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The lattice sandwich structure as a new periodic sandwich model involves high stiffness and superior strength to density ratio, which can be applied for modeling lightweight systems. Compared to conventional sandwich models, it includes additional potential due to the presence of open space in the core. In other words, because of the property of 3D open-pore, the pyramid truss core can be considered as a creative model in process technology. Nevertheless, the acoustic characteristics of these types of cores can also be important in vibroacoustic performance of doubly curved sandwich systems. Accordingly, this study develops an analytical model for the first time to determine the sound transmission loss (STL) coefficient of a doubly curved sandwich shell with solid trusses considering various unit cells containing pyramidal, tetrahedral, and 3D-kagome. Modeling the system based on diffuse field, a numerical strategy is developed to obtain the limiting angle wherein no sound transmits into the system. To verify the accuracy of the offered formulation based on shear deformation shallow shell theory (SDSST), the results are validated with those experimental and numerical outcomes. It is found that modeling a shell as a truss core sandwich structure either attenuates the sound transmitted into the system or shifts the first dip point of the STL curve (curvature frequency) to lower frequencies. Numerical simulations indicate that the various terms of truss core have a different effect on STL of the modeled structure. [ABSTRACT FROM AUTHOR]

In the ocean, bubbles rarely appear alone and are often not evenly distributed, which makes it complicated to predict the effect of ocean bubbles on sound propagation. To solve this problem, researchers have tried to use approximations such as equivalent and multiple scattering models, but these approximations are accompanied by large errors. Therefore, we propose a semi-numerical and semi-analytical calculation method for underwater sound fields containing non-homogeneous bubbles in this paper. Based on the attenuation cross section and scattering cross section of a single bubble, the non-homogeneous medium is divided into multiple layers of uniform medium. Each layer of the bubble group is regarded as a whole, which can fully reflect the influence of bubble group vibration and scattering on sound wave propagation and is conducive to faster calculation of the sound field of non-homogeneous bubbly liquids. Compared with the classic coupling model, the calculation process of this method is simpler and faster, which solves the problem of fast calculation of sound fields in bubbly liquids and simulation of distributed bubble groups containing non-homogeneous distributed bubbles. [ABSTRACT FROM AUTHOR]

In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound generated by these floating turbines has the potential to affect marine ecosystems, although the extent of this impact remains underexplored. This study models the sound radiated by three planned floating wind farms in the Strait of Sicily (Italy), an area of significant interest for such developments. These wind farms vary in size (from 250 MW to 2800 MW) and environmental characteristics, including bathymetry and seabed substrates. Propagation losses were modeled in one-third-octave bands using JASCO Applied Sciences' Marine Operations Noise Model, which is based on the parabolic equation method, combined with the BELLHOP beam-tracing model. Two sound speed profiles, corresponding to winter and summer, were applied to simulate seasonal variations in sound propagation. Additionally, sound from an offshore supply ship was incorporated with one of these wind farms to simulate maintenance operations. Results indicate that sound from operating wind farms could reach a broadband sound pressure level (Lp) of 100 dB re 1 µPa as far as 67 km from the wind farm. Nevertheless, this sound level is generally lower than the ambient sound in areas with intense shipping traffic. The findings are discussed in relation to local background sound levels and current guidelines and regulations. The implications for environmental management include the need for comprehensive monitoring and mitigation strategies to protect marine ecosystems from potential acoustic disturbances. [ABSTRACT FROM AUTHOR]

This study was conducted with 37 11th grade secondary school students and had as its focus to verify the different levels of sophistication in students' explanations regarding the propagation of sound in air. A pre- and a post-test were conducted after a one-month intervention, focusing on learning about sound propagation in air. Data analysis allowed for comparing the progressions in the sophistication of students' explanations and validating the proposed categorical structure of the hierarchical levels of learning progressions (LPs). The validity was confirmed by the consistency of the category hierarchy, assessed in terms of the difficulty coefficients of LPs levels, which were distinct in the two tests but maintained the established order in the construct maps. In the pretest, the more sophisticated levels of LPs were not elucidated, but after instruction, in the posttest, there were explanations at all levels. The results also reveal the importance of instruction focused on LPs, so that students can present more sophisticated explanations, and their utility for future investigations using this approach. [ABSTRACT FROM AUTHOR]

This work introduces a comprehensive model of sound propagation on Mars, in light of the recent operation of several microphones on the Martian surface. The main outcome of this work is an operational acoustic model capable of simulating the sound field created by any source, at any location on the Martian surface, at any time. Expanding on the result of previous work (Gillier et al., 2024, https://doi.org/10.1029/2023je008257), we use the parabolic equation method for sound propagation in order to obtain the overall sound field produced by a source, in a given atmospheric composition and state, and accounting for ground properties. The resulting model enables the study of acoustics on Mars, and has the potential also to be used to probe the properties of the Martian environment using acoustic measurements with known sources. We investigate the effects of the Martian ground and the vertical profile of temperature and wind, on sound propagation. We find that the ground has a minor effect on sound propagation, and the wind profile strongly influences sound propagation as on Earth. However, the midday near surface temperature profiles on Mars are shown to cause refraction, which generates non‐negligible acoustic losses that are an order of magnitude stronger than typical refraction‐related acoustic losses on Earth. We show that the effect of the Martian atmospheric turbulence is to slightly reduce the acoustic losses due to refraction. Finally, we apply our model to show that refraction and atmospheric turbulence have a negligible effect on the propagation of sound from Ingenuity to the Perseverance rover. Plain Language Summary: Sound provides new ways for exploring the Martian environment. Whether to examine the characteristics of sound sources on Mars or to infer atmospheric properties from the behavior of sound waves in the Martian atmosphere, an accurate model of sound propagation on Mars is needed. This model must account for the path traveled by the sound waves in the atmosphere as well as their interactions with the planet's surface. We propose a model that allows us to compute the sound that would be received by a microphone depending on its relative position to a source given a set of atmospheric conditions. We investigate the effects of the ground, the vertical gradient of temperature and the wind speed, as well as the effects of atmospheric turbulence. We find that, because of the strong temperature gradient at noon on Mars, sound is bent upwards creating a quieter zone close to the ground. This effect also occurs on Earth, but is much stronger on Mars. The main outcome of this work is a model that can simulate the sound field created by any source for any location at the Martian surface at any time of year and any time of day. Key Points: We have developed a model to compute the sound field created by a specific sound source at any time and place near the Martian surfaceModel predictions show that the main parameters affecting sound propagation are the temperature and wind speed profilesRefraction and atmospheric turbulence have a small effect on acoustic waves at the altitude of the Ingenuity rotorcraft [ABSTRACT FROM AUTHOR]

To solve the problem of array detection performance in environments with mesoscale eddies, this study utilizes the Gaussian eddy model to describe the sound speed structure disturbed by eddies. Through numerical simulations, the corresponding sound field is obtained, and the transmission loss influenced by the eddy is analyzed. Furthermore, to investigate the relation between the array gain and spatial correlation in the eddy environments, the differences in vertical correlation at different positions and their effects on the vertical array gain of conventional beamforming (CBF) are studied. When the source is around the eddy center, the conclusions drawn are as follows: (1) The presence of an eddy changes the turning-point depth and the sound field distribution, significantly affecting the direct sound region and the first convergence zone, while having a minor impact on the first shadow zone. (2) In different eddy-induced environments, the first convergence zone maintains a high vertical correlation, but the vertical correlation of the direct sound region is greatly influenced by the eddy. (3) The array gain of CBF is consistent with the vertical correlation. When the correlation between each element of the sound field is great, the array gain increases with the number of array elements. [ABSTRACT FROM AUTHOR]

In the ocean, bubbles rarely appear alone and are often not evenly distributed, which makes it complicated to predict the effect of ocean bubbles on sound propagation. To solve this problem, researchers have tried to use approximations such as equivalent and multiple scattering models, but these approximations are accompanied by large errors. Therefore, we propose a semi-numerical and semi-analytical calculation method for underwater sound fields containing non-homogeneous bubbles in this paper. Based on the attenuation cross section and scattering cross section of a single bubble, the non-homogeneous medium is divided into multiple layers of uniform medium. Each layer of the bubble group is regarded as a whole, which can fully reflect the influence of bubble group vibration and scattering on sound wave propagation and is conducive to faster calculation of the sound field of non-homogeneous bubbly liquids. Compared with the classic coupling model, the calculation process of this method is simpler and faster, which solves the problem of fast calculation of sound fields in bubbly liquids and simulation of distributed bubble groups containing non-homogeneous distributed bubbles.

To evaluate the sound insulation capacity of small panels made of polymeric materials by 3D printing, a Taguchi L18-type factorial experiment with eight independent variables was designed and materialized. The independent variables were the panel thickness, polymer material type, 3D printing speed, infill percent, infill pattern, layer thickness, frequency, and sound volume. Empirical mathematical models were determined through the mathematical processing of the experimental results using specialized software. These empirical mathematical models highlight the meaning and intensity of the influence exerted by the input factors in the process on the acoustic pressure level of the energy absorbed after the passage of sounds through the small panels manufactured by 3D printing from polylactic acid and polyethylene terephthalate glycol. The factor with the strongest influence was the frequency of the sounds, with a maximum of the sound pressure level for a frequency of 13,000 Hz. A polylactic acid panel between the sound source and the sound-receiving sensor reduces the sound pressure level by about 45% from 95.8 to 65.8 dB. The power function type mathematical model in the case of the energy absorbed by the panel highlights the fact that the highest values of the exponents are those attached to the sound frequency (exponent equal to 1.616) and, respectively, to the thickness of the panel (exponent equal to −0.121). [ABSTRACT FROM AUTHOR]

In the shift toward sustainable energy production, offshore wind power has experienced notable expansion. Several projects to install floating offshore wind farms in European waters, ranging from a few to hundreds of turbines, are currently in the planning stage. The underwater operational sound generated by these floating turbines has the potential to affect marine ecosystems, although the extent of this impact remains underexplored. This study models the sound radiated by three planned floating wind farms in the Strait of Sicily (Italy), an area of significant interest for such developments. These wind farms vary in size (from 250 MW to 2800 MW) and environmental characteristics, including bathymetry and seabed substrates. Propagation losses were modeled in one-third-octave bands using JASCO Applied Sciences’ Marine Operations Noise Model, which is based on the parabolic equation method, combined with the BELLHOP beam-tracing model. Two sound speed profiles, corresponding to winter and summer, were applied to simulate seasonal variations in sound propagation. Additionally, sound from an offshore supply ship was incorporated with one of these wind farms to simulate maintenance operations. Results indicate that sound from operating wind farms could reach a broadband sound pressure level (Lp) of 100 dB re 1 µPa as far as 67 km from the wind farm. Nevertheless, this sound level is generally lower than the ambient sound in areas with intense shipping traffic. The findings are discussed in relation to local background sound levels and current guidelines and regulations. The implications for environmental management include the need for comprehensive monitoring and mitigation strategies to protect marine ecosystems from potential acoustic disturbances.

Since the industrial revolution, oceans have become substantially noisier. The noise increase is mainly caused by increased shipping, resource exploration, and infrastructure development affecting marine life at multiple levels, including behavior and physiology. Together with increasing anthropogenic noise, climate change is altering the thermal structure of the oceans, which in turn might affect noise propagation. During this century, we are witnessing an increase in seawater temperature and a decrease in ocean pH. Ocean acidification will decrease sound absorption at low frequencies (<10 kHz), enhancing long-range sound propagation. At the same time, temperature changes can modify the sound speed profile, leading to the creation or disappearance of sound ducts in which sound can propagate over large distances. The worldwide effect of climate change was explored for the winter and summer seasons using the (2018 to 2022) and (2094 to 2098, projected) atmospheric and seawater temperature, salinity, pH and wind speed as input. Using numerical modelling, we here explore the impact of climate change on underwater sound propagation. The future climate variables were taken from a Community Earth System Model v2 (CESM2) simulations forced under the concentration-driven SSP2-4.5 and SSP5-8.5 scenarios. The sound modeling results show, for future climate change scenarios, a global increase of sound speed at different depths (5, 125, 300, and 640 m) except for the North Atlantic Ocean and the Norwegian Sea, where in the upper 125 m sound speed will decrease by as much as 40 m s-1. This decrease in sound speed results in a new sub-surface duct in the upper 200 m of the water column allowing ship noise to propagate over large distances (>500 km). In the case of the Northeast Atlantic Ocean, this sub-surface duct will only be present during winter, leading to similar total mean square pressure level (SPLtot) values in the summer for both (2018 to 2022) and (2094 to 2098). We observed a strong and similar correlation for the two climate change scenarios, with an increase of the top 200 m SPLtot and a slowdown of Atlantic Meridional Overturning Circulation (AMOC) leading to an increase of SPLtot at the end of the century by 7 dB. [ABSTRACT FROM AUTHOR]

To solve the problem of array detection performance in environments with mesoscale eddies, this study utilizes the Gaussian eddy model to describe the sound speed structure disturbed by eddies. Through numerical simulations, the corresponding sound field is obtained, and the transmission loss influenced by the eddy is analyzed. Furthermore, to investigate the relation between the array gain and spatial correlation in the eddy environments, the differences in vertical correlation at different positions and their effects on the vertical array gain of conventional beamforming (CBF) are studied. When the source is around the eddy center, the conclusions drawn are as follows: (1) The presence of an eddy changes the turning-point depth and the sound field distribution, significantly affecting the direct sound region and the first convergence zone, while having a minor impact on the first shadow zone. (2) In different eddy-induced environments, the first convergence zone maintains a high vertical correlation, but the vertical correlation of the direct sound region is greatly influenced by the eddy. (3) The array gain of CBF is consistent with the vertical correlation. When the correlation between each element of the sound field is great, the array gain increases with the number of array elements.

The northern part of the South China Sea is a complex ocean environment with a large range of tidal waves and the stable Luzon cold eddy, which significantly influence the sound propagation characteristics through their impact on sound speed. This study uses a 3D ocean-acoustic framework consisting of MITgcm and BELLHOP ray model to investigate the coupled effects of the Luzon cold eddy and tidal waves. Firstly, the model incorporates tidal assimilation to reconstruct the hydrographic field and compute the sound speed field. Subsequently, the sound propagation in a representative region in the northern South China Sea is simulated to compare the response of sound propagation characteristics to the Luzon cold eddy only, tide only, and the coupled effect of both. The results demonstrate that the cold eddy shifts the location of the convergence zone forward by over 5 km at most. Further, it also makes the acoustic energy focus on the first few arrivals and delays the arrival time of rays by about 0.1 s. The tidal waves intensify these effects, resulting in a further increase of the forward distance of the convergence zone by 2-5 km and a delay in arrival time by 0.02 s. Sound propagation in the coupled influence of these two dynamic processes is exposed to steady perturbations from the cold eddy and spatial-temporal perturbations from tidal waves. The model in this study provides valuable insight for underwater detection and positioning in the realistic ocean environment.

Since the industrial revolution, oceans have become substantially noisier. The noise increase is mainly caused by increased shipping, resource exploration, and infrastructure development affecting marine life at multiple levels, including behavior and physiology. Together with increasing anthropogenic noise, climate change is altering the thermal structure of the oceans, which in turn might affect noise propagation. During this century, we are witnessing an increase in seawater temperature and a decrease in ocean pH. Ocean acidification will decrease sound absorption at low frequencies (500 km). In the case of the Northeast Atlantic Ocean, this sub-surface duct will only be present during winter, leading to similar total mean square pressure level (SPLtot) values in the summer for both (2018 to 2022) and (2094 to 2098). We observed a strong and similar correlation for the two climate change scenarios, with an increase of the top 200 m SPLtot and a slowdown of Atlantic Meridional Overturning Circulation (AMOC) leading to an increase of SPLtot at the end of the century by 7 dB.

The application of frequency-resonance method (FRM) for precise log bending testing is limited by complex geometry; usually the cone with variable cross. This case study presents the relationship among non-destructively tested material parameters of sugar maples and the numerical analysis of effect of simplifications in FRM. Four standing stems were measured to find basic geometry parameters, 3D scanned for precise geometry description, tested by pulling test (PT) to obtain elastic parameters, and, finally, cut down to process the logs. Four logs were measured by stress wave propagation (SWP) using an acoustic tomography (AT) device to obtain longitudinal sound velocities and then evaluated by the FRM to obtain natural frequencies in bending and longitudinal vibrations. Comparison was made between the dynamic moduli of elasticity (MOE), calculated from SWP and the FRM, and the static MOE calculated from the PT. In-situ experimental evaluation was accompanied by modal analysis by finite element method (FEM) working at three levels of geometry simplification (beam model, simplified solid model, and scan-based solid model); the natural frequencies of bending and longitudinal mode shapes were analyzed. The influence of geometry precision on the resulting dynamic response of logs was found regarding comparison to the experimental values. [ABSTRACT FROM AUTHOR]

Nonlinear differential equations are being used in many applied science fields such as engineering, there are more and more applications, such as musical instrumentation, chemistry, aerodynamics, cybernetics, signal and image processing, biophysics, complex media dynamics, etc. Mainly based on the analysis of the vibration and attenuation characteristics of piano strings, and on the theoretical basis of the discussion on the resonance effect of the resonance system, the model of the piano music simulation system is constructed, investigated a class of fractional nonlinear differential (integrative-differential) equations and systems of equations, fractional nonlinear differential equations on unbounded domains, and with multiple different fractional derivatives, and the existence of solutions to integral nonlinear impulse differential equations, uniqueness, multiple solutions, eigenvalue interval, as well as monotonic iterative sequences and error estimates that converge to the solutions of the corresponding equations. Finally, from the pitch frequency detection, formant point frequency estimation, and three aspects of spectrogram analysis, subjective evaluation experiments are carried out on the algorithm, and the experimental results verify the effectiveness of musical simulation.

The paper introduces a framework for comprehensive simulation workflow of the built environment using the Pachyderm Acoustics plugin inside the Grasshopper 3D interface. It aims to model the shared relationship between residential buildings and hardscape. The findings indicate different levels of absorption and scattering coefficient in reference to the hardscape specifications during the A-weighted SPL measurements and varying intensities of sound power energy source wave emissions. The author evaluated and simulated a seven-zoned district using two hardscape materials’ specifications. Results indicate that medium sound power intensity has the greatest impact on noise reduction, with a value in the range of 1.5 dB(A) to 5.9 dB(A), the lowest power is 1.3 dB(A) to 3.2 dB(A) and the highest power is 1 dB(A) to 3.5 dB(A). Additionally, the shielding effect occurring between buildings aids in noise reduction due to the multitude and long paths of sound rays that can mitigate the embodied energy.

This paper presents a multimodal method for the computation of the acoustic field in an axisymmetric varying duct with or without liner and in the presence of mean flow. The original three-dimensional equations are rearranged into a set of coupled one-dimensional equations by projecting the acoustic field over transverse basis functions. To maintain the computational efficiency of the original multimodal method (applicable without flow), only the leading-order effects of the mean flow are modeled using a multiple-scales approach. A matching procedure is also given to deal with liner discontinuities in such a duct. Two different transverse bases are used: one is based on Fourier-Bessel functions to evaluate the effect of modal scattering and the other is based on Fourier-Chebyshev polynomials to improve the method efficiency. The formulation is evaluated against analytical models based on the Wentzel-Kramers-Brillouin technique and against finite-element solutions. It is shown to give consistent results for minor computational cost for modes propagating in ducts with or without acoustic liners. This method can be easily adapted to take into account more complex flows and geometries. [ABSTRACT FROM AUTHOR]

The acoustic features of old resonance wood in violins exhibit a superior quality when compared to those from new resonance wood. This study focuses on an assessment of the sound quality of two types of wood for musical instruments, spruce and maple (class A and D), before and after aging via thermal and UV exposure. The samples were characterized before and after UV aging in terms of color change (using a Chroma meter), surface morphology (using a MarSurf XT20 instrument), chemical changes (monitored by FTIR spectroscopy), and sound propagation speed (using an ultrasound device). After UV treatment, the wavier surface increased the area of exposure and degradation. Also, the color changes were found to be more accentuated in the case of spruce compared to sycamore maple. The FTIR results indicated more advanced aging processes for spruce when compared to maple under the same experimental conditions. This difference resulted mostly from the increased formation of carbonyl-containing chromophores via oxidative processes in spruce rather than in maple, which is in agreement with the color change findings. Exposure of both species to thermal and UV radiation led to an increase in sound propagation speed, both longitudinally and radially, and to a greater extent in wood quality class A when compared to quality class D. [ABSTRACT FROM AUTHOR]

This paper addresses one of the major obstacles arising in the high-fidelity scale-resolving simulations of turbulent flows inside ducts with the walls covered by acoustic liners in order to attenuate the sound radiated from the duct. It consists of the development of spatial hydrodynamic (convective) instability over the treated walls at the low values of the acoustic resistance of the liner. For reasons that remain unclear, the growth rate of this instability and its effect on sound propagation through the duct is strongly overestimated by the CFD simulations using the macroscopic concept of the locally reacting acoustic impedance. A new damping volume source term ("body force") is proposed, whose introduction into the momentum equation resolves this issue by means of artificially suppressing the instability while remaining within the framework of the computationally efficient model of the impedance wall, i.e., without trying to simulate the liner microscopically. Examples are presented of the application of the developed methodology to the flows in the grazing impedance tubes with two different liners. They suggest that the proposed form of the damping source term can be considered universal and that the suppression of the hydrodynamic instability ensured by this term is not accompanied by any significant distortion of the propagation of the sound waves and the turbulence statistics, except for a very narrow near-wall region. [ABSTRACT FROM AUTHOR]

To evaluate the sound insulation capacity of small panels made of polymeric materials by 3D printing, a Taguchi L18-type factorial experiment with eight independent variables was designed and materialized. The independent variables were the panel thickness, polymer material type, 3D printing speed, infill percent, infill pattern, layer thickness, frequency, and sound volume. Empirical mathematical models were determined through the mathematical processing of the experimental results using specialized software. These empirical mathematical models highlight the meaning and intensity of the influence exerted by the input factors in the process on the acoustic pressure level of the energy absorbed after the passage of sounds through the small panels manufactured by 3D printing from polylactic acid and polyethylene terephthalate glycol. The factor with the strongest influence was the frequency of the sounds, with a maximum of the sound pressure level for a frequency of 13,000 Hz. A polylactic acid panel between the sound source and the sound-receiving sensor reduces the sound pressure level by about 45% from 95.8 to 65.8 dB. The power function type mathematical model in the case of the energy absorbed by the panel highlights the fact that the highest values of the exponents are those attached to the sound frequency (exponent equal to 1.616) and, respectively, to the thickness of the panel (exponent equal to −0.121).

Seismic airgun sound was measured with an autonomous passive acoustic recorder as a function of distance from 18.6 to 164.2 km in shallow water (

An acoustic experiment to measure the sound field during internal wave activity was conducted in the South China Sea. During the experiment, a train of strong internal solitary waves (ISWs) moved from the acoustic source to the receiver array along the acoustic path, and the propagation direction of the ISWs train was almost parallel to the acoustic path. Here, a study of the characteristics and physical mechanisms of the acoustic temporal coherence in this scenario is reported. The temporal coherence was analyzed by using the simulation results and experimental data. The results show that the temporal correlation coefficients oscillate quasi-periodically with both time and time delay, and the predominant oscillation periods are the same as the periods of the ISWs. The predominant fluctuation frequencies of the sound field correspond to some specific modes and lead to the periodicity of the temporal correlation coefficients. In the shallow layer, the spectrum structures of the temporal correlation coefficients are simpler because of the fewer effective modes. [ABSTRACT FROM AUTHOR]

Passive acoustic monitoring of biodiversity is growing fast, as it offers an alternative to traditional aural point count surveys, with the possibility to deploy long‐term acoustic surveys in large and complex natural environments. However, there is still a clear need to evaluate how the frequency‐ and distance‐dependent attenuation of sound as well as the ambient sound level impact the acoustic detection distance of the soniferous species in natural environments over the diel cycles and across seasons. This is of great importance to avoid pseudoreplication and to provide relevant biodiversity indicators, including species richness, species abundance and species density.To address the issue of detection distance, we tested a field‐based protocol in a Neotropical rainforest (French Guiana, France) and in an Alpine coniferous forest (Jura, France). This standardized and repeatable method consists in a recording session of the ambient sound directly followed by an experiment using a calibrated white noise sound broadcast at different positions along a 100 m linear transect. We then used acoustic laws to reveal the basic physics behind sound propagation attenuation.We demonstrate that habitat attenuation in two different kinds of forests can be modelled by an exponential decay law with a linear dependence on frequency and distance. We also report that habitat attenuation, as first approximation, can be summarized by a single value, the coefficient of attenuation of the habitat.Finally, we show that the detection distance can be predicted knowing the contribution of each attenuation factor, the coefficient of attenuation of the habitat, the ambient sound pressure level and the amplitude and frequency bandwidth characteristics of the transmitted sound. We show that the detection distance mostly depends on the ambient sound and may vary by a factor of up to 5 over the diel cycle and across seasons. These results reinforce the need to take into account the variation of the detection distance when performing passive acoustic surveys and producing reliable biodiversity indicators. [ABSTRACT FROM AUTHOR]

In this work we present a simple experiment that seeks to show the influence of atmospheric air temperature on the speed of sound propagation. The experiment consists of the simultaneous observation of air temperature and the speed of propagation of sound, using diurnal temperature variations. The experiment is based on an acoustic range finder and makes use of an Arduino Uno board with a datalogger shield. [ABSTRACT FROM AUTHOR]

The paper presents a comparison analysis of the noise generated by wind turbines and the one generated by a ventilation shaft of a working coal mine. The aim of the research was to compare the frequency and amplitude distribution of those sources, especially in the infra range. The ultimate aim it is evaluate possible environmental impact on human annoyance or severity. During the research noise signals were recorded utilizing low frequency microphones, shielded by windscreens. Microphones were localized at the heights of 0.0 m, 1.5 m (approximate location of a human ear in a standing position) and 4 m. Additionally, a measurement position of a microphone in relation to the ground surface was observed. Measurements at ground level were performed according to the standard PN-EN 61400-11:2013-07 and in vertical position, where the microphone was mounted "upside down" with the grid flush with the board. The possible influence of wind speed was also monitored. The results of the measurements are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the acoustic analogy method in relation to the sound radiation of a turbulent subsonic jet. This method of describing aerodynamic sound generation by turbulent flows is based on the use of a linear propagation operator with a random source on the right side. The main problem here is the choice of an effective way to separate the left side of the equation, which is responsible for the propagation of sound waves, and the right part, which is responsible for sound generation, so that the noise calculation result corresponds to experimental data and physical ideas about noise generation by turbulence. One of the unsolved problems of the approach, which is common in most acoustic analogies, is the problem of the so-called "shear noise" associated with the excitation of shear flow disturbances by sources and the additional contribution of these disturbances to sound radiation. It is still unclear whether the shear component of the noise is a reflection of real physical processes or is associated with the transformation of equations and inaccurate modeling of sources. Here, within the framework of the problem formulated above, we consider an acoustic analogy, in which the linearized Euler equations are used as the propagation operator. In this description, the propagation operator contains vortex modes, which leads to the appearance of a shear noise component that arises due to the pumping of vortex disturbances by the sources. When modeling sound sources, hypotheses about the quadrupole nature isotropy of sound sources, as well as the spatial uncorrelation of sound source production, are used. To validate the model, the measurement data of the sound emission of the jet using the azimuthal decomposition method are used. The comparison of the model and experiment indicates the absence of a shear component in the jet noise. This makes it possible to conclude that the idea of pumping linear vortex perturbations of the mean flow by nonlinear turbulent pulsations that is used in the considered acoustic analogy does not correspond to the real mechanism of noise generation by a turbulent jet. Possible causes of the discrepancy between the model and the data of acoustic measurements are analyzed. Possible ways of solving this problem, which make it possible to effectively separate the left side of the equation that is responsible for the propagation of sound waves and the right nonlinear part that is responsible for sound generation are considered. [ABSTRACT FROM AUTHOR]

• The vibro-acoustic properties of the ballast should be represented by using as an extended reaction model. • The ballast should be treated as a poro-elastic medium by considering its absorption, vibration and internal sound propagation. • The absorption of the ballast has a much smaller influence on the sleeper radiation compared with the effect of the ballast vibration and sound transmission. • The vibration of the ballast and the propagation of sound through its pores affect the radiation from the sleepers at low frequencies. Conventional railway track is laid in a layer of coarse stones known as ballast. Due to the gaps between the stones, the railway ballast behaves as a porous acoustic material, with absorptive properties that are important for the noise produced by the railway system. Sound radiated by the bottom of the sleepers may also be transmitted through the ballast. Moreover, during a train pass-by the ballast can vibrate, which may contribute to the radiated noise. To consider all three effects simultaneously, the ballast is treated here as a poro-elastic medium. To obtain the properties of the ballast as a porous medium, transfer function measurements are performed in a vertical impedance tube to determine the surface impedance and absorption coefficient of different depths of reduced scale ballast. The complex wavenumber is also determined through transfer function measurements within the ballast in the vertical tube. Porosity and flow resistivity are determined by non-acoustic measurements, and the Johnson-Champoux-Allard model for porous materials is then fitted to the measured wavenumbers, allowing the remaining parameters to be determined. Comparison is made with the measured impedance and normal incidence absorption coefficient. The model is then used to predict the diffuse field absorption coefficients of both the reduced scale ballast and full-size ballast, which are compared with measurements, showing acceptable agreement. Finally, the effects on the sleeper radiation of introducing the poro-elastic ballast model are estimated and the sensitivity of the results to a practical range of ballast properties is assessed. The ballast vibration increases the sleeper radiation at low frequency, and especially between 120 and 280 Hz. This is caused by the structural vibration of the ballast driven by the sleepers, which has a resonance around 250 Hz. The acoustic velocity within the ballast is 180° out of phase with the structural velocity, and this leads to a small reduction in the sound radiation around 100 Hz. These effects could not be predicted using a surface impedance model for the ballast. Compared with the effect of the ballast vibration and sound transmission, the absorption of the ballast has a much smaller influence on the sleeper radiation. [ABSTRACT FROM AUTHOR]

Underwater recordings of seismic airgun surveys in the deep-water Beaufort Sea and on the shallow-water Chukchi Sea shelf were made from sites on the continental slope and shelf break north-northwest of Point Barrow, Alaska. Airgun pulses from the deep-water survey were recorded more than 500 km away, and from the shallow-water survey up to ~100 km. In the deep-water, received sound pressure levels show spherical spreading propagation; whereas, sound exposure levels exhibit cylindrical spreading propagation. Over the shallow-water shelf, transmission losses were much greater than spherical spreading, due to energy loss in the seafloor. Understanding how sound propagates across large spatial scales in the Arctic Ocean is important for better management and mitigation of anthropogenic noise pollution in marine soundscapes, especially as diminished ice in the Arctic Ocean allows for longer range sound propagation.

Like other odontocetes, Risso's dolphins actively emit clicks and passively listen to the echoes during echolocation. However, the head anatomy of Risso's dolphins differs from that of other odontocetes by a unique vertical cleft along the anterior surface of the forehead and a differently-shaped lower jaw. In this study, 3D finite-element sound reception and production models were constructed based on computed tomography (CT) data of a deceased Risso's dolphin. Our results were verified by finding good agreement with experimental measurements of hearing sensitivity. Moreover, the acoustic pathway for sounds to travel from the seawater into the dolphin's tympanoperiotic complexes (TPCs) was computed. The gular reception mechanism, previously discovered in Delphinus delphis and Ziphius cavirostris , was also found in this species. The received sound pressure levels and relative displacement at TPC surfaces were compared between the cases with and without the mandibular fats or mandible. The results demonstrate a pronounced wave-guiding role of the mandibular fats and a limited bone-conductor role of the mandible. For sound production modelling, we digitally filled the cleft with neighbouring soft tissues, creating a hypothetical 'cleftless' head. Comparison between sound travelling through a 'cleftless' head vs. an original head indicates that the distinctive cleft plays a limited role in biosonar sound propagation., (Creative Commons Attribution license.)

A unified model of a dilute Bose–Einstein condensate is proposed, combining the logarithmic and Gross–Pitaevskii (GP) nonlinear terms in a wave equation, where the GP term describes two-body interactions, as suggested by the standard perturbation theory; while the logarithmic term is essentially nonperturbative, and takes into account quantum vacuum effects. The model is shown to have excellent agreement with sound propagation data in the condensate of cold sodium atoms known since the now classic works by Andrews and collaborators. The data also allowed us to place constraints on two of the unified model's parameters, which describe the strengths of the logarithmic and GP terms. Additionally, we suggest an experiment constraining the value of the third parameter (the characteristic density scale of the logarithmic part of the model), using the conjectured attraction–repulsion transition of many-body interaction inside the condensate. [ABSTRACT FROM AUTHOR]

It is the need of an era to develop efficient traffic noise prediction models with optimum accuracy. In this context, the present work tries to comprehend the performance-related potential parameters based on earlier published articles worldwide that are responsible for deviation in noise values for different traffic noise prediction models and find out critical gaps. This study reviewed the process involved in source modeling and sound propagation algorithms, applicability, limitations, and recent modification in 9 principal traffic noise prediction models adapted by different countries all around the globe. The result of this review shows that many researchers had carried out comparative analysis among various traffic noise prediction models, but no emphasis was made on the recent modifications, limitations associated with those models, and strategies involved without ignoring the propagation and attenuation mechanism in the developing phase of these models. The findings of this study revealed that the major challenge for any traffic noise prediction model to be efficient enough is the inclusion of all the factors responsible for the generation and deviation of traffic noise before reaching the receiver. These responsible factors include a factor for source emission, sound propagation and attenuation, road characteristics, and other miscellaneous factors such as absorption characteristics of building facades, honking, and dynamic behavior of traffic. This study adds to the broader domain of research and will be used as reference material for future traffic noise modeling strategies. [ABSTRACT FROM AUTHOR]

One of the most complex tasks performed by sensory systems is "scene analysis": the interpretation of complex signals as behaviorally relevant objects. The study of this problem, universal to species and sensory modalities, is particularly challenging in audition, where sounds from various sources and localizations, degraded by propagation through the environment, sum to form a single acoustical signal. Here we investigated in a songbird model, the zebra finch, the neural substrate for ranging and identifying a single source. We relied on ecologically and behaviorally relevant stimuli, contact calls, to investigate the neural discrimination of individual vocal signature as well as sound source distance when calls have been degraded through propagation in a natural environment. Performing electrophysiological recordings in anesthetized birds, we found neurons in the auditory forebrain that discriminate individual vocal signatures despite long-range degradation, as well as neurons discriminating propagation distance, with varying degrees of multiplexing between both information types. Moreover, the neural discrimination performance of individual identity was not affected by propagation-induced degradation beyond what was induced by the decreased intensity. For the first time, neurons with distance-invariant identity discrimination properties as well as distance-discriminant neurons are revealed in the avian auditory cortex. Because these neurons were recorded in animals that had prior experience neither with the vocalizers of the stimuli nor with long-range propagation of calls, we suggest that this neural population is part of a general-purpose system for vocalizer discrimination and ranging.SIGNIFICANCE STATEMENT Understanding how the brain makes sense of the multitude of stimuli that it continually receives in natural conditions is a challenge for scientists. Here we provide a new understanding of how the auditory system extracts behaviorally relevant information, the vocalizer identity and its distance to the listener, from acoustic signals that have been degraded by long-range propagation in natural conditions. We show, for the first time, that single neurons, in the auditory cortex of zebra finches, are capable of discriminating the individual identity and sound source distance in conspecific communication calls. The discrimination of identity in propagated calls relies on a neural coding that is robust to intensity changes, signals' quality, and decreases in the signal-to-noise ratio.

The concept of soundscape was originally coined to study the relationship between humans and their sonic environment. Since then, several definitions of soundscapes have been proposed based on musical, acoustical and ecological perspectives. However, the causal mechanisms that underlie soundscapes have often been overlooked. As a consequence, the term “soundscape” is frequently used in an ambiguous way, alternatively pointing to objective realities or subjective percepts. Through an interdisciplinary review, we identified the main biotic and abiotic factors that condition non-anthropogenic terrestrial soundscapes. A source-filter approach was used to describe sound sources, sound propagation phenomena and receiver’s characteristics. Interdisciplinary information was cross-referenced in order to define relationships between factors, sound sources and filters. Those relationships and the associated references were organized into a functional block diagram. This representation was used to question the different uses and meanings of the soundscape concept found in the literature. Three separate categories were then suggested: distal soundscape, proximal soundscape and perceptual soundscape. Finally, practical examples of these different categories were described, in relation to the diagram. This new systemic approach to soundscapes should help ecoacousticians, bioacousticians, psychoacousticians and environmental managers to better understand soundscapes and protect natural areas in a more significant way.

Marine phenomena that disturb the stratification cause oscillations in the acoustic signals. Among them, Eddies can be effective factors in mixing the ocean and create significant disturbances in the sound field. In this paper, the different parameters of Eddy and the effects of Eddy on sound propagation were analyzed in a hypothetical environment and conditions, and the amount and way of loss of sound signals in the presence of Eddy were also determined. The analyses showed that when the sound source is over the Eddy and near the surface, the sound propagation is limited to the surface sound channel. But when the sound source is in the mid-depth or under the Eddy, the sound propagation expands and dark spots decrease. in this condition (when the sound source is in the middle depth) with the increase in speed and radius of the Eddy, the amount of loss increases too.

Current best practice aircraft noise calculations primarily focus on strategic noise mapping to assess compliance with legal noise limits. To date, the effects of shielding by buildings or reflections from buildings, forests or cliffs have not been considered in noise mapping, despite their potential impact on results, particularly in mountainous and/or densely built urban areas. In this study, the effects of shielding by buildings and reflections from buildings, forests and cliffs on aircraft noise results were assessed. Calculations were performed with the sonAIR simulation tool for a residential area close to the runway of a military airfield in a mountain valley in Switzerland. The calculations revealed that shielding and reflections may locally strongly affect the results. While this may yield valuable insights for special investigations, calculations without accounting for these effects are still recommended for large-scale noise mapping, to obtain a better overview of the noise exposure and legal compliance. • Analysis of shielding from buildings, reflections from buildings, cliffs and forest. • Barrier effects are more important for large-scale noise exposure than reflections. • In acoustical shadows zones, reflections play a significant role. • For aircraft noise mapping, accounting for these effects is not recommended. • The studied effects may be of interest for special and/or local investigations. [ABSTRACT FROM AUTHOR]

The acoustic features of old resonance wood in violins exhibit a superior quality when compared to those from new resonance wood. This study focuses on an assessment of the sound quality of two types of wood for musical instruments, spruce and maple (class A and D), before and after aging via thermal and UV exposure. The samples were characterized before and after UV aging in terms of color change (using a Chroma meter), surface morphology (using a MarSurf XT20 instrument), chemical changes (monitored by FTIR spectroscopy), and sound propagation speed (using an ultrasound device). After UV treatment, the wavier surface increased the area of exposure and degradation. Also, the color changes were found to be more accentuated in the case of spruce compared to sycamore maple. The FTIR results indicated more advanced aging processes for spruce when compared to maple under the same experimental conditions. This difference resulted mostly from the increased formation of carbonyl-containing chromophores via oxidative processes in spruce rather than in maple, which is in agreement with the color change findings. Exposure of both species to thermal and UV radiation led to an increase in sound propagation speed, both longitudinally and radially, and to a greater extent in wood quality class A when compared to quality class D.

Implementing measures for the reduction of aircraft noise impact, such as optimization of flight paths and aircraft, requires sophisticated simulation capabilities. These tools have to incorporate simulation of aircraft noise generation at the source (i.e., emission) and account for prevailing sound propagation effects to ultimately predict noise levels as received on the ground. Obviously, understanding the associated uncertainties is crucial when aiming at a reliable and meaningful assessment. It also becomes essential when comparing different technologies, mixing experimental and numerical data, or using simulation methods of different fidelity (e.g., semi-empirical and first-order methods). This research focuses on quantifying uncertainties in the first step in aircraft noise simulation (i.e., the prediction of the emission situation). The quantified uncertainties reflect imperfections of models for different aircraft noise sources and variability of model input parameters at different operating conditions. A general framework is presented, which also accounts for limited knowledge of the underlying data distributions, and quantitative comparisons of different uncertainty methods are provided. In particular, the first-order second-moment analysis is compared to higher-order polynomial chaos methods, and the advantages and disadvantages of the different methods are discussed. [ABSTRACT FROM AUTHOR]

Leptodactylus fragilis is a recently introduced frog in Cuba, where it may impact local populations of amphibians in different ways. Here, we combined two methods to predict the invasion of the acoustic niche of Cuban amphibians by L. fragilis. We first use species distribution models to predict the spread and establishment of L. fragilis in Cuba. We then performed sound propagation experiments to evaluate the potential invasion of the acoustic niche in predicted suitable areas for the presence of L. fragilis. This species could have a successful establishment, spreading mainly in open areas, where its advertisement calls propagate efficiently, with low attenuation and discrete temporal-spectral degradation at short distances. The optimal transmission of acoustic signals in such areas might interfere with the acoustic communication of the endemic bufonid Peltophryne empusa, with potential negative effects on mate choice and breeding success. Predictions of habitat suitability, in combination with evidences of optimal transmission of advertisement calls of invasive amphibians, could be a valuable tool for rapid prediction of the potential impact of such species and the identification of prioritized areas to implement management strategies.

Adaptations to sound production behaviour can reduce the detectability of animal signals by eavesdroppers in a phenomenon known as acoustic crypsis. We propose that acoustic crypsis can include selection of locations that affect how sound transmits through the environment: habitats with poor acoustic propagation can minimize the range of detectability of animal signals. We investigated the potential for the preferred habitats of southern right whales to confer acoustic crypsis. We modelled acoustic propagation and range of detection of calls from southern right whales in the shallow, sandy, near shore waters where mothers and calves aggregate during the calving season. At three nursery sites across three continents in the southern hemisphere, results showed that the depth at which right whales are most commonly sighted has the most limited acoustic detection range for their calls. Thus, these habitats allow mother–calf pairs to remain acoustically cryptic from potential eavesdroppers, both predators and conspecifics, when their calves are the most vulnerable. Our results provide preliminary evidence that, in addition to other behavioural strategies, the use of habitats with poor acoustic propagation can contribute to acoustic crypsis. This adaptation may be a widespread and underappreciated mechanism for avoidance of eavesdroppers.

This paper studies the problem of sound propagation above a finite impedance plane. For this purpose, a spherical wave based half-space transfer function with velocity is derived and then is applied in the equivalent source method (ESM) to consider the influence of reflections caused by the finite impedance plane. With the half-space transfer function matching the surface velocity to the equivalent sources, the ESM is applied to estimate the sound filed above a finite impedance plane. Through two numerical simulation experiments, in which two vibrating objects, e.g., an oscillating sphere and a simply supported plate, are respectively used, the proposed model is examined. The results validate that the proposed model is feasible and effective to estimate the sound field above a finite impedance plane. [ABSTRACT FROM AUTHOR]