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Passive acoustic monitoring is a valuable ecological and conservation tool that allows researchers to collect data from vocal species across large geographic areas and temporal spans. Grassland bird populations, many of which are indicators of ecosystem health, have experienced precipitous declines over the past several decades. Acoustic monitoring of grassland bird populations provides opportunities to monitor declines and focus conservation practices, yet the ability to identify species efficiently and accurately from acoustic data is challenging. Therefore, development of automated classifiers such as convolutional neural networks (CNNs) are at the forefront of streamlining detection and identification of individual species. Here, we present a CNN classifier for 5 key grassland bird species across southcentral Oklahoma, a part of the southern Great Plains: northern bobwhite (Colinus virginianus), painted bunting (Passerina ciris), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), and Bell's vireo (Vireo bellii). We compiled a high‐quality training dataset consisting of 6,933 calls, built semiautonomously using template matching that can be expanded easily to any bird species of interest. Our trained multilabel CNN achieved a high level of classification accuracy (≥98%) for the 5 species using the library of test calls and field recordings played using a programmable game caller. The ability to conduct acoustic wildlife surveys across large spatial extents will allow for more efficient monitoring of wildlife to determine key population parameters and trends and effects of biotic and abiotic factors (e.g., vegetation, disturbance, weather) on these key species. [ABSTRACT FROM AUTHOR]

To improve the computational accuracy and eliminate the element matching in the traditional method based on the finite and infinite elements, the coupling of the meshfree weak-form method with the variable order infinite acoustic wave envelope element (WEE) is studied in this paper and achieved by forming continuous acoustic shape function on an artificial interface, by which the infinite domain is divided into two subdomains where the meshfree and WEE methods are applied respectively. A coupled meshfree weak-form method is developed for use in predicting acoustic radiation in infinite domain. A key feature of the present method is the ability of properly modelling the amplitude decay of the outgoing travelling wave and significantly improving the prediction accuracy. The impacts of the meshfree shape function approximation/interpolation scheme and the space scale of the region used for the coupling on the proposed method are investigated. Simulation and experiment are performed to test the applicability and performance of the method, and show that the method is a valuable approach for predicting exterior acoustic radiation in infinite domain. [ABSTRACT FROM AUTHOR]

Due to the “wave velocity error” between the discretized model and continuum systems, the accuracy of numerical results using standard finite element method (FEM) in time domain acoustic problems is unsatisfactory with increasing frequency. Such wave velocity error is strongly related to the balance between the “stiffness” and “mass” of discretized systems. By adjusting the location of integration point of mass matrix, the redistribution of the mass is able to “tune” the balance between the stiffness and mass. Thus, the wave velocity error can be minimized in time domain acoustic problems with a balance system. On the other hand, it is found that the stability of discretized model of time domain acoustic problems can be improved by the softened stiffness. Furthermore, it is found that the balance between the smoothed stiffness and mass can also be achieved with the tuning of integration point r in the mass matrix. [ABSTRACT FROM AUTHOR]

Purpose The design of main rotor blade tips is of interest to helicopter manufactures since the tip details affect the performance and acoustics of the rotor. The paper aims to discuss this issue.Design/methodology/approach In this paper, computation fluid dynamics is used to simulate the flow around hovering helicopter blades with different tip designs. For each type of blade tip a parametric study on the shape is also conducted for comparison calculations were performed the constant rotor thrust condition. The collective pitch and the cone angles of the blades were determined by at an iterative trimming process.Findings Analysis of the distributed blade loads shows that the tip geometry has a significant influence on aerodynamics and aeroacoustics especially for stations where blade loading is high.Originality/value The aeroacoustic characteristics of the rotors were obtained using Ffowcs Williams-Hawkings equations. [ABSTRACT FROM AUTHOR]

This work aims to investigate the mode-matching (MM) and low frequency approximation (LFA) solutions of a two dimensional waveguide problem with flanged junction. The relative merits of each approach are compared for the scattering of fluid-coupled wave. The boundary value problem involving higher order derivatives at boundaries becomes a non-Sturm-Liouville problem where the use of standard orthogonality relation (OR) enables the MM solution. The derivation of LFA is made which proves to be surprisingly accurate for structure-borne mode incident. In order to validate the truncated model expansion the distribution of power in duct regions is discussed and Gibbs oscillations are incorporated by reconstruction of the normal velocity field using Lanczos filter. [ABSTRACT FROM AUTHOR]

This paper experimentally investigates the measurement of acoustic streaming in a 7 m long-standing wave air-filled acoustic resonator. One can describe the acoustic streaming as a second-order steady flow, which is superimposed on the dominant acoustic velocity. It is induced by the nonlinearities of the acoustic propagation inside the resonator. The exploration of the acoustic velocity field by the synchronized PIV (stands for Particle Image Velocimetry) technique enabled to highlight and quantify these secondary flows. The PIV measurements of the acoustic velocity fields at different phases over the excitation signal period gave information on streaming profiles and the post processing applied allowed plotting the acoustic velocity over time. These results were compared to the outcome of a 2D numerical study performed with the commercial software Fluent, where good agreements were found. It indicates the ability of this method to accurately measure second order steady flow variations of the acoustic velocity field. [ABSTRACT FROM AUTHOR]

Abstract: Steganography is well known as a method of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message. This paper presents a new data hiding scheme that uses a steganographic approach that is based on transforming the data to be covertly transmitted into a high-frequency signal, which is then carried by an audible public music signal. The principle is as follows: The secret message is translated into a digital form, which is then transformed into a high-frequency signal. This high-frequency signal, which is above the threshold of human audibility, is integrated into a public music signal, which can be actively downloaded by legal receivers. The receiver will demodulate the high-frequency signal and recover the data. This proposed scheme greatly reduces the risk of exposure of the secret message during transmission. Experimental simulations and comparisons are performed to investigate the practicability of the proposed method and its outperformance of competing data hiding schemes. [Copyright &y& Elsevier]

Abstract: The closer proximity between airports and residential areas has created a growing attention regarding noise pollution. The noise abatement procedures established by the aeronautical authorities and the models for computing noise contours around airports are proof of that. There are also models for identifying aircraft taking off which have focused on the correlation between the aircraft position and the noise signal. However, this correlation has been made so far without spatial information. The present study proposes a method to estimate the geo-referenced flight path followed by an aircraft taking off, using the spatio-temporal information extracted from the noise signal and improved with a smoothing algorithm. A microphone array with twelve sensors is used in order to evaluate different sensor spacings and the spatial aliasing effect when working with take-off noise signals. The flight path estimation method assumes that the aircraft is following a ground track collinear to the runway and was compared against radar information and Automatic Dependent Surveillance-Broadcast (ADS-B) data. The average method accuracy was between 3 and 6 meters. The estimated flight path has a ground length of about two kilometers, including locations at least one kilometer apart from the measurement point. [Copyright &y& Elsevier]

Abstract: The standard finite element method (FEM) is unreliable to compute approximate solutions of the Helmholtz equation for high wave numbers due to the dispersion. This paper presents an application of the cell-based smoothed radial point interpolation method (CS-RPIM) and focuses on the dispersion analysis in two-dimensional (2D) Helmholtz problems. The dispersion error is mainly caused by the ‘overly stiff’ feature of the discrete model. Therefore a properly “softened” stiffness for the discrete model is much more essential to the root of the numerical dispersion error. Owing to the proper softening effects provided by the cell-based gradient smoothing operations, the CS-RPIM model, therefore, can significantly reduce the dispersion error in the numerical solution. Numerical results demonstrated that, the CS-RPIM yields considerably better results than the FEM and EFGM, because of the crucial effectiveness in handling dispersion. [Copyright &y& Elsevier]

Abstract: This paper presents accurate numerical solutions for nonlinear eigenvalue analysis of three-dimensional acoustic cavities by boundary element method (BEM). To solve the nonlinear eigenvalue problem (NEP) formulated by BEM, we employ a contour integral method, called block Sakurai–Sugiura (SS) method, by which the NEP is converted to a standard linear eigenvalue problem and the dimension of eigenspace is reduced. The block version adopted in present work can also extract eigenvalues whose multiplicity is larger than one, but for the complex connected region which includes a internal closed boundary, the methodology yields fictitious eigenvalues. The application of the technique is demonstrated through the eigenvalue calculation of sphere with unique homogenous boundary conditions, cube with mixed boundary conditions and a complex connected region formed by cubic boundary and spherical boundary, however, the fictitious eigenvalues can be identified by Burton–Miller's method. These numerical results are supported by appropriate convergence study and comparisons with close form. [Copyright &y& Elsevier]

Abstract: Disceretization of boundary integral equations leads to complex and fully populated linear systems. One inherent drawback of the boundary element method (BEM) is that, the dense linear system has to be constructed and solved for each frequency. For large-scale problems, BEM can be more efficient by improving the construction and solution phases of the linear system. For these problems, the application of common direct solver is inefficient. In this paper, the corresponding linear systems are solved more efficiently than common direct solvers by using the iterative technique called CMRH (Changing Minimal Residual method based on Hessenberg process). In this method, the generation of the basis vectors of the Krylov subspace is based on the Hessenberg process instead of Arnoldi''s one that the most known GMRES (Generalized Minimal RESidual) solver uses. Compared to GMRES, the storage requirements are considerably reduced in CMRH. [Copyright &y& Elsevier]

Some animals exhibit call-and-response behaviors that can be exploited to facilitate detection. Traditionally, acoustic surveys that use call-and-respond techniques have required an observer's presence to perform the broadcast, record the response, or both events. This can be labor-intensive and may influence animal behavior and, thus, survey results. We developed an automated acoustic survey device using commercially available hardware (e.g., laptop computer, speaker, microphone) and an author-created (JS) software program ('HOOT') that can be used to survey for any animal that calls. We tested this device to determine 1) deployment longevity, 2) effective sampling area, and 3) ability to detect known packs of gray wolves ( Canis lupus) in Idaho, USA. Our device was able to broadcast and record twice daily for 6-7 days using the internal computer battery and surveyed an area of 3.3-17.5 km2 in relatively open habitat depending on the hardware components used. We surveyed for wolves at 2 active rendezvous sites used by closely monitored, radiocollared wolf packs and obtained 4 responses across both packs over 3 days of sampling. We confirmed reproduction in these 2 packs by detecting pup howls aurally from the resulting device recordings. Our device can broadcast and record animal calls and the computer software is freely downloadable. This automated survey device can be used to collect reliable data while reducing the labor costs traditionally associated with acoustic surveys. © 2011 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, we present a simple wave-splitting procedure for instantaneously reacting anisotropic media that includes spatial variation in depth. The method includes both the traditional (approximate) and a ‘true amplitude’ wave-field decomposition. The results are presented in time-Laplace domain. One of the main advantages of the method presented here is that it gives an explicit asymptotic representation of the linear acoustic-admittance operator to all orders of smoothness for the smooth, positive definite anisotropic material parameters considered here. Once the admittance operator is known we obtain an explicit asymptotic wave-splitting solution. [Copyright &y& Elsevier]

Abstract: Accurate modeling of pulse propagation and scattering in dispersive medium is a problem in many disciplines (i.e. electromagnetics and acoustics). The inclusion of an additional term in the wave equation (the derivative of the convolution between the causal time-domain propagation factor and the acoustic pressure) that takes into account the dispersive nature of the medium is utilized to make these problems tractable. The resulting modified wave equation (either homogeneous or heterogeneous) is applicable to either linear or non-linear propagation. For the case of an acoustic wave propagating in a two-dimensional heterogeneous dispersive medium, a finite-difference time-domain (FDTD) representation of the modified linear wave equation can been used to solve for the acoustic pressure. The method is applied to the case of scattering from and propagating through a 2D infinitely long cylinder with real world material properties. It is found that ignoring the heterogeneity in the medium can lead to significant error in the propagated/scattered field. [Copyright &y& Elsevier]

Abstract: The goal of this paper is to investigate jump conditions for unsteady small perturbations at impermeable interfaces, slip or bonded, plane or not, between fluids and structures in the presence of initial flow and prestress. Based on conservative equations obtained from a mixed Eulerian–Lagrangian description, interface conditions are first derived in an elegant and straightforward manner thanks to the concept of generalized functions in distribution theory. These conditions are validated with exact conditions derived from a direct linearization of the standard jump conditions. For a straightforward comparison between both approaches, all conditions are written in terms of a curvilinear coordinate system attached to the interface. The normal Lagrangian displacement continuity across the interface is proved to be a sufficient condition. The jump conditions for mass, momentum, energy and entropy are discussed, yielding conditions for the Lagrangian perturbations of displacement, stress, heat flux and temperature. Displacement and stress jump conditions are shown to coincide with literature results. The mixed Eulerian–Lagrangian description is likely to be advantageous over its fully Eulerian or Lagrangian counterparts. It yields an interesting unification between existing formulations for inviscid fluids (Galbrun’s equation) and solids (updated Lagrangian formulation), together with simpler jump conditions. [Copyright &y& Elsevier]

Abstract: The scattering problem of an incident plane sound wave with a fixed wave number by a thin soft-sound torus with arbitrary shaped cross-section is considered. The method of matched asymptotic expansions is used to construct a formal asymptotic solution of the problem. The asymptotic model, which is described by a well-posed integral equation, is constructed with the help of a modified matching procedure. The leading terms of the asymptotics for the farfield amplitude and the scattering cross-section are obtained. The case of a circular torus with constant cross-section is considered in detail. The constructed asymptotic solution is valid at low and medium frequencies where the acoustic wavelength ranges, as compared with the characteristic size of the obstacle, from a very much large value down to one comparable with its size. [Copyright &y& Elsevier]

Abstract: The scattering problem of an incident plane sound wave by a finite number of small soft-sound arbitrarily shaped bodies is considered. A system of first-class Fredholm integral equations is posed which, for the small bodies, yields a system of potential equation sequences for power solution expansion. Reciprocity relations were exploited to construct the first and second order asymptotic models which give approximate solutions valid for a large number of small bodies. The leading two terms of the asymptotics for the farfield amplitude and the scattering cross section are obtained. The case of a several elliptic discs is considered in detail. [Copyright &y& Elsevier]

Abstract: A new approach to the calculation of the scattering of waves by the edge of a thin plate or the edge of a wedge of any angle is presented. It has a number of advantages relative to previous methods. It is intuitively easy to grasp, being close in spirit to ray optics methods for solving problems. It deals with the whole range of configurations in the one way, rather than the patchwork of ways that has evolved in the past. It provides extremely good approximate solutions with minimal effort. The mathematics involved is reasonably simple. It promises to be applicable to a range of problems which have yet to be solved by other methods. In particular, we show how it can be applied in principle to obtain successive approximations to the solution of the problem of diffraction by a permeable wedge, where its relationship to the ray optics method is very clear. [Copyright &y& Elsevier]

Abstract: Accurate modeling of pulse propagation and scattering is a problem in many disciplines (i.e. electromagnetics and acoustics). For the case of an acoustic wave propagating in a two-dimensional non-dispersive medium, a routine 2nd order in time and space Finite-Difference Time-Domain (FDTD) scheme representation of the linear wave equation can be used to solve for the acoustic pressure. However when the medium is dispersive, one is required to take into account the frequency dependent attenuation and phase speed. Until recently to include the dispersive effects one typically solved the problem in the frequency domain and not in the time domain. The frequency domain solutions were Fourier transformed into the time domain. However by using a theory first proposed by Blackstock [D.T. Blackstock, J. Acoust. Soc. Am. 77 (1985) 2050. ], the linear wave equation has been modified by adding an additional term (the derivative of the convolution between the causal time-domain propagation factor and the acoustic pressure) that takes into account the dispersive nature of the medium. In the case of acoustic propagation through water, the water environment becomes strongly dispersive due to the presence of air bubbles that are present below the air–water interface. [Copyright &y& Elsevier]

Mangoes (Mangifera indica L., cv. 'Irwin ') grown in plastic greenhouses in the Okinawa Islands, Japan, were obtained and stored at 5°C, 10°C, 15°C, and in ambient conditions (20°C to 25°C) for 21 clays. Their sound velocity was recorded by an instrument named the "Firm Tester," which uses an acoustic transmission technique to indicate firmness index as a function of transmission velocity (TV). Magnitude of TV indicates fruit firmness. As the storage period advanced, the transmission velocity decreased. It was evident that ripened mangoes could be stored at 5°C without occurrence of chilling injury (CI), but non-ripened mangoes stored at the same temperature showed signs of CI. The Firm Tester provided a true firmness index of Irwin mangoes non-destructively. Commercialization of the Firm Tester could help the growers, packers, and retailers judge the firmness of fruit non-destructively. [ABSTRACT FROM AUTHOR]

An algorithm using speech recognition technology was developed to distinguish pistachio nuts with closed shells from those with open shells. It was observed that upon impact with a steel plate, nuts with closed shells emit different sounds than nuts with open shells. Features extracted from the sound signals consisted of mel-cepstrum coefficients and eigenvalues obtained from the principle component analysis (PCA) of the autocorrelation matrix of the sound signals. Classification of a sound signal was performed by linearly combining the mel-cepstrum and PCA feature vectors. An important property of the algorithm is that it is easily trainable, as are most speech-recognition algorithms. During the training phase, sounds of nuts with closed shells and with open shells were used to obtain a representative vector of each class. During the recognition phase, the feature vector from the sample under question was compared with representative vectors. The classification accuracy of closed-shell nuts was more than 99% on the validation set, which did not include the training set. [ABSTRACT FROM AUTHOR]

She also played other 1989 hits [ABSTRACT FROM PUBLISHER]