Flat Fresnel and axicon acoustic lenses were developed and characterized both numerically and experimentally. Flat lenses have a compact profile leading to less attenuation and phase distortion in the bulk lens material. Fresnel lenses approximate spherical focusing to a fixed point whereas the axicon focuses to a narrow focal line, producing a tighter lateral beam over a longer depth. Numerical models of the sound pressure field from both types of lenses were done using the angular spectrum method. The lenses were 3D printed with polylactic acid (PLA) and also lathe cut with transparent polystyrene. Pulse-echo measurements of the sound speed were done for both materials. Pressure field scans were conducted using a 1.2 MHz planar transducer in a hydrophone scanning tank. These scans demonstrate the focusing effect of both types of lenses and are in agreement with the numerical model.
{"title":"Focal zone characteristics of stepped Fresnel and axicon acoustic lenses","authors":"R. Lirette, J. Mobley","doi":"10.1121/2.0000703","DOIUrl":"https://doi.org/10.1121/2.0000703","url":null,"abstract":"Flat Fresnel and axicon acoustic lenses were developed and characterized both numerically and experimentally. Flat lenses have a compact profile leading to less attenuation and phase distortion in the bulk lens material. Fresnel lenses approximate spherical focusing to a fixed point whereas the axicon focuses to a narrow focal line, producing a tighter lateral beam over a longer depth. Numerical models of the sound pressure field from both types of lenses were done using the angular spectrum method. The lenses were 3D printed with polylactic acid (PLA) and also lathe cut with transparent polystyrene. Pulse-echo measurements of the sound speed were done for both materials. Pressure field scans were conducted using a 1.2 MHz planar transducer in a hydrophone scanning tank. These scans demonstrate the focusing effect of both types of lenses and are in agreement with the numerical model.","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85140485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Douglas J. Leaffer, Rafia Mailk, B. Tracey, D. Gute, A. Hastings, C. Roof, George J. Noel
Transportation-derived particulate matter and chronic ambient noise exposure frequently occur concomitantly in urban areas, adversely impacting population health outcomes. Noise is identified as an important confounder in epidemiological studies, yet few health studies have included both air pollution and noise in health effects models. Several noise exposure studies have associated intensity and duration of transportation noise with chronic health effects; comparatively few studies have assessed airborne particulate concentrations with co-exposure to transportation noise of specific frequency. This study will present methodologies for the measurement, visualization and analysis of traffic-noise frequency and particulate emissions developed through concurrent sampling at two Greater Boston locations under varying meteorological conditions. We present methods for evaluating co-located measurement of both transportation noise and associated particulate emissions, with emphasis placed on Ultrafine Particulat...
{"title":"Correlating transportation noise frequencies with ultrafine particulate emissions by source: Implications for environmental health studies","authors":"Douglas J. Leaffer, Rafia Mailk, B. Tracey, D. Gute, A. Hastings, C. Roof, George J. Noel","doi":"10.1121/2.0000545","DOIUrl":"https://doi.org/10.1121/2.0000545","url":null,"abstract":"Transportation-derived particulate matter and chronic ambient noise exposure frequently occur concomitantly in urban areas, adversely impacting population health outcomes. Noise is identified as an important confounder in epidemiological studies, yet few health studies have included both air pollution and noise in health effects models. Several noise exposure studies have associated intensity and duration of transportation noise with chronic health effects; comparatively few studies have assessed airborne particulate concentrations with co-exposure to transportation noise of specific frequency. This study will present methodologies for the measurement, visualization and analysis of traffic-noise frequency and particulate emissions developed through concurrent sampling at two Greater Boston locations under varying meteorological conditions. We present methods for evaluating co-located measurement of both transportation noise and associated particulate emissions, with emphasis placed on Ultrafine Particulat...","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75082368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method for detecting loosened bolts in a structural joint based upon open-loop acoustic measurement is presented. The acoustic measurement is taken directly on the bolt head. The response of the bolt to a proximal hammer impact is evaluated and characterized using wavelet decomposition of the signal measured from the bolt head. Data were also taken from an accelerometer mounted longitudinally and transversely on the bolt head. Results from the stethoscope and the accelerometer are presented from a set of structural bolts in several conditions of preload and looseness. A stethoscope applied to the loose bolt and a proximal bolt during impact recorded a marked difference between tight, finger tight, and loose bolts. The study could enable a quick and simple method for detecting and evaluating detorqued bolts in structural joints.
{"title":"Detection of structural bolt detorquing using direct stethoscope measurement","authors":"J. Guarino, R. Hamilton","doi":"10.1121/2.0000547","DOIUrl":"https://doi.org/10.1121/2.0000547","url":null,"abstract":"A method for detecting loosened bolts in a structural joint based upon open-loop acoustic measurement is presented. The acoustic measurement is taken directly on the bolt head. The response of the bolt to a proximal hammer impact is evaluated and characterized using wavelet decomposition of the signal measured from the bolt head. Data were also taken from an accelerometer mounted longitudinally and transversely on the bolt head. Results from the stethoscope and the accelerometer are presented from a set of structural bolts in several conditions of preload and looseness. A stethoscope applied to the loose bolt and a proximal bolt during impact recorded a marked difference between tight, finger tight, and loose bolts. The study could enable a quick and simple method for detecting and evaluating detorqued bolts in structural joints.","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73579740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Using low shear resistant cores in metal plastic composites offers the possibility of an increased damping and therefrom improved acoustic properties of extensive metal sheet structures which are sensitive to vibrations.The damping of the single components in the composite shows an amplitude dependency. Established numerical material models in the finite element method do not consider any amplitude dependency. Therefore, the influence of the damping on the radiated sound power is evaluated numerically for monolithic rectangular steel plates and subsequently extended for the metal plastic composite. The results of the experimental characterization of the amplitude dependency for the components of the composite are described. Relevant parameter ranges are identified and their effect on the sound radiation is outlined.
{"title":"Sensitivity of the radiated sound power to amplitude dependent damping","authors":"M. Wuehrl, M. Klärner, L. Kroll","doi":"10.1121/2.0000550","DOIUrl":"https://doi.org/10.1121/2.0000550","url":null,"abstract":"Using low shear resistant cores in metal plastic composites offers the possibility of an increased damping and therefrom improved acoustic properties of extensive metal sheet structures which are sensitive to vibrations.The damping of the single components in the composite shows an amplitude dependency. Established numerical material models in the finite element method do not consider any amplitude dependency. Therefore, the influence of the damping on the radiated sound power is evaluated numerically for monolithic rectangular steel plates and subsequently extended for the metal plastic composite. The results of the experimental characterization of the amplitude dependency for the components of the composite are described. Relevant parameter ranges are identified and their effect on the sound radiation is outlined.","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85584786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The simulation-based design of dynamically loaded and acoustically sensitive components essentially includes the determination of the radiated sound power. Regarding several simplifications different approaches based on the surface velocity can be applied, such as the equivalent radiated sound power (ERP). The required frequency steps of steady state dynamic simulations are determined using efficient modal super imposed models. For single modes of rectangular plates, universal amplitude-frequency functions shall be identified. Considering the damping ratio of the mode, only one resonant frequency step is further needed for the estimation of the radiated sound power in the whole given frequency range. Computationally expensive steady state simulations thus are significantly reduced.
{"title":"Characteristic amplitude-frequency functions of the radiated sound power","authors":"M. Klärner, M. Wuehrl, L. Kroll, S. Marburg","doi":"10.1121/2.0000549","DOIUrl":"https://doi.org/10.1121/2.0000549","url":null,"abstract":"The simulation-based design of dynamically loaded and acoustically sensitive components essentially includes the determination of the radiated sound power. Regarding several simplifications different approaches based on the surface velocity can be applied, such as the equivalent radiated sound power (ERP). The required frequency steps of steady state dynamic simulations are determined using efficient modal super imposed models. For single modes of rectangular plates, universal amplitude-frequency functions shall be identified. Considering the damping ratio of the mode, only one resonant frequency step is further needed for the estimation of the radiated sound power in the whole given frequency range. Computationally expensive steady state simulations thus are significantly reduced.","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84709465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Head-related impulse responses (HRIRs) and transfer functions (HRTFs) have primarily been computed using frequency-domain boundary element methods or finite-difference time domain methods. The possibility of computing HRIRs and HRTFs using transient equivalent sources is examined here using a lumped parameter technique for enforcing the specified boundary condition. The computation is performed as a scattering problem with rigid boundary conditions specified for the surface of the head and torso. It is shown that performing the computations in the time domain is advantageous because only a few thousand time steps are needed to fully define the HRIRs. In addition to uniform meshes sized for different upper frequencies, the possibility of performing the computations using a nonuniform mesh is also explored. Comparisons between direct and reciprocal computations are given to demonstrate solution consistency. Various tests are performed to illustrate the variation in the solution with time step size and inner...
{"title":"Applying time domain equivalent sources to the computation of head related impulse responses and transfer functions","authors":"J. B. Fahnline","doi":"10.1121/2.0000548","DOIUrl":"https://doi.org/10.1121/2.0000548","url":null,"abstract":"Head-related impulse responses (HRIRs) and transfer functions (HRTFs) have primarily been computed using frequency-domain boundary element methods or finite-difference time domain methods. The possibility of computing HRIRs and HRTFs using transient equivalent sources is examined here using a lumped parameter technique for enforcing the specified boundary condition. The computation is performed as a scattering problem with rigid boundary conditions specified for the surface of the head and torso. It is shown that performing the computations in the time domain is advantageous because only a few thousand time steps are needed to fully define the HRIRs. In addition to uniform meshes sized for different upper frequencies, the possibility of performing the computations using a nonuniform mesh is also explored. Comparisons between direct and reciprocal computations are given to demonstrate solution consistency. Various tests are performed to illustrate the variation in the solution with time step size and inner...","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91020296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. H. Swift, K. Gee, T. Neilsen, J. Downing, Michael M. James
Crackling signals cannot be identified using any sound level or quality metric that relies solely on the long-term spectrum as input. In order to identify sound quality metrics that might succeed in modeling human perception of crackling and non-crackling sounds a set of metrics sensitive to temporal properties of signals is applied to a set of signals with equivalent spectra but exhibiting varying degrees of crackle. Several methods for altering signals including some that remove crackling sound quality from an acoustic signal were drawn from previous work [Swift, Gee, Neilsen, 2014, Swift, Gee, Neilsen, 2017]. In this paper, an additional alteration which can partially remove crackle—randomizing the Fourier phase of a crackling signal in the frequency domain in selected frequency ranges—is considered. Variables from time-varying sound quality metrics such as loudness and sharpness, as well as roughness to signals exhibiting varying degrees of crackle are explored and relationships between them that can ...
{"title":"Exploring the use of time-sensitive sound quality metrics and related quantities for detecting crackle","authors":"S. H. Swift, K. Gee, T. Neilsen, J. Downing, Michael M. James","doi":"10.1121/2.0000544","DOIUrl":"https://doi.org/10.1121/2.0000544","url":null,"abstract":"Crackling signals cannot be identified using any sound level or quality metric that relies solely on the long-term spectrum as input. In order to identify sound quality metrics that might succeed in modeling human perception of crackling and non-crackling sounds a set of metrics sensitive to temporal properties of signals is applied to a set of signals with equivalent spectra but exhibiting varying degrees of crackle. Several methods for altering signals including some that remove crackling sound quality from an acoustic signal were drawn from previous work [Swift, Gee, Neilsen, 2014, Swift, Gee, Neilsen, 2017]. In this paper, an additional alteration which can partially remove crackle—randomizing the Fourier phase of a crackling signal in the frequency domain in selected frequency ranges—is considered. Variables from time-varying sound quality metrics such as loudness and sharpness, as well as roughness to signals exhibiting varying degrees of crackle are explored and relationships between them that can ...","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86578133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pieter Thomas, Reinout Verburgh, M. Catrysse, D. Botteldooren
Microphone arrays are becoming increasingly popular for conferencing applications and near-field speech recording. In this work, a 16-element cylindrical microphone array is designed for beamforming toward a nearby speaker, while reducing the influence of competing talkers. A two-stage approach is used to obtain the desired array directivity pattern, optimizing both microphone locations and filter weights. The positions of the microphones are optimized by using a hybrid optimization technique, taking into account the influence of the nearby acoustic environment (array shape and conferencing desk). FIR filter coefficients for each microphone are derived from a regularized least-squares (LSQR) solution, combined with null-steering. An implementation of the array is made with digital MEMS microphones and the performance of the design is evaluated experimentally and compared with a classically used goose-neck microphone.
{"title":"Design of a microphone array for near-field conferencing applications","authors":"Pieter Thomas, Reinout Verburgh, M. Catrysse, D. Botteldooren","doi":"10.1121/2.0000541","DOIUrl":"https://doi.org/10.1121/2.0000541","url":null,"abstract":"Microphone arrays are becoming increasingly popular for conferencing applications and near-field speech recording. In this work, a 16-element cylindrical microphone array is designed for beamforming toward a nearby speaker, while reducing the influence of competing talkers. A two-stage approach is used to obtain the desired array directivity pattern, optimizing both microphone locations and filter weights. The positions of the microphones are optimized by using a hybrid optimization technique, taking into account the influence of the nearby acoustic environment (array shape and conferencing desk). FIR filter coefficients for each microphone are derived from a regularized least-squares (LSQR) solution, combined with null-steering. An implementation of the array is made with digital MEMS microphones and the performance of the design is evaluated experimentally and compared with a classically used goose-neck microphone.","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86020565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
People, especially when blind, use echolocation to detect obstacles, orient themselves and get an awareness of their environment. Echolocation describes how people use reflected sounds to obtain information about their ambient world. Echolocation with long canes while walking is possible but difficult. Different spectral composition of the emitted sounds from canes had no differential effects. Sound recordings in anechoic and conference rooms from non-walking, static situations, later presented in a laboratory showed a better performance in an ordinary room with reflections, than in an anechoic room. Longer sounding sounds resulted in a higher performance than short clicks. Among the difficulties for the blind are how to avoid masking of sounds. There may exist a time gap, acoustic gaze, for how blind people use clicks. The results of previous studies were reanalyzed by using auditory models. Thresholds based on local non-parametric fitting, were determined for distance, pitch, loudness and sharpness. The...
{"title":"Human echolocation in different situations and rooms: Threshold values","authors":"B. Schenkman, Vijay Kiran Gidla","doi":"10.1121/2.0000536","DOIUrl":"https://doi.org/10.1121/2.0000536","url":null,"abstract":"People, especially when blind, use echolocation to detect obstacles, orient themselves and get an awareness of their environment. Echolocation describes how people use reflected sounds to obtain information about their ambient world. Echolocation with long canes while walking is possible but difficult. Different spectral composition of the emitted sounds from canes had no differential effects. Sound recordings in anechoic and conference rooms from non-walking, static situations, later presented in a laboratory showed a better performance in an ordinary room with reflections, than in an anechoic room. Longer sounding sounds resulted in a higher performance than short clicks. Among the difficulties for the blind are how to avoid masking of sounds. There may exist a time gap, acoustic gaze, for how blind people use clicks. The results of previous studies were reanalyzed by using auditory models. Thresholds based on local non-parametric fitting, were determined for distance, pitch, loudness and sharpness. The...","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80077896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A ball sensor, part of virtually any seatbelt retractor, is investigated experimentally and by numerical simulation to predict its acoustical behavior under vertical excitation. Impact forces among mating surfaces are computed with flexible multibody system analysis, employing Craig-Bampton modes to approximate the vibrations of acoustically relevant substructures. Acoustic radiation is determined by the boundary element method. Two distinct rattle plateaus are identified on a test rig via acceleration-amplitude ramp-ups with harmonic base frequency. These plateaus are caused by (i) ball lift-off bouncing against the sensor cradle and (ii) impact of the lever on the clutch disk. The dominant peaks in the sound pressure spectrum (SPL) are associated with system-eigenmodes and are therefore independent from the excitation as long as this excitation is strong enough. On sensitivity analysis, variation of the stiffness of sensor housing and lever, sensor gap, excitation frequency and sensor mass does not caus...
{"title":"Ball sensor rattle: Experimental and numerical sensitivity study for seatbelt applications","authors":"K. Machens, J. Neumann, J. Scholz, M. Markiewicz","doi":"10.1121/2.0000531","DOIUrl":"https://doi.org/10.1121/2.0000531","url":null,"abstract":"A ball sensor, part of virtually any seatbelt retractor, is investigated experimentally and by numerical simulation to predict its acoustical behavior under vertical excitation. Impact forces among mating surfaces are computed with flexible multibody system analysis, employing Craig-Bampton modes to approximate the vibrations of acoustically relevant substructures. Acoustic radiation is determined by the boundary element method. Two distinct rattle plateaus are identified on a test rig via acceleration-amplitude ramp-ups with harmonic base frequency. These plateaus are caused by (i) ball lift-off bouncing against the sensor cradle and (ii) impact of the lever on the clutch disk. The dominant peaks in the sound pressure spectrum (SPL) are associated with system-eigenmodes and are therefore independent from the excitation as long as this excitation is strong enough. On sensitivity analysis, variation of the stiffness of sensor housing and lever, sensor gap, excitation frequency and sensor mass does not caus...","PeriodicalId":20469,"journal":{"name":"Proc. Meet. Acoust.","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85242761","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：