Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wav...Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering.展开更多
In view of the discrete characteristics of biological tissue, doublet mechanics has demonstrated its advantages in the mathematic description of tissue in terms of high frequency （〉 10 MHz） ultrasound. In this pape...In view of the discrete characteristics of biological tissue, doublet mechanics has demonstrated its advantages in the mathematic description of tissue in terms of high frequency （〉 10 MHz） ultrasound. In this paper, we take human breast biopsies as an example to study the influence of the internodal distance, a microscope parameter in biological tissue in doublet mechanics, on the sound velocity and attenuation by numerical simulation. The internodal distance causes the sound velocity and attenuation in biological tissue to change with the increase of frequency. The magnitude of such a change in pathological tissue is distinctly different from that in normal tissue, which can be used to differentiate pathological tissue from normal tissue and can depict the diseased tissue structure by obtaining the sound and attenuation distribution in the sample at high ultrasound frequency. A comparison of sensitivity between the doublet model and conventional continuum model is made, indicating that this is a new method of characterizing ultrasound tissue and diagnosing diseases.展开更多
One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight i...One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow D_(exc)(ω)~ω^(2)in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.展开更多
A novel self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration is proposed to solve the problem of large disturbances to sediments of the in situ equipments already in exist...A novel self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration is proposed to solve the problem of large disturbances to sediments of the in situ equipments already in existence. By using a hydraulic driving device, the system drives four acoustic probes into sediments at an even speed, and this decreases disturbances to sediments introduced by the penetration of acoustic probes. By means of the special design of the central control unit, the system can work full-automatically and the data are stored self-containedly, and this avoids the requirement of real-time remote controlling from the ship. Its operating water depth, measuring depth and measuring frequency is 500m, 1.0m and 30kHz respectively. A set of in situ sound speeds and attenuation coefficients of sediments are obtained at 40 stations using the system. The results confirm that the data obtained by the in situ sediment acoustic system are accurate and credible.展开更多
Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor min...Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor mining environment. Based on the KZK （Khokhlov-Zabolotkaya-Kuznetsov） equation, the method of sound field analysis in turbid water is proposed. Firstly, based on the analysis of absorption in clean water and viscous absorption of suspended sediments, the sound attenuation coefficient as a function of frequency in the mining environment is calculated. Then, based on the solution of KZK equation in frequency domain, the axial sound pressure of transducer in clear water as well as turbid water is simulated using MATLAB. Simulation results show that the influence of the suspended sediments on the pressure of near field is negligible. With the increase of distance, the axial sound pressures of transducer decay rapidly. Suspended sediments seriously affect the pressure in far-field. To verify the validity of this numerical method, experiment is designed and the axial sound pressure of transducer with a frequency of 200 kHz and a beam width of 7.5~ is measured in simulated mining experiment. The results show that the simulation results agree well with the experiments, and the KZK equation can be used to calculate the sound field in turbid water.展开更多
The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecif...The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.展开更多
A new in-situ seabed acoustic measurement system is developed for direct in-situ measurement of sediment geoacoustic properties （compressional wave velocity and attenuation）. The new in-situ system consists of two p...A new in-situ seabed acoustic measurement system is developed for direct in-situ measurement of sediment geoacoustic properties （compressional wave velocity and attenuation）. The new in-situ system consists of two parts： the deck control unit and the underwater measurement unit. The underwater measurement unit emits sonic waves that propagate through the seafloor sediment, receives the returning signals, and transmits them to the deck control unit for waveform display and analysis. The entire operation is controlled and monitored in real time by the deck control unit on the research vessel and can provide recording of full waveforms to determine the sound velocity and attenuation. This paper outlines the design of the system, the measurement process, and demonstrates its application in tests carded out on seabed sediment off the Qingdao coast, China. The test results show that the system performed well and rapidly provided accurate in-situ acoustic velocity and attenuation estimates of the seafloor sediment.展开更多
Utilizing metamaterials or acoustic black holes(ABHs)to control wave propagation and then to realize vibration control and sound radiation attenuation is a hot topic in recent years.However,using elastic metasurfaces ...Utilizing metamaterials or acoustic black holes(ABHs)to control wave propagation and then to realize vibration control and sound radiation attenuation is a hot topic in recent years.However,using elastic metasurfaces that possess similar wave manipulation abilities with metamaterials and ABHs to attenuate sound radiation has not been reported yet.In this paper,a circular total-reflection elastic metasurface(CTREM)composed of subunits with cubic profiles similar with ABHs is proposed to realize vibration isolation and achieve broadband sound radiation attenuation of a plate below the cut-on frequency of the ABH.Compared with the corresponding bare plate and the plate containing a single ABH with a conventional design,the sound radiation efficiencies of the CTREM plate within and outside the vibration isolation band are both substantially attenuated.This phenomenon can be attributed to two distinct mechanisms:the total reflection of flexural waves caused by vibration isolation,and the local resonances of subunits.Analyses of the wavenumber spectra obtained from normal vibration velocities of the CTREM plate,both experimentally and numerically,along with the supersonic intensity patterns,reveal that the confined vibration energies are subsonic components localized within ineffective sound radiation areas.This,in turn,reduces the coupling strength of sound and vibration,thereby significantly attenuating sound radiation efficiency.The proposed CTREM provides a lossless and lightweight method for sound radiation attenuation.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51279165 and 51479170)the National Defense Basic Scientific Research Program of China(Grant No.B2720133014)
文摘Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB921504 and 2011CB707902)the National Natural Science Foundation of China(Grant No.11274166)+3 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.1113020403 and 1101020402)the State Key Laboratory of Acoustics,Chinese Academy of Sciences(Grant No.SKLA201401)the China Postdoctoral Science Foundation(Grant No.2013M531313)the Priority Academic Program Development of Jiangsu Provincial Higher Education Institutions and Scientific Research Foundation for Returned Overseas Chinese Scholars,State Education Ministry,and the Project of Interdisciplinary Center of Nanjing University,China(Grant No.NJUDC2012004)
文摘In view of the discrete characteristics of biological tissue, doublet mechanics has demonstrated its advantages in the mathematic description of tissue in terms of high frequency （〉 10 MHz） ultrasound. In this paper, we take human breast biopsies as an example to study the influence of the internodal distance, a microscope parameter in biological tissue in doublet mechanics, on the sound velocity and attenuation by numerical simulation. The internodal distance causes the sound velocity and attenuation in biological tissue to change with the increase of frequency. The magnitude of such a change in pathological tissue is distinctly different from that in normal tissue, which can be used to differentiate pathological tissue from normal tissue and can depict the diseased tissue structure by obtaining the sound and attenuation distribution in the sample at high ultrasound frequency. A comparison of sensitivity between the doublet model and conventional continuum model is made, indicating that this is a new method of characterizing ultrasound tissue and diagnosing diseases.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12374202 and 12004001)Anhui Projects(Grant Nos.2022AH020009,S020218016,and Z010118169)+1 种基金Hefei City(Grant No.Z020132009)Anhui University(start-up fund)。
文摘One hallmark of glasses is the existence of excess vibrational modes at low frequenciesωbeyond Debye’s prediction.Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses.However,there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations.In particular,excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow D_(exc)(ω)~ω^(2)in 2D glasses with an inverse power law potential.Yet,the universality of the quadratic scaling remains unknown,since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum.Here,we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion.Moreover,we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion,which is accompanied by a suppression of the strength of the sound attenuation.Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.
文摘A novel self-contained in situ sediment acoustic measurement system based on hydraulic driving penetration is proposed to solve the problem of large disturbances to sediments of the in situ equipments already in existence. By using a hydraulic driving device, the system drives four acoustic probes into sediments at an even speed, and this decreases disturbances to sediments introduced by the penetration of acoustic probes. By means of the special design of the central control unit, the system can work full-automatically and the data are stored self-containedly, and this avoids the requirement of real-time remote controlling from the ship. Its operating water depth, measuring depth and measuring frequency is 500m, 1.0m and 30kHz respectively. A set of in situ sound speeds and attenuation coefficients of sediments are obtained at 40 stations using the system. The results confirm that the data obtained by the in situ sediment acoustic system are accurate and credible.
基金Project（51374245） supported by the National Natural Science Foundation of China Project（10C0681） supported by Education Department of Hunan Province, China
文摘Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor mining environment. Based on the KZK （Khokhlov-Zabolotkaya-Kuznetsov） equation, the method of sound field analysis in turbid water is proposed. Firstly, based on the analysis of absorption in clean water and viscous absorption of suspended sediments, the sound attenuation coefficient as a function of frequency in the mining environment is calculated. Then, based on the solution of KZK equation in frequency domain, the axial sound pressure of transducer in clear water as well as turbid water is simulated using MATLAB. Simulation results show that the influence of the suspended sediments on the pressure of near field is negligible. With the increase of distance, the axial sound pressures of transducer decay rapidly. Suspended sediments seriously affect the pressure in far-field. To verify the validity of this numerical method, experiment is designed and the axial sound pressure of transducer with a frequency of 200 kHz and a beam width of 7.5~ is measured in simulated mining experiment. The results show that the simulation results agree well with the experiments, and the KZK equation can be used to calculate the sound field in turbid water.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)for financial support through grants to D.J.M., D.R.N.,and A.E.M.N.the Animal Behaviour Society+1 种基金the American Ornithological Societythe Society of Canadian Ornithologists for research grants to S.L.D.
文摘The nest environment may limit the ability of nest-bound birds to hear sounds from the outside world.In vocal learning species,such as humans and songbirds,it is vital for young animals to hear the voices of conspecific animals early in life.In songbirds,nest structure varies considerably across species,and the resulting impact on sound transmission may have consequences for vocal learning in nestlings.In this study,we tested the hypothesis that the nest environment attenuates song of Savannah Sparrows(Passerculus sandwichensis),grassland songbirds that build nests on the ground under cover of dense vegetation.We recorded live Savannah Sparrows singing at variable distances from 21 nests.We recorded songs using one microphone inside the nest(the typical position of a nestling)and another placed 1 m directly above the nest(a typical position of an adult).We found a substantial reduction in signal-to-noise ratio,where songs recorded inside the nest were an average of 11 dB lower than songs recorded directly above the nest.We estimate that the attenuation imposed by the nest reduced the maximum acoustic environment from 117.7 m(for recordings above the nest),to 78.6 m(for recordings within the nest),which is analogous to listening from a position 39.1 m farther away from the singer.Previous research estimated that song transmits up to 100 m in this species,so any adult male within 100 m of a young bird was previously considered a potential vocal tutor.By reducing the nestling acoustic environment from 100 m to 78.6 m,the number of male tutors available to nestlings is reduced by an average of 27%.Given the growing evidence that song learning begins very early in life,future research on vocal development should account for how the structural properties of the natal environment affect the songs that nestlings hear.
基金Supported by the National Special Research Fund for Non-Profit Marine Sector(No.200905025)
文摘A new in-situ seabed acoustic measurement system is developed for direct in-situ measurement of sediment geoacoustic properties （compressional wave velocity and attenuation）. The new in-situ system consists of two parts： the deck control unit and the underwater measurement unit. The underwater measurement unit emits sonic waves that propagate through the seafloor sediment, receives the returning signals, and transmits them to the deck control unit for waveform display and analysis. The entire operation is controlled and monitored in real time by the deck control unit on the research vessel and can provide recording of full waveforms to determine the sound velocity and attenuation. This paper outlines the design of the system, the measurement process, and demonstrates its application in tests carded out on seabed sediment off the Qingdao coast, China. The test results show that the system performed well and rapidly provided accurate in-situ acoustic velocity and attenuation estimates of the seafloor sediment.
基金supported by the National Natural Science Foundation of China(Nos.12072276 and 11972296)the 111 Project of China(No.BP0719007)the Basic and Applied Basic Research Foundation of Guangdong Province(No.2022A1515011497).
文摘Utilizing metamaterials or acoustic black holes(ABHs)to control wave propagation and then to realize vibration control and sound radiation attenuation is a hot topic in recent years.However,using elastic metasurfaces that possess similar wave manipulation abilities with metamaterials and ABHs to attenuate sound radiation has not been reported yet.In this paper,a circular total-reflection elastic metasurface(CTREM)composed of subunits with cubic profiles similar with ABHs is proposed to realize vibration isolation and achieve broadband sound radiation attenuation of a plate below the cut-on frequency of the ABH.Compared with the corresponding bare plate and the plate containing a single ABH with a conventional design,the sound radiation efficiencies of the CTREM plate within and outside the vibration isolation band are both substantially attenuated.This phenomenon can be attributed to two distinct mechanisms:the total reflection of flexural waves caused by vibration isolation,and the local resonances of subunits.Analyses of the wavenumber spectra obtained from normal vibration velocities of the CTREM plate,both experimentally and numerically,along with the supersonic intensity patterns,reveal that the confined vibration energies are subsonic components localized within ineffective sound radiation areas.This,in turn,reduces the coupling strength of sound and vibration,thereby significantly attenuating sound radiation efficiency.The proposed CTREM provides a lossless and lightweight method for sound radiation attenuation.
