bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on ‘‘Training Japanese listeners to identify English /r/ and /l/: A first report’’ [J. S. Logan, S. E. Lively, and D. B. Pisoni, J. Acoust. Soc. Am. 89, 874–886 (1991)]
Authors: Pruitt John S.
Published: October 2005

An attempt to improve our understanding of how laboratory training affects cross-language speech perception was reported recently by Logan et al. [J. Acoust. Soc. Am. 89, 874–886 (1991)]. However, several problems in methodology have prompted a critique of their report. The following discussion explores these problems in an effort to clarify the issues and assess the claims of the authors.
Biot–Stoll model of the high-frequency reflection coefficient of sea ice
Authors: Sammelmann Gary Steven
Published: October 2005

This article describes a simple multilayered Biot–Stoll model of sea ice as a function of the salinity of the ice, temperature of the ice, porosity of the dendritic layer, and thickness of the dendritic layer. This model is based upon the Biot model of the elastic moduli of sea ice developed by Williams et al. at The Applied Physics Laboratory at The University of Washington.
An efficient boundary element algorithm for multi-frequency acoustical analysis
Authors: Wu T. W. , Li W. L. , Seybert A. F.
Published: October 2005

In this article, a new boundary element algorithm in acoustics is proposed. This new algorithm uses a so-called ‘‘Green’s function interpolation technique’’ so that it is ideally suited to a multi-frequency analysis. In the numerical implementation of this new algorithm, the Green’s function used in the boundary integral equation is interpolated by a set of shape functions. Numerical integration is then confined to a frequency-independent part only, and hence, is carried out only once at the first frequency of a multi-frequency run. At subsequent frequencies, only the nodal values of the Green’s function have to be re-calculated for the formation of the boundary element coefficient matrices. Compared to the recently developed ‘‘frequency interpolation technique,’’ this new algorithm requires much less disk space and can be easily extended to half-space problems and problems with planes of symmetry.
Sound propagation with a linear sound-speed profile over a rough surface
Authors: Uscinski B. J.
Published: October 2005

The distribution of an acoustic field propagating at grazing angles over a hard rough surface is described by an integral equation that results from the Helmholz integral in the parabolic approximation. The Green’s function corresponding to the case when the sound speed varies linearly with distance from the surface is found. The integral equation is solved analytically for the case of a flat surface. The field distribution in the space above the surface, obtained by numerical methods, is presented for a flat surface and for a rough surface. In both cases, the sound speed varies linearly with distance from the surface.
Application of the finite element method to two-dimensional radiation problems
Authors: Assaad Jamal , Decarpigny Jean-Noël , Bruneel Christian , Bossut Régis , Hamonic Bernard
Published: October 2005

Acoustic fields radiated by vibrating elastic bodies immersed in an infinite fluid domain are, in general, quite difficult to compute. This paper demonstrates in the two-dimensional (2-D) case that the radiated near field can be easily obtained using the finite element method if dipolar damping elements are attached to the mesh external circular boundary. These elements are specifically designed to absorb completely the first two components of the asymptotic expansion of the radiated field. Then, the paper provides a new extrapolation method to compute far-field pressures from near-field pressures, using the 2-D Helmholtz equation and its solution obeying the Sommerfeld radiation condition. These developments are valid for any radiation problem in 2D. Finally, two test examples are described, the oscillating cylinder of order m and a finite width planar source mounted in a rigid or a soft baffle. This approach is the generalization to 2-D problems of a previously described approach devoted to axisymmetrical and three-dimensional (3-D) problems [R. Bossut et al., J. Acoust. Soc. Am. 86, 1234–1244 (1989)]. It has been implemented in the ATILA code. It is well suited to the modeling of high-frequency transducers for imaging and nondestructive testing.
A theoretical study of sonoluminescence
Authors: Kamath V. , Prosperetti A. , Egolfopoulos F. N.
Published: October 2005

The production of OH radicals by dissociation of water vapor in oscillating argon bubbles is studied theoretically to examine a possible mechanism for the emission of the 310-nm line observed in sonoluminescence experiments. Accurate models are used for the calculation of the temperature field in the gas and for the description of the associated chemical kinetics. Heat transfer between the bubble and the liquid is found to play a dominant role in the process. At the low excitation amplitudes considered, the bubble radius is also an important parameter.
Normal mode sound propagation in an ocean with random narrow-band surface waves
Authors: Anand G. V. , George Mathews K.
Published: October 2005

Normal mode sound propagation in an isovelocity ocean with random narrow-band surface waves is considered, assuming the root-mean-square wave height to be small compared to the acoustic wavelength. Nonresonant interaction among the normal modes is studied using a straightforward perturbation technique. The more interesting case of resonant interaction is investigated using the method of multiple scales to obtain a pair of stochastic coupled amplitude equations which are solved using the Peano–Baker expansion technique. Equations for the spatial evolution of the first and second moments of the mode amplitudes are also derived and solved. It is shown that, irrespective of the initial conditions, the mean values of the mode amplitudes tend to zero asymptotically with increasing range, the mean-square amplitudes tend towards a state of equipartition of energy, and the total energy of the modes is conserved.
Propagation of shock waves in elastic solids caused by cavitation microjet impact. II: Application in extracorporeal shock wave lithotripsy
Authors: Zhong P. , Chuong C. J. , Preminger G. M.
Published: October 2005

To better understand the mechanism of stone fragmentation during extracorporeal shock wave lithotripsy (ESWL), the model developed in Part I [P. Zhong and C. J. Chuong, J. Acoust. Soc. Am. 94, 19–28 (1993)] is applied to study cavitation microjet impingement and its resultant shock wave propagation in renal calculi. Impact pressure at the stone boundary and stress, strain at the propagating shock fronts in the stone were calculated for typical ESWL loading conditions. At the anterior surface of the stone, the jet induced compressive stress can vary from 0.82∼4 times that of the water hammer pressure depending on the contact angles; whereas the jet-induced shear stress can achieve its maximum, with a magnitude of 30%∼54% of the water hammer pressure, near the detachment of the longitudinal (or P) wave in the solid. Comparison of model predictions with material failure strengths of renal calculi suggests that jet impact can lead to stone surface erosion by combined compressive and shear loadings at the jet impacting surface, and spalling failure by tensile forces at the distal surface of the stone. Comparing responses from four different stone types suggests that cystine is the most difficult stone to fragment in ESWL, as observed from clinical experience.
A model of cochlear mechanics with outer hair cell motility
Authors: Neely Stephen T.
Published: October 2005

The outer hair cell (OHC) is known to have the ability to change its length in response to voltage changes across its membrane. The apparent function of this OHC motility is to enhance the tuning of the basilar membrane. The model presented in this paper represents the displacement-to-voltage and voltage-to-displacement transducers of the OHC explicitly, each as low-pass filter functions. The model results show that this OHC representation is sufficient to provide a model of cochlear mechanics with mechanical tuning at the inner hair cell which is comparable to the threshold tuning curves observed in single auditory nerve fibers. The enhancement of tuning provided by OHC motility can be interpreted as the combined action of a cochlear amplifier and a second filter. This model demonstrates that realistic cochlear tuning does not require intrinsic resonance in any cochlear structure other than the basilar membrane.
Ultrasonic wave interaction with a thin anisotropic layer between two anisotropic solids. II. Second-order asymptotic boundary conditions
Authors: Rokhlin S. I. , Huang W.
Published: October 2005

In this paper, using a transfer matrix method, second-order asymptotic boundary conditions (B.C.) are introduced to model an anisotropic interfacial layer when the layer is thin compared to the wavelength. Compared with the first-order asymptotic B.C. which have previously been introduced by Rokhlin and Huang [J. Acoust. Soc. Am. 92, 1729–1742 (1992)], the second-order B.C. greatly improve the accuracy and consistency of approximation and at the same time preserve the same order of simplicity. Other attractive features are that unlike the first-order approximation the wave solutions for the second-order B.C. exactly satisfy energy balance and give zero scattering from a homogeneous substrate/layer/substrate system. Furthermore, for decoupled symmetric and antisymmetric problems, the second-order B.C. can be simplified through lower-order stiffness matrices so that the rank of the system of equations is reduced by half. Here the second-order B.C. are presented for a thin orthotropic layer between two solids which is rotated about one of its axes of symmetry with respect to the incident plane. Such boundary conditions couple the in-plane and out-of-plane stresses and displacements on the interface even for isotropic substrates. The results are illustrated by numerical examples of ultrasonic wave scattering from an imperfect interface between anisotropic solids by comparison with exact solutions.
Acoustic harmonic plane wave scattering from infinite elastic plates with a line impedance discontinuity
Authors: Pathak Ardhendu G. , Stepanishen Peter R.
Published: October 2005

A general integral transform technique is applied to the problem of the acoustic harmonic plane wave scattering from a vacuum-backed infinite elastic plate having a single line impedance discontinuity. Since the theory of elasticity is used to model the plate, no restrictive assumptions are made about the frequency–plate-thickness product. The exact formal expressions for the scattered pressure in the fluid and the normal velocity of the plate surfaces are derived. A simple expression for the far-field nonspecular scattered pressure is presented using the stationary phase method. Numerical results are then presented for the far-field pressure directionality patterns for a simply supported plate insonified by a plane harmonic wave at low, intermediate, and high frequencies. The influence of the boundary conditions on the lower surface of the plate on the nonspecular scattered pressure in the fluid is explained with the help of the plots for the velocity distribution within the plate. A FFT technique is used to compute the pressure on the top surface of the plate and the normal velocity of both the plate surfaces. These results are then related to the interfacial wave field characteristics on the plate surfaces.
The asymptotic method for predicting low-frequency acoustic radiation from a cylindrical shell of finite length
Authors: Lebedev A. V.
Published: October 2005

This paper is concerned with acoustic radiation by a thin cylindrical shell of finite length. This method is based on the idea that was proposed by Skudrzyk [J. Acoust. Soc. Am. 64, 1105–1135 (1980)] for the dynamic response analysis of complex structures. The main idea of this paper is the search for an asymptotic solution where the small parameter is the acoustic power that completes the vibration power relation. The solution is represented by the superposition of the different order wave contributions. Analytical equations can be obtained in the case of small radiation loading when the contribution of continuous spectrum waves is negligible. Finally, the expression for the radiation field represents the superposition of two terms. The first term describes the mean value of radiation that corresponds to waves traveling from the drive point. The second term describes the contribution of waves reflected at the shell ends. The radiation of the shell is analogous to the radiation of the antenna consisting of three multipole sources groups that are localized in the axial direction. Such a representation of the solution simplifies the analysis essentially and singles out the characteristic peculiarities corresponding to shell geometry, to the dispersion relation, and to other aspects of the problem. Results of the calculation in the frames of the proposed model are compared to the known data. The agreement between the calculations allows one to use the proposed model as the first approximation in more accurate studies of structure radiation.
On the power limitations of sonic transducers
Authors: Moffett Mark B.
Published: October 2005

When the mechanical quality factor Q of a transducer is less than the optimum value, the maximum power output of the transducer at resonance is electric- (or magnetic-) field-limited. When Q is greater than this optimum value, the transducer power is stress-limited. Traditional estimates of the field and stress limits and of the optimum Q, based on a simple equivalent circuit, are often too high for the field limit and too low for the stress limit and the optimum Q. Consideration is given to two extra compliance elements that are useful in flextensional transducer models and in representing glue-joint and stress-bias-rod compliances that occur in practical transducer configurations. When these compliances are included in the transducer equivalent circuit, the effect is to introduce a scale factor α (so that αQ is substituted for Q in the expressions for the power limits) and a second parameter β whose practical effect is less important. The result is that the field limit is reduced by the factor α while the stress limit is increased by approximately 1/α. At the same time, the optimum value of Q is also increased by approximately 1/α, but the maximum power (at the optimum Q) is little changed. An illustration of this effect is given by a lead zirconate titanate (PZT) barrel-stave flextensional transducer with α=0.34 and β=0.53.
Informational masking for multicomponent maskers with spectral gapsa)
Authors: Neff Donna L. , Dethlefs Theresa M. , Jesteadt Walt
Published: October 2005

Simultaneous maskers comprised of a few random-frequency sinusoids can produce considerable informational (uncertainty-based) masking if the component frequencies are drawn from a wide range and changed with each stimulus presentation. The present experiments examined the effect on informational masking of removing masker energy from large frequency regions around the signal. Threshold for a 1000-Hz signal was measured in the presence of maskers comprised of 2, 4, 6, 10, 50, or 100 random-frequency sinusoids, notched-noise, or two fixed-frequency sinusoids. The multicomponent maskers had a maximum frequency range of 300–3000 Hz, typically excluding a 160-Hz band around the signal. In comparison conditions, masker frequencies were limited to the high or low side of the signal, or the gap around the signal was progressively widened. Four listeners showed substantial informational masking which was not eliminated even by extreme spectral gaps in the maskers. Four other listeners showed much smaller effects of masker uncertainty across all conditions. Notched-noise measures of auditory-filter width did not distinguish the two subject groups, but indices of processing efficiency were typically poorer for the high-threshold listeners, as were measures of both the width and processing efficiency of presumed ‘‘attentional filters’’ under conditions of masker-frequency uncertainty.
Effects of frequency on the detection of decrements and increments in sinusoids
Authors: Moore Brian C. J. , Peters Robert W. , Glasberg Brian R.
Published: October 2005

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of decrement duration and of frequency (250, 1000, and 4000 Hz) in nine normally hearing subjects. Thresholds for detecting a brief increment in level were also measured. The sinusoids were presented in a background noise intended to mask spectral splatter associated with the decrement or increment. Performance tended to improve with increasing frequency, for all decrement durations and for increment detection. The results were analyzed using a model consisting of an array of bandpass filters (the auditory filters), each followed by a nonlinearity, a sliding temporal integrator and a decision device. The analysis indicated that the worsening in performance with decreasing frequency can be attributed mainly to changes in the efficiency of the decision device following the temporal integrator; at lower frequencies a larger change is required at the output of the integrator for threshold to be reached. At 250 Hz, the effect of the auditory filter in ‘‘smoothing’’ the internal representation of the stimuli appears to be comparable to the effect of the temporal integrator, making it difficult to determine the characteristics of the integrator.
Adaptive feedback cancellation with frequency compression for hearing aids
Authors: Joson Harry Alfonso L. , Asano Futoshi , Suzuki Yōiti , Sone Toshio
Published: October 2005

The use of an adaptive feedback canceler (AFC) for howling suppression in hearing aids seems very attractive since it is not only unaffected by the changes in the operating environment, but it also limits signal degradation due to the feedback signal. This, however, requires a reference signal which is correlated with the feedback signal but not with the input signal. In hearing aids, such a signal is hard to obtain. The output signal could be used as reference if its correlation with the input signal could sufficiently be removed. If the reference signal is correlated with the input signal, the input signal will also be canceled by the AFC. Here, the use of a frequency compressor as a decorrelator is proposed. The performance of this system is then investigated via digital simulation. Results indicated that with the use of the proposed system and the proper choice of system parameters, an increase of about 18 dB in the howling margin could be achieved with minimal deterioration in output signal quality.
A slightly inhomogeneous surface wave in a two-layered medium involving an isotropic layer and weakly anisotropic half-space
Authors: Rossikhin Yuriy A. , Shitikova Marina V.
Published: October 2005

The problem of transformation of a volume SH wave propagating along an isotropic elastic half-space with a free boundary into a new wave as a result of the half-space change (through small variations of elastic moduli) into a two-layered medium involving an isotropic layer and a weakly anisotropic half-space with cubic symmetry is investigated. The isotropic elastic moduli of a layer’s material therewith are equal to isotropic parts of the anisotropic moduli of a half-space material. Two types of the two-layered medium are considered: the medium wherein the shear wave velocity in the half-space is the same as the layer (‘‘neutral’’ layer) and the medium wherein the shear wave velocity in the layer is smaller than the shear wave velocity in the half-space (‘‘decelerating’’ layer). The new waves that evolve from these cases are demonstrated to be slightly inhomogeneous quasitransverse surface waves of the SH type, because among the three displacement components of these waves the transverse one, which is parallel to the interface of two media, predominates. As an example, two-layered media are considered where materials for the layer and half-space are isotropic and anisotropic tungsten, respectively.
The effective depth approximation for sound propagation in shallow water over a sediment layer and a hard rock basement
Authors: Glegg Stewart A. L.
Published: October 2005

This paper describes an effective depth approximation for a constant depth ocean waveguide with a layered bottom. It is shown that a good approximation to the acoustic field can be obtained by using an effective depth approximation based on the bottom impedance, and that attenuation of the modes propagating in the waveguide can be included if the complex form of the impedance is utilized. It has also been shown that the approximation of the field should include both effective depth modes, which are similar to those in a pressure release waveguide and rigid bottom modes which are similar to those in a wave guide with a rigid bottom. A simple criteria has been given to distinguish between these two types of modes depending on the bottom impedance, and the attenuation factors for each type of mode has been shown to be of a different form. Finally, a formula is given for the calculation of the distance between nulls in the long-range transmission loss in terms of the effective depth of the water channel.
Extraction of the seabed reflectivity function using ice cracking noise as a signal source
Authors: Zakarauskas Pierre , Verrall Ronald I. , Greening Michael V.
Published: October 2005

A technique is described for measuring the reflection coefficient of the Arctic seabed with a single vertical array of hydrophones. Naturally occurring ice cracking noises were used as the acoustic sources. This method circumvents the difficulties and expense of introducing artificial sound sources through the thick Arctic pack ice. The measurements were made in April 1988, with a 22-element array suspended from the ice in 420 m of water. The range of the source is first determined using the direct arrival and multiple reflections from the seabed and underice surface. Then the source directivity is parametrized using the direct arrival path only, and extrapolated to reflected path angles. A plot of the reflection coefficient versus grazing angle clearly indicates the value of the critical angle. The sound speed of the sea bottom corresponding to this critical angle agrees well with that measured from a bottom grab sample taken during the field trip. Finally, an interesting phenomenon was an anomalous increase of the received pressure level around a grazing angle of 60°. This is associated with a leaky plate wave radiating at the ice–water interface.
The sounds of bicolor damselfish (Pomacentrus partitus): Predictors of body size and a spectral basis for individual recognition and assessment
Authors: Myrberg Arthur A. , Ha Samuel J. , Shamblott Michael J.
Published: October 2005

Evidence is provided that the ‘‘chirp,’’ a sound commonly produced by males of the bicolor damselfish (family: Pomacentridae) possesses an anatomical constraint: The peak frequency within its power spectrum reflects a clear inverse relationship to body size. For every 1-mm change in the standard length of a male (range: 50–69 mm), the peak frequency of its sounds shifts by approximately 20 Hz. The ultimate constraint appears to be the volume of an individual’s gas bladder. This provides an individualistic feature to the sounds of different sized colony members, all of whose sounds possess an otherwise extremely stereotyped temporal pattern of their included pulses. This finding may aid in clarifying the mechanism that provides the clue for the already established acoustical recognition of individuals within colonies of the species.
Acoustic scattering from a cylindrical shell bounded by hemispherical endcaps. Resonance interpretation with surface waves propagating in cylindrical and spherical shells
Authors: Décultot D. , Lecroq F. , Maze G. , Ripoche J.
Published: October 2005

The studies of the acoustic scattering from infinite cylinders or spheres have shown the strong influence of the propagation of surface waves. Two types of surface waves are distinguished: the Rayleigh or Whispering Gallery waves and the Scholte–Stoneley wave. In this paper, theoretical and experimental results obtained on objects constituted by a cylindrical shell bounded by two hemispherical shells are presented, when these objects are insonified in the direction parallel to their main axis. To explain the experimental results, the stationary condition is written in the meridian plane of these objects. To apply this condition, the phase velocities of the waves propagating in the cylindrical and in the spherical parts must be known. First, the phase velocity of waves propagating along the length of cylindrical shells is theoretically and experimentally studied. Then an experimental study of the phase velocities of the waves propagating on spherical shells is carried out. Finally, the results of these two studies are used to explain the acoustic behavior of objects constituted by a cylindrical shell bounded by two hemispherical endcaps in the case of axial excitation.
A new high-frequency analysis of coatings using leaky Lamb waves
Authors: Xu P.-C. , Lindenschmidt K.-E. , Meguid S. A.
Published: October 2005

This study applies the leaky Lamb wave (LLW) technique to the quantitative characterization of coatings. A new decoupling method for the efficient inversion of the measured LLW data to determine the unknown elastic wave speeds of coatings is presented. The method is based on the effects of the elastic wave speeds in the substrate and coating on the frequency difference between adjacent modes known as the modal frequency spacing (MFS) at high frequency. LLW measurements were carried out on titanium and aluminum samples with 0.2–0.3 mm plasma-sprayed coating. The measured data were analyzed and inverted with the help of the proposed MFS method and excellent agreement between measurements and predictions of coating is observed. The LLW technique is shown to be potentially viable for real-time inspection of coating quality.
Low-frequency sound detection by a bottlenose dolphin
Authors: Turl Charles W.
Published: October 2005

The results of an underwater hearing experiment suggest that an Atlantic bottlenose dolphin (Tursiops truncatus) may detect low-frequency sound by some mechanism other than conventional hearing. At 300 and 200 Hz the dolphin’s hearing threshold was similar to previously reported data. Between 50 and 150 Hz, the dolphin’s response patterns to the test signal were similar to patterns shown for higher frequencies; however, after three to five reversals, the dolphin’s sensitivity suddenly improved and resumed reporting signal-present trials at levels near ambient noise. Since the subject was in the near field of the acoustic source, it is suspected that the dolphin was detecting particle velocity or some combination of pressure and velocity.
Detection of stochastic signals in non-Gaussian noisea)
Authors: Poor H. Vincent
Published: October 2005

A new technique for the detection of Gaussian signals in the presence of non-Gaussian noise is developed. This technique involves an approximation to the likelihood-ratio statistic for such situations, which in turn is based on the Masreliez approximation of nonlinear filtering. This approximation allows calculation of the likelihood-ratio statistic using a pair of sufficient statistics satisfying nonlinear recursive filtering equations. The performance of the proposed detector in impulsive noise is compared with that of the quadratic detector, and considerable performance gain is seen to result from the proposed technique in this case. A locally optimum (small signal-to-noise ratio) detection statistic for this situation is also presented.
Interface waves on a compliant coating bounded by a fluid flow, and their excitation by acoustic resonance
Authors: Talmant Maryline , Überall Herbert , Madigosky Walter
Published: October 2005

The stability of interface waves on a compliant coating, attached to a rigid substrate and exposed to a laminar or turbulent fluid flow, has been the subject of several theoretical studies, and of experimental investigations in which the onset and growth of instability waves was determined. Solutions of the characteristic equation of the problem have been obtained, which furnish dispersion curves and stability information for the interface waves, assuming a compressible fluid in order to attain the correct static limit. It is shown that the excitation of these interface waves by incident inhomogeneous acoustic signals can occur in a resonant fashion. Using this approach, an accurate experimental determination of the dispersion curves, of the onset of instability, and of the growth properties of interface waves appears to be possible.
Respiratory and laryngeal measures of children during vocal intensity variation
Authors: Stathopoulos Elaine T. , Sapienza Christine
Published: October 2005

Simultaneous aerodynamic, acoustic, and kinematic measurements from the laryngeal and respiratory systems were made in order to study mechanisms for changing vocal intensity. Aerodynamic and acoustic measures include an approximation of open quotient, maximum flow declination rate, alternating glottal airflow, estimated tracheal pressure, sound pressure level, and fundamental frequency. Respiratory measures included lung volume, rib cage, and abdominal displacements. Adults were used as a comparison group to twenty 4-year-olds and twenty 8-year-olds. Laryngeal and respiratory results indicate that speech production differences between the children and adults are based both on size and function. For example, children’s absolute anteroposterior diameters of the rib cage are smaller than adults, but their rib cage movement is larger and encompasses a different range during speech breathing. Since children are functionally different than adults, age specific speech production models need to be developed.
Intensity perception. XIV. Intensity discrimination in listeners with sensorineural hearing lossa)
Authors: Florentine Mary , Reed C. M. , Rabinowitz W. M. , Braida L. D. , Durlach N. I. , Buus So/ren
Published: October 2005

Intensity discrimination of pulsed tones (also called level discrimination) was measured as a function of level in 13 listeners with sensorineural hearing impairment of primarily cochlear origin, one listener with a vestibular schwannoma, and six listeners with normal hearing. Measurements were also made in normal ears presented with masking noise spectrally shaped to produce audiograms similar to those of the cochlearly impaired listeners. For unilateral impairments, tests were made at the same frequency in the normal and impaired ears. For bilateral-sloping impairments, tests were made at different frequencies in the same ear. The normal listeners showed results similar to other data in the literature. The listener with a vestibular schwannoma showed greatly reduced intensity resolution, except at a few levels. For listeners with recruiting sensorineural impairments, the results are discussed according to the configuration of the impairment and are compared across configurations at equal SPL, equal SL, and equal loudness level. Listeners with increasing hearing losses at frequencies above the test frequency generally showed impaired resolution, especially at high levels, and less deviation from Weber’s law than normal listeners. Listeners with decreasing hearing loss at frequencies above the test frequency showed nearly normal intensity-resolution functions. Whereas these trends are generally present, there are also large differences among individuals. Results obtained from normal listeners who were tested in the presence of masking noise indicate that elevated thresholds and reduced dynamic range account for some, but not all, of the effects of recruiting sensorineural impairment on intensity resolution.
Ambient noise characteristics of the northwestern Barents Sea
Authors: Bourke R. H. , Parsons A. R.
Published: October 2005

In support of the 1988–1989 CEAREX drift experiment three ANMET ambient noise buoys were inserted on ice floes in a triangular pattern approximately 120 km on a side about 200 km north of Svalbard in mid-September 1988. The buoys drifted southward passing to the east of Svalbard providing hourly measurements of the noise field from 5–4000 Hz for 2–4 months. Extensive environmental data were available with which to examine the effect of wind stress and ice motion on the noise field. The median spectra from these three buoys were quite similar with differences of about 3 dB being observed, the larger differences being at the higher frequencies where local noise effects dominate. The spectra were comparable to those found in the Eurasian Basin in winter. A 12-h periodicity was noted in both the noise and ice speed data, the result of forcing by tidal or inertial oscillations. A 52-h periodicity was noted at one buoy which lasted through the winter and was subjected to recurring synoptic scale storms. For frequencies below 100 Hz the temporal coherency was about 15 h. At low frequencies wind stress was the most important noise correlate, followed closely by ice speed. The noise field responded rapidly to the passage of storms generated by the Icelandic Low which migrated over the northern Barents Sea with the arrival of the noise peak being associated with the time of passage of the storm front past each buoy.
The compact Green’s function for a semi-infinite elastic plate, with application to trailing edge noise and blade–vortex interaction noise
Authors: Howe M. S.
Published: October 2005

Analytic representations are derived for the acoustic Green’s function governing the production of aerodynamic sound by sources near the edge of a thin, semi-infinite elastic plate. Simple closed-form expressions are obtained for the compact Green’s function, which is applicable when the length scale of the source flow near the edge is much smaller than both the acoustic and bending wavelengths. This requires that the characteristic flow Mach number M and frequency f satisfy M2≪f/fc≪1, where fc is the coincidence frequency, above which the bending wave speed in vacuo exceeds the speed of sound in the fluid. At such frequencies the flexural response of the plate can significantly affect the level of sound generation by sources in the neighborhood of the edge. This is illustrated by applications to sound production by (i) turbulent boundary layer flow over an elastic trailing edge (which includes a comparison with more complete predictions applicable for arbitrary values of f/fc≲1), and (ii) the interaction of a rectilinear vortex with the leading and trailing edges of a large plate. Comparisons with analogous predictions for a rigid edge indicate that surface compliance can result in a significant reduction in the intensity of edge-generated sound.
The adiabatic mode parabolic equation
Authors: Collins Michael D.
Published: October 2005

An efficient method is developed for solving problems involving three-dimensional acoustic propagation in a thin spherical shell. The method is based on the adiabatic mode approximation, which assumes that energy coupling between modes is negligible, and the parabolic equation (PE) method, which efficiently handles spatial variations in the acoustic properties. The PE method is used to solve two-dimensional wave equations for the adiabatic mode coefficients over latitude and longitude. Due to this reduction in dimension, the adiabatic mode PE should be practical for solving global-scale ocean acoustics problems. These types of problems, which are currently of great interest [Heaney et al., J. Acoust. Soc. Am. 90, 2586–2594 (1991); Baggeroer and Munk, Phys. Today 45(9), 22–30 (1992)], are too large to solve with other existing three-dimensional models.
Segment durations and accent as cues to word segmentation in Dutch
Authors: Quené Hugo
Published: October 2005

This paper investigates the relative contributions of accentuation and of durational word boundary cues to listeners’ perceived word segmentation in Dutch. A listening experiment is reported, in which 36 two-word phrases with an ambiguous word boundary were used as stimuli. Four groups of 20 subjects each had to make a forced binary choice between the two contrastive boundary positions. Accent position on either the first or second word was varied between stimulus phrases. In both contrastive realizations of each ambiguous phrase, two durational boundary cues were manipulated, viz. duration of the pivotal consonant and rise time of the postboundary vowel. Results show that durational word boundary markers are perceptually relevant for subjects’ perceived word segmentation, but only if the manipulated segment is realized as word-initial. Secondly, accuracy in perceived word segmentation is higher if the second word (following the ambiguous boundary position) is accented. The latter result is probably due to the higher acoustic and perceptual salience of durational as well as spectral boundary cues, which occur in initial position in the second word. Hence, the contribution of accent to word segmentation may be partly due to its ‘‘enhancing’’ effect on phonetic word boundary markers.
Superdirective arrays for hearing aids
Authors: Kates James M.
Published: October 2005

Microphone arrays are the most effective of the techniques that have been proposed for improving speech intelligibility in noise for the hearing impaired. However, classical delay-and-sum beamforming provides very small amounts of array gain at low frequencies, while adaptive array processing has been shown to cancel the desired signal in the presence of strong room reflections. Superdirective arrays offer a heretofore overlooked solution in which optimal performance can be obtained for a stationary random noise field, but where the desired signal will not be canceled. A short constrained superdirective array suitable for hearing-aid applications is proposed in this paper, and its theoretical performance is evaluated.
The laser-generated ultrasonic phased array: Analysis and experiments
Authors: Noroy Marie-Hélène , Royer Daniel , Fink Mathias
Published: October 2005

Focused ultrasonic waves have been generated in a solid by irradiating its surface with a multiple beam-pulsed YAG laser. A set of 16 rectilinear sources is used, equivalent to a phased array of ultrasonic transducers. Longitudinal waves are focused in the sample by introducing an appropriate time delay between each laser pulse. The elastic waves are detected either by a broadband optical heterodyne probe to analyze the wide ultrasonic signal spectrum (0–20 MHz), or by a narrow-band piezoelectric transducer to achieve the sectorial acoustic beam scanning of the sample. Neglecting heat diffusion in the solid and considering the source as a surface center of expansion, the impulse directivity patterns of laser-generated longitudinal acoustic waves have been computed. Experiments performed on duraluminum samples in the thermoelastic regime and steel samples in the ablation regime are presented and compared with this analysis. It is shown that a high focusing and a significant improvement of the signal sensitivity for longitudinal waves can be achieved with this technique.
Acoustics of perceptual centers in speech
Authors: Harsin Charles A.
Published: October 2005

An investigation of the acoustic correlates of perceptual centers (p centers) in CV and VC syllables was conducted. Subjects located the p centers of the syllables by placing the syllables into perceptual isochrony with a series of 1000 Hz, 5-ms clicks. In all syllables the vowel was /a/. The CV syllables used the consonants /ŝ/, /r/, /n/, /t/, /d/, /k/, and /g/, while the VC syllables used the consonants /ŝ/, /r/, and /n/. Consonant duration was varied within each VC combination and within the CV combinations which did not begin with a stop. Energy modulations of between 3 and 42 Hz were extracted from the syllables and were weighted according to an acoustic modulation sensitivity function. The rate, magnitude, and location of energy modulations within the syllables were all found to affect p-center location. In each syllable, the largest energy modulation, which was associated with the vowel onset, had the greatest effect on p-center location. In CV syllables, the modulation associated with the consonant had a secondary effect, while in VC syllables the initial vowel modulation was apparently the only determinant of p-center location. The nature of the relevant modulation energy parameters suggests that they could be acting as information about velocities and/or accelerations of articulators, and that p-centers might signify an integration of multiple articulatory events into a single syllabic event.
Vibration analysis of an alpine ski
Authors: Chapman Richard , Hegewald Karl-Arne , Humphreys Steve , Meckstroth Scott
Published: October 2005

An investigation into the vibrational behavior of an alpine ski excited by a single-point force applied at the tip of the ski was conducted. The single-point force was used to model small amplitude perturbations in the snow for a flat running ski to investigate ski chatter. In this respect, the bindings were assumed to remain in constant contact with the snow surface and the test ski was clamped at these locations for the experiment. An accelerometer and a personal computer were used to measure the ski’s response to tip excitation and a FFT was used to determine the ski’s harmonics. Numerical models were constructed utilizing (i) a finite element approximation, and (ii) a finite difference solution, to determine frequencies at 21 distinct points of the ski. Results from the model were then compared with experimental data and the model was validated. Experimental results showed the first three harmonics for the front of the ski to be 2±0.5 Hz, 22±1 Hz, and 43±4 Hz. This compared with theoretical values of 5, 25, and 37 Hz. Experimental results for the higher harmonics and other parts of the ski were found to be within an order of magnitude of the theoretically predicted values.
Modulation-frequency dependence of the nonlinear sensitivity of a Brüel & Kjær 8103 hydrophone in parametric demodulation of amplitude-modulated ultrasound
Authors: Zeng Shengke , Beard Richard B.
Published: October 2005

The interference demodulation by the nonlinearity of hydrophones cannot be ignored in parametric demodulation of amplitude-modulated (AM) ultrasound in the near-field media, where the intensity of the primary incident waves on hydrophones is very high. The interference demodulation, which is caused by the second-order sensitivity of a hydrophone, N(f), is proportional to the square of the incident pressure p2 [Moffett and Blue, Naval Underwater System Center, Tech. Memo. 801150 (1980); Humphrey and Hsu, Proceeding of Specialists Conference on Underwater Acoustic Applications (1980)]. It is found in the measurement of parametric demodulation of AM ultrasound by a Brüel & Kjær 8103 hydrophone that the N(f) is not only the function of the carrier frequency f, but also the function of the modulation frequency F. At a fixed carrier frequency f0=2.3 MHz, the interference demodulation can be observed at the modulation frequencies below 6 kHz, and becomes stronger toward low modulation frequencies at a distance of 150 mm between the transducer and the hydrophone. The interference demodulation by the nonlinearity of the hydrophone can be distinguished from parametric demodulation by observing the directivity pattern difference between them. N(f, F) is observed in the above parametric demodulation to be proportional to F1.32 [S. Zheng, Ph.D. dissertation, Drexel University (1993)]. [Work partially supported by Electro-Stim Corp.]
Nonscattering of sound by sound: Exact second-order transient solutions
Authors: Westervelt Peter J.
Published: October 2005

The bilinear interaction of two primary waves p1 and p2 generates a scattered wave ps satisfying ⧠2ps=−q̇s=−A(p1ṗ2+ṗ1p2), where A= (ρ0c04)−1[2+ρ0c0−2 (d2p/dρ2)ρ0]. Here, p1=pd+pm was chosen in which pd=−∇⋅[(4πr)−1ι̂G(t−c0−1r)] and pm=−(4πc0r)−1Ġ(t−c0−1r). This combination of dipole and monopole sources located at r=0 has a far-field cardioid pattern with a null in the ι̂ direction. Also chosen was p2= c0U(ι̂⋅r+r0)σ[t−c0−1(ι̂⋅r+r0)], a plane wave originating at r=−r0ι̂ and traveling in the ι̂ direction. G(t) and σ(t) may each have arbitrary time dependence, however, in order to avoid the bilinear interaction of primary waves with their sources, the sources were activated at t=0 and terminated at 0<t<c0−1r0. The function W=−1/2c02A(π2π̇m+π̇2πm) exists in which π̇2=p2 and π̇m=pm such that ⧠2Ẇ=q̇s, hence ⧠2(ps+Ẇ)=0. Since the far-field solution of this equation is ps=−Ẇ this means that wherever p2 or pm and therefore p1 vanish, so too must ps vanish. That is, there is no scattering outside the region of interaction. As mentioned earlier [P. J. Westervelt, in Proceedingsofthe 13thISNA, edited by H. Hobœk (Elsevier Science, London, 1993)] this theory is easily extended to apply to transducers of arbitrary configuration.
Phase-conjugate array focusing in a moving medium
Authors: Dowling David R.
Published: October 2005

Theoretical formulas are developed that demonstrate the effect of a constant convection velocity on the focusing characteristics of a phase-conjugate (or time-reversing) acoustic array. The convection velocity influences the conjugate-array focus field by displacing it relative to its location in a nonmoving medium. For a planar array and a convection velocity that is less than the acoustic speed, the focal displacement is parallel to the plane of the array, and is proportional the propagation distance and the convection-velocity component parallel to the plane of the array. The convection-velocity component perpendicular to a planar phase-conjugate array only changes the phase of the array’s response. It does not influence the size or location of the phase-conjugate array’s focus.
Ocean mixed layers and acoustic pulse propagation in the Greenland Sea
Authors: Sutton P. J. , Worcester P. F. , Masters G. , Cornuelle B. D. , Lynch J. F.
Published: October 2005

A simple one-dimensional ocean mixed layer model is used to study the effect of the transition between summer and winter conditions in the Greenland Sea on range-independent acoustic propagation. Acoustic normal modes propagated through the evolving sound-speed profile simulate broadband acoustic receptions from the Greenland Sea Tomography Experiment. The resulting changes in arrival structure and travel time are compared with data recorded between two of the tomographic moorings. The starting state for the model is the average of measured summer temperature and salinity profiles. At each time step the surface layer is modified by the removal of heat (modeling heat loss to the atmosphere) and the removal of fresh water (modeling evaporation minus precipitation). When necessary, static stability is maintained by mixing the surface layer into deeper layers. The acoustic normal modes exhibit large changes in behavior as the profile changes. In both summer (seasonal thermocline) and winter (adiabatic sound-speed profile) individual modes show minimal frequency dispersion. Intermediate profiles with a shallow surface mixed layer give highly dispersive modes, delaying the final acoustic energy cutoff by several hundred milliseconds relative to the summer and winter cases. This is the largest travel time signal observed in the data. The largest peak in the late continuous acoustic energy is due to minimally dispersed modes and corresponds to ray arrivals with near horizontal receiver angles. The amplitude of the arrival is low when significant dispersion is present.