The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E ...The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E 1050-12.The Creality Ender-3,a 3D printer,was used for printing the honeycomb structures,and polylactic acid(PLA)material was employed for their construction.The organic,inorganic,and polymeric compounds within the composites were identified using fourier transformation infrared(FTIR)spectroscopy.The structure and homogeneity of the samples were examined using a field emission scanning electron microscope(FESEM).To determine the sound absorption coefficient of the 3D printed honeycomb structure,numerous samples were systematically developed using central composite design(CCD)and analysed using response surface methodology(RSM).The RSM mathematical model was established to predict the optimum values of each factor and noise reduction coefficient(NRC).The optimum values for an NRC of 0.377 were found to be 1.116 wt% carbon black,1.025 wt% aluminium powder,and 3.151 mm distance between parallel edges.Overall,the results demonstrate that a 3Dprinted honeycomb structure filled with nanofillers is an excellent material that can be utilized in various fields,including defence and aviation,where lightweight and acoustic properties are of great importance.展开更多
The acoustical scattering cross section is usually employed to evaluate the scattering ability of the bubbles when they are excited by the incident acoustic waves. This parameter is strongly related to many important ...The acoustical scattering cross section is usually employed to evaluate the scattering ability of the bubbles when they are excited by the incident acoustic waves. This parameter is strongly related to many important applications of performance prediction for search sonar or underwater telemetry, acoustical oceanography, acoustic cavitation, volcanology, and medical and industrial ultrasound. In the present paper, both the analytical and numerical analysis results of the acoustical scattering cross section of a single bubble under multi-frequency excitation are obtained. The nonlinear characteristics（e.g.,harmonics, subharmonics, and ultraharmonics） of the scattering cross section curve under multi-frequency excitation are investigated compared with single-frequency excitation. The influence of several paramount parameters（e.g., bubble equilibrium radius, acoustic pressure amplitude, and acoustic frequencies） in the multi-frequency system on the predictions of scattering cross section is discussed. It is shown that the combination resonances become significant in the multi-frequency system when the acoustic power is big enough, and the acoustical scattering cross section is promoted significantly within a much broader range of bubble sizes and acoustic frequencies due to the generation of more resonances.展开更多
An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging app...An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging applications, wide bandwidth and short time duration are required. The approach we have used consists of impedance matching the front face of the piezoelectric transducer to the propagating medium with a quarter wavelength impedance matching layer and inserting an nnmatching quarter wavelength acoustical layer between the rear face and backing material. A heavy backing would degrade the wide-band phenomena, but show a time duration shorter than 0.5 μs for imaging applications. PSPICE code of the controlled source model is implemented to precisely predict the performance of the matched transducers such as impedance, insertion loss, bandwidth and duration of the impulse response. Good agreement between the simulation and experimental results has been achieved.展开更多
The relationship between urban development and noise pollution was analyzed. The analysis, based on a wide range of measurements and statistical data,revealed the changes of the ambient noise resulting from city deve...The relationship between urban development and noise pollution was analyzed. The analysis, based on a wide range of measurements and statistical data,revealed the changes of the ambient noise resulting from city development. In conclusion, some fundamental measures for improving the acoustical environment were suggested, such as the division of cities into functional areas and the development of a well designed road network. In addition, the town planning, architecture and the implementation of appropriate regulations could also help to reduce noise levels was suggested as well.展开更多
The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder,insonified by acoustic...The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder,insonified by acoustic standing waves having an arbitrary angle of incidence in the polar(transverse)plane.The host medium of wave propagation and the eccentric liquid-like cylinder are non-viscous.Numerical computations illustrate the theoretical analysis with particular emphases on the eccentricity of the cylinder,the angle of incidence and the dimensionless size parameters of the inner and coating cylindrical fluid materials.The method to derive the acoustical scattering,and radiation force and torque components conjointly uses modal matching with the addition theorem,which adequately account for the multiple wave interaction effects between the layer and core fluid materials.The results demonstrate that longitudinal and lateral radiation force components arise.Moreover,an axial radiation torque component is quantified and computed for the non-absorptive compound cylinder,arising from geometrical asymmetry considerations as the eccentricity increases.The computational results reveal the emergence of neutral,positive,and negative radiation force and torque depending on the size parameter of the cylinder,the eccentricity,and the angle of incidence of the insonifying field.Moreover,based on the law of energy conservation applied to scattering,numerical verification is accomplished by computing the extinction/scattering energy efficiency.The results may find some related applications in fluid dynamics,particle trapping,mixing and manipulation using acoustical standing waves.展开更多
A non- invasive acoustical system was developed for the measurement of transmission properties of acoustic waves in the hip joints.The instrumentation consisted of three sub- system s. An excitation system employed ...A non- invasive acoustical system was developed for the measurement of transmission properties of acoustic waves in the hip joints.The instrumentation consisted of three sub- system s. An excitation system employed a vibratory force at the sacrum of the test subjects.A transduction system included a pair of identical microphones installed in the tubes of two stethoscopes,which were placed at the greater trochanters on both sides for picking up the acoustical signals transm it- ted across the hip joints.The data acquisition and analysis system was a portable signal analyzer with a program of dual channel digital filter for m easuring the power of acoustical signal in 1/ 3- oc- tave frequency bands.2 7normal adults,2 0 normal pre- school children and 4 0 norm al neonates were random ly selected for testing.Coherence function (CF) and discrepancy(D) was measured during the testing.Results from the three groups showed that there was a high coherence of the signals (CF>0 .9) and a sm all discrepancy(D<3d B) between bilateral hips in the frequency range of2 0 0— 315 Hz.For normal neonates,there was a wider frequency range of16 0 - 315 Hz in which the acoustical signals m aintained a high coherence (CF>0 .93) and a smaller discrepancy (D <2 d B) was observed.This study showed that the development of the acoustical technique pro- vided a practical m ethod with objective parameters.The results obtained in this study can offer a baseline for further investigation of hip disorders particularly those related to structural abnorm ali- ties of the hip.展开更多
The dynamics between sound decay and soundscape determines the acoustical worship heritage in a worship space that needs to be conserved along interventions in time.The soundscape of Schmerzhaften Mutter Gottes,Vilger...The dynamics between sound decay and soundscape determines the acoustical worship heritage in a worship space that needs to be conserved along interventions in time.The soundscape of Schmerzhaften Mutter Gottes,Vilgertshofen was measured by derived Acoustical Worship Parameters:Sacred Awe(SAWE),Sacred Intelligibility(SINT),and Sacred Silence(SSIL)for“TOCCATA”of Johann Sebastian Bach rendered on the pipe organ.The sound energy decay in the church,conducted from two sources:choir loft and altar,generated acoustical monaural measures(RT60,EDT,D50,C80,TS,STI,Leq)in accordance with ISO-3382.The Reverberation Time(RT60)spectral analysis and Loudness(Leq)positional analysis showed the church to be more reverberant for the impulse from the altar location on the sanctuary floor and optimally loud for the impulse from the pipe-organ location on the choir-loft.SAWE,SINT and SSIL significantly related with subjective acoustical quality of Balance(SAQBAL)and Loudness(Leq)(p≤0.05).SAQBAL showed positive correlation with rapid speech transmission index(RASTI)(p=0.18).展开更多
The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of d...The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of detection. Nonstationarity conditions of sound propagation and specific interference caused by shipping are the major factors. The various algorithms for the space-time signal processing have been tested and some experimental results are presented. It has been shown that the use of clipped mode in conjunction with the correlation processing of wideband signals and subsequent speckle tracking allow realizing high efficiency of monitoring.展开更多
Dolphins produce various types of sounds in a wide range of frequencies. Characteristics of some sounds till now have not been correctly registered, that influenced on interpretation of their functions. Studying of th...Dolphins produce various types of sounds in a wide range of frequencies. Characteristics of some sounds till now have not been correctly registered, that influenced on interpretation of their functions. Studying of the characteristics and functions of dolphins’ acoustical signals is the purpose of the present work. In this work the acoustical signals of two dolphins (Tursiops truncatus) were registered by two-channel system in the frequencies band up to 200 kHz at quasi-stationary position of the dolphins. The dolphins along with whistles are producing the packs of coherent and non-coherent broadband pulses. The waveform and spectrum of coherent pulses was invariable within a pack, but considerably varies from a pack to a pack. The waveform of each non-coherent pulse vary from a pulse to a pulse in each pack, therefore their spectrum also vary from a pulse to a pulse and have many extremums in the band of 6 - 200 kHz. It is very likely that the non-coherent pulses play a part of phonemes of a dolphin spoken language and the probing signals of dolphin’s non- coherent sonar. The use possibility of the signals by dolphins for communication and orientation was considered, as the signals apparently are bimodal. Results of the work have significance for further studying of the dolphin’s sonar and spoken language.展开更多
The composite materials based on nanopowder dispersed liquid crystals are important both from fundamental research and device applications due to their unique properties such as improvement in various properties like ...The composite materials based on nanopowder dispersed liquid crystals are important both from fundamental research and device applications due to their unique properties such as improvement in various properties like electrical,optical,thermal,energy storage and spontaneous polarization etc.The proper selection of nanoparticle and its size which to be dispersed in particular liquid crystals is very important for a particular application.In the present study,a ferroelectric nanopowder of Barium Titanate(BaTiO3)was dispersed in cholesteric liquid crystal and the same was confirmed by Fourier Transform Infrared(FTIR)Spectroscopy.The various acoustical properties like ultrasonic velocity,density,Adiabatic Compressibility,Rao Constant,Wada Constant and Acoustic Impedance were investigated by ultrasonic interferometer at room temperature at fixed frequency.The dielectric constant was determined by Precision Impedance Analyzer.In addition to these investigations,particle size and surface area were also measured.Our investigation shows enhanced in dielectric and acoustical properties which may be useful for device applications extensively in microelectronics,low cost-photovoltaic devices,and custom-shaped containers possibly applied as a coating.展开更多
The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system fo...The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.展开更多
As a widely used measurement technique in rock mechanics,spatial correlation modeling of acoustic emission(AE)scattering signals is attracting increasing focus for describing mechanical behavior quantitatively.Unlike ...As a widely used measurement technique in rock mechanics,spatial correlation modeling of acoustic emission(AE)scattering signals is attracting increasing focus for describing mechanical behavior quantitatively.Unlike the statistical description of the spatial distribution of randomly generated AE signals,spatial correlation modeling is based mainly on short-range correlation considering the interrelationship of adjacent signals.As a new idea from percolation models,the covering strategy is used to build the most representative cube cluster,which corresponds to the critical scale at peak stress.Its modeling process of critical cube cluster depends strongly on the full connection of the main fracture network,and the corresponding cube for coverage is termed the critical cube.The criticality pertains to not only the transition of local-to-whole connection of the fracture network but also the increasing-to-decreasing transition of the deviatoric stress with an obvious stress drop in the brittle failure of granite.Determining a reasonable critical cube guarantees the best observation scale for investigating the failure process.Besides,the topological connection induces the geometric criticality of three descriptors,namely anisotropy,pore fraction,and specific surface area,which are evaluated separately and effectively.The results show that cluster modeling based on the critical cube is effective and has criticality in both topology and geometry,as well as the triaxial behavior.Furthermore,the critical cube length presents a high confidence probability of being correlated to the mineral particle size.Besides,its pore fraction of cube cluster is influenced strongly by the critical cube length and confining pressure.展开更多
The mutually antagonistic processes producing adaptations and counter-adaptations in avian brood parasites and their hosts provide a model system for the study of coevolution;this topic has long been an area of focus ...The mutually antagonistic processes producing adaptations and counter-adaptations in avian brood parasites and their hosts provide a model system for the study of coevolution;this topic has long been an area of focus in ornithology and evolutionary biology.Although there is an extensive body of literature dealing with avian brood parasitism,few empirical studies have considered the effects of the coevolutionary processes associated with brood parasitism on the acoustic characteristics of parent–offspring communication.Under the strong selection pressures associated with brood parasitism,parasitic birds may,for instance,produce deceptive songs.The host may in turn evolve the ability to recognize these sounds as deceptive.At present,the mechanisms underlying the different competitive strategies employed by hosts and parasitic birds remain unclear.Here,we reviewed previous studies that investigated acoustic traits in scenarios of brood parasitism,highlighting possible adaptive functions.Using a meta-analysis,we identified no heterogeneity among studies of begging call adaptations in parasitic nestlings.However,our results may have been affected by the small number of applicable papers available for analysis.Our meta-analysis also suggested that studies of acoustic communication and transmission in adult hosts were highly heterogenous,suggesting that research methods were inconsistent among studies.Finally,we identified knowledge gaps and proposed several lines of future research.展开更多
This paper presents the acoustic modal theory for a damped rectangular enclosure based on the acoustic wave equation, analyses the complex damping parameters and their experimental determination and the measuring syst...This paper presents the acoustic modal theory for a damped rectangular enclosure based on the acoustic wave equation, analyses the complex damping parameters and their experimental determination and the measuring system for the acoustic mode pattern in the enclosure designed by utilizing the adaptive filtering technique and high speed digital signal processor TMS320C25. Computer simulation and adaptive measuring test are carried out in an enclosure of 2.0×0 4×0 4m 3,and the acoustic modal distribution in the enclosure is found. Experimental results verify the analysis based upon the acoustic modal theory.展开更多
Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have lit...Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have little or no effect on stabilizing dimensions or vibrational properties. Moisture changes have a great negative effect on both the musical quality of wooden musical instruments and limit the length of time they can be played without loss of musical quality. It is possible to stabilize both the wood and the vibrational properties by chemically modifying the wood. One technology that can do this is the reaction of wood with acetic anhydride. Acetylation of wood slightly increases density, and slightly （about 5%） reduces both sound velocity and sound absorption when compared to unreactedwood. Acetylation does not change the acoustic converting efficiency. Acetylation reduces the amount of moisture in the cell wall decreasing the effect of moisture on the viscose properties of wood. This allows a wooded musical instrument to be played longer without having to let it dry out. This gives an instrument made from acetylated wood a greater range of moisture conditions it can be played in without losing tone quality. Acetylation also greatly stabilizes the physical dimensions of the wood. The major effect of acetylation of wood, therefore, is to stabilize acoustic properties. The technology can be applied to almost any wood though more easily to permeable types so non-traditional wood species can be used. A violin, a piano soundboard, a guitar, a recorder, a bagpipe chanter, and trumpet and trombone mouthpieces have been made using acetylated wood with very positive results. Several more wooden instruments made from acetylated wood are presently being made for further testing and early market development.展开更多
The availability of ideal conditions like anechoic chamber to characterize some sound parameters, like sound intensity and sound power necessities the determination of free field and cut off frequency measurements. In...The availability of ideal conditions like anechoic chamber to characterize some sound parameters, like sound intensity and sound power necessities the determination of free field and cut off frequency measurements. In this article, full experiment was executed at Wayne State University (Detroit-Michigan), to determine the cut off frequency in all directions;the obtained results showed that the free field can be determined for a specified space. So other tests can take place in this space avoiding regions where reflections and consequently noise can be found. Upon these results tests related to noise abatement in vehicles can be done in such environment.展开更多
On the purpose of accurate data acquisition for the aeroacoustic testing mostly in open jet test section of aeroacoustic wind tunnel, the large scale anechoic chamber is specifically designed to build the low backgrou...On the purpose of accurate data acquisition for the aeroacoustic testing mostly in open jet test section of aeroacoustic wind tunnel, the large scale anechoic chamber is specifically designed to build the low background noise environment. A newly acoustic test section is presented in this paper, of which the contour is similar as the closed test section, and the wall is fabricated by the fiber fabric, both the characteristics of closed and open jet test section of conventional wind tunnel are combined in it. By thoroughly researching on the acoustics and aerodynamics of this acoustically transparent test section, significant progress in reducing the background noises in test section and improving the ratio of energy of the wind tunnel and some other aspects have been achieved. Acoustically transparent test section behaves better in acoustics and aerodynamics than conventional acoustic test section because of their high definition in detecting the sound sources and great performance in transmitting sounds.展开更多
This paper discusses a pilot project involving the direct monitoring of ventilation,indoor-air quality and the acoustical conditions in selected nominally‘green’and non-‘green’buildings located on a university cam...This paper discusses a pilot project involving the direct monitoring of ventilation,indoor-air quality and the acoustical conditions in selected nominally‘green’and non-‘green’buildings located on a university campus.The objectives were to measure parameters quantifying these three aspects of indoor environmental quality,determine the relationships between them and the building-design concepts,and evaluate the implications of the results for ventilation-system design,especially in‘green’buildings.Measurements were made in rooms,with and without acoustical treatment,in buildings with natural ventilation or mechanical(displacement and/or mixed-flow)ventilation systems.Measurements were made of ventilation rates(air changes per hour),indoor air quality(respirable-fibre,total-VOC and ultrafine-particulate concentrations),and the acoustical conditions(noise levels and reverberation times).Correlations between the environmental results,the building concept,the ventilation concept and the building window status were explored.In rooms with natural ventilation,low-frequency noise and total sound-pressure levels were lower;however,the rooms had higher ultrafine-particulate counts and lower ventilation rates.Rooms with mechanical ventilation had higher low-frequency and total sound-pressure levels,higher ventilation rates and fibre concentrations,but lower concentrations of ultrafine particulates.It was concluded that,in general,mechanical ventilation can provide better indoor air-quality,but that HVAC noise is an issue if the system is not properly designed.In‘green’buildings,noise levels were acceptable when the windows were closed,but increasing the ventilation rate by opening the windows resulted in higher noise levels.The results suggest that the acceptability of environmental factors in buildings depends on the degree of compliance of the design and its implementation with standards and design guidelines(i.e.for ventilation,air quality,thermal comfort,etc.),whether the original design concept is‘green’or non-‘green’.展开更多
To explain the reactions of the building occupants to their acoustical environments,meetings with the designers,walk-through surveys,and detailed acoustical measurements were done.The objective was to determine how de...To explain the reactions of the building occupants to their acoustical environments,meetings with the designers,walk-through surveys,and detailed acoustical measurements were done.The objective was to determine how design decisions affect office acoustical environments,and how to improve the acoustical design of‘green’office buildings.Design-performance criteria were established.Measurements were made of noise level,reverberation time,speechintelligibility index(SII),and noise isolation.Noise levels were atypically low in unoccupied buildings with no mechanical ventilation,but excessive in areas near external walls next to noisy external noise sources—especially with windows open for ventilation—and in occupied buildings.Reverberation times were excessive in areas with large volumes and insufficient sound absorption.Speech intelligibility was generally adequate,but speech privacy was inadequate in shared and open-office areas,and into private offices with the doors open for ventilation.Improvement of the acoustical design of‘green’buildings must include increasing the external-internal noise isolation and that between workplaces,and the use of adequate sound absorption to control reverberation and noise.展开更多
Low speech privacy in shared and private offices in one of the early generation of a“green”building resulted in occupants’dissatisfaction.This problem is experienced in Liu institute with a natural-ventilation syst...Low speech privacy in shared and private offices in one of the early generation of a“green”building resulted in occupants’dissatisfaction.This problem is experienced in Liu institute with a natural-ventilation system.Such a system requires low air-flow resistance which is achieved by large openings which will result in noise transmission between various spaces within the building.The poor acoustical quality in this building resulted in occupants’noise complaints which were further investigated by way of relevant acoustical measurements.CATT-Acoustic software was utilized to modify the acoustical quality of the building without any disturbance to the occupants.The optimized design of the transfer box above the office door was selected based on CATT-Acoustic predictions.The acoustical measurements were conducted after installation of the transfer box above the office door.The measurements’results agreed with the predictions which led to improved speech privacy to an acceptable level between the office and the corridor in Liu Institute.More work should be done to improve the acoustical quality of natural-ventilated building to conform to ANSI standards.1 The results of this study strongly support including acoustics in“green”building designs with natural ventilation to avoid users’complaints.展开更多
文摘The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E 1050-12.The Creality Ender-3,a 3D printer,was used for printing the honeycomb structures,and polylactic acid(PLA)material was employed for their construction.The organic,inorganic,and polymeric compounds within the composites were identified using fourier transformation infrared(FTIR)spectroscopy.The structure and homogeneity of the samples were examined using a field emission scanning electron microscope(FESEM).To determine the sound absorption coefficient of the 3D printed honeycomb structure,numerous samples were systematically developed using central composite design(CCD)and analysed using response surface methodology(RSM).The RSM mathematical model was established to predict the optimum values of each factor and noise reduction coefficient(NRC).The optimum values for an NRC of 0.377 were found to be 1.116 wt% carbon black,1.025 wt% aluminium powder,and 3.151 mm distance between parallel edges.Overall,the results demonstrate that a 3Dprinted honeycomb structure filled with nanofillers is an excellent material that can be utilized in various fields,including defence and aviation,where lightweight and acoustic properties are of great importance.
基金Project supported by the National Natural Science Foundation of China(Grant No.11674074)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT1228)
文摘The acoustical scattering cross section is usually employed to evaluate the scattering ability of the bubbles when they are excited by the incident acoustic waves. This parameter is strongly related to many important applications of performance prediction for search sonar or underwater telemetry, acoustical oceanography, acoustic cavitation, volcanology, and medical and industrial ultrasound. In the present paper, both the analytical and numerical analysis results of the acoustical scattering cross section of a single bubble under multi-frequency excitation are obtained. The nonlinear characteristics（e.g.,harmonics, subharmonics, and ultraharmonics） of the scattering cross section curve under multi-frequency excitation are investigated compared with single-frequency excitation. The influence of several paramount parameters（e.g., bubble equilibrium radius, acoustic pressure amplitude, and acoustic frequencies） in the multi-frequency system on the predictions of scattering cross section is discussed. It is shown that the combination resonances become significant in the multi-frequency system when the acoustic power is big enough, and the acoustical scattering cross section is promoted significantly within a much broader range of bubble sizes and acoustic frequencies due to the generation of more resonances.
基金supported by the National Science Council of the Republic China (No.NSC 98-2221-E-468-023)
文摘An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging applications, wide bandwidth and short time duration are required. The approach we have used consists of impedance matching the front face of the piezoelectric transducer to the propagating medium with a quarter wavelength impedance matching layer and inserting an nnmatching quarter wavelength acoustical layer between the rear face and backing material. A heavy backing would degrade the wide-band phenomena, but show a time duration shorter than 0.5 μs for imaging applications. PSPICE code of the controlled source model is implemented to precisely predict the performance of the matched transducers such as impedance, insertion loss, bandwidth and duration of the impulse response. Good agreement between the simulation and experimental results has been achieved.
文摘The relationship between urban development and noise pollution was analyzed. The analysis, based on a wide range of measurements and statistical data,revealed the changes of the ambient noise resulting from city development. In conclusion, some fundamental measures for improving the acoustical environment were suggested, such as the division of cities into functional areas and the development of a well designed road network. In addition, the town planning, architecture and the implementation of appropriate regulations could also help to reduce noise levels was suggested as well.
文摘The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder,insonified by acoustic standing waves having an arbitrary angle of incidence in the polar(transverse)plane.The host medium of wave propagation and the eccentric liquid-like cylinder are non-viscous.Numerical computations illustrate the theoretical analysis with particular emphases on the eccentricity of the cylinder,the angle of incidence and the dimensionless size parameters of the inner and coating cylindrical fluid materials.The method to derive the acoustical scattering,and radiation force and torque components conjointly uses modal matching with the addition theorem,which adequately account for the multiple wave interaction effects between the layer and core fluid materials.The results demonstrate that longitudinal and lateral radiation force components arise.Moreover,an axial radiation torque component is quantified and computed for the non-absorptive compound cylinder,arising from geometrical asymmetry considerations as the eccentricity increases.The computational results reveal the emergence of neutral,positive,and negative radiation force and torque depending on the size parameter of the cylinder,the eccentricity,and the angle of incidence of the insonifying field.Moreover,based on the law of energy conservation applied to scattering,numerical verification is accomplished by computing the extinction/scattering energy efficiency.The results may find some related applications in fluid dynamics,particle trapping,mixing and manipulation using acoustical standing waves.
文摘A non- invasive acoustical system was developed for the measurement of transmission properties of acoustic waves in the hip joints.The instrumentation consisted of three sub- system s. An excitation system employed a vibratory force at the sacrum of the test subjects.A transduction system included a pair of identical microphones installed in the tubes of two stethoscopes,which were placed at the greater trochanters on both sides for picking up the acoustical signals transm it- ted across the hip joints.The data acquisition and analysis system was a portable signal analyzer with a program of dual channel digital filter for m easuring the power of acoustical signal in 1/ 3- oc- tave frequency bands.2 7normal adults,2 0 normal pre- school children and 4 0 norm al neonates were random ly selected for testing.Coherence function (CF) and discrepancy(D) was measured during the testing.Results from the three groups showed that there was a high coherence of the signals (CF>0 .9) and a sm all discrepancy(D<3d B) between bilateral hips in the frequency range of2 0 0— 315 Hz.For normal neonates,there was a wider frequency range of16 0 - 315 Hz in which the acoustical signals m aintained a high coherence (CF>0 .93) and a smaller discrepancy (D <2 d B) was observed.This study showed that the development of the acoustical technique pro- vided a practical m ethod with objective parameters.The results obtained in this study can offer a baseline for further investigation of hip disorders particularly those related to structural abnorm ali- ties of the hip.
文摘The dynamics between sound decay and soundscape determines the acoustical worship heritage in a worship space that needs to be conserved along interventions in time.The soundscape of Schmerzhaften Mutter Gottes,Vilgertshofen was measured by derived Acoustical Worship Parameters:Sacred Awe(SAWE),Sacred Intelligibility(SINT),and Sacred Silence(SSIL)for“TOCCATA”of Johann Sebastian Bach rendered on the pipe organ.The sound energy decay in the church,conducted from two sources:choir loft and altar,generated acoustical monaural measures(RT60,EDT,D50,C80,TS,STI,Leq)in accordance with ISO-3382.The Reverberation Time(RT60)spectral analysis and Loudness(Leq)positional analysis showed the church to be more reverberant for the impulse from the altar location on the sanctuary floor and optimally loud for the impulse from the pipe-organ location on the choir-loft.SAWE,SINT and SSIL significantly related with subjective acoustical quality of Balance(SAQBAL)and Loudness(Leq)(p≤0.05).SAQBAL showed positive correlation with rapid speech transmission index(RASTI)(p=0.18).
文摘The article considers peculiarities of underwater monitoring of moving objects in the shallow water areas, particularly seaports. These areas are characterized by a multitude of factors influencing the efficiency of detection. Nonstationarity conditions of sound propagation and specific interference caused by shipping are the major factors. The various algorithms for the space-time signal processing have been tested and some experimental results are presented. It has been shown that the use of clipped mode in conjunction with the correlation processing of wideband signals and subsequent speckle tracking allow realizing high efficiency of monitoring.
文摘Dolphins produce various types of sounds in a wide range of frequencies. Characteristics of some sounds till now have not been correctly registered, that influenced on interpretation of their functions. Studying of the characteristics and functions of dolphins’ acoustical signals is the purpose of the present work. In this work the acoustical signals of two dolphins (Tursiops truncatus) were registered by two-channel system in the frequencies band up to 200 kHz at quasi-stationary position of the dolphins. The dolphins along with whistles are producing the packs of coherent and non-coherent broadband pulses. The waveform and spectrum of coherent pulses was invariable within a pack, but considerably varies from a pack to a pack. The waveform of each non-coherent pulse vary from a pulse to a pulse in each pack, therefore their spectrum also vary from a pulse to a pulse and have many extremums in the band of 6 - 200 kHz. It is very likely that the non-coherent pulses play a part of phonemes of a dolphin spoken language and the probing signals of dolphin’s non- coherent sonar. The use possibility of the signals by dolphins for communication and orientation was considered, as the signals apparently are bimodal. Results of the work have significance for further studying of the dolphin’s sonar and spoken language.
文摘The composite materials based on nanopowder dispersed liquid crystals are important both from fundamental research and device applications due to their unique properties such as improvement in various properties like electrical,optical,thermal,energy storage and spontaneous polarization etc.The proper selection of nanoparticle and its size which to be dispersed in particular liquid crystals is very important for a particular application.In the present study,a ferroelectric nanopowder of Barium Titanate(BaTiO3)was dispersed in cholesteric liquid crystal and the same was confirmed by Fourier Transform Infrared(FTIR)Spectroscopy.The various acoustical properties like ultrasonic velocity,density,Adiabatic Compressibility,Rao Constant,Wada Constant and Acoustic Impedance were investigated by ultrasonic interferometer at room temperature at fixed frequency.The dielectric constant was determined by Precision Impedance Analyzer.In addition to these investigations,particle size and surface area were also measured.Our investigation shows enhanced in dielectric and acoustical properties which may be useful for device applications extensively in microelectronics,low cost-photovoltaic devices,and custom-shaped containers possibly applied as a coating.
基金Supported by the National Natural Science Foundation of China(No.61575119)Science and Technology on Near-Surface Detection Laboratory(No.TCGZ2015A005)State Key Laboratory of Precision Measuring Technology and Instruments(PIL1402)
文摘The 3D characteristic diagram of acoustically induced surface vibration was employed to study the influence of different buried landmines on the acoustic detection signal. By using the vehicular experimental system for acoustic landmine detection and the method of scanning detection, the 3D characteristic diagrams of surface vibration were measured when different objects were buried underground, including big plastic landmine, small plastic landmine, big metal landmine and bricks. The results show that, under the given conditions, the surface vibration amplitudes of big plastic landmine, big metal landmine, small plastic landmine and bricks decrease in turn. The 3D characteristic diagrams of surface vibration can be used to further identify the locations of buried landmines.
基金the National Natural Science Foundation of China(No.51504257)the State Key Research Development Program of China(No.2016YFC0600704)+1 种基金the Fund of Yueqi Outstanding Scholars(No.2018B051616)the Open Fund of the State Key Laboratory of Coal Mine Disaster Dynamics and Control(No.2011DA105287-FW201604).
文摘As a widely used measurement technique in rock mechanics,spatial correlation modeling of acoustic emission(AE)scattering signals is attracting increasing focus for describing mechanical behavior quantitatively.Unlike the statistical description of the spatial distribution of randomly generated AE signals,spatial correlation modeling is based mainly on short-range correlation considering the interrelationship of adjacent signals.As a new idea from percolation models,the covering strategy is used to build the most representative cube cluster,which corresponds to the critical scale at peak stress.Its modeling process of critical cube cluster depends strongly on the full connection of the main fracture network,and the corresponding cube for coverage is termed the critical cube.The criticality pertains to not only the transition of local-to-whole connection of the fracture network but also the increasing-to-decreasing transition of the deviatoric stress with an obvious stress drop in the brittle failure of granite.Determining a reasonable critical cube guarantees the best observation scale for investigating the failure process.Besides,the topological connection induces the geometric criticality of three descriptors,namely anisotropy,pore fraction,and specific surface area,which are evaluated separately and effectively.The results show that cluster modeling based on the critical cube is effective and has criticality in both topology and geometry,as well as the triaxial behavior.Furthermore,the critical cube length presents a high confidence probability of being correlated to the mineral particle size.Besides,its pore fraction of cube cluster is influenced strongly by the critical cube length and confining pressure.
基金This work was supported by the National Natural Science Foundation of China(Grant No.31672303 to CY).
文摘The mutually antagonistic processes producing adaptations and counter-adaptations in avian brood parasites and their hosts provide a model system for the study of coevolution;this topic has long been an area of focus in ornithology and evolutionary biology.Although there is an extensive body of literature dealing with avian brood parasitism,few empirical studies have considered the effects of the coevolutionary processes associated with brood parasitism on the acoustic characteristics of parent–offspring communication.Under the strong selection pressures associated with brood parasitism,parasitic birds may,for instance,produce deceptive songs.The host may in turn evolve the ability to recognize these sounds as deceptive.At present,the mechanisms underlying the different competitive strategies employed by hosts and parasitic birds remain unclear.Here,we reviewed previous studies that investigated acoustic traits in scenarios of brood parasitism,highlighting possible adaptive functions.Using a meta-analysis,we identified no heterogeneity among studies of begging call adaptations in parasitic nestlings.However,our results may have been affected by the small number of applicable papers available for analysis.Our meta-analysis also suggested that studies of acoustic communication and transmission in adult hosts were highly heterogenous,suggesting that research methods were inconsistent among studies.Finally,we identified knowledge gaps and proposed several lines of future research.
文摘This paper presents the acoustic modal theory for a damped rectangular enclosure based on the acoustic wave equation, analyses the complex damping parameters and their experimental determination and the measuring system for the acoustic mode pattern in the enclosure designed by utilizing the adaptive filtering technique and high speed digital signal processor TMS320C25. Computer simulation and adaptive measuring test are carried out in an enclosure of 2.0×0 4×0 4m 3,and the acoustic modal distribution in the enclosure is found. Experimental results verify the analysis based upon the acoustic modal theory.
文摘Many of the traditional woods used for musical instruments have been selected not only for their natural beauty but for the high content of waxes and resins that help increase water repellency of the wood but have little or no effect on stabilizing dimensions or vibrational properties. Moisture changes have a great negative effect on both the musical quality of wooden musical instruments and limit the length of time they can be played without loss of musical quality. It is possible to stabilize both the wood and the vibrational properties by chemically modifying the wood. One technology that can do this is the reaction of wood with acetic anhydride. Acetylation of wood slightly increases density, and slightly （about 5%） reduces both sound velocity and sound absorption when compared to unreactedwood. Acetylation does not change the acoustic converting efficiency. Acetylation reduces the amount of moisture in the cell wall decreasing the effect of moisture on the viscose properties of wood. This allows a wooded musical instrument to be played longer without having to let it dry out. This gives an instrument made from acetylated wood a greater range of moisture conditions it can be played in without losing tone quality. Acetylation also greatly stabilizes the physical dimensions of the wood. The major effect of acetylation of wood, therefore, is to stabilize acoustic properties. The technology can be applied to almost any wood though more easily to permeable types so non-traditional wood species can be used. A violin, a piano soundboard, a guitar, a recorder, a bagpipe chanter, and trumpet and trombone mouthpieces have been made using acetylated wood with very positive results. Several more wooden instruments made from acetylated wood are presently being made for further testing and early market development.
文摘The availability of ideal conditions like anechoic chamber to characterize some sound parameters, like sound intensity and sound power necessities the determination of free field and cut off frequency measurements. In this article, full experiment was executed at Wayne State University (Detroit-Michigan), to determine the cut off frequency in all directions;the obtained results showed that the free field can be determined for a specified space. So other tests can take place in this space avoiding regions where reflections and consequently noise can be found. Upon these results tests related to noise abatement in vehicles can be done in such environment.
文摘On the purpose of accurate data acquisition for the aeroacoustic testing mostly in open jet test section of aeroacoustic wind tunnel, the large scale anechoic chamber is specifically designed to build the low background noise environment. A newly acoustic test section is presented in this paper, of which the contour is similar as the closed test section, and the wall is fabricated by the fiber fabric, both the characteristics of closed and open jet test section of conventional wind tunnel are combined in it. By thoroughly researching on the acoustics and aerodynamics of this acoustically transparent test section, significant progress in reducing the background noises in test section and improving the ratio of energy of the wind tunnel and some other aspects have been achieved. Acoustically transparent test section behaves better in acoustics and aerodynamics than conventional acoustic test section because of their high definition in detecting the sound sources and great performance in transmitting sounds.
文摘This paper discusses a pilot project involving the direct monitoring of ventilation,indoor-air quality and the acoustical conditions in selected nominally‘green’and non-‘green’buildings located on a university campus.The objectives were to measure parameters quantifying these three aspects of indoor environmental quality,determine the relationships between them and the building-design concepts,and evaluate the implications of the results for ventilation-system design,especially in‘green’buildings.Measurements were made in rooms,with and without acoustical treatment,in buildings with natural ventilation or mechanical(displacement and/or mixed-flow)ventilation systems.Measurements were made of ventilation rates(air changes per hour),indoor air quality(respirable-fibre,total-VOC and ultrafine-particulate concentrations),and the acoustical conditions(noise levels and reverberation times).Correlations between the environmental results,the building concept,the ventilation concept and the building window status were explored.In rooms with natural ventilation,low-frequency noise and total sound-pressure levels were lower;however,the rooms had higher ultrafine-particulate counts and lower ventilation rates.Rooms with mechanical ventilation had higher low-frequency and total sound-pressure levels,higher ventilation rates and fibre concentrations,but lower concentrations of ultrafine particulates.It was concluded that,in general,mechanical ventilation can provide better indoor air-quality,but that HVAC noise is an issue if the system is not properly designed.In‘green’buildings,noise levels were acceptable when the windows were closed,but increasing the ventilation rate by opening the windows resulted in higher noise levels.The results suggest that the acceptability of environmental factors in buildings depends on the degree of compliance of the design and its implementation with standards and design guidelines(i.e.for ventilation,air quality,thermal comfort,etc.),whether the original design concept is‘green’or non-‘green’.
文摘To explain the reactions of the building occupants to their acoustical environments,meetings with the designers,walk-through surveys,and detailed acoustical measurements were done.The objective was to determine how design decisions affect office acoustical environments,and how to improve the acoustical design of‘green’office buildings.Design-performance criteria were established.Measurements were made of noise level,reverberation time,speechintelligibility index(SII),and noise isolation.Noise levels were atypically low in unoccupied buildings with no mechanical ventilation,but excessive in areas near external walls next to noisy external noise sources—especially with windows open for ventilation—and in occupied buildings.Reverberation times were excessive in areas with large volumes and insufficient sound absorption.Speech intelligibility was generally adequate,but speech privacy was inadequate in shared and open-office areas,and into private offices with the doors open for ventilation.Improvement of the acoustical design of‘green’buildings must include increasing the external-internal noise isolation and that between workplaces,and the use of adequate sound absorption to control reverberation and noise.
文摘Low speech privacy in shared and private offices in one of the early generation of a“green”building resulted in occupants’dissatisfaction.This problem is experienced in Liu institute with a natural-ventilation system.Such a system requires low air-flow resistance which is achieved by large openings which will result in noise transmission between various spaces within the building.The poor acoustical quality in this building resulted in occupants’noise complaints which were further investigated by way of relevant acoustical measurements.CATT-Acoustic software was utilized to modify the acoustical quality of the building without any disturbance to the occupants.The optimized design of the transfer box above the office door was selected based on CATT-Acoustic predictions.The acoustical measurements were conducted after installation of the transfer box above the office door.The measurements’results agreed with the predictions which led to improved speech privacy to an acceptable level between the office and the corridor in Liu Institute.More work should be done to improve the acoustical quality of natural-ventilated building to conform to ANSI standards.1 The results of this study strongly support including acoustics in“green”building designs with natural ventilation to avoid users’complaints.
