bluuebunny/crossref_metadata_2025 huggingface dataset:
Inaccurate results from benchmark accurate ocean acoustic propagation models: It’s the implementation, not the model
Authors: Chin-Bing Stanley A. , King David B. , Zingarelli Robert A.
Published: February 2014

Despite numerous publications that document the benchmark accuracy of several ocean acoustic propagation models, some users of these models continue to get inaccurate results. The problem is not with the model, but with the implementation of the model. The most common mistake in implementing range-dependent acoustic models (e.g., parabolic equation models) is the selection of model parameters (e.g., step size, grid spacing, attenuating bottom depth). Another common mistake is lack of sufficient environmental data to the model. The number of implementation errors could be significantly reduced, if the user would abandon the erroneous belief that the model is a ‘‘black box’’ that will always produce the correct answer in a single run. Knowledgeable users methodically vary the input parameters and make repeated runs until model convergence is evident. It is possible to preselect model parameters, and couple the acoustic model with its environmental databases, so that a general user can obtain an accurate result. The U.S. Navy has done this with its Navy Standard Propagation models for nearly a decade. The models and their revisions are documented, configuration managed, and verified by applications to over 500 test cases. Selected examples will be presented. [Work supported by ONR/NRL.]
Complex ray solutions to the 3-D wedge ASA benchmark problems
Authors: Westwood Evan K.
Published: February 2014

In support of the ASA’s effort to benchmark shallow-water, range-dependent acoustic propagation models, a complex ray approach is applied to the three-dimensional wedge problems. The ray model [Westwood, J. Acoust. Soc. Am. 92, 2212–2222 (1992)] is designed specifically for the case of a point source in a 3-D wedge, where the receiver may lie cross slope, as well as downslope or upslope, from the source, and where the wedge of water and the bottom are isovelocity. The total field in the 3-D wedge is expressed as a sum of ray fields, each of which corresponds to a saddle point of a double integral over plane waves. The broadband case of the benchmarking problem is solved by finding frequency-dependent eigenrays at coarsely spaced frequencies and interpolating the eigenray characteristics. Eigenray diagrams provide an intuitive picture of the horizontal refraction effects associated with three-dimensional underwater acoustic propagation. [Work supported by ONR.]
Geoacoustic inversion in range-dependent environments: A plane-wave reflection coefficient approach
Authors: Stotts Steven A. , Knobles David P.
Published: February 2014

One of the most challenging aspects of geoacoustic inversion in ocean waveguides involves range-dependent problems, such as in shallow water or continental shelf environments. Inversion calculations may require tens or hundreds of thousands of calls to an acoustic propagation model. When the forward propagation model is range dependent, the computation time can become extremely large. If, however; the range dependence is known, an approximation is introduced that significantly simplifies the problem. Using the measured bathymetry and range-dependent sound-speed profile, the geometrical optics approximation is used to compute the eigenrays between sources and receivers. Assuming a rigid bottom boundary condition, the medusa algorithm is used for this purpose. This range-dependent ray theory calculation separates the propagation in the water column from that in the seabed. The modeled broadband pressure fields are obtained by computing the plane-wave reflection coefficient (PWRC) at the angles and frequencies as needed in the eigenray expansion. Namely, each perturbation of the seabed does not require a new range-dependent calculation of eigenrays, only a recalculation of the PWRC. Examples are shown that demonstrate the accuracy, efficiency, and limitations of the approach. [Research supported by SPAWAR and ONR.]
Theory of acoustic radiation over a 3-D hyperbolic ocean ridge
Authors: Berger Thomas K.
Published: February 2014

An analytic solution to a 3-D problem of ocean acoustics involving horizontal refraction is presented. An expression for the acoustic field due to a harmonic point source in an isovelocity ocean overlying a hyperbolic ridge with perfectly reflecting boundaries is given as a finite modal sum of integrals. The integrals are in terms of Mathieu functions, the eigenfunctions of the reduced wave equation in the elliptical coordinate system. These eigenfunctions are approximated away from the low-frequency limit by standard WKB techniques and the resulting integrals are then estimated by first- and second-order stationary-phase asymptotics. This gives an approximation in terms of elliptical functions for which standard numerical routines are available. The approximation is very accurate in the shallow depth and gentle slope limits appropriate to the physical situation of ridges in an isovelocity ocean. The solution includes the locations of the caustics and shadow zones and predicts a complicated intramodal interference pattern resulting from the intersection of up to three rays in a given mode. The intermodal interference from the finite modal sum is also evident in the full solution. The explicit representation of the features arising from horizontal refraction makes this model useful as a 3-D benchmark solution.
Numerical simulations with 3D WAPE considering shallow water range-dependent environments
Authors: Sturm Frédéric
Published: February 2014

A three-dimensional parabolic equation based model, 3-D WAPE, is run considering several shallow water range-dependent environments. This 3-D model is based on a higher-order Padé approximation in depth and a linear approximation in azimuth. Broadband modeling is handled using a Fourier synthesis approach. We focus on the numerical method chosen to solve the inherent initial- and boundary-value problem. When one is concerned with solving sound propagation problems in any three-dimensional waveguides, one of the main issues is to reduce the azimuthal sampling so as to achieve 3-D computations in a more reasonable time with the same accuracy. The efficiency of using higher-order finite difference schemes in azimuth is discussed. Some numerical results obtained using 3-D WAPE on various test case scenarios are presented, including the ASA 3-D penetrable wedge-shaped waveguide benchmark. For each test case, CPU time comparisons are performed. Another interesting aspect of the marching algorithm used is its ability to be parallelized. Parallel computing appears to be very promising for solving large scale numerical problems. The advantage of using parallel computing is also discussed.
Fisheries applications of Doppler sonar
Authors: Zedel Len
Published: February 2014

Signal processing inherent to broadband Doppler current profiling systems has great potential for applications in fisheries monitoring. The large bandwidth (25%–50% of the carrier frequency) contains information that can be used in target characterization, the system determines current profiles and there is the potential to make direct measurements of fish swimming speed. The capabilities of these systems are explored: field data collected with an RD Instruments 307-kHz Workhorse Acoustic Doppler Current Profiler (ADCP) demonstrate observations of large herring schools, performance is also evaluated using observations made in a tow-tank facility. For large concentrations of fish, speed and direction can be determined but for lower concentrations of fish new data processing techniques are required. For the system configuration as tested, single ping estimates have a standard deviation as low as 10 cms−1. This accuracy is substantially better than the accuracy of ≂40 cms−1 expected and suggests that for isolated targets the approach is equivalent to fully coherent Doppler processing. There is a difficulty discriminating discrete targets because of the long pulse code sequences transmitted. [This research was funded by the Natural Sciences and Engineering Council of Canada, and by Fisheries and Oceans Canada.]
Inference of size and orientation of swim-bladdered fish from high-frequency acoustic echograms
Authors: Chu Dezhang , Lavery Andone , Jech J. Michael
Published: February 2014

It is well known that the volume scattering strength is very sensitive to the size and orientation of scattering objects such as swim-bladdered fish. Such behavioral information is in general not always available. Inadequate knowledge of target orientations limits our ability to correctly estimate the size and abundance of fish acoustically. To extract orientation information of individual fish and/or fish schools, a scattering-model-based image processing method is presented. For fish aggregations within which individual fish can be resolved from the echogram, the geometric shapes and acoustic intensities of the identifiable highlights can potentially be used to infer the sizes and orientations of the individual targets. For fish schools within which individual fish cannot be resolved, the mean fish size and orientation can still potentially be inferred by examining the statistics of the amplitude distribution of the patches resulting from strong backscattering from fish schools. The scattering model is based on the Kirchhoff approximation. The requirements to improve the performance of the presented method and its limitations are discussed.
New system for remotely monitoring the three-dimensional movement of acoustically tagged fish
Authors: Steig Tracey W. , Johnston Samuel V. , Ransom Bruce H.
Published: February 2014

A passive acoustic tag system was developed to monitor the three-dimensional movements of migrating fish with submeter resolution. The acoustic tag receiver monitors an array consisting of up to 16 omnidirectional hydrophones, with received signals synchronized to determine the arrival times for each pulse transmitted by the acoustic tag. Arrival times are then used to calculate the three-dimensional position of a tagged fish as it moves through the array. Algorithms were developed to precisely calculate the three-dimensional positions of the hydrophones, and of each acoustic tag. Over the last 4 years, this system was used at several dams in the United States. Most studies to date monitored downstream migrating juvenile salmonids as they approached and passed turbine intakes, spillways, and juvenile bypass systems at hydroelectric dams. Fish movement patterns were tracked in three dimensions over time, typically with submeter resolution. Tagged fish were 160–240 mm long. Acoustic tags were approximately 7 mm in diameter by 23 mm long, weighted 2 g, and transmitted at 307 kHz. Tag codes (up to 500), pulse width (typically 1–5 ms), and ping rate (typically 0.3–3 pings/s) were field programmable. Current tags incorporate signal encoding for an improved signal-to-noise ratio, and weigh as little as 1 g.
Acoustically characterizing detritus with a 420-kHz echosounder
Authors: Di Massa Diane E.
Published: February 2014

This paper presents the new application of hydroacoustically measuring and characterizing detritus (here defined as suspended decomposing plant material) for shallow-water environments such as bays, estuaries, or rivers. Detrital material was measured hydroacoustically using a 420-kHz digital echosounder, first in a controlled laboratory test and then in an open estuary. Controlled tests on both small matted masses and individual grass strands produced signals clearly visible (6–15 dB) above the background noise. Field tests were performed using ship-mounted downward looking sonar and echo integration software to determine the feasibility of using hydroacoustics to measure, characterize, and potentially quantify the detrital biomass. A vertical series of plankton nets, slightly downstream of the echosounder, and flow velocity measurements by a 1200-kHz acoustic doppler current profiler (ADCP) slightly upstream provided ground-truth information of local concentrations. Hydroacoustics proved successful in identifying variable material concentrations both spatially and temporally, with typical backscatter intensities of −70 db. Echo amplitude information from the ADCP showed a first-order correlation with backscatter detected by the echosounder and with net sample volumes.
A quantitative echo sounder with multiple beams, model KFC-3000
Authors: Kuratsu Kenji , Satho Takahiro , Miyanohana Yoichi , Sawada Kouichi , Takao Yoshimi
Published: February 2014

We have developed a quantitative echo sounder with various features such as effective combination of dual beam and split beam methods. This system is designed in accordance with the established designing method of a quantitative echo sounder. The method specifies source power, operating frequency, and so on for a given measuring object and range under the principle of minimum estimation error. Ideal omnidirectional and symmetrical simultaneous split beam methods detect the three-dimensional position of an individual target. An omnibus display on the multiwindows provides full echo information. Raw data for post-processing is used for accurate biomass evaluation. The easy operation of this system offers a wider range of users more adequate and reliable data for fishery resource surveys.
Hydroacoustic performance of fishery survey instruments
Authors: Knudsen Hans P. , Ona Egil , Svellingen Ingvald
Published: February 2014

Accurate estimation of fish stock abundance by acoustic surveying methods is now essential for long-term assessment of many of the world’s largest fish stocks and the status of their ecosystems. Significant improvements of the acoustic oceanic surveying methodology have been achieved over the last decade, in particular in calibration stability, receiver design, post-processing systems and transducer installations for oceanic, bad-weather operation. Experiences with introducing these new elements on four ocean-going research vessels, with examples, are presented and discussed. Since many of the potential survey errors related to the technical instrumentation seem to be overcome or minimized, the present focus for improvements must now be on biotic factors such as target strength variability, vessel avoidance and vertical distribution of the fish relative to the acoustic sampling volumes. The effect of significantly reducing vessel-emitted noise and improved observation methods in the echo sounder dead zones are discussed.
Detection range of acoustic instruments for fisheries
Authors: Furusawa Masahiko , Park Jusam , Kang Myounghee , Fan Chumming
Published: February 2014

Detection ranges of acoustic instruments mainly used for fisheries and their research are derived as the range bordered by a certain signal-to-noise ratio (SNR) threshold. The SNR is depicted by several factors on transmitting and receiving, sound propagation, scattering by objects, and mainly self-ship noise. The detection ranges are shown for several fisheries instruments: fisheries echo sounder, quantitative echo sounder, and bio-telemetry system. The results can be used for designing the instruments, examining the capability of user’s own instruments, and interpreting obtained data or echograms. Some examples of the results follow. Increasing transmitting power is not as effective for high frequencies as for low frequencies to increase the detection range. Comparison of volume backscattering strengths obtained by the quantitative echo sounder at several frequencies for the purpose of rough species’ identification should be done within the same detection range. By applying the concept of the detection range for the bio-telemetry receiver beams, the number of the beams and the beamwidths can be determined.
Measurements of attenuation and backscattering in trabecular bones over a large frequency range
Authors: Padilla Frederic , Chaffai Sana , Berger Genevieve , Laugier Pascal , Peyrin Francoise
Published: February 2014

In order to understand the propagation of ultrasound through trabecular bones, measurements of attenuation and backscattering coefficients were performed. Attenuation was measured on 14 human calcanei, over a large frequency bandwidth (0.2–1.7 MHz). The experimental attenuation coefficient values were modeled with a nonlinear power fit α(f)=a0+a1fn. The attenuation coefficient was found to increase as f1.09±0.3. A highly significant relationship was noted between a1 and BMD. No correlation was found between n and BMD. The backscatter coefficient was measured in 19 bones specimen in the frequency range 0.4–1.2 MHz. The experimental frequency dependence was found to be f3.4±0.3. A twofold theoretical approach was then adopted. The analytical model of Faran for spherical and cylindrical elastic cylinders showed a qualitative agreement with experimental data. A better agreement was found with a weak scattering medium model, where the backscatter coefficient is related to the autocorrelation function of the propagating medium. These results first open interesting prospects for the investigation of the influence of bone microarchitecture on ultrasonic scattering; second it seems to indicate that scattering is not the main mechanism of ultrasonic attenuation, because of the two different frequency dependencies, as confirmed by a numerical fit (absorption + scattering).
Active ultrasound imaging of breast tumors: Forward and inverse scattering methods
Authors: Zeng Yanqing , Zhang Zhongqing , Liu Qinghuo
Published: February 2014

Ultrasonic imaging for the detection of breast tumors is an important technique to complement existing x-ray mammography. The potential advantages of the ultrasound imaging technique stems mainly from the relatively high contrast of acoustic properties between tumors and normal breast tissue. However, this high contrast also increases the difficulty of forming an accurate image because of the increased multiple scattering. To address this issue, we have developed fast forward methods based on a combination of extended Born approximation, conjugate- and biconjugate-gradient methods, and fast Fourier transform; we propose two nonlinear ultrasound imaging algorithms to improve the resolution for the high-contrast media encountered in ultrasound breast tumor detection. The measured data are simulated with a forward method. The inverse scattering algorithms account for the complicated multiple scattering (diffraction) effects. Numerical results show that our algorithms can accurately model and invert the high-contrast media in breast tissue. The outcome of the inversion is a high-resolution digital image containing the physical properties of the tissue and potential tumors. Compared with a conventional x-ray mammography, the ultrasound imaging system with an accurate imaging algorithm has the potential to provide better specificity between benign and malignant tissues.
Cymbal panels: Low-frequency acoustic projectors for underwater vehicle SONARS
Authors: Tressler James F. , Howarth Thomas R.
Published: February 2014

The Naval Research Laboratory is developing low frequency SONAR systems for an unmanned underwater vehicle (UUV) for shallow-water applications. Included among the onboard SONAR systems are three thin, lightweight, low-volume occupation acoustic sources known as cymbal panels. Each panel features miniature Class V flextensional driver elements, called cymbals, sandwiched between two stiff, lightweight radiating plates where each of the three panels is designed with a tailored cymbal element parameter in order to cover a different frequency band. NRL is placing each of these panels next to each other on the UUV in order to cover the desired frequency range from 1 kHz to over 6 kHz. A duplicate set of three panels is also placed on the opposite side of the UUV to provide some directivity means. This presentation will provide an overview of the program objectives, the acoustic source objectives, the element and panel designs, and recent underwater electroacoustic calibration data. [Work supported by Jan Lindberg of the Office of Naval Research Code 321SS and Bruce Johnson of the Office of Naval Research Code 321TS.]
Geometrically phased ‘‘doily’’ array
Authors: Hughes W. Jack
Published: February 2014

The theory and development of geometrically phased arrays will be presented. The array has evolved from a multibeam PVDF receiver, where its shape looks like a ‘‘doily,’’ to a 1–3 composite pulse-echo imaging array that can be a 1-D or 2-D array capable of 3-D imaging. The main advantage of the doily array is that it can form a set of steered beams without the need for electronically applying phase shifts, drastically reducing the cost and complexity of a system. The steering angle is a function of frequency, allowing the design of multiple steered beams or an imaging array if an FM sweep or large bandwidth pulse is used. In a manner similar to geometric shaping of a transducer for low side lobes, to form steered beams the transducer uses an amplitude function shaped as a cosine and sine aperture, shifting one signal 90 deg. Several arrays have been fabricated using electroplated and etched electrodes on piezoelectric materials such as PVDF and 1–3 composite materials. Beam formation and imaging results will be shown. [Work supported by ONR and DARPA.]
Design of a steerable parametric-mode array
Authors: Forsythe Steve , Benjamin Kim
Published: February 2014

A design is presented for a steerable parametric array that operates in the range of 40–60 kHz. The array design is based on three technologies: (1) Parametric array technology: the nonlinear interaction of two narrow high-frequency beams used to create a virtual endfire array with a very narrow beam at a much lower frequency; (2) Frequency-steered array design based on the ideas developed at Penn State University [Hughes and Thompson, J. Acoust. Soc. Am. 59, 1040 (1976)]; (3) Use of 1-3 piezocomposite as the active element of the array. The array is steered in two directions with minimum complexity of the required drive electronics. Steering along one axis is done by a simple change of primary frequencies, while steering along the other axis uses time-delay between elements. This allows the resulting parametric beam to be steered independently in two directions. The array is designed by discretizing the real and imaginary parts of the inverse DFT of the desired far-field patterns of the primaries. Scaling the 2-D DFT of the discretized array pattern allows an easy verification of the final array performance. Implementation issues, such as efficient element interconnection, drive electronics, and fabrication, will also be discussed.
Acoustic intensity scattered from an elliptic cylinder
Authors: Kim Kang , Lauchle Gerald C.
Published: February 2014

A computational study is described where a 2-D elliptic cylinder is insonified by a plane acoustic wave. The elliptic cross section of the cylinder has a fineness ratio of 5:1, the incidence angle of the plane wave is 30 and 60 degrees relative to the major axis of the ellipse, and ka=20, where a is the major axis of the elliptic cross section and k is the acoustic wave number. The calculations are performed using the finite element method of solution for partial differential equations. The MATLAB formulation solves the Helmholtz equation with reflection-free conditions imposed on the computational outer boundary, and rigid conditions imposed on the surface of the scatterer. Of particular practical interest in this study is the spatial distribution of the total active acoustic intensity, i.e., the sum of the incident and scattered intensity components. Active intensity amplitude, and the phase between pressure and particle velocity, are computed and compared to pressure amplitude only. The results show that there is significant phase distortion in the forward scattered direction that could be useful in localizing targets in active bi-static operations if p−u-type acoustic intensity probes were employed. [Work supported by ONR, Code 321 SS.]
Pipe impedance and sound spectrum measurements of the khaen and the sheng
Authors: Hoover Daniel R. , Cottingham James P.
Published: February 2014

Although the Asian free reed mouth organs all employ metal free reeds mounted in resonating pipes, there are significant differences among different families of these instruments. The sheng employs the free reed at the end of a closed pipe resonator with both conical and cylindrical sections. The khaen pipe has an unusual configuration for a wind instrument, with the free reed placed at approximately one-fourth the length of an open cylindrical pipe. Impedance curves have been measured for several pipes from a sheng and for artificial khaen tubes constructed from PVC pipe. These are compared with the sound spectra produced when the pipes are played. The sounding frequencies for both types of pipes are typically found to be above the natural frequency of the reed and close to, but slightly above, the frequency of the first impedance peak of the pipe. For khaen pipes constructed with the fundamental frequency of the pipe substantially below that of the reed, the sounding frequency is close to the second harmonic of the pipe. These results are consistent with those of some earlier studies as well as with theoretical considerations.
Nonlinear scattering of crossed ultrasonic beams in the presence of turbulence: Experiments performed with continuous waves
Authors: Roush Marlene , Korman Murray S.
Published: February 2014

Experiments are reported where two primary cw (f1=2.35 MHz and f2=1.65 MHz) beams are generated by 2.54-cm-diam transducer units (T1 and T2) of focal length 14 cm. The 4-MHz receiving unit (R) is a 2.54-cm-diam circular plane array. Turbulence is generated by a D=0.635-cm-diam submerged water jet (exit velocity 7 m/s) whose orifice is 56D from the interaction region. All transducer beam axes and jet axis form a common plane. The ensemble averaged spectrum (near 4 MHz) is measured (using a Tektronix digital oscilloscope) as a function of the ‘‘symmetry’’ scattering angle θ*. After transferring the data to a computer, ‘‘notebooks’’ in Mathematica are developed to curve fit the Doppler shift 〈fd〉 and the n=2nd, 3rd, and 4th spectral moments 〈(f−〈fd〉)n〉 vs θ* to the theory in an effort to measure the mean flow and turbulent velocity correlation functions of the turbulence [Korman and Parker, in 13th ISNA, Bergen 1993, Advances in Nonlinear Acoustics, edited by H. Hobaek (World Scientific, Singapore, 1993), pp. 650–655]. For example, for n=2, 2nd order correlations 〈v2x〉, 〈vxvy〉, and 〈v2y〉 can be measured.
Impression of sound environments formed by verbal explanation
Authors: Abe Kouji , Sone Toshio , Suzuki Yôiti , Ozawa Kenji
Published: February 2014

Our research results suggested that additional verbal and visual information on sound environments may recall existing impressions of specific sounds and affect the auditory evaluation of environmental sounds (Y. Suzuki et al., Proc. Internoise 2000, 2000, pp. 2285–2291). In order to verify this result, we conducted a new series of experiments as follows: At first, only a written verbal explanation of sound environments on sound fields and sound sources was presented to new subjects. In this experiment, we expected that some impression on the sound environments could be formed by the verbal explanation. Then, an experiment in which the stimulus sound only was presented as well as another experiment in which the stimulus sound was presented along with the verbal explanation were also conducted. The results from these experiments were analyzed by factor analysis. The results showed that the factors to evaluate the sound environments based only on the verbal information were similar to those in the evaluation with listening to the sounds. Moreover, analysis of the significant changes of factor scores among experiments showed that the performed impression on the sound environments by the verbal information affects evaluation of the sound.
Soundscapes in the sense of reaction to sound and vibration
Authors: Schulte-Fortkamp Brigitte
Published: February 2014

Evaluation of soundscapes in urban areas has to focus on different aspects like the structure of urban areas, people living in those areas, architectural and social parameters designing those areas, and acoustical and visual parameters. A measurement is needed which refers to objective and subjective parameters. The structure of the residential area, the combination of noise sources, and the soundscape are for the judgment of annoyance as well as important as subjective parameters which are relevant according to the people’s point of view; moreover the relationship of both define the background for assessments. When carrying out a survey on noise and vibration different subject-centered methodological procedures have been taken into account to develop a suitable measurement procedure. The survey focusing on perception of sound and vibration was conducted with about 600 subjects from different European countries. Procedures and results of these tests will be presented with respect to improvement of social surveys, especially addressing the meaning of noise and vibration in a defined environment. [Work supported by BRITE-EURAM project IDEA PACI/BE97-4056.]
Focused pulse of pressure for boosting sonoluminescence
Authors: Thomas Jean-Louis , Forterre Yoel , Fink Mathias
Published: February 2014

Single bubble sonoluminescence is characterized by a great concentration of energy conducting to the generation of UV photon with ultrasound of centimetric wavelength. Several teams have tried to again increase more of the energy concentration, but most of these trials have rapidly reached the boundaries of the narrow stability domain of sonoluminescence. The idea developed in this work is to overcome this limitation by adding a high-frequency pressure pulse to the monochromatic low-frequency field used in the now classical setup. For instance, the pressure in the neighborhood of the bubble can be dramatically increased during a single collapse of the bubble. This pressure pulse is generated with eight high-frequency transducers adaptively focused on the bubble and synchronized with its low-frequency cycle. With this setup, a transient amplitude of 8 atmospheres has been reached on the bubble, without destroying it, and a significant increase of the emitted light intensity has been observed on a single flash. This process is no longer limited by the domain of stability of sonoluminescence and could lead, in the future, to much more efficient inertial confinement of the gas contained in the bubble.
Cuts with a negative Poisson’s ratio in Si
Authors: Tokmakova Svetlana
Published: February 2014

Poisson’s ratio is the ratio of lateral strain in the direction n to the longitudinal strain during the stretching of a cylindrical rod along rod axis m. The Poisson ratio is a constant in an isotropic solid. The Poisson ratio of an anisotropic solid depends on directions m and n. In the paper the stereographic projections of Poisson’s ratio for some crystals were computed (germanium, quartz, lithium niobate, langasite, zinc, copper, etc.). From the stereographic projections the Poisson ratio for any directions of m and n were calculated. Orientations of axes of a rod m and directions of lateral strain n with extreme (negative) values of Poisson’s ratio were determined. Only for Si and HgCl was a decrease of rod cross-section under the uniaxial compression predicted for some orientations of the rod axis. For the Si rod the axis of the rod should lay within the 30-deg cone (the axis of the cone is the [001] direction of the Si crystal). Materials having a negative Poisson ratio may find a lot of applications, for example, as electrodes that amplify the response of piezoelectric sensors [Baughman et al., Nature (London) 392, 362–365 (1998)].
Crosstalk between acoustic sensors in a MEMS array
Authors: Pierce Allan D. , Johnson Harley T. , Cleveland Robin O. , Pascual Daniel N. , Bifano Thomas G.
Published: February 2014

The sensor array considered is in bare essentials a regular rectangular array of square holes in a slab of single crystalline silicon. The actual sensing of an incident pressure wave is achieved by optical sensing of the acoustically induced vibrations of recessed membranes (plates) within the holes. The present study addresses the crosstalk question by investigating the effect of the spacing between the holes (sensors) on the vibration of the individual membranes. The no crosstalk limit is taken as when adjacent holes are asymptotically very far apart. When they are closer together the amplitude changes because of two primary effects: (1) elastic waves originating at each of the individual holes and stimulating vibrations of the membranes in adjacent holes, and (2) reradiation of sound from one hole and subsequent diffraction into an anjacent hole. Complementary analyses are carried out using a finite element program and the geometrical theory of diffraction. For the array under study the dominant effect results from diffraction through the fluid itself; structure-borne sound has a minor effect.
Effect of masker harmonicity on threshold: Auditory filter envelope-modulation rate variability versus equidistant spacing of partial frequencies
Authors: Treurniet William C. , Boucher Darcy R.
Published: February 2014

In a previous paper [W. C. Treurniet and D. R. Boucher, J. Acoust. Soc. Am. 109, 306–320 (2001)], a model was presented which successfully accounted for the lower threshold obtained using a harmonic masker instead of a similar inharmonic masker. For the harmonic masker, the frequencies of partials were separated by a fixed amount, so the envelope modulation-rates of auditory filter outputs remained the same across filters. However, for the inharmonic masker, the interval between adjacent partials was not fixed and this resulted in a decreased uniformity of modulation-rates across filters. The model proposed that the lower uniformity impedes detection of a probe-induced change in the modulation rates, thus accounting for the masked threshold difference. This paper shows that an inharmonic masker yields results similar to a harmonic masker provided that the modulation rates are uniform across affected auditory filters. Thus, the lowered threshold associated with a harmonic masker appears to arise from invariant modulation-rates across auditory filters, and does not require that all partial-frequencies be integer multiples of a fundamental.
Loudness functions for long and short tones
Authors: Florentine Mary , Epstein Michael , Buus So/ren
Published: February 2014

This study tests the equal-loudness ratio hypothesis [Florentine et al., J. Acoust. Soc. Am. 99, 1633–1644 (1996)], which states that the loudness ratio between equal-SPL long and short tones is independent of SPL. The amount of temporal integration (i.e., the level difference between equally loud long and short sounds) is maximal at moderate levels. Therefore, the equal-loudness ratio hypothesis predicts that the loudness function is shallower at moderate levels than at low and high levels. Equal-loudness matches and cross-modality string-length matches were used to assess the form of the loudness function for 200- and 5-ms tones at 1 kHz. Results from nine normal listeners show that (1) the amount of temporal integration is largest at moderate levels in agreement with previous studies, and (2) the loudness function is shallowest at moderate levels. For eight of the nine listeners, the loudness ratio between the 200- and 5-ms tones is approximately constant, except at low levels where it tends to increase. The average data show good agreement between the two methods, but discrepancies are apparent for some individuals. These findings support the equal-loudness ratio hypothesis, except perhaps at low levels. [Work supported by NIH/NIDCD Grant No. R01DC02241.]
Equal-loudness contours at high frequencies reconsidered
Authors: Hellman Rhona , Takeshima Hisashi , Suzuki Yôiti , Ozawa Kenji , Sone Toshio
Published: February 2014

To add to the database and to clarify the spacing of the equal-loudness contours at high frequencies, equal-loudness relations determined from 1 to 16 kHz in a recent study [Hellman et al., J. Acoust. Soc. Am. 103, 2812 (1998)] are reevaluated. Relative to the linear loudness-level function with a slope of 1.0 observed for a standard 1-kHz tone, above 10 kHz the overall shapes and slopes of the loudness-level functions are both level and frequency dependent. Below 60 phons, the slopes of the loudness-level functions at 12.5 kHz and higher increase progressively with frequency from 1.31 at 12.5 kHz to 1.79 at 16 kHz. Conversely, above 60 phons the slopes decrease from 0.98 at 12.5 kHz to 0.74 at 16 kHz. The data imply that for frequencies between 1 and 10 kHz, the spacing between the equal-loudness contours is independent of loudness level. In contrast, above 10 kHz the equal-loudness contours are more closely spaced below 60 phons than at higher loudness levels. Moreover, in accord with the early work of Robinson [IRE Trans. Audio 1, 6–13 (1958)], the higher the frequency, the more strongly does the spacing vary with loudness level. [Work supported by NEDO, Japan.]
Theoretical and experimental modal analysis of brake pads
Authors: Triches Mario , Gerges Samir N. Y. , Tousi Shahram
Published: February 2014

Disc brake squeal noise is a complicated dynamic problem that has confronted automobile manufacturers for decades. The reduction of brake squeal noise is an important technological subject in terms of making vehicles quieter. Two main mechanisms are correlated with squeal noise in disc brake systems. The first one is related to the velocity dependency of the friction coefficient. The second one is the modal coupling of the rotor and the pads. In this case, the modes of the pads and rotor are coupled and the system may become unstable. To extract the natural frequencies and the vibration modes of pads is of great importance for the forecast of the dynamic behavior of the complete system. Thus, it can predict the behavior of the pads with the noise generated by the system. In this work, results of experimental modal analysis of the pads are presented and compared with the results obtained through use of the finite-element method (FEM). Different conditions of temperature were applied to the pads and simulated by FEM, verifying the influence of the work temperature in the natural frequencies.
Reflection of sh waves from an irregular free-end in a semi-infinite elastic plate
Authors: Sobh Nahil A. , Al-Nassar Yagoub N.
Published: February 2014

The problem of anti-plane-wave reflection off an inclined free-end in a semi-infinite elastic plate is investigated. An artificial internal boundary is constructed which divides the plate into two regions. One region contains the irregular free-end while the other contains the rest of the semi-infinite plate. Each admits a separable solution of the wave equation and satisfies all its physical boundary conditions. The full wave solution is finally constructed by matching displacement and stress continuities at the internal boundary. A number of numerical studies illustrate the variation of the reflected modal energy as a function of the free-end inclination and the incident modal energy.
Reordering disordered speech: The search for speech prostheses
Authors: Bunnell H. Timothy
Published: February 2014

The development over the last quarter century of computer-based speech processing has allowed investigators to (a) modify disordered speech as a means of gaining a better understanding of its nature, and (b) look toward the possibility of altering disordered speech to enhance its perceived naturalness or its intelligibility. Harry Levitt and his colleagues [H. Levitt, IEEE Trans. Audio. Electroacoust. 21, 269–273 (1973); M. J. Osberger and H. Levitt, J. Acoust. Soc. Am. 66, 1316–1324 (1979)] were among the first to examine the possibility of enhancing disordered speech via computer speech processing. Since then, a number of other investigators have taken up this line of research, employing a variety of speech processing techniques to examine issues raised by Levitt (1973), particularly regarding the relative importance of temporal versus spectral distortions in determining the intelligibility or naturalness of disordered speech. In this work, I will trace some of the history of this line of research, including work that Grace Yeni-Komshian and the author have conducted [J. Acoust. Soc. Am. 104, 637–647 (1998)], and subsequent related studies.
Feedback cancellation in hearing aids
Authors: Kates James M.
Published: February 2014

Harry Levitt was an early advocate of digital signal processing for hearing aids. His interest included not only algorithms for compression and speech enhancement, but also more practical issues such as obtaining the desired hearing aid versus frequency response at the ear drum. Acoustic feedback is one problem that can limit the maximum gain possible in a hearing aid. Feedback cancellation, in which the acoustic feedback signal is estimated and subtracted from the microphone input, allows for greater hearing-aid signal amplification, and feedback cancellation was included in the work that Harry supported in his research group. In this presentation, the effects of feedback on the hearing-aid response will be reviewed. Digital adaptive filter techniques for feedback cancellation will then be presented, along with measurements indicating the limitations of feedback cancellation.
Confocal imaging of sensory organ formation during Xenopus inner ear development
Authors: Serrano Elba E. , Quick Quincy A.
Published: February 2014

During Xenopus larval development, the otic vesicle gradually gives rise to several auditory and vestibular sensory organs that are innervated by the eighth cranial nerve. Confocal imaging methods were used to examine the appearance of stereociliary bundles in the various sensory epithelia during Xenopus development (stages 28–50), and to gather comparative developmental data that show how the inner ear gradually forms distinct auditory and vestibular compartments discernable by larval stage 50. A BioRad MRC-1024 confocal microscope was used to collect digitized images from inner ears labeled with Alexa 488 phalloidin to detect the actin cytoskeleton, and propidium iodide to highlight DNA in cell nuclei. Confocal images from whole inner ears clearly show the developmental emergence of uniquely organized sensory epithelia populated by hair cell bundles of varying morphology, as well as the position of the sensory ganglia relative to the endorgans. Images from sectioned tissue provide additional information about cell morphology and the arrangement of the sensory epithelium in relation to neural innervation. Taken together, the image data illustrate the complex structural changes that underlie inner ear organogenesis and morphogenesis. [Work supported by grants to EES (NIH NIGMS, NASA) and awards to QQ (NASA NMSGC Fellowship, NIGMS RISE).]
The auditory system as a window onto the processes of prenatal development
Authors: McFadden Dennis
Published: February 2014

Otoacoustic emissions (OAEs), auditory evoked potentials (AEPs), and hearing sensitivity all exhibit sex differences of several types in humans, and these sex differences are highly similar in newborns and adults. The strong implication is that these differences originate during prenatal development and persist through life. The most parsimonious explanation is that these sex differences are produced by androgenic processes operating on the ear and brain of the developing fetus. Certain special populations of humans have been shown to have OAEs and/or AEPs that differ from the sex-typical values, and again the most parsimonious explanation is that the degree of androgen exposure is the basis for these differences. Certain nonauditory measures from these special populations are in accord with this interpretation. The data from special populations will be summarized and a number of alternative explanations considered. Implications for research on the development of hearing will be discussed. [Work supported by NIDCD.]
Pattern adaptation in midbrain and medullar auditory units of the frog
Authors: Bibikov Nikolay G.
Published: February 2014

The responses of medullar and midbrain auditory cells to prolonged amplitude-modulated tone stimulation were recorded extracellularly in the dorsal medullar nucleus, superior olive and torus semicircularis of curarized grass frogs (Rana temporaria). The majority of the cells with tonic response to tone bursts showed a significant adaptation in their firing rate within first 20 to 30 s and then stabilized gradually. The temporal course of the rate adaptation was approximated by a single or double exponent plus a steady component corresponded to sustained firing. The dependence of the time constant of the rate decrease and the sustained firing value upon mean carrier intensity, modulation depth and modulation frequency have been studied for 128 medullar and 105 midbrain units. Generally, adaptation was stronger for midbrain versus medullar units. In each auditory nuclei the adaptation decreased with the increase in carrier intensity and modulation depth. The weakest adaptation (the highest value of sustained rate) was usually observed when a low-frequency noise was used as a modulating waveform. The comparison to the mammalian central auditory units is discussed.
The fish swimbladder as an acoustic waveguide
Authors: Francis David T. I. , Foote Kenneth G.
Published: February 2014

The possible role of the fish swimbladder as a sound-sensing organ is investigated using numerical models based on the boundary-element method. A number of gadoid specimens are considered. For each specimen, wire-frame models of the swimbladder surface are derived from morphometric data. The response of each swimbladder to a continuous incident wave is calculated at discrete frequencies up to 50 kHz. Pressure distributions within the swimbladders and velocity distributions on the surfaces are presented. Results reveal high-pressure and high-velocity regions around the anterior horns of the swimbladders. [This work originated in European Community RTD—Contract No. MAS3-CT95-0031 (BASS).]
A two-dimensional amplitude-steered array for real-time volumetric imaging
Authors: Frazier Catherine H. , Hughes W. Jack , O’Brien William D.
Published: February 2014

Real-time three-dimensional acoustic imaging is difficult in water or tissue because of the medium’s slow sound speed. Conventional pulse-echo data acquisition, which uses at least one transmit pulse per line in the image, does not allow for the real-time update of a volume of data at practical ranges. Recently, we presented a linear amplitude-steered array [J. Acoust. Soc. Am. 107, 2430 (2000)], based on an earlier concept [J. Acoust. Soc. Am. 59, 1040 (1976)], that allows the collection of a plane of data with a single transmit pulse by spatially separating frequencies in the lateral direction. The linear-phased amplitude-steered array uses frequency separation to determine vertical position and conventional beamforming to determine horizontal location. To image a volume of interest with a single transmit pulse, the received signal must contain information to give vertical, horizontal, and range position of the target. The target range is obtained from the time elapsed until the reflected signal is received. The vertical position information is determined by the returned signal’s frequency. The target’s horizontal position is found by using conventional, linear phased array processing. In this study, we describe the volumetric imaging system, giving the two-dimensional array design, and describing data acquisition and image processing strategies. [Work supported by DARPA’s Sonoelectronics Program.]