bluuebunny/crossref_metadata_2025 huggingface dataset:
Shape correlation of low-frequency underwater sounds
Authors: Seem Dennis A. , Rowe Neil C.
Published: October 2005

Standard correlation methods work poorly for significantly distorted signals. Good examples are 1-to 50-Hz underwater sounds correlated across hundreds of kilometers to locate ships, earthquakes, and large marine mammals. Current correlation methods for these sounds require either laborious human examination of graphical displays or automatic checking of enormous numbers of combinations. This paper reports on a program for automatically recognizing, classifying, and correlating such signals in a more efficient, higher level way. Ideas from computer vision are used to describe overall sound shapes rather than their details. The program uses a blackboard architecture and a time-shift transform analogous to the Hough transform. In experiments, the program ran an estimated 250 times faster than a conventional correlation approach. The program identified 69% of apparent whale moans having marked sound distortions with distance (and 100% of earthquakes), but nonetheless was nearly perfect in correlating whale moans between hydrophones 340 km apart in the presence of noisy earthquakes.
A dual filter model describing single-fiber responses to clicks in the normal and noise-damaged cochlea
Authors: Schoonhoven R. , Keijzer J. , Versnel H. , Prijs V. F.
Published: October 2005

This paper presents a composite model of the normal and noise-damaged guinea pig cochlea. The model incorporates a phenomenologically defined cochlear filter, and physiological descriptions of inner hair cell transduction, synaptic adaptation, and spike generation. The latter three model sections were taken from recent literature. The paper first deals with validation and evaluation of the model and adaptation of the relevant parameters to the guinea pig. Then the model is applied to explore to what extent changes in the cochlear filter can be held responsible for abnormal responses to clicks that were recorded in single auditory nerve fibers in noise-damaged animals. Focus is on those fibers in which the tip-to-tail sensitivity ratio of the frequency threshold curve (FTC) has decreased and/or in which the FTC tail has become hypersensitive. Inspired by this type of W-shaped FTC the mechanical response of the basilar membrane is phenomenologically modeled by two parallel filters, one responsible for the tip of the FTC, the other for its tail. Model simulations show that most abnormal temporal response properties can be explained by pathological alterations in the mechanical response. Residual discrepancies between model and experiment are identified which presumably point to pathological changes in other stages of cochlear processing.
The middle ear muscle of frogs does not modulate tympanic responses to sound
Authors: Hetherington Thomas E.
Published: October 2005

The effect of the opercularis (=middle ear) muscle on the acoustic responsiveness of the tympanic middle ear of anuran amphibians was studied using laser vibrometric measurements of tympanic responses to sound. Removal of the muscle or direct stimulation of denervated muscles had no measurable effects on tympanic responses to sound in either American bullfrogs (Rana catesbeiana) or green treefrogs (Hyla cinerea) at any frequency or at any sound-pressure level studied. These results suggest that, contrary to proposed hypotheses, the opercularis muscle of the anuran middle ear is not capable of modulating the responsiveness of the tympanic middle ear. Instead, the opercularis system most likely functions as an independent system involved in acoustic reception.
A computer model of amplitude-modulation sensitivity of single units in the inferior colliculus
Authors: Hewitt Michael J. , Meddis Ray
Published: October 2005

A computer model is presented of a neural circuit that replicates amplitude-modulation (AM) sensitivity of cells in the central nucleus of the inferior colliculus (ICC). The ICC cell is modeled as a point neuron whose input consists of spike trains from a number of simulated ventral cochlear nucleus (VCN) chopper cells. Input to the VCN chopper cells is provided by simulated spike trains from a model of the auditory periphery [Hewitt et al., J. Acoust. Soc. Am. 91, 2096–2109 (1992)]. The performance of the model at the output of the auditory nerve, the cochlear nucleus and ICC simulations in response to amplitude-modulated stimuli is described. The results are presented in terms of both temporal and rate modulation transfer functions (MTFs) and compared with data from physiological studies in the literature. Qualitative matches were obtained to the following main empirical findings: (a) Auditory nerve temporal-MTFs are low pass, (b) VCN chopper temporal-MTFs are low pass at low signal levels and bandpass at moderate and high signal levels, (c) ICC unit temporal-MTFs are low pass at low signal levels and broadly tuned bandpass at moderate and high signal levels, and (d) ICC unit rate-MTFs are sharply tuned bandpass at low and moderate signal levels and flat at high levels. VCN and ICC units preferentially sensitive to different rates of modulation are presented. The model supports the hypothesis that cells in the ICC decode temporal information into a rate code [Langner and Schreiner, J. Neurophysiol. 60, 1799–1822 (1988)], and provides a candidate wiring diagram of how this may be achieved.
Acoustic correlates of [b] and [w] produced by normal young to elderly adults
Authors: Slawinski Elzbieta B.
Published: October 2005

Various studies indicate that temporal characteristics of articulated subphonemic segments and syllables change as a function of age. The purpose of the present study was to investigate age-related changes in the production of a phonetic contrast—in particular that of the stop consonant [b] versus the semivowel [w]. Thirty-nine subjects with normal hearing and belonging to three age groups (20–30, 50–60, 70–80 years old) were tested. Acoustic analyses of the recorded syllables [b■] and [w■] indicated that duration of syllables, prevoicing, release, and vowel transition became significantly longer with the speaker’s age, except for the vowel transition in the [w] context. However, acoustic cues, such as the difference in amplitude change in the vicinity of the release segment, were not sensitive to the effects of aging.
A perceptual study of source coding of Fourier phase and amplitude of the linear predictive coding residual of vowel sounds
Authors: Ma Changxue , O’Shaughnessy D.
Published: October 2005

A practical question in a Fourier transform coding of speech signals is to what accuracy their amplitude and phase spectra have to be represented without perceptible distortions. In this paper a concern is with the audibility of quantization noise signals which are produced by quantizing the amplitude and phase spectra of vowel sounds. Experiments show that the detection of the noise targets with maskers of a low fundamental frequency is determined mainly by the sharpest temporal resolution of the auditory system in the high-frequency region. For maskers of a high fundamental frequency the detection is determined mainly by the sharpest spectral resolution in the low-frequency region. Noise targets with global random phase and amplitude are relatively more difficult to detect than those produced by a local randomization. Local random phase noise targets are generally more detectable than those produced by local amplitude randomization. The relative importance of phase and magnitude spectra in the Fourier transform coding is strongly dependent on the fundamental frequency of the vowel sounds and the window size used in the short-time Fourier analysis.
Production and perception of coarticulated tones
Authors: Xu Yi
Published: October 2005

In the present study, the distinctive tones of Mandarin were found to coarticulate with adjacent tones in running speech. However, the amount of deviation of a tone from its canonical form due to coarticulation varied depending on the nature of the tonal context. In a context where adjacent tonal values agree (a ‘‘compatible’’ context), the deviation was relatively small. In a context where adjacent tonal values disagree (a ‘‘conflicting’’ context), the deviation was much greater, sometimes even to the extent of changing the direction of a dynamic tone. To examine the perception of coarticulated tones, naturally produced words and phrases were used as stimuli for tone identification. However, their semantic information was removed through waveform editing while all the tonal information contained in the signal remained intact. Identification of tones in the compatible context was highly accurate with or without the original tonal context. Tonal identification for the conflicting context remained accurate only when the tones were presented with the original tonal context. Without the original context, i.e., in isolation, correct tone identification dropped below chance. When the original tonal context was altered, listeners compensated for the altered context as if it had been there originally. It thus seems that, in tone perception, listeners compensate for variations due to coarticulation. Nevertheless, even with the presence of the original context, perceptual identification was better for the compatible context than for the conflicting context, indicating that variation due to coarticulation is not always completely compensated for by listeners.
Fundamental frequency estimation of musical signals using a two-way mismatch procedure
Authors: Maher Robert C. , Beauchamp James W.
Published: October 2005

Fundamental frequency (F0) estimation for quasiharmonic signals is an important task in music signal processing. Many previously developed techniques have suffered from unsatisfactory performance due to ambiguous spectra, noise perturbations, wide frequency range, vibrato, and other common artifacts encountered in musical signals. In this paper a new two-way mismatch (TWM) procedure for estimating F0 is described which may lead to improved results in this area. This computer-based method uses the quasiharmonic assumption to guide a search for F0 based on the short-time spectra of an input signal. The estimated F0 is chosen to minimize discrepancies between measured partial frequencies and harmonic frequencies generated by trial values of F0. For each trial F0, mismatches between the harmonics generated and the measured partial frequencies are averaged over a fixed subset of the available partials. A weighting scheme is used to reduce the susceptibility of the procedure to the presence of noise or absence of certain partials in the spectral data. Graphs of F0 estimate versus time for several representative recorded solo musical instrument and voice passages are presented. Some special strategies for extending the TWM procedure for F0 estimations of two simultaneous voices in duet recordings are also discussed.
Impulse-response method to predict echo responses from targets of complex geometry. Part III. Application to nondestructive testing
Authors: Lhémery Alain , Raillon Raphaële
Published: October 2005

A theoretical model has been proposed for predicting the radiation of transient ultrasonic pulses, their scattering by targets of complex shape, and their reception. [A. Lhémery, ‘‘Impulse-response method to predict echo responses from targets of complex geometry. Part I. Theory,’’ J. Acoust. Soc. Am. 90, 2799–2807 (1991)]. Its computer implementation and experimental validation have also been considered [A. Lhémery and R. Raillon, ‘‘Impulse-response method to predict echo responses from targets of complex geometry. Part II. Computer implementation and experimental validation,’’ J. Acoust. Soc. Am. 95, 1790–1800 (1994)]. The accuracy of the model allows its application to a problem arising in classical NDT pulse-echo methods, namely, the discrimination of small defects and misoriented cracks. The echo-response from these two types of defects can produce the same B- or C-scan images in certain circumstances, leading to the possibility of serious misinterpretations. First, the relative importance of both the geometric and the electroacoustical parameters involved in the echo-forming mechanism is determined by a computer study conducted with our model’s implementation. Simple relations are found between the echo responses of the two kinds of defects. Insight gained from modeling such responses has led to the development of a new signal processing method to identify the defect. An example of its efficiency on measured waveforms is given.
Acoustic coupling to membrane waves on elastic shells
Authors: Norris Andrew N. , Rebinsky Douglas A.
Published: October 2005

The interaction of an acoustic field with a smooth thin shell in a fluid is described by the superposition of a background field plus membrane waves on the shell. The former is defined by a local impedance condition, which accounts for the inertia of the shell, but takes no account of the in-surface, membrane effects. The shell’s flexural stiffness turns out to be of secondary importance. The bulk of the paper deals with the coupling mechanism between the acoustic field and the supersonic membrane waves, both longitudinal and shear. The coupling is mediated by the shell curvature, and vanishes when the curvature vanishes. Ray methods are used to express the membrane waves by curved wave fronts with amplitudes subject to a transport equation over the curved shell surface. The coupling, and decoupling or launching, then reduces to solving an ordinary differential equation for the unknown ray amplitude. In essence, the transport equation is forced, or ‘‘beaten’’ by the locally phase-matched background field. Explicit expressions are obtained for the coupling and detachment coefficients on arbitrarily curved regions. These are combined, using ray theory for the propagation over the shell, to give the scattered field due to rays traveling over the shell. The general results are explicitly tested on the cylinder and sphere, for which the ensemble of surface rays can be summed into a resonance form, and numerical comparisons are made with the exact results for these canonical geometries.
The asymptotic computational ansatz: Application to critical angle beam transmission boundary integral equation solution
Authors: Roberts R. A.
Published: October 2005

Surface wave generation arising from critical angle beam transmission at a smooth but arbitrarily curved fluid–solid interface is studied using a numerical boundary integral equation (BIE) technique that incorporates a priori field information to significantly reduce computation. The technique substitutes a GTD-type computational ansatz into the BIE, where the phase factors of the ansatz are prescribed via asymptotic analysis, thus transforming the unknown variables to slowly varying amplitude factors. In situations where the asymptotic evaluation of these amplitude factors becomes intractable or inaccurate, common numerical integral equation methods are employed to determine the amplitude factors. The technique yields exact (in the numerically convergent sense) results for high-frequency scattering problems unsolvable by prevalent analytic or numeric techniques. Numerical implementation of the technique for critical angle beam transmission is demonstrated.
Sound scattering by slender bodies of arbitrary shape
Authors: Tran Van Nhieu Michel , Ywanne Frédérique
Published: October 2005

Scattering of a spherical wave from a perfectly rigid slender body of arbitrary shape is considered. The point source is assumed to be located in the far field of each body cross section but may be placed in the near field of the target. The problem is investigated theoretically with the matched asymptotic expansions method and an approximate solution is derived for the scattered pressure, which takes into account the curvature of the incident wave front. The presented formalism combines the so-called slender-body approximation and the two-dimensional Kirchhoff theory. It allows a great simplification in the geometrical description of the body surface and leads to a practical method even for bodies of complex shape. In the monostatic case, it is theoretically shown that the obtained solution is asymptotically equivalent to that provided by geometrical optics for a large class of finite scatterers. Lastly, monostatic and bistatic angular distributions are computed for a prolate spheroid in the near and far fields to support the present theory.
On the determination of the elastic moduli of anisotropic media from limited acoustical data
Authors: Ditri John J.
Published: October 2005

The determination of the elastic moduli of generally anisotropic media from acoustic information has a long history. It is known that, given measurements of the three wave speeds and corresponding polarization vectors in various directions n̂∈R3, all 21 elastic moduli can be determined [A. N. Norris, Q. J. Mech. Appl. Math. 42, 413 (1989)]. However, in some practical cases, depending upon the type of loading a structure will see, not all 21 elastic moduli are needed, and it is therefore of interest to know how many of the constants can be determined from a less robust data set. In this paper, upper bounds are placed on the number of elastic constants that can be determined from acoustic data, which is limited to one or two planes. It is shown that for generally anisotropic media, 15 elastic constants can be uniquely obtained from data taken in one plane, and 20 of the 21 elastic constants can be uniquely obtained from data taken in two planes. Specific examples are given to illustrate the general results.
Calculation of transient tube-wave signals in cross-borehole acoustics
Authors: de Hoop Adrianus T. , de Hon Bastiaan P. , Kurkjian Andrew L.
Published: October 2005

Closed-form expressions are obtained for the transient acoustic pressure in a borehole, due to the action of a volume injection (acoustic monopole) source in another borehole in a typical cross-well seismic setting with a homogeneous isotropic solid formation. At the relatively low frequencies involved the acoustic wave motion inside a fluid-filled borehole, which may be surrounded by a structure of perfectly bonded circularly cylindrical solid shells, is dominated by tube waves. The excitation and propagation properties of the tube wave are modeled by regarding the borehole as an acoustic waveguide with a compliant inner wall. The corresponding elastic wave-field quantities at the outer borehole wall are evaluated through a plane-strain elastostatic transfer of the stress and the elastic displacement across the shell structure. For the radiation of the wave-field quantities into the formation, the elastodynamic Kirchhoff–Huygens integral representation is used. The acoustic pressure on the axis of the receiving borehole is evaluated with the aid of the fluid/solid acoustic reciprocity theorem. Various physical phenomena are described by the resulting expressions, including pre- and postcritical phenomena (conical waves) for slow formations, and tunnelinglike phenomena for proximate boreholes in fast formations.
Oscillation modes of underexpanded jets issuing from square and equilateral triangular nozzles
Authors: Umeda Y. , Ishii R.
Published: October 2005

The oscillation modes of underexpanded jets exhausted from square and equilateral triangular nozzles were investigated experimentally. Two stages were observed for both jets. The oscillation modes corresponding to these stages were identified by using optical and acoustical methods. The experimental results show that oscillation modes for both jets are first axisymmetric and then sinuous with increasing jet pressure ratio. The helical oscillation mode, which appeared for the circular jet, was not observed in these jets. The hysteresis phenomenon found for the circular jet cannot be seen in these jets.
A small-slope theory of rough surface scattering
Authors: McDaniel Suzanne T.
Published: October 2005

A method due to Urusovskii [Sov. Phys. Acoust. 5, 362–369 (1959)] is applied to predict the field scattered by rough pressure release surfaces. Comparison of the predictions of this theory for scattering from a sinusoidal surface shows that his method yields results closer to an exact solution than do other approximations. When applied to predict the coherent field scattered by a random rough surface, the predictions agree well with those of the Kirchhoff approximation provided that the horizontal wave-number component of the incident field is much greater than the wave numbers at which the spectral decomposition of the surface irregularities attains its maximum value. For high-frequency scatter near the forward direction, Urusovskii’s theory yields a new result that provides a significant improvement to the Kirchhoff approximation.
Long-range backscatter from the Mid-Atlantic Ridge
Authors: Makris Nicholas C. , Berkson Jonathan M.
Published: October 2005

Acoustic backscatter returns measured with a vertical source and horizontal receiving array are beamformed and charted to respective scattering sites on the western flank of the Mid-Atlantic Ridge (MAR). Well-defined patterns of high-level backscatter resembling bottom morphology occur within the direct path and at convergence zone ranges. Measured backscatter is compared with modeled two-way transmission loss using the wide-angle parabolic equation (PE) and high-resolution supporting bathymetry. The level of backscatter is found to be strongly dependent upon two-way transmission loss (TL). Specifically, TL selects prominent bathymetric features from which high backscatter is returned, with backscatter maxima corresponding to TL minima. Scattering strength estimated for the wide area surveyed shows low variance and relatively minimal spatial variation. Apparently, distinct scattering contributions are so well mixed in long-range backscatter, that dominant variations are generally due to propagation. These results indicate that it is possible to forecast the range and azimuth of prominent MAR backscatter returns simply by propagation modeling if high-resolution bathymetry is available. They also have led to the development of a new technique for ambiguity removal in reverberation data measured with a horizontal line array. The method takes advantage of environmental asymmetry provided by TL in highly range-dependent environments and does not require multiple measurements as do other existing methods.
A theoretical study of low-frequency oceanic ambient noise
Authors: Og̃uz H. N.
Published: October 2005

This paper describes a theoretical model that predicts the wind-dependent ambient noise level in the ocean. Wave breaking and subsequent formation of whitecaps are assumed to be the sole source of sound at the sea surface and their contributions are computed by the use of a simple model for the bubble cloud generated by this process. Inverted hemispherical shapes for which an analytical solution to the wave equation is given are employed to describe the cloud geometry. The input physical parameters to the model are the bubble-size distribution, the dipole strength of the entrained bubbles, the cloud size distribution and growth rate, and the void fraction of the bubble cloud. By using an empirical relation between the whitecap coverage ratio and the wind speed, the underwater ambient noise and surface source levels are computed as a function of frequency and wind speed. Calculated noise levels are in good agreement with the field measurements.
Acoustical measurements of microbubbles within ship wakes
Authors: Trevorrow Mark V. , Vagle Svein , Farmer David M.
Published: October 2005

High-frequency sonar measurements of target strength due to microbubbles were obtained within the wakes of three oceanographic vessels. Two self-contained, high-frequency acoustics instruments suspended at 25-m depth were used to measure the wake acoustic properties during three separate sea trials. The backscatter cross section per unit volume, Mv, as a function of depth and time was calculated from the echo intensity of six upward-looking, conical beam sonars (28–400 kHz). Four 100-kHz steerable sidescans allowed measurement of wake locations, widths, and persistence. In the near-surface core of the wake Mv reached peak values of approximately 0.3 m−1 for the 120- and 200-kHz sonars. The volumetric scattering cross sections were observed to be roughly constant at all frequencies within the top 5–6 m of the wake, suggesting a roughly homogeneous vertical bubble distribution. However, differences in the volumetric backscatter at different acoustical frequencies suggest a higher relative concentration of larger bubbles (≳100 μm) in the center of the wake. The ship wakes were observed to spread to typical widths of up to 66 m (ship speed 10 kn) and to depths of 7–12 m and to persist as strong acoustic scatterers for approximately 7.5 min. Gas diffusion causing bubble dissolution is suggested as the mechanism for decay of the wake bubble clouds.
Mode theory as a framework for the investigation of the generation of a Stoneley wave at a liquid–solid interface
Authors: Briers R. , Leroy O. , Shkerdin G. N. , Gulyaev Yu. V.
Published: October 2005

A theoretical model, based on mode theory for acoustic waves, is presented in order to describe the complicated scattering of an ultrasonic volume or surface wave at the boundary between two adjacent liquids abutting a single solid. Analytical expressions for the displacement fields of the scattered and mode-converted waves are derived. In particular, it is shown that a volume wave incident from the liquid of the first liquid/solid structure can generate a Stoneley wave along the interface of the second liquid/solid structure. The relative amplitude of the displacement of the excited Stoneley wave is calculated for several (liquid–liquid)/solid configurations. The angle of most efficient excitation can be derived from the maximum of the function describing the interaction between a radiation mode and a Stoneley eigenmode in the division plane separating both liquid/solid structures.
A fundamental study of the excitation of a Stoneley wave at a liquid–solid interface: Rayleigh angle and Gaussian beam incidence
Authors: Briers R. , Leroy O. , Shkerdin G. N.
Published: October 2005

Theoretical calculations show that near the Rayleigh angle the amplitude of the Stoneley wave generated by a homogeneous plane wave incident at the intersection between two liquids overlying a single solid has a local maximum. This maximum is very small compared with the one obtained for almost normal incidence at the mentioned intersection when the most efficient excitation occurs. The paper also presents numerical results for the generation of a Stoneley wave by means of an incident Gaussian beam. Finally, a very simple to interpret expression for the amplitude of the excited Stoneley wave is given.
An analytical evaluation of the heating of low-frequency sonar projectors
Authors: Dubus Bertrand , Boucher Didier
Published: October 2005

Heating has become a critical issue for low-frequency projectors for sonar and oceanography due to their high dissipated power density and long excitation time. An analysis of the transducer heating requires a description of the heat conduction in the structure and of the heat exchanges with the surrounding medium. To solve this problem for the steady-state case, an analytical model of the heat transfer in the projector, based on thermoelectrical analogies, is proposed. The model is applied to the analysis of heat transfer in two geometries of low-frequency projectors: a double-ended longitudinal vibrator and a class IV flextensional transducer. In each case, temperature and heat fluxes are calculated and compared to numerical results from a finite element analysis.
Image-derived second-order differential microphones
Authors: Elko Gary W. , West James E. , Kubli Robert A. , McAteer Jeffrey P.
Published: October 2005

Second-order differential toroidal and unidirectional microphones derived using a bipolar first-order differential sensor and a reflecting plane are described. The bipolar first-order differential microphone is positioned with its axis perpendicular to and suspended a few centimeters from a large acoustically reflecting surface. The resulting sensor image is phase reversed resulting in a transducer that is a linear quadrupole. The linear quadrupole can be described by two dimensions, the distance corresponding to the dipole distance and twice the distance from the reflecting plane. If the reflecting surface is large enough or if the wall of a room is used, the resulting microphone becomes a second-order differential unidirectional microphone. The match between the sensor and its image from a good acoustic reflector results in a second-order differential microphone with 3-dB beamwidth of ±33° and no grating lobes below 3 kHz for a 2.5-cm spacing between the sensor and reflecting surface. A wall-mounted toroid can be formed by using two bipolar first-order sensors at right angles to each other and with the axis of each sensor at 45° to the reflecting surface and a spacing between transducers that is twice the height of the transducers from the reflecting plane. A table-mounted toroid can be realized by properly combining a filtered version of a suspended first-order sensor and an omnidirectional sensor flush mounted to the reflecting table top.
Pilot study on cross-language transformation of vowels
Authors: Huang Caroline B.
Published: October 2005

This pilot study explores an aspect of speaker individuality, the individual’s vowel space, when one person speaks two languages. It is asked whether a speaker’s characteristic range of vowel formant frequencies can be measured in one language and used, in conjunction with vowel data found in the literature, to model the speaker’s vowel space in the other language. One practical application of the results would be to make a computer speech recognition system used as a pronunciation trainer speaker-adaptive. Vowel data are being gathered from a small set of bilingual speakers of English and Italian and English and Mandarin Chinese. Linear and nonlinear transformations for converting the F2 vs F1 plots of each of the bilinguals between the appropriate languages will be explored, in an approach similar to those of Disner [J. Acoust. Soc. Am. 67, 253–261 (1980)] and DiBenedetto [ICSLP 92, 579–582 (1990)]. The adequacy of the transformations and of the simple vowel representation employed, i.e., F1 and F2 midpoints, will be discussed.
Acoustical rainfall analysis
Authors: Nystuen Jeffrey A.
Published: October 2005

Acoustical rainfall analysis (ARA) will provide the means to make needed rainfall measurements in oceanic regions. A prototype ARA algorithm will be presented. It consists of (1) the detection of rainfall in the presence of other underwater noise sources, (2) the classification of rainfall type based on drop size distribution, and (3) the acoustic quantification of rainfall rate. Historical data will be presented to document the acoustic detection of rainfall in oceanic situations. Recent field data demonstrating acoustic classification of rainfall type will be presented and explained using laboratory studies of sound produced by individual raindrops. Classification of rainfall type (stratiform/convective) will allow meteorologists to infer the vertical distribution of latent heat release in the atmosphere. Quantification of rainfall rate can be achieved by several different types of algorithms. Selected quantification algorithms will be presented, compared, and evaluated.
A study of the Patterson and Holdsworth auditory model and its utility in automated recognition of the plosive consonants
Authors: Pardo Bryan , Josephson John
Published: October 2005

The suitability of the Patterson and Holdsworth auditory model as a front end for speech recognition was studied by measuring the ability of neural networks trained on input from the P&H model to distinguish between the plosive consonants, using networks trained on fast Fourier transform (FFT) input as a control. Numerous experiments were performed to control for speaker dependence, network weight and architecture bias, utterance ordering, and other variables. The results indicate that the P&H model provides an advantage over a plain FFT. In every experiment, agents trained on the P&H mode categorized test stimulus more accurately than did FFT trained networks, while maintaining comparable training times. A typical experiment gave a result of 66% correct stimulus response for the P&H trained networks versus 12% for the FFT trained networks. Moreover, errors made by the P&H trained networks were ‘‘good’’ ones, such as mistaking /b/ for /p/, indicating learning took place. The Patterson and Holdsworth model processes the audio signal through (among other steps) adaptive thresholding and, especially, triggered temporal integration of the signal. The results of this experiment may be useful in focusing future research on studying the acoustic features made prominent by the P&H model and their importance to speech.
Vocal effort as a cue for linguistic stress
Authors: Sluijter Agaath M. C.
Published: October 2005

Intensity differences as a function of stress are mainly located above 0.5 kHz [A. M. C. Sluijter and V. J. van Heuven, Proc. ESCA Workshop on Prosody, Lund, 246–249 (1993)]. Results of a perception experiment bear out that intensity manipulations in this region provide stronger stress cues than uniform intensity differences do, and are close in strength to duration differences. The differences in energy in the higher bands were arguably caused by a difference in the shape of the glottal-pulse waveform. However, energy differences were measured in separate filter bands, thereby not removing the effects of vocal tract and lip radiation. These latter effects could also be different for stressed and unstressed syllables. Now, instead of investigating the energy differences in separate filter bands, voice source and vocal tract were studied separately. Ten American subjects produced minimal stress pairs. The differences in the glottal-pulse shape with which the vowels were produced were determined using inverse filtering. By removing the vocal tract and the lip-radiation effects, the glottal-pulse waveform is revealed. The hypothesis was tested that the glottal-pulse waveform of a stressed vowel is more pulse-like than that of an unstressed vowel, which in turn has a more sinusoidal shape.
In vitro measurements of the cavitation thresholds and the corresponding value of the Mechanical Index (MI)
Authors: Xu Qihong , Zheng Xiaoyu , Apfel Robert
Published: October 2005

To study the potential for cavitation-related bio-effects, invitro microcavitation events were generated using 2.46- and 4.3-MHz transducers and were detected in both distilled water seeded with polystyrene particles and in human blood under conditions similar to those found in the application of clinical diagnostic ultrasound. For the 2.46-MHz transducer, the measured cavitation thresholds range from 4 MPa in whole blood to 1 MPa in distilled water seeded with the polystyrene particles of 0.1 μm diam. The mechanical index (MI) corresponding to the above cavitation thresholds was calculated and found to be in the upper range of the MIs achievable with some commercial diagnostic ultrasound equipment. [This work was supported by NIH through Grant. No. R01 CA39374.]
Signals and processing for acoustic monitoring of ocean processes
Authors: Birdsall Theodore G. , Metzger Kurt
Published: October 2005

The ultimate goal of acoustic monitoring of ocean processes is to provide quality measurements of the right type to be assimilated into worldwide climate models. The immediate goals are to achieve the travel time resolution and accuracy necessary to provide the oceanographer and climate modeler with identifiable receptions of multipath or multimode arrivals. The economic antagonists are the hardware costs. The natural antagonists are signal spreading, attenuation, dispersion, scattering, continual change, human uncertainty, and noise. This paper illustrates how a signal processor can help organize the balances, lay out the interactions, and provide workable solutions. Examples from current measurements will be used to illustrate effective signal handling.
Evidence for physiological correlates of the precedence effect in the inferior colliculus of kittens
Authors: Litovsky Ruth Y.
Published: October 2005

Physiological correlates of the precedence effect (PE) were studied by recording from single cells in the inferior colliculus of young kittens and adult cats. This effect is interesting from a developmental perspective since it appears to be absent in newborn animals including human infants and dogs, but develops after the first few months of life [Clifton, in AuditoryDevelopmentinInfancy (Plenum, New York, 1985)]. Experiments were conducted in an anechoic chamber. PE stimuli were generated by presenting two successive clicks from two different speakers, with a variable time delay between them. Kittens were studied at the ages of 5–28 days postnatal. At all ages, most units displayed ‘‘echo suppression;’’ they responded to both the leading and lagging sounds at long delays (≳30–60 ms), with a suppressed response to the lagging sound at short delays. There seem to be no differences in the physiological manifestations of the PE between kittens and adult cats. Correlates of psychophysics related to the PE, which were found in the responses of adult neurons, were also present in kitten neurons. It seems that the neural circuitry involved in the initial stages of the PE may develop very early in life, prior to the onset of corresponding behaviors. [Work supported by NIH.]
An algorithm for fast computing spatial array three-dimensional sound directivity
Authors: Huang Dehua , Boucher Stephen
Published: October 2005

The ability to quickly predict spatial array radiation or receiver directivity is vital to acoustical array design, directivity synthesis, reflective wave cancellation by object active spatial (nonplanar surface) array, etc. A fast algorithm is developed to numerically simulate spatial array three-dimensional directivity, based on local element or subarray directivity and system spatial array directivity mapping technique. The spatial array is composed of a set of single elements or subarrays with an arbitrary weighting function. Further, the normal direction of the element or subarray active surface in the spatial array can be rotated in any direction in the system coordinates. Both theoretical derivation and mathematical approach are demonstrated. Numerical simulations and experimental verification of various examples are presented. The baffle effects due to finite baffle size and different backing materials of the array are considered by introducing a baffle function during the numerical simulation.
Acoustic remote sensing instrumentation for sediment transport research
Authors: Hay Alex E.
Published: October 2005

Sediment transport in the oceanic bottom boundary layer involves threefold coupling among: (1) the motion of sediment grains; (2) the response of the bed; and (3) the fluid forcing. The appeal of acoustic remote sensing methods is that in principle all three components of the problem can be addressed with minimal disturbance to the system. This paper reviews the progress that has been made to date toward developing acoustic instrumentation systems for sediment transport measurements in the nearshore zone, where sand is the principal component of the bottom sediments. Instrument developments are discussed in relation to several types of measurement requiring multiple acoustic beams: (1) range-gated multifrequency backscatter to obtain profiles of suspended sediment concentration and size, and the associated inverse problem; (2) bedform imaging with fan-beam sonars; (3) suspended sediment fluctuations under waves. The results provide revealing insights into the sediment transport process, and thus demonstrate the effectiveness of the multibeam approach. The results also raise a number of fundamental questions. Some of these questions can be addressed with the instrumentation currently at hand. Others will require a new generation of instruments.
Acoustical scattering from plumes of sediment suspended in open waters
Authors: Ogushwitz Paul R.
Published: October 2005

Acoustical data from a field survey at a disposal site for dredged materials near Mobile Bay, Alabama, are analyzed. During the survey, two independent acoustical instruments provided measurements of echo strength from vertical plumes of suspended sediments. Particulate concentrations and grain size distributions were determined from insitu water samples. Quantitative analysis of the measurements indicates that the acoustical echoes from the suspended sediments are dominated by Rayleigh backscattering. The best fit to data is achieved when the measured decrease of grain size with decreasing concentration is explicitly accounted for. Attenuation appears to play a significant role at high concentrations (i.e., within the dense part of the plume). For the grain sizes studies here (1–200 m), viscous effects account for at least 90% of the attenuation. When the theoretical estimates are subtracted from the data, the residual echo strength is seen to increase with decreasing concentration; some possible causes of this are beam-to-beam variability, effects of grain shape, and factors related to experimental design. One of the instruments measured echo strength on four beams simultaneously; the average beam-to-beam variability was about 3 dB, corresponding to a precision of about 50% in the measured concentration. [Work supported by U.S. Army, Corps of Engineers, Dredging Research Program.]
Scattering of underwater sound by algae
Authors: Shenderov E. L.
Published: October 2005

The theoretical investigation of scattering underwater sound waves by algae has been performed. The dependencies of sound level in the reflection waves upon parameters of the algae (sizes, biomass) are determined. For this purpose physical models corresponding to the typical kinds of the algae are developed. Scattering of sound by the algae are considered as the diffraction of the sound wave on the random set of the three-dimensional curved elastic bodies. By solving Helmholtz equation for the definite boundary conditions on the surface of the bodies, sound pressure in the waves scattered by the acoustic semi-transparent curved plates and rods corresponding to the plates and stems of the algae are computed. The obtained results can be used for the development of hydroacoustic methods of investigation of the continental shelf and also for reconnaissance of the algae abundance.
Electrostriction in polyurethanes as measured by laser Doppler vibrometry
Authors: Balizer E. , Lee J. D. , Guillot F. , Jarzynski J.
Published: October 2005

The electrostriction of polyurethanes of two widely different morphologies were measured by laser Doppler vibrometry (LDV). The typical morphology of a polyurethane is that of two separated phases, one of hard regions embedded in the second of a soft elastic matrix. In contrast to this is a polyurethane of a single homogenous phase (i.e., phase mixed). A postulated mechanism for electrostriction is the relaxation, under electric field, of the elastic matrix which is strained in the phase separated system and not in the phase mixed system. To test this hypothesis, both of these systems were synthesized and their d33 coupling coefficient was determined from measurements of the out-of-plane displacement. The measured electrostriction coefficient at 250 Hz, for bilayers, for the phase separated system is 0.20 A/V (514 V/mil bias) and for the phase mixed system is 0.55 A/V (316 V/mil bias). The larger value for the phase mixed system is in accord with its modulus being less than that of the phase separated system and not a mechanism due to a prestrained soft segment. Details of sample mounting specific to thin films (1 mil) and sampling statistics for d33 as measured by LDV will be given.
Accent-bearing units
Authors: Turk Alice E.
Published: October 2005

This paper presents acoustic evidence for the nature of accent-bearing units in American English. The interactive effects of accent and syllable affiliation on consonant duration were examined to see if the effect of accent on syllable margins depends on their syllable affiliation. Results show a greater effect of accent on syllable onsets than on syllable codas. Although the nature of the rime is known to influence the location of stress placement in English, the findings presented here suggest that the entire syllable, rather than the nucleus or rime, is the accent-bearing unit. [Work supported by NIH Grant Nos. R01DC00219 and T32-DC00036 to SUNY at Buffalo.]
Acoustical modeling for use in the engineering design of waveguides
Authors: Tsai Jianming
Published: October 2005

Many situations exist in which sound waves are constrained to propagate in waveguides. If the diameter is small compared to the wavelength of sound to be propagated, it implies that only plane waves propagate in a cylindrical tube or spherical waves in a horn. The input impedance of any axially symmetric waveguide is of primary importance to simulate fluid resonance behavior before an actual engineering design is made. This acoustical model implements a frequency domain characteristic based on the ABCD transformation matrix [A. H. Benade, J. Acoust. Soc. Am. 83, 1764–1769 (1988)]. The input impedance is expressed in terms of the ABCD matrix, which relates ‘‘input-end’’ (p1, u1) pressure and flow to the ‘‘output-end’’ pressure and flow (p2, u2). Any complicated waveguide system can be treated as a combination of a number of uniformly shaped waveguides, and thus the resultant ABCD matrix can be the product of the individual matrices from the input to the output ends. Experimental results as well as numerical predictions for a nozzle used in an industrial ink jet printer are presented and discussed.
A robust method for computing the reflection coefficient from a multilayered bottom with shear
Authors: Westwood Evan K. , Levinson Scott J.
Published: October 2005

An analytic method for computing the plane wave reflection coefficient from a multilayered ocean bottom with shear has been developed. The compressional (p-) and shear (s-) wave sound speeds may either be constant in a layer or have a gradient (in which case coupling is ignored). Propagator matrices that involve exponentials or Airy functions are used to solve for the p-wave and s-wave displacement potentials at the top of each layer in terms of the same quantities at the bottom of each layer. Several key steps are critical to making the calculations robust: (1) Reflection coefficients (p-p, p-s, s-s, and s-p), rather than potentials, are computed at the top of each layer, (2) numerically unstable Wronskian terms are replaced by their analytic formulas in the p-s and s-p reflection coefficients, and (3) exponential factors common to the p-s and s-p reflection coefficients are kept track of separately. Analytic derivatives of the reflection coefficients with respect to angle and frequency have been derived and implemented. The method requires very little computer storage, and the analytic form is computationally efficient compared to numerical methods, especially as the frequency increases. [Work supported by the ARL Independent Research and Development Program.] a)On leave from Appl. Res. Lab., The University of Texas at Austin.
Visualization of displacement waves, sound-power flow and other elastic quantities in underwater structures excited by incident sound
Authors: Hickling Robert
Published: October 2005

Visualization methods are presented for the computed elastic response of underwater structures excited by continuous sound. Video animations show that the elastic behavior is dominated by waves whose displacement moves on paths around a center of oscillation. Such rotational waves, or turbules, occur even inside thin shells, the function of the waves being to change the direction of flexural motion. Computed results are presented for canonical shapes such as spheres and spherical shells. For more complex structures the elastic response will be similar. Different types of visualization of the amplitude and direction of vector quantities are discussed. Also discussed is visualization of the behavior of different elastic quantities in the structure.