Study Of Sound Propagation Research Articles

Prediction of one-dimensional acoustic field with axial temperature gradient using neural networks

The study of sound propagation inside the ducts finds extensive application in aerospace, automobiles, speech, and biomedical sectors. This paper presents a neural network-based formulation to estimate the acoustic field inside a uniform duct with temperature gradient along the axial direction. The governing differential equation is derived from the momentum, energy, and state equations. The acoustic field is approximated with a feedforward neural network, and the problem is converted to an unconstrained optimization problem using the trial solution method. The training process is performed using the L-BFGS optimizer and the sine activation function. The acoustic field inside the duct is predicted up to 2000 Hz for linear and exponential temperature profiles. The predicted results are in good agreement with those obtained from the traditional Range-Kutta solver with a maximum relative error of 0.1%. Furthermore, the classical Helmholtz equation without the temperature gradient is solved using the developed neural network formulation. Using these results, a comparative study is conducted to understand the effect of the temperature gradient on the acoustic field inside the duct.

Influence of convective amplification on aeroacoustics oscillations in main gas pipeline

Influence of convective amplification on aeroacoustics oscillations in main gas pipeline

Air temperature profiling over different littoral surfaces

There are many factors that must be considered in the study of atmospheric sound propagation over long distances; these include surface characteristics as well as wind speed and air temperature profiles. This work presents measurements of air temperature profiles over various surfaces. Building a catalogue of this type can enable more realistic case assumptions to be made in an atmospheric acoustic transmission loss model. Accurate air temperature profiles are critical because of the potentially significant impact on the transmission loss predictions. Air temperature profile measurements have been collected by solar radiation shielded temperature loggers mounted 1 m apart on a 7 m mast. Long duration measurements were taken to capture the variability in day and nighttime temperature differentials present over surfaces such as: gravel, vegetated shoreline, marsh grass, lawn grass, water, and asphalt. In particular, measurements performed off shore were done by placing the sensor array on the deck of a pontoon boat. The initial results revealed that this configuration captures a very low elevation warming due to re-radiation from the deck of a boat instead of the true over water temperature. This study highlights the influence of wind speed on the development of the near surface temperature inversions.

Gaussian beam tracing for three-dimensional sound propagation problems in subsonic moving medium

The study of sound propagation in moving medium is important in various fields, such as atmospheric sound and underwater acoustics. To address this problem, a three-dimensional Gaussian beam tracing model is developed for subsonic moving medium, based on the Helmholtz equation of velocity potential for high-frequency sound wave in a moving medium with arbitrary Mach numbers. The dynamic ray equations in the moving medium are derived by using the beam tracing method, and further the partial differential equation is transformed into ordinary differential equations, so as to be able to more efficiently and accurately calculate the three-dimensional sound field in the moving medium. The Gaussian beam tracing method reveals that the expansion of the beam in a moving medium is more complex than in a static medium, and the energy in the ray tube is not necessarily conserved. The model is applied to several problems, including point source sound propagation in a semi-infinite homogeneous medium, three-dimensional long-range sound propagation in horizontally layered atmospheres, and three-dimensional sound propagation in the Gulf Stream. The results of the point source sound propagation problem in the semi-infinite homogeneous medium verify the effectiveness and accuracy of the model. The results of the atmospheric sound propagation problem indicate that compared with the commonly used <i>N</i> × 2D method, the three-dimensional Gaussian beam tracing in a moving medium fully considers the effect of medium motion, especially the effect of crosswind, and can calculate the sound pressure field more accurately. Although the Mach number of the ocean current is very small, its effect cannot be ignored. The ocean current can quantitatively change the sound propagation mode and affect the convergence zone position. In some areas, the difference between calculation results with and without considering the ocean current is more than 5 dB. Moreover, the deviation of rays caused by lateral flow is much smaller, and even in the areas with complex terrain, the deviation becomes more obvious only after being reflected by the interface. Moreover, the influence of lateral flow on sound propagation is much smaller than that caused by flow velocity parallel to the propagation direction. In conclusion, the developed Gaussian beam tracing method provides an accurate and efficient approach for solving the sound propagation problem in subsonic moving media.

Acoustic properties and shallow water propagation distances of Caribbean spiny lobster sounds (Panulirus argus)

Marine crustaceans produce broadband sounds that are useful for passive acoustic monitoring to support conservation and management efforts. However, the propagation characteristics and detection ranges of their signals are poorly known, limiting our leveraging of these sounds. Here, we used a four-hydrophone linear array to measure source levels (SLs) and sound propagation from Caribbean spiny lobsters (Panulirus argus) of a wide range of sizes within a natural, shallow water habitat (3.3 m depth). Source level in peak-peak (SLpp) varied with body size; larger individuals produced SLpp up to 166 dB re 1 μPa. However, transmission losses (TL) were similar across all sizes, with a global fitted TL of 12.1 dB. Correspondingly, calculated detection ranges varied with body size, ranging between 14 and 364 m for small and large individuals (respectively). This increased up to 1612 m for large spiny lobsters when considering lower ambient noise levels. Despite the potential ease of tank studies, our results highlight the importance of empirical in situ sound propagation studies for marine crustaceans. Given the important ecological and economic role of spiny lobsters, these data are a key step to supporting remote monitoring of this species for fisheries management and efforts to acoustically quantify coral reefs' health.

Preface to the Special Issue on the New Frontiers of Acoustic Modeling and Optimization

The field of acoustics involves the study of sound propagation, both in free and closed environments, through the development of both forecasting simulations and experimental techniques [...]

Making Sense of Landscape: A New Study of Sound Propagation between Tarquinian Funerary and Habitation Settings

Abstract The study of pre-Roman landscape settings has progressed across a long trajectory in its consideration of urban and rural adaptations in Etruria. Such studies, while providing valuable details regarding social organization, have not considered the unique aural nature of the landscape, particularly with respect to funerary settings. Nowhere is this more evident than with painted chambered tombs. Our understanding of Etruscan painted tombs is still largely guided by analytic studies of tomb paintings, epigraphic sources, and typologies. Thus, the bilateral relationship between each tomb’s landscape setting and habitation contexts has been explored from a solely visual perspective, rather than from a multisensory perspective, and consequently, ritual performed in and around the tomb space remains unclear. A further understanding of perceptual constructs involving aural information offers a new way forward in confronting these realities. This article utilizes acoustic modeling tools to illustrate the potential range of audibility between the Necropoli dei Monterozzi in Tarquinia and various locations in the landscape. Acoustic and spatial data collected in 2019 inside a series of painted tombs in the Calvario area of the Necropoli dei Monterozzi in Tarquinia provides further information regarding the painted tomb’s landscape setting and its environs. The preliminary study suggests that aural information can greatly enhance our understanding of funerary practices in Tarquinia, particularly with respect to how habitation areas in Tarquinia may have engaged with funerary landscapes.

Pioneering study of outdoor sound propagation.

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

Experimental study on the insertion loss of multilayer panels featuring a periodic structure

Acoustic panels with different configurations (layered structure with different absorbing materials) are broadly used to attenuate the noise. Multiple panels are preferred due to the presence of multiple air cavities and the repeated reflections which lead to increased sound attenuation. The paper presents an experimental study of sound propagation through multiple panels. A novel design of acoustic panel is proposed by incorporating the sonic crystal in the air cavities of the panel. Sonic crystal (SC) consists of a periodic arrangement of sound hard scatterers which provide the sound reduction in a particular frequency range due to destructive interference in periodic scatterers. The results are based on experimental observations which are supported by the literature. The results show that increasing the number of panels increases the sound insertion loss from the multiple panel structure. However, the panels with air cavity suffer from the sound insertion loss dip, which makes the panel ineffective. The novel acoustic panel (double and triple panel with SC) provides an additional sound reduction due to SC which can be tailored for certain frequency band. For the present case, SC is designed to overcome the insertion loss dip. The novel panel provides an additional insertion loss, reaching a maximum value of 19 and 11 dB, respectively (for the double and triple panel), overcoming the insertion loss dip due to structural vibration.

Of knitting needles and surround sound

The author began his association with Dick Lyon in 1972 when he became a graduate student in the Acoustics and Vibration Lab at MIT. Their personal and professional relationship continued, on and off, through the mid 1990s. While early studies of outdoor sound propagation and transportation noise will be discussed, this presentation will focus primarily on their work together at RHLyonCorp in the study of vibration-induced failure mechanisms and in commercial product development, including early efforts in sound quality jury trials.

Using constructed impulse responses to study the influence of sound speed profiles on outdoor acoustic propagation

Time-domain predictions can be accomplished by either explicitly calculating within the time domain, such as with the Finite-Difference, Time-Domain method, or by processing frequency-domain calculations into impulse responses. While the FDTD method has been used extensively in outdoor sound propagation studies, the requirement for extensive computational resources greatly limits the computational domain. The impulse response method, while well-utilized in underwater sound propagation has seen limited use in outdoor sound studies. For a given environmental scenario, the impulse response may be obtained from the inverse Fourier transform of transmission loss simulations in the frequency-domain. When it is convolved with the time variation of the source, the receiver signal may be readily predicted. One may re-use the impulse response for any new source, so long as the sampling criteria are met, and the source and receiver positions and environment match those of the modeled situation. A discussion of the implications of frequency resolution and example comparisons to measurements are presented. [This work was funded by the Assistant Secretary of the Army (Acquisition, Logistics, and Technology) [ASA(ALT)] with portions funded under 0602784/T40/24 and 0602146/AR9/01. Distribution Statement A: Approved for public release; Distribution is unlimited.]

Bayesian inference of material properties in disordered media using sound characteristics

A simulation study of sound wave propagation is used to characterise material properties. The synthetic model consisting of a one-dimensional chain of particles with different mass distributions is used to generate space-time responses. The standard deviation of this mass distribution is chosen as the disorder parameter ξ, which eventually gives information about the longitudinal wave propagation (P-wave). The space-time responses obtained from the synthetic model are used by a Bayesian inference technique to infer the most probable values of the parameter ξ, which would have caused the responses. While it is found that, during the sampling process, the sampler could effectively choose a region in the neighborhood of the true causative ξ, results show that the estimation in a low disordered setting are acceptable when . A frequency domain analysis is also carried out which shows superior performance in identifying the true region, suggesting that it is a more suitable approach for inference in random media.

Characterization of sound waves propagating in a fluctuating ocean: experimental validation with ALMA

The authors present an acoustic system, designed by DGA Naval Systems, dedicated to the study of sound propagation in challenging environments. The system is called ALMA for Acoustic Laboratory for Marine Applications. Shallow and coastal waters, where oceanographic phenomena (such as linear internal waves, tides and 3-D effects) interact with acoustic propagation, represent the main area of deployments. Since 2014, 5 at-sea campaign have been successfully conducted in the Mediterranean Sea and in the Atlantic Ocean. They mainly consisted in propagating sound waves in the 1–15 kHz frequency band using fixed or towed sources towards a modular passive acoustic array. The latter is composed of 8 rigid arms carrying 16 hydrophones each. These arms can be, and actually were, arranged in various shapes, depending on the goal of the experiment. Environmental sensing using thermistor strings and CTD cast complete the experimental equipment. The analysis of the 2016 campaign demonstrates the ability of the system to gather data representative what was described as the “saturation” theory by S. Flatté in the 1980s. In fact, criteria based on the mutual coherence function and the normalized acoustic intensity probability density function allow to explain the observed variability of detection performance on a 4x32-hydrophones vertical comblike passive acoustic array. A global progress report on the use of data gathered by the ALMA system, as well as future plans—including deployment in high latitudes environments—will be discussed.

Effects of front width on acoustic ducting by a continuous curved front over a sloping bottom.

The behavior of sound near an ocean front in a region with wedge bathymetry is examined. The front is parameterized as a zone of variation with inshore and offshore boundaries parallel to a straight coastline. The importance of frontal width and frontal sound speed on the ducting of acoustic energy is examined. Previous analytical studies of sound propagation and parameter sensitivity in an idealized wedge environment use an unphysical but convenient single interface front representation, which is here replaced by a continuous sound speed profile. The continuous profile selected is convenient for analytical investigation, but encourages the use of asymptotic approximation methods which are also described. The analytical solution method is outlined, and numerical results are produced with an emphasis on comparing to the single interface front. These comparisons are made to highlight the strengths and weaknesses of the idealized model for capturing the horizontal ducting effects.

Experimental studies of sound propagation over vertical and slanted paths in a turbulent atmosphere

Sound propagation over vertical and slanted paths differs from horizontal paths due to the height dependence of turbulence parameters and atmospheric stratification. Vertical and slanted paths are important for several applications, such as localization of unattended aerial systems (UASs) with ground-based acoustic microphone arrays, detection of ground-based sources with elevated arrays, and the effect of atmospheric turbulence on sonic booms. This paper describes a comprehensive experiment on near-vertical sound propagation conducted over five days in September 2018 at the National Wind Technology Center (NWTC), located near Boulder, CO. The experiment involved the NWTC 135-m meteorological tower with meteorological instruments installed at 17 heights. Nine microphones were located on three horizontal booms attached to the tower at different heights, and a speaker was placed on the ground. Two reference microphones where located near the speaker. About 65% of the time, the speaker transmitted nine or twelve tones. During the remaining time, 6-ms chirps were transmitted. A preliminary analysis of the signal statistics is presented and compared with theoretical predictions.

Wave Propagation and Imaging in Moving Random Media

We present a study of sound wave propagation in a time dependent random medium and an application to imaging. The medium is modeled by small temporal and spatial random fluctuations in the wave spe...

3D underwater sound propagation in coastal environments

Underwater sound propagation in a coastal ocean can be influenced by a variety of physical oceanographic conditions that are unique in the coastal and estuarine environment, such as salt wedge fronts, river-plume induced nonlinear internal gravity waves, strong tidal currents, surf zone waves, etc. The confined boundaries in the area can also produce reflection, diffraction and even scattering of sound due to shoaling seafloor. The morphological dynamics in the area is complex and results in corrugated and channeled bathymetry, which may cause 3D ducting and trapping of sound. In this talk, we will present our numerical study of 3D underwater sound propagation in Long Island Sound, a tidal estuary of the Atlantic Ocean. The Unstructured Grid Finite Volume Community Ocean Model (FVCOM) will be utilized to simulate physical oceanographic processes and produce water-column environmental input to the sound propagation model. A bathymetric database from high-resolution multibeam surveys will also be used to in...

A new simple method for determining the sound absorption coefficient

Taking into account the influence of the length and diameter of the impedance tube on the process of decay of sound waves, a new study of sound propagation in an impedance tube is presented, on the basis of which it is easier to determine the sound absorption coefficient. The new simple method of determining the absorption coefficient, based on the decay of reverberating waves, is fairly stable and demonstrates a low sensitivity for all errors made in the measurement. The presented method makes it possible to measure the sound absorption coefficient without laboratories and precision measuring instruments in a wide range at the level of separate consumers.

Uniform theory of diffraction (UTD)-based solution for sound diffraction caused by an array of obstacles.

A formulation based on the uniform theory of diffraction (UTD) for the analysis of the multiple-diffraction of a spherical sound wave caused by a series of wedges or knife-edges is hereby presented. The receiver location has to be considered at the same height as the preceding obstacles and at the same inter-obstacle distance from the last wedge. The solution, which is based on a UTD-physical optics formulation for radio-wave multiple-diffraction and has been validated through comparison with a geometrical theory of diffraction acoustic model, is computationally more efficient than other existing methods thanks to the fact that only single diffractions are involved in the calculations (high-order diffraction terms are not considered in the diffraction coefficients), thus allowing for the consideration of a great number of obstacles. In such a way, the proposed solution overcomes the limitations of previous works when multiple acoustic diffraction caused by an array of elements of equal height is to be analyzed. Therefore, the results can be applied in the study of sound propagation in scenarios where multiple-diffraction over a series of edges of equal height and periodical spacing has to be considered, such as the typical audience seating of a concert hall.

A new analytical approach for the modeling of sound propagation in a stratified medium

• An analytical method is proposed to describe sound propagation in stratified mediums. • The proposed method is easy to implement. • Both the acoustical indicators and field variables are found analytically. • The proposed method combines the advantages of other, existing methods in a single one. • The proposed method is verified by analyzing three different examples. In this article, the operator decoupling technique, which has been used in Green's function solution methods of partial differential equations, is adapted to provide a solution methodology for sound propagation in a stratified medium that does not require modification for different media. The developed technique can be employed to solve wave equations in different media including Biot equations, so it can be used for the analytical study of sound propagation in a stratified medium. The method is named the operator decoupling method (ODM) and as an example of implementing it, the normal sound propagation in a laterally infinite porous layer, which is analyzed by one-dimensional Biot equations, is explored. Then, a simple expression for the surface impedance is derived by satisfying the boundary conditions in a different manner. In addition, by using the operator decoupling method, the oblique incidence of a sound wave to a laterally infinite porous layer whose governing equations are two-dimensional Biot equations are investigated. Additionally, the analytical study of the oblique sound incidence to a laterally infinite medium with four layers is completed. Finally, the advantages of the method are compared with the other analytical solution methods. The operator decoupling method encompasses the capabilities of the other methods in a single method. Furthermore, it is easy to implement, and readily gives a detailed description of sound propagation in stratified media.