Achieving broadband noise attenuation at low frequencies is still a significant challenge. Helmholtz resonators offer good low-frequency noise attenuation but are effective only over a narrow band; the cavity volume required at these frequencies is also larger. This article proposes a new broadband acoustic metamaterial (AMM) absorber, which uses polyurethane (PU) foam embedded with small-size resonators tuned to different frequencies. The AMM design is achieved in three phases: (1) develop a transfer-matrix-based one-dimensionalmodel for a resonator with intruded neck; (2) use this model to develop a novel band broadeningmethod, to select appropriate resonators tuned to different frequencies; and (3) construct a unit cell metamaterial embedded with an array of resonators into PU foam. A small-size resonator tuned to 415 Hz is modified, by varying the intrusion lengths of the neck, to achieve natural frequencies ranging from 210 to 415 Hz. Using the band broadening methodology, 1 unit cell metamaterial is constructed; its effectiveness is demonstrated by testing in an acoustic impedance tube. The broadband attenuation characteristics of the constructed unit cell metamaterial are shown to match well with the predicted results. To demonstrate further the effectiveness of the idea, a metamaterial is formed using 4 periodic unit cells and is tested in a twin room reverberation chamber. The transmission loss is shown to improve significantly, at low frequencies, due to the inclusion of the resonators.
{"title":"Broadband low-frequency noise reduction using Helmholtz resonator-based metamaterial","authors":"Jhalu Gorain, C. Padmanabhan","doi":"10.3397/1/376932","DOIUrl":"https://doi.org/10.3397/1/376932","url":null,"abstract":"Achieving broadband noise attenuation at low frequencies is still a significant challenge. Helmholtz resonators offer good low-frequency noise attenuation but are effective only over a narrow band; the cavity volume required at these frequencies is also larger. This article proposes\u0000 a new broadband acoustic metamaterial (AMM) absorber, which uses polyurethane (PU) foam embedded with small-size resonators tuned to different frequencies. The AMM design is achieved in three phases: (1) develop a transfer-matrix-based one-dimensionalmodel for a resonator with intruded neck;\u0000 (2) use this model to develop a novel band broadeningmethod, to select appropriate resonators tuned to different frequencies; and (3) construct a unit cell metamaterial embedded with an array of resonators into PU foam. A small-size resonator tuned to 415 Hz is modified, by varying the intrusion\u0000 lengths of the neck, to achieve natural frequencies ranging from 210 to 415 Hz. Using the band broadening methodology, 1 unit cell metamaterial is constructed; its effectiveness is demonstrated by testing in an acoustic impedance tube. The broadband attenuation characteristics of the constructed\u0000 unit cell metamaterial are shown to match well with the predicted results. To demonstrate further the effectiveness of the idea, a metamaterial is formed using 4 periodic unit cells and is tested in a twin room reverberation chamber. The transmission loss is shown to improve significantly,\u0000 at low frequencies, due to the inclusion of the resonators.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42148486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Silencers used in the power generation industry generally have large ducts entering and leaving the silencer. With large cross-sectional dimensions, the plane wave cutoff frequency will be exceeded at a low frequency so that transmission loss can no longer be evaluated by assuming constant sound pressure over a cross-section. More sophisticated calculation and processing approaches are necessary. In this research, the boundary element method is used in conjunction with a reciprocal identity method to determine the transmission loss for rectangular and circular cross-sections: the two configurations that cover most real-world designs. The boundary element method is compared to a finite element method strategy where the transmission loss is determined using an automatically matched layer boundary condition at the inlet and outlet. This approach can be used in most commercial software. Although these two approaches have little in common, transmission loss results compare well with one other. Validation by comparison is helpful because analytical solutions are only available for simple axisymmetric cases. Methods are compared for practical configurations like parallel-baffle silencers and reactive silencers.
{"title":"Case study: Correlation between boundary and finite element determination of large silencer transmission loss","authors":"K. Ruan, T. Wu, D. Herrin","doi":"10.3397/1/376927","DOIUrl":"https://doi.org/10.3397/1/376927","url":null,"abstract":"Silencers used in the power generation industry generally have large ducts entering and leaving the silencer. With large cross-sectional dimensions, the plane wave cutoff frequency will be exceeded at a low frequency so that transmission loss can no longer be evaluated by assuming constant\u0000 sound pressure over a cross-section. More sophisticated calculation and processing approaches are necessary. In this research, the boundary element method is used in conjunction with a reciprocal identity method to determine the transmission loss for rectangular and circular cross-sections:\u0000 the two configurations that cover most real-world designs. The boundary element method is compared to a finite element method strategy where the transmission loss is determined using an automatically matched layer boundary condition at the inlet and outlet. This approach can be used in most\u0000 commercial software. Although these two approaches have little in common, transmission loss results compare well with one other. Validation by comparison is helpful because analytical solutions are only available for simple axisymmetric cases. Methods are compared for practical configurations\u0000 like parallel-baffle silencers and reactive silencers.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46300818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Liyan, Chenxi Li, Hu Ying, Haitao Wang, Ran Qing, Haiquan Wu
This article aims to investigate the sound absorbing properties of a thick microperforated panel (MPP) with tapered sections with finite element analysis (FEA) models. The FEA model was validated by using the measured sound absorption coefficients of a classic MPP sample and a proposed MPP sample. The FEA simulation and the experiments indicate that the tapered section can enhance the sound absorption coefficient. Moreover, the FEA model shows that the structural parameters of the tapered section can be optimized. The resonance frequency of the sound absorption coefficient moves to the high-frequency range, and the maximum sound absorption coefficient increases in three conditions, the tapered section moving toward the backing cavity, and the increase of the thickness and the bottom radius of the tapered section. Although the optimized configurations of the tapered section may vary with the structure parameters of the MPP, the tapered section can improve the sound absorbing properties of the classic MPP and could be promising in the noise and vibration engineering projects.
{"title":"Sound absorption of a thick micro-perforated panel with tapered sections","authors":"H. Liyan, Chenxi Li, Hu Ying, Haitao Wang, Ran Qing, Haiquan Wu","doi":"10.3397/1/376930","DOIUrl":"https://doi.org/10.3397/1/376930","url":null,"abstract":"This article aims to investigate the sound absorbing properties of a thick microperforated panel (MPP) with tapered sections with finite element analysis (FEA) models. The FEA model was validated by using the measured sound absorption coefficients of a classic MPP sample and a proposed\u0000 MPP sample. The FEA simulation and the experiments indicate that the tapered section can enhance the sound absorption coefficient. Moreover, the FEA model shows that the structural parameters of the tapered section can be optimized. The resonance frequency of the sound absorption coefficient\u0000 moves to the high-frequency range, and the maximum sound absorption coefficient increases in three conditions, the tapered section moving toward the backing cavity, and the increase of the thickness and the bottom radius of the tapered section. Although the optimized configurations of the\u0000 tapered section may vary with the structure parameters of the MPP, the tapered section can improve the sound absorbing properties of the classic MPP and could be promising in the noise and vibration engineering projects.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48708452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elspeth A. Wing, Steven J. Herr, Alexander D. Petty, Alexander K. Dufour, Frederick H. Hoham, Morgan E. Merrill, Donovan W. Samphier, Weimin Thor, Kushagra Singh, Y. Xue, D. Huston, J. Bolton
The perplexing acoustical properties of a landscape architecture feature of Academy Park on the Purdue University campus have long been the subject of speculation. The feature, known informally as the "Clapping Circle", consists of sixty-six concentric rings of stone tiles. When someone claps while at the middle of the circle, they hear a high-pitched squeak immediately afterwards. Experiments were conducted by the Purdue student chapter of the Acoustical Society of America to characterize this effect. The response to a clap played from an omnidirectional speaker placed at the center of the circle was recorded using a microphone positioned above the loudspeaker. Spectrograms of the recorded responses revealed the squeak to consist of a descending tone and its harmonics. This tone disappeared from the spectrogram when the tiles were covered with absorbing blankets. A model based on scattering from the bevels between the tile rings reproduced the descending frequency of the squeak. Similarly to famous stepped structures with notable acoustics, the tiles were found to scatter sound best when the wavelength was not larger than the tiles' spatial period. Thus, it was concluded that the squeak is an example of an acoustical diffraction grating which creates a repetition pitch caused by scattering from the tile formation.
{"title":"Case study: Purdue University's \"Clapping Circle\": An acoustical investigation","authors":"Elspeth A. Wing, Steven J. Herr, Alexander D. Petty, Alexander K. Dufour, Frederick H. Hoham, Morgan E. Merrill, Donovan W. Samphier, Weimin Thor, Kushagra Singh, Y. Xue, D. Huston, J. Bolton","doi":"10.3397/1/376928","DOIUrl":"https://doi.org/10.3397/1/376928","url":null,"abstract":"The perplexing acoustical properties of a landscape architecture feature of Academy Park on the Purdue University campus have long been the subject of speculation. The feature, known informally as the \"Clapping Circle\", consists of sixty-six concentric rings of stone tiles.\u0000 When someone claps while at the middle of the circle, they hear a high-pitched squeak immediately afterwards. Experiments were conducted by the Purdue student chapter of the Acoustical Society of America to characterize this effect. The response to a clap played from an omnidirectional speaker\u0000 placed at the center of the circle was recorded using a microphone positioned above the loudspeaker. Spectrograms of the recorded responses revealed the squeak to consist of a descending tone and its harmonics. This tone disappeared from the spectrogram when the tiles were covered with absorbing\u0000 blankets. A model based on scattering from the bevels between the tile rings reproduced the descending frequency of the squeak. Similarly to famous stepped structures with notable acoustics, the tiles were found to scatter sound best when the wavelength was not larger than the tiles' spatial\u0000 period. Thus, it was concluded that the squeak is an example of an acoustical diffraction grating which creates a repetition pitch caused by scattering from the tile formation.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45637494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhaoping Tang, Min Wang, Xiaoying Xiong, Manyu Wang, Jianping Sun, Li Yan
Under high-speed operating conditions, the noise caused by the vibration of the traction gear transmission system of the Electric Multiple Units (EMU) will distinctly reduce the comfort of passengers. Therefore, analyzing the dynamic characteristics of traction gears and reducing noise from the root cause through comprehensive modification of gear pairs have become a hot research topic. Taking the G301 traction gear transmission system of the CRH380A high-speed EMU as the research object and then using Romax software to establish a parametric modification model of the gear transmission system, through dynamics, modal and Noise Vibration Harshness (NVH) simulation analysis, the law of howling noise of gear pair changes with modification parameters is studied. In the small sample training environment, the noise prediction model is constructed based on the priority weighted Back Propagation (BP) neural network of small noise samples. Taking the minimum noise of high-speed EMU traction gear transmission as the optimization goal, the simulated annealing (SA) algorithm is introduced to solve the model, and the optimal combination of modification parameters and noise data is obtained. The results show that the prediction accuracy of the prediction model is as high as 98.9%, and it can realize noise prediction under any combination of modification parameters. The optimal modification parameter combination obtained by solving the model through the SA algorithm is imported into the traction gear transmission system model. The vibration acceleration level obtained by the simulation is 89.647 dB, and the amplitude of the vibration acceleration level is reduced by 25%. It is verified that this modification optimization design can effectively reduce the gear transmission.
{"title":"Optimal design of noise reduction and shape modification for traction gears of EMU based on improved BP neural network","authors":"Zhaoping Tang, Min Wang, Xiaoying Xiong, Manyu Wang, Jianping Sun, Li Yan","doi":"10.3397/1/376934","DOIUrl":"https://doi.org/10.3397/1/376934","url":null,"abstract":"Under high-speed operating conditions, the noise caused by the vibration of the traction gear transmission system of the Electric Multiple Units (EMU) will distinctly reduce the comfort of passengers. Therefore, analyzing the dynamic characteristics of traction gears and reducing noise\u0000 from the root cause through comprehensive modification of gear pairs have become a hot research topic. Taking the G301 traction gear transmission system of the CRH380A high-speed EMU as the research object and then using Romax software to establish a parametric modification model of the gear\u0000 transmission system, through dynamics, modal and Noise Vibration Harshness (NVH) simulation analysis, the law of howling noise of gear pair changes with modification parameters is studied. In the small sample training environment, the noise prediction model is constructed based on the priority\u0000 weighted Back Propagation (BP) neural network of small noise samples. Taking the minimum noise of high-speed EMU traction gear transmission as the optimization goal, the simulated annealing (SA) algorithm is introduced to solve the model, and the optimal combination of modification parameters\u0000 and noise data is obtained. The results show that the prediction accuracy of the prediction model is as high as 98.9%, and it can realize noise prediction under any combination of modification parameters. The optimal modification parameter combination obtained by solving the model through\u0000 the SA algorithm is imported into the traction gear transmission system model. The vibration acceleration level obtained by the simulation is 89.647 dB, and the amplitude of the vibration acceleration level is reduced by 25%. It is verified that this modification optimization design can effectively\u0000 reduce the gear transmission.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42976222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Microperforated panels (MPPs) are recognized as suitable absorbers for noise control applications demanding special clean and health requirements.While it is relatively easy to design single-layer MPPs for sound absorption in one-to-two octave bands at medium-high frequencies, the performance for low frequencies (below 600 Hz) leads to a rather narrow-band absorption, similar to that of a Helmholtz resonator. However, multiple-layer MPPs can be designed as sound absorbers that yield low-frequency absorption in a wide frequency band. Recently, multiple-cavity perforated panels have been proposed to improve the performance of MPPs in the low-frequency range. In this article, the capability of multiple-layer and multiple-cavity MPPs to provide sound absorption at low frequencies is analyzed.
{"title":"Comparison of multiple-layer versus multiple-cavity microperforated panels for sound absorption at low frequency","authors":"P. Cobo, F. Simón, C. Colina","doi":"10.3397/1/376931","DOIUrl":"https://doi.org/10.3397/1/376931","url":null,"abstract":"Microperforated panels (MPPs) are recognized as suitable absorbers for noise control applications demanding special clean and health requirements.While it is relatively easy to design single-layer MPPs for sound absorption in one-to-two octave bands at medium-high frequencies, the performance\u0000 for low frequencies (below 600 Hz) leads to a rather narrow-band absorption, similar to that of a Helmholtz resonator. However, multiple-layer MPPs can be designed as sound absorbers that yield low-frequency absorption in a wide frequency band. Recently, multiple-cavity perforated panels have\u0000 been proposed to improve the performance of MPPs in the low-frequency range. In this article, the capability of multiple-layer and multiple-cavity MPPs to provide sound absorption at low frequencies is analyzed.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42432098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An imperfect sealing system would be the main path of the noise propagating into the interior compartment of a high-speed vehicle. The study on the sound insulation modeling of automotive door sealing systems, which involve complicated threedimensional sealing structures and gap cavities, has attracted more and more attention. This study employs hybrid finite element–statistical energy analysis (FE-SEA) models to predict the sound transmission loss of three simplified sealing specimens and an actual automotive door sealing system. For the actual sealing system under compression, a three-dimensional FEmodel is built to simulate the nonlinear compression, which can acquire the compressed geometries and pre-stress modal results of the seals for further prediction of the sound transmission loss. The hybrid FE-SEA method is firstly verified by the experimental result of a double plate vibro-acoustic system and another numerical method. Several factors concerning the modeling, including the boundary conditions, the equivalent elastic modulus for the hyper-elastic rubber, the specimen length, and the structural grid size, are considered to study their impacts on the sound transmission loss. The effects of using shell elements and using solid elements to model the sealing rubber layers are also compared. The results of this study can provide guides regarding the trade-off between the modeling efficiency and accuracy, so that it has significance for engineering modeling, as well as the design and optimization of automotive door sealing systems.
{"title":"Study on sound transmission loss modeling through simplified sealing specimens and an automotive door sealing system","authors":"Guoming Deng, Jianwang Shaob, Songlin Zheng, Xian Wu","doi":"10.3397/1/376929","DOIUrl":"https://doi.org/10.3397/1/376929","url":null,"abstract":"An imperfect sealing system would be the main path of the noise propagating into the interior compartment of a high-speed vehicle. The study on the sound insulation modeling of automotive door sealing systems, which involve complicated threedimensional sealing structures and gap cavities, has attracted more and more attention. This study employs hybrid finite element–statistical energy analysis (FE-SEA) models to predict the sound transmission loss of three simplified sealing specimens and an actual automotive door sealing system. For the actual sealing system under compression, a three-dimensional FEmodel is built to simulate the nonlinear compression, which can acquire the compressed geometries and pre-stress modal results of the seals for further prediction of the sound transmission loss. The hybrid FE-SEA method is firstly verified by the experimental result of a double plate vibro-acoustic system and another numerical method. Several factors concerning the modeling, including the boundary conditions, the equivalent elastic modulus for the hyper-elastic rubber, the specimen length, and the structural grid size, are considered to study their impacts on the sound transmission loss. The effects of using shell elements and using solid elements to model the sealing rubber layers are also compared. The results of this study can provide guides regarding the trade-off between the modeling efficiency and accuracy, so that it has significance for engineering modeling, as well as the design and optimization of automotive door sealing systems.","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42109966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Loudness, Descriptors of Noise, Noise Criteria and Instrumentation","authors":"C. Hansen, K. Hansen","doi":"10.1201/9780429428876-2","DOIUrl":"https://doi.org/10.1201/9780429428876-2","url":null,"abstract":"","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":"21 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80905928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-18DOI: 10.4324/9780203473948_chapter_4
C. Hansen, K. Hansen
{"title":"Sound in Rooms","authors":"C. Hansen, K. Hansen","doi":"10.4324/9780203473948_chapter_4","DOIUrl":"https://doi.org/10.4324/9780203473948_chapter_4","url":null,"abstract":"","PeriodicalId":49748,"journal":{"name":"Noise Control Engineering Journal","volume":"113 1","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77605916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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