5_6.

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Mechel, Fridolin P. "Porous Absorbers." In Formulas of Acoustics, 272–328. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-07296-7_6.

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Mechel, Fridolin P. "Compound Absorbers." In Formulas of Acoustics, 329–430. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-07296-7_7.

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Fuchs, Helmut V. "Passive Absorbers." In Applied Acoustics: Concepts, Absorbers, and Silencers for Acoustical Comfort and Noise Control, 31–42. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-29367-2_4.

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Conference papers on the topic "Acoustic absorber"

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Gieva, Elitsa Emilova, Ivelina Nikolaeva Ruskova, Krasimir Ivanov Nedelchev, and Ivan Mladenov Kralov. "COMSOL Numerical Investigation of Acoustic Absorber." In 2018 IX National Conference with International Participation (ELECTRONICA). IEEE, 2018. http://dx.doi.org/10.1109/electronica.2018.8439315.

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Azbaid El Ouahabi, Abdelhalim, Victor V. Krylov, and Daniel J. O'Boy. "Quasi-flat acoustic absorber enhanced by metamaterials." In 148th Meeting of the Acoustical Society of America. Acoustical Society of America, 2015. http://dx.doi.org/10.1121/2.0000010.

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Climente, Alfonso, Daniel Torrent, and Jose´ Sa´nchez-Dehesa. "Noise Reduction by Perfect Absorbers Based on Acoustic Metamaterials." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65247.

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We have designed a cylindrical perfect absorber based on acoustic metamaterials. The absorber consists of a metamaterial shell that surrounds a center that dissipates the acoustic energy. The metamaterial shell is designed so that perfectly matches the acoustic impedance of the air background and guides the sound to the center. Numerical simulations are reported about the efficiency of the absorber as a function of the absorbing material employed at the center.
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Völker, Christine, and Ulrike Thesing. "Acoustic Optimization of a Blow Molded Resonant Absorber." In SAE 2003 Noise & Vibration Conference and Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2003. http://dx.doi.org/10.4271/2003-01-1568.

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Bellizzi, Sergio, Bruno Cochelin, Philippe Herzog, Pierre-Olivier Matte´i, and Ce´dric Pinhe`de. "Experimental Investigation of Low Frequency Noise Reduction Using a Nonlinear Vibroacoustic Absorber." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47431.

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This work deals with the energy pumping phenomenon for acoustical applications. The concept of energy pumping is to passively reduce the vibrations of a primary system by attaching to it an essentially nonlinear damped oscillator also named Nonlinear Energy Sink (NES) creating a strongly nonlinear coupling which localizes and dissipates the vibrational energy. In the context of acoustics, a vibroacoustic coupling is used. In an earlier work, we showed experimentally that a loudspeaker used as a Suspended Piston (SP) working outside its range of linearity can be used as a NES. In this work, the performance and efficiency of a SP NES is studied numerically and experimentally. The considered acoustic medium is a resonant pipe. The coupling between the pipe and the NES is ensured acoustically by a small acoustic compliance (the air in a coupling box). Various observed aspects of energy pumping are presented: behavior under sinusoidal forcing, pumping threshold, resonance capture and transient response. As a SP NES technology permits an easy control of the moving mass of the NES, the effect of this parameter is also studied.
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Umnova, Olga, Andy S. Elliott, and Rodolfo Venegas. "Omnidirectional acoustic absorber with a porous core - theory and measurements." In ICA 2013 Montreal. ASA, 2013. http://dx.doi.org/10.1121/1.4799727.

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Redmann, Daniel, Reinhard Pongratz, and Joergen Zillmann. "Aeroacoustic liner applications of the broadband special acoustic absorber concept." In 19th AIAA/CEAS Aeroacoustics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-2176.

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Kusrini, Ayu Sinta, Iwan Yahya, Harjana, and Ubaidillah. "Acoustic performance of porous sound absorber based on Sterculia foetida Linn." In ADVANCED INDUSTRIAL TECHNOLOGY IN ENGINEERING PHYSICS. Author(s), 2019. http://dx.doi.org/10.1063/1.5095340.

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Mehta, P. G., A. C. Zander, W. P. Patrick, and Y. Zhang. "Active acoustic treatment (AAT)-a step toward a perfect sound absorber." In Proceedings of the 1998 American Control Conference (ACC). IEEE, 1998. http://dx.doi.org/10.1109/acc.1998.703108.

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Dan Yang, Qi-bai Huang, Lv-hui Ding, and Qian Zhang. "A transfer matrix approach for acoustic analysis of underwater piezoelectric composite absorber." In 2009 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA 2009). IEEE, 2009. http://dx.doi.org/10.1109/spawda.2009.5428939.

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Reports on the topic "Acoustic absorber"

1

Noise Absorption Behavior of Aluminum Honeycomb Composite. SAE International, September 2020. http://dx.doi.org/10.4271/2020-28-0453.

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Natural fibers are one of the major ways to improve environmental pollution. In this study experimental investigation and simulation of honeycomb filled with cotton fabric, wood dust and polyurethane were carried out. This study determines the potential use of cotton fabric, wood dust as good sound absorbers. Automotive industries are looking forward to materials that have good acoustic properties, lightweight, strong and economical. This study provides a better understanding of sound-absorbing material with other mechanical properties. With simulation and experimental results, validation of works provides a wider industrial application for the interior of automotive industries including marine, aviation, railway industry and many more.
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