bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic scattering from a simulated cavity in steel
Authors: Lawu Tjundewo , Ueda Mitsuhiro , Tabei Makoto
Published: October 2005

The scattering of wideband ultrasonic pulses from simulated cavities in a metal block was estimated using a mathematical description of the echo based on the expression for echoes reflected from a strongly scattering object. The theoretically estimated echo waveforms and the corresponding Fourier power spectra of the scattered pulses are compared with those obtained experimentally with good agreement. Interpretations show that both the pulse-time record and the power spectrum can be utilized to detect roughly the shape of a cavity in a metal block.
A three-dimensional dyadic Green’s function for elastic waves in multilayer cylindrical structures
Authors: Lu Cai-Cheng , Liu Qing-Huo
Published: October 2005

The three-dimensional dyadic Green’s function for multilayer cylindrical structures is very important for solutions of elastic waves with arbitrary sources in such media. Both the primary and reflected parts of this Green’s function are expressed as a Fourier integral in z (axial coordinate) and a Fourier series in θ (azimuthal coordinate). In this spectral domain, the reflection matrices can be found recursively by using the boundary conditions at the layer interfaces. Inverse transforming this solution yields the dyadic Green’s function in the spatial domain. The Green’s function derived and implemented is applicable to arbitrary cylindrically layered media, including three types of interfaces: (i) fluid/solid interfaces, (ii) well-bonded solid/solid interfaces, and (iii) unbonded solid/solid interfaces. Various numerical results from previous methods for simpler cases and several specially designed simulations validate the numerical implementation. With the Green’s function, one can solve for fields due to an arbitrary source located at an arbitrary position using the superposition principle. This provides a powerful tool for the modeling of effects from defects and material inhomogeneities in cylindrical structures.
Energy-conserving reflection and transmission coefficients for a solid–solid boundary
Authors: Ainslie Michael A. , Burns Peter W.
Published: October 2005

Intensity reflection and transmission coefficients are considered for a solid–solid boundary. Commonly used definitions are shown to lead to an apparent conflict with the energy conservation principle, because their sum can exceed unity, even when the propagation vector of the incident wave is real. An alternative definition is proposed, based on the acoustic Poynting vector, and explicitly conserving energy. The complex ‘‘instantaneous energy’’ introduced by Deschamps [J. Acoust. 3, 251–261 (1990)] is also discussed, leading to a simple equation relating the amplitude coefficients, which can be used as a check on their numerical values.
Expressive timing in Schumann’s ‘‘Träumerei:’’ An analysis of performances by graduate student pianists
Authors: Repp Bruno H.
Published: October 2005

Statistical analyses were conducted on the expressive timing patterns of performances of Schumann’s ‘‘Träumerei’’ by ten graduate student pianists who played from the score on a Yamaha Disclavier after a brief rehearsal. A previous study of acoustic recordings of ‘‘Träumerei’’ by 24 famous pianists [B. H. Repp, J. Acoust. Soc. Am. 92, 2546–2568 (1992)] provided ‘‘expert’’ timing data for comparison. In terms of group average timing pattern, individual shaping of ritardandi, and within-performance consistency, the students turned out to be quite comparable to the experts. This demonstrates that precision in expressive timing does not require extensive study and practice of the music at hand, only general musical and technical competence. Subsequent principal components analyses on the students’ timing patterns revealed that they were much more homogeneous than the experts’. Individual differences among student pianists seemed to represent mainly variations around a common performance standard (the first principal component), whereas expert performances exhibited a variety of underlying timing patterns, especially at a detailed level of analysis. Experienced concert artists evidently feel less constrained by a performance norm, which makes their performances more interesting and original, hence less typical. Since the norm may represent the most natural or prototypical timing pattern, relatively spontaneous performances by young professionals may be a better starting point for modeling expressive timing than distinguished artists’ performances.
Compensation strategies for the perturbation of the rounded vowel [u] using a lip tube: A study of the control space in speech production
Authors: Savariaux Christophe , Perrier Pascal , Orliaguet Jean Pierre
Published: October 2005

A labial perturbation of the French rounded vowel [u] was used to examine the respective weights of the articulatory and acoustic levels in the control of vowel production. A 20-mm-diam lip tube was inserted between the lips of the speakers. Acoustic and x-ray articulatory data were obtained for isolated vowel productions by 11 native French speakers in normal and lip-tube conditions. Compensation abilities were evaluated through accuracy of the F1–F2 pattern. Possible compensations were examined from nomograms using the new model of Fant [ISCLP 92 Proceedings (University of Alberta, Edmonton, 1992)]. Acoustic interpretations of the articulatory changes were made by generating area functions from midsagittal views, used together with a harmonic acoustic model. For the first perturbed trial, immediately after the insertion of the tube, no speaker was able to produce a complete compensation, but clear differences between speakers were observed: Seven of them moved the tongue and hence limited the deterioration of the F1–F2 pattern, whereas the remaining four did not show any pertinent articulatory change. These data support the idea of speaker-specific internal representations of the articulatory-to-acoustic relationships. The results for the following 19 perturbed trials indicate that speakers used the acoustic signal in order to elaborate an optimal compensation strategy. One speaker achieved complete compensation by changing his constriction location from a velo-palatal to a velo-pharyngeal region of the vocal tract. Six others moved their tongues in the right direction, achieving partial acoustic compensation, while the remaining four did not compensate.

The control of speech production thus seems to be directed toward achieving an auditory goal, but completely achieving the goal may be impossible because of speaker-dependent articulatory constraints. It is suggested that these constraints are due more to speaker-specific internal representation of articulatory-to-acoustic relationships rather than to anatomical or neurophysiological limitations. Speech control could thus be ensured partly with the use of this internal representation, and partly—particularly under perturbed conditions—by monitoring the acoustic signal.
Enhancement of female esophageal and tracheoesophageal speech
Authors: Qi Yingyong , Weinberg Bernd , Bi Ning
Published: October 2005

Qi [J. Acoust. Soc. Am. 88, 1228–1235 (1990)] has demonstrated that (1) linear predictive (LP) methods can be used to separate vocal tract transfer functions from source functions of vowels produced by alaryngeal talkers and that (2) vowels synthesized with reconstructed transfer functions and totally synthetic voicing excitation sources have improved source-related properties over those present in the original vowels. Here, an extension of this work which is directed to the general goal of developing systems (devices) to enhance the quality of alaryngeal speech is reported. The specific goal of the present project was to determine whether speech, i.e., words spoken by female esophageal and tracheoesophageal talkers, could be enhanced by means of LP-based analysis and synthesis methods. Words spoken by four female alaryngeal talkers were analyzed and synthesized. A perceptual evaluation was completed to permit the quality of the synthetic and the original words to be compared. Listeners generally preferred to listen to the synthesized words, indicating that alaryngeal speech enhancement was accomplished.
Detectability of simultaneously masked signals as a function of signal bandwidth for different signal delays
Authors: Wright Beverly A.
Published: October 2005

The improvement in signal detectability as signal onset is delayed from masker onset was measured as a function of signal bandwidth for wideband and notched-noise maskers. The signal was centered at 2500 Hz. In two conditions, the 20-ms signal was gated 1 or 250 ms after the onset of a 420-ms masker. Although there were marked individual differences, the signal was consistently more difficult to detect in the short-delay than in the long-delay condition. The difference in detectability decreased as signal bandwidth increased and was similar in magnitude across the two masker types. This result indicates that an across-channel process contributes to the improvement in detectability as the signal delay is increased, because the masking components at the signal frequency in the wideband masker exerted very little influence on the size of the effect. In a third condition, the signal was gated 1 ms after the onset of a 23-ms masker. The signal was hardest to detect in this burst condition, and performance varied differently as a function of signal bandwidth in this than in the other two conditions, particularly for the notched-noise maskers. This outcome suggests the presence of a second across-channel process that is sunsitive%to masker%ocfsets, especi‘lly when theze are no%masking componegts%at tha smgnal%frequency. Finally, the pattezn%of%results obtained across the thzee conditions using Thd%sidec‘nd masker was consistent with the i‘ea that the critical bandwidth narrows as the signal is delayed from masker onset.
Comment on ‘‘On the crossing points of Lamb wave velocity dispersion curves’’ [J. Acoust. Soc. Am. 93, 1893–1895 (1993)]
Authors: Freedman Albert
Published: October 2005

In their paper ‘‘On the crossing points of Lamb wave velocity dispersion curves’’ [J. Acoust. Soc. Am. 93, 1993–1995 (1993)], Zhu and Mayer (ZM) presented procedures to predict the locations of crossing points of antisymmetric and symmetric Lamb mode branches. Attention is drawn here to relevant earlier work. Two separate formulas in ZM’s paper for the phase velocities at the crossings are seen to reduce to a single solution agreeing with a solution by Mindlin, but omitting an important, necessary proviso. Thus ZM’s solution can yield false results. It is noted that the above crossings of the dispersion curves for Lamb modes coincide with crossings of dispersion curves for two families of conversion modes and that there are additional crossings when the Poisson ratio is less than 0.263.
Acoustic coupling to supersonic helical waves in cylindrical shells
Authors: Cole John E.
Published: October 2005

An aspect of shear and compressional wave propagation in thin cylindrical shells is examined as it relates to the mechanism of enhanced scattering. It is shown that the Cartesian definition of helical wave numbers in the shell coincides with antiresonances of the radial shell motion excited by radial loads. At these precise wave numbers, shear or compressional resonances in the shell are not excited by an acoustical wave incident on the shell’s cylindrical surface.
Auditory filter shapes at high frequencies
Authors: Zhou Bin
Published: October 2005

The shape of the auditory filter was estimated at center frequencies of 4, 12, 14, and 16 kHz for normally hearing subjects, using the notched-noise method. A specially designed sound delivery system was used to generate a high-frequency masking noise with a flat spectrum. For all test frequencies, the auditory filter shapes were estimated at a noise spectrum level (N0) of 40 dB. The mean equivalent rectangular bandwidths (ERBs) of the auditory filter at 4, 12, and 14 kHz were close to the extrapolated values given by Glasberg and Moore [Hear. Res. 47, 103–108 (1990)]. At 16 kHz, the mean ERB was close to the extrapolated value given by Moore and Glasberg [J. Acoust. Soc. Am. 74, 750–753 (1983)]. At 12 and 14 kHz, the auditory filter shapes were also estimated at a noise spectrum level of 50 dB. The mean ERBs of the auditory filter were wider for the higher spectrum level, consistent with previous results obtained at lower center frequencies.
Perceptual constancy of a global spectral property: Spectral slope discrimination
Authors: Li Xiaofeng , Pastore Richard E.
Published: October 2005

The current study investigated perceptual constancy for spectral slope discrimination when fundamental frequency (F0) and spectral shape were varied across three complex stimuli within a single trial. The three stimulus variables were global or emergent properties of a complex sound. The selection of the stimulus variables was in keeping with notions that perception may be organized in terms of a source-filter model of complex sound production; F0 and spectral slope represent properties of sound sources and spectral shape typically represents a filter property. According to the source-filter model, interaction between stimulus properties should depend upon whether the typical origin of the property was common to the source spectrum or the filter transfer function. The four experiments in the current study demonstrated a significant performance decrement in spectral slope discrimination when F0 (a second source property) was varied. However, spectral slope discrimination was minimally altered when spectral shape (a filter property) was varied. The study supported claims that listeners treat source properties as a unit which, in perception, is relatively independent of filter properties.
Electrode ranking of ‘‘place pitch’’ and speech recognition in electrical hearing
Authors: Nelson David A. , Van Tasell Dianne J. , Schroder Anna C. , Soli Sigfrid , Levine Samuel
Published: October 2005

The ability to distinguish electrical stimulation of different electrodes on the basis of ‘‘pitch or sharpness’’ was evaluated with an electrode ranking procedure in 14 individual users of the Nucleus cochlear implant. Prior to the electrode ranking test, absolute thresholds and maximum comfortable loudness levels were measured, and loudness balancing was accomplished across all usable electrodes. Performance on the electrode ranking task was defined in terms of d′ per mm of distance between comparison electrodes. Large individual differences were found among cochlear-implant users. In subjects with good to excellent place-pitch sensitivity, the electrode ranking task was limited by a ceiling effect; however, in those with poor to moderate sensitivity d′/mm was relatively constant with spatial separation between electrodes. Place pitch was typically ordered from apical to basal electrodes, i.e., basal electrodes were judged to be higher in pitch than more apical electrodes. However, instances of reversals in place-pitch ordering were seen on some electrodes in some subjects.

Instances were also seen of better electrode ranking in the apical half of the electrode array than in the basal half, and vice-versa. Analyses of the electrode ranking functions in terms of d′ per stimulus indicated that, in some subjects, perfect performance was reached with as little as 0.75 mm between comparison electrodes, the minimum possible. In other subjects, perfect performance was not reached until the spatial separation between comparison electrodes was over 13 mm, more than three quarters of the entire length of the electrode array. Ten of the subjects also participated in a closed-set recognition task of intervocalic consonants. Although the maximum transmitted information for place of consonant articulation (which is based primarily on spectral speech cues) was only 34%, correlations between place-pitch sensitivity and transmitted speech information were as high as 0.71. This was surprising considering the excellent place-pitch sensitivity exhibited by some of the subjects, and may reflect limitations of the Nucleus speech coding strategy for representing spectrally coded speech information. The two prelingual subjects performed notably poorer on the speech task than the postlingual subjects, even though one of the prelingual subjects demonstrated very good place-pitch sensitivity.
Outer hair cell length changes in an external electric field. I. The role of intracellular electro-osmotically generated pressure gradients
Authors: Jerry Rocco A. , Popel Aleksander S. , Brownell William E.
Published: October 2005

Brownell et al. [Science 227, 194–196 (1985)] observed that an isolated, cylindrically shaped cochlear outer hair cell can change its length when an electric field is applied. In their experiments, the cell was fixed at one end, and located between two electrodes which lie on the cell axis but were positioned far from the cell. Kachar et al. [Nature 322, 365–368 (1986)] had suggested that the cell’s electrically evoked elongation could be caused by pressure gradients resulting from electro-osmosis of the intracellular fluid. A mathematical model is developed which predicts the length change that would result from electro-osmotically generated pressure gradients inside the cell. Estimated parameter values are included to demonstrate that the pressures generated by electro-osmosis inside the cell would result in elongations that are at least two orders of magnitude below the experimentally measured values.
Outer hair cell length changes in an external electric field. II. The role of electrokinetic forces on the cell surface
Authors: Jerry Rocco A. , Popel Aleksander S. , Brownell William E.
Published: October 2005

An isolated cochlear outer hair cell can elongate or shorten when electrically stimulated, as discovered by Brownell et al. [Science 227, 194–196 (1985)]. In their experiments, the cylindrically shaped cell was fixed at one end, and was positioned between two electrodes which lie on the cell axis, but were far from the cell (transcellular stimulation). A model is developed to predict the component of the cell’s elongation which arises from only electrokinetic phenomena. Outside the cell, electro-osmosis produces a drag on the lateral wall which almost exactly balances the electrophoretic force. In contrast to previous theories, we find that the electrokinetic response is governed by the free end of the cell, not the lateral wall. If the surface charge density of the free end lies between −0.004 and −0.07 C/m2 (corresponding to the zeta potential between −5 and −60 mV), then our model predicts elongations that are comparable in magnitude to experimentally measured values.
Estimating residual noise in the auditory brain-stem response
Authors: Pepe Margaret Sullivan , Neely Stephen T.
Published: October 2005

Estimation of the residual noise in the auditory brain-stem response waveform is considered. The residual noise measures one aspect of waveform quality. Moreover, it is an important component of signal detection algorithms used for automatic termination of the test. It is shown that the most commonly used method for estimating residual noise can be severely biased. Reasons for this bias are explored and two alternative estimators are presented.
Power considerations in acoustic emission
Authors: Barnett John T. , Clough Roger B. , Kedem Benjamin
Published: October 2005

In stochastic acoustic emission, both theory and experiments suggest that the power of the acoustic emission signal is proportional to the source energy. Hence, inference about the power is equivalent to inference about the source energy except for a constant multiple. In this regard, the connection between peaks exceeding a fixed level and the power in random acoustic emission waves is explored when the source energy is an impulse of short duration. Under certain conditions, the peak distribution is sensitive to power changes, determines it, and is determined by it. The maximum-likelihood estimator of the power from a random sample of peaks—the peak estimator—is more efficient than the maximum-likelihood estimator—average sum of squares—from a random sample of the same size of signal values. When evaluated from nonrandom samples, indications are that the peak estimator may still have a relatively small mean-square error. A real data example indicates that the left-truncated Rayleigh probability distribution may serve as an adequate model for high peaks.
Estimation of locations and strengths of broadband planar and spherical noise sources using coherent signal subspace
Authors: Choi Jae-Woong , Kim Yang-Hann
Published: October 2005

This paper presents the estimation methods of the planar and spherical wave sources with broadband frequency by using two types of coherent signal-subspace processing; one uses frequency correction of the unwrapped phase of the measured sound pressures at the microphone array in space domain, and the other uses the focusing procedures by using the focusing matrix. The simulations show that the method based on frequency correction has a rather simple procedure compared to that of the methods based on focusing procedures. The performances of these methods have been also investigated in terms of the frequency band, and the distance between sources. The MUSIC power spectrum by the former gives broader peaks than that of the latter but the latter makes some spurious peaks in the MUSIC power spectrum when the bearing angle between the sources and/or the frequency band of interest increases, provided that one assumes a planar wave field. For the spherical wave field, these phenomena were less sensitive than those of the planar wave field.
Estimation of the spatial impulse response of an ultrasonic transducer using a tomographic approach
Authors: Sandell Magnus , Grennberg Anders
Published: October 2005

The impulse response method is often used to study the ultrasonic field radiated by planar or gently curved transducers. These investigations can be extended to include the reflected echoes from point reflectors, which can be used in synthesizing echoes from reflectors of known shapes. The single point echo can be measured directly but there are however certain problems associated with this. This paper proposes an alternative method to estimate the echo from a pointlike reflector by measuring the echoes from sliding half-planes. Using a tomographic approach, the single point echo is estimated from these measurements. To perform the tomographic inversion, a truncated weighted singular value decomposition (SVD) is used in order to catch essential features of the ultrasonic echoes, where the weight functions are chosen especially to suit this application. Numerical solutions are given for the chosen weight functions and an error analysis is carried out.
Determination of elastic constants of a concrete specimen using transient elastic waves
Authors: Wu T.-T. , Fang J.-S. , Liu G.-Y. , Kuo M.-K.
Published: October 2005

This paper presents the results of measuring the Rayleigh wave as well as longitudinal wave velocities in a concrete specimen using transient elastic waves. The Rayleigh surface wave generated by a steel ball impact on a concrete material is studied in detail and then a method for the determination of Rayleigh surface wave velocity based on the cross-correlation method is proposed. The longitudinal wave velocity of a concrete specimen is determined by measuring the wavefront arrival of a longitudinal wave. A special triggering device for the accurate determination of the impact time origin is utilized. The measured velocities of both the Rayleigh wave and the longitudinal wave in the concrete specimen are in good agreement with those measured by utilizing the conventional ultrasonic method. It is noted that with the Rayleigh wave and the longitudinal wave velocities measured, the Young’s modulus as well as the shear modulus of a concrete specimen can be obtained in a straightforward way.
Vibration and sound radiation of a cylindrical shell under a circumferentially moving load
Authors: Panneton Raymond , Berry Alain , Laville Frédéric
Published: October 2005

A theoretical model is developed to evaluate the vibration and sound radiation of a thin cylindrical shell excited by a constant point load continuously traveling along the circumferential direction at a rotational speed Ω. This rotating load model takes into account the exterior fluid loading due to the sound pressure radiated by the shell. The three equations of the vibroacoustic problem are the shell equations of motion, the Helmholtz equation in the exterior fluid medium and the continuity equation at fluid–shell interface. The rotating load model is based on a frequency-domain solution which is convenient for the interpretation of the vibratory and acoustic responses in terms of shell modes. The equations of motion are expanded over the shell modes to give the modal equations of motion. A frequency-domain representation of the rotating load shows that its frequency content is a series of equal amplitude harmonics NΩ. Each harmonic excites exclusively the circumferential mode N. For this rotating excitation, vibration and radiation critical speeds are identified. They give, respectively, an indication at which rotational speeds high vibration levels and sound radiation efficiency are expected. Finally, a good correlation between the rotating load model and experiments are obtained.
Active control of sound radiation using volume velocity cancellation
Authors: Johnson M. E. , Elliott S. J.
Published: October 2005

The active control of sound transmission through a panel has been formulated using a near-field approach. The effects of minimizing the sound power radiated by the panel and of canceling the net volume velocity of the panel are compared not only in terms of the reduction in sound radiation but also in terms of the change in the space average mean-squared velocity of the panel and the space average mean-squared pressure at its surface. Simulations of a thin panel excited by an incident acoustic plane wave and a piezoelectric control actuator show that volume velocity cancellation gives similar reductions in the transmitted sound power to the minimization of sound power radiation up to frequencies at which the size of the plate is about half an acoustic wavelength. The acoustic radiation is analyzed in terms of the radiation modes of the panel which are also used to explain spillover effects. Spillover, which leads to increases in the mean-squared velocity of the panel and to increases in near-field pressure levels when using a piezoelectric patch as a secondary actuator can be removed by using an actuator which generates a uniform force over the surface of the panel. Such an actuator is the reciprocal of the volume velocity sensor and could be fabricated in the same way. The transfer function between such a matched actuator/sensor pair is shown to be minimum phase, so that the performance of a feedback control system should be as good as a feedforward one, which would allow control of arbitrary broadband excitation of the panel.
Velocity variabilities and other physical properties of marine sediments measured by crosswell acoustic tomography
Authors: Yamamoto Tokuo
Published: October 2005

High-resolution images of the compressional wave velocity structure within various bottom sediments have been determined from high-frequency crosswell acoustic tomography. The three-dimensional wave-number spectra of the velocity variabilities were determined for each measured velocity image. The sediment velocity variability spectra are anisotropic in general. The variability frequency in the vertical direction is much higher than in the horizontal direction. The aspect ratio of the two is found to be approximately 5.0. In addition, the major and minor axes of the anisotropy are often tilted from the vertical and the horizontal direction, respectively. The angle of tilt called dip is found to be as much as 33 deg. The measured velocity power spectra approximate a power law. The spectral strength depends on the sediment type and the location. Based on the rock mechanics transformation procedure by Yamamoto et al. [Geophysics 59, 1530–1541 (1994)], the sediment porosity, density, permeability, and shear strength images have been transformed from the velocity images. These sediment properties, determined from the acoustic crosswell tomography, have been supported by direct measurements on cores and boreholes. The density variabilities of the sediment are found to be similar to the velocity variabilities. Unlike in ocean water, the relative density variabilities in the sediments are much larger than the relative velocity variabilities.
Application of three sound scattering models to threadfin shad (Dorosoma petenense)
Authors: Jech Josef M. , Schael D. M. , Clay C. S.
Published: October 2005

Three sound scattering models [T. K. Stanton, J. Acoust. Soc. Am. 86, 691–705 (1989), C. S. Clay, J. Acoust. Soc. Am. 89, 2168–2179 (1991), and C. S. Clay and J. Horne, J. Acoust. Soc. Am. 96, 1661–1668 (1994)] were used to model backscatter measurements from individual threadfin shad. Thirty three threadfin shad from Lake Norman, North Carolina were insonified at 120, 200, and 420 kHz to determine acoustic backscattering cross sections. The measurements covered the range of fish total length (TL) over acoustic wavelength (λ) of 4<TL/λ<25. The finite bent cylinder and low-resolution acoustic scattering models require conversion of fish body and swimbladder morphology to equivalent cylindrical parameters. There appears to be a direct relationship between fish morphology and cylindrical parameters. The ray-mode model uses the actual morphology of the swimbladder and body. Probability density functions (PDF’s) from the same fish at 120 and 420 kHz support the idea that knowledge of fish orientation in the field is important and the effect of orientation becomes more significant at higher frequencies. The scattering curves can be used in the inverse method along with multiple frequency sonar systems to investigate the adequacy of classification and identification of fish.
Simulated tomographic reconstruction of ocean features using drifting acoustic receivers and a navigated source
Authors: Duda Timothy F. , Pawlowicz Richard A. , Lynch James F. , Cornuelle Bruce D.
Published: October 2005

Numerically simulated acoustic transmission from a single source of known position (for example, suspended from a ship) to receivers of partially known position (for example, sonobuoys dropped from the air) are used for tomographic mapping of ocean sound speed. The maps are evaluated for accuracy and utility. Grids of 16 receivers are employed, with sizes of 150, 300, and 700 km square. Ordinary statistical measures are used to evaluate the pattern similarity and thus the mapping capability of the system. For an array of 300 km square, quantitative error in the maps grows with receiver position uncertainty. The large and small arrays show lesser mapping capability than the mid-size array. Mapping errors increase with receiver position uncertainty for uncertainties less than 1000-m rms, but uncertainties exceeding that have less systematic effect on the maps. Maps of rms error of the field do not provide a complete view of the utility of the acoustic network. Features of maps are surprisingly reproducible for different navigation error levels, and give comparable information about mesoscale structures despite great variations in those levels.
Intensity resolution and loudness in broadband noise
Authors: Schlauch Robert S. , Harvey Stephanie , Lanthier Nicole
Published: October 2005

Intensity resolution and loudness matching behavior for pure tones was studied in quiet and in two levels of noise (15 and 40 dB spectrum level) to test the predictions of several models for relating these phenomena. Five normally hearing listeners participated. The Weber functions in noise were elevated compared to the ones in quiet when comparisons were made at equal sound-pressure levels (SPLs). Loudness matching functions (dB SPL in quiet versus dB SPL in noise) showed a slope greater than unity. Modified power functions with threshold corrections were fitted to the matching data to estimate the loudness function exponent. The best-fitting loudness exponent for individual and group data (range=0.24–0.35) was in the range of values typically found using magnitude estimation procedures for the loudness equation yielding the best fit. Three models for predicting Weber functions from loudness were evaluated with this loudness representation. One of these models, the subjective analog to Weber’s law, yielded results inconsistent with the observed data. The other models, McGill and Goldberg’s [J. Acoust. Soc. Am. 44, 576–581 (1968)] neural counting model and the proportional-jnd theory, predicted Weber functions that are consistent with the observed data if the variance of the decision variable is assumed to change in quiet and noise backgrounds. The proportional-jnd theory has such a change built into the model, but the underlying physiological mechanisms responsible for its success are unknown.
Comments on ‘‘Reflection from a corrugated surface revisited’’ [J. Acoust. Soc. Am. 96, 1116–1129 (1994)]
Authors: Kazandjian Luc
Published: October 2005

In the subject paper, Chesneaux and Wirgin use stochastic arithmetic to investigate the equivalence of the Rayleigh and extinction theorem methods implemented by the Fourier scheme. The purpose here is to discuss remarks made by the authors about the following points: The interpretation of the result of a previous paper dealing with the problem, a conjecture about the identity of the perturbation series derived from the two methods, an assertion about the numerical convergence of the Waterman–Fourier method.
Transient effects during the chopping response of LSO neurons
Authors: Zacksenhouse Miriam , Johnson Don H. , Tsuchitani Chiyeko
Published: October 2005

The initial transient chopping response of LSO neuron discharges to both monaural and binaural tone-burst stimuli in the context of a previously developed point process model of the later sustained response is analyzed and modeled. The analysis reveals the nature of the initial transient response to stimulus onset: The model’s stimulus-dependent parameters vary with poststimulus-onset time while the neuron’s intrinsic recovery characteristics remain constant throughout the response. By applying maximum-likelihood estimation techniques to determine the time course of the stimulus-dependent parameters, it was found that the initial excitatory and inhibitory effects decay exponentially, with their ratio determining the instantaneous rate of firing and their relative latency determining the extent of the initial chopping pattern. The ‘‘absolute’’ and apparent deadtime also vary exponentially during the transient portion of the response. It is concluded that the recovery characteristics of LSO neurons and the exponential nature of the transient effects give rise to a tightly distributed latency period and a regular chopping response pattern that could encode azimuthal information.
Spatially dependent acoustic cues generated by the external ear of the big brown bat, Eptesicus fuscus
Authors: Wotton Janine M. , Haresign Tim , Simmons James A.
Published: October 2005

To measure the directionality of the external ear of the echolocating bat, Eptesicus fuscus, the left or right eardrum of a dead bat was replaced by a microphone which recorded signals received from a sound source that was moved around the stationary head. The test signal was a 0.5-ms FM sweep from 100 kHz to 10 kHz (covering all frequencies in the bat’s biosonar sounds). Notches and peaks in transfer functions for 7 tested ears varied systematically with changes in elevation. For the most prominent notch, center frequency decreased from about 50 kHz for elevations at or near the horizontal to 30–40 kHz for elevations 30°–40° below the horizontal. A second notch shifted from about 85 kHz to 70 kHz over these same elevations. Above the horizontal, a peak that flanks these notches changed in amplitude by 15 dB with changes in elevation. Removal of the tragus from the external ear disrupted the systematic movement of notch frequencies with elevation but did not disrupt changes in the peak’s amplitude. Smaller changes in notch frequency also occurred with changes in azimuth, so monaural notch information alone cannot determine the position of sound sources away from the median plane. However, because bats routinely keep the head pointed at the target’s azimuth, median-plane localization occurs with monaural cues delivered to the two ears. Corresponding changes with elevation occurred in the impulse-response, which consists of a series of 3–6 peaks spaced 10–20 μs apart. The time separation of two prominent impulse peaks systematically increased from 22–26 μs above the horizontal to about 36–40 μs below the horizontal, and removal of the tragus disrupted this time shift below the horizontal.
Statistical characteristics of moving acoustic sources in ocean waveguides
Authors: Stein David W. J.
Published: October 2005

The statistical characteristics of the response of an array of hydrophones to a moving narrow-band acoustic source in an ocean waveguide are investigated. The discrete Fourier transform of a solution of the wave equation with a moving source is calculated, and the sequence of the amplitudes of the Fourier coefficients at particular frequencies are shown to contain oscillatory terms that depend upon the environment, the source frequency, position and velocity, and the resolution of the DFT. This analysis suggests that Gaussian mixture densities may apply to time series of Fourier coefficients of data received from a moving source. This is verified by analyzing data from a deep water Navy experiment. Simulations are then carried out which show that the fluctuations caused by source motion are sufficient to favor Gaussian mixture densities over Gaussian densities and that the applicability of the Gaussian model, but not the Gaussian mixture model, depends upon the velocity and position of the source.
Modeling three-dimensional vibration of elliptic bars
Authors: Liew K. M. , Hung K. C. , Lim M. K.
Published: October 2005

This paper presents a three-dimensional vibration analysis of elliptic bars with various end constraints. The theoretical derivation is established based on the linear, small-strain, three-dimensional elasticity principle. With the expansion of the displacements in a three-dimensional spatial coordinate, the integral expressions for strain and kinetic energies are developed. Using the orthogonal polynomials to represent the three-dimensional displacement field, a governing eigenvalue equation is obtained by minimizing the energy functional according to the Ritz principle. To demonstrate the applicability of this method, several numerical examples are solved. The accuracy of the frequency solutions is established by checking with the existing refined beam theories. First known results in terms of frequency parameters and displacement mode shape plots of the elliptic bar with different end support conditions are presented. The new results may serve as a useful reference to future research into the refined beam theories.
Nonlinear wave transmission in a monocoupled elastic periodic system
Authors: Vakakis Alexander F. , King Melvin E.
Published: October 2005

The free dynamics of a monocoupled nonlinear periodic system of infinite extent is analyzed. The system under consideration consists of an infinite number of elastic layers with material nonlinearities, coupled by means of linear stiffnesses. It is shown that, in analogy to linear theory, the system possesses nonlinear attenuation and propagation zones (AZs and PZs) in the frequency domain. Responses in AZs correspond to standing waves with spatially attenuating or expanding envelopes, and are synchronous motions of all points of the periodic system. These motions are analytically examined by employing the notion of ‘‘nonlinear normal mode,’’ thereby reducing the response problem to the solution of an infinite set of singular nonlinear partial differential equations. An asymptotic methodology is developed to solve this set. Motions in PZs correspond to traveling waves, i.e., to nonsynchronous oscillations. These motions are analyzed by applying the method of multiple scales in space and time. Numerical computations are carried out to complement the analytical findings. The analytical and numerical methodologies developed in this work can be applied to the study of the free motions of a general class of monocoupled nonlinear periodic systems, and can be extended to investigate motions of nonlinear periodic systems with more than one coupling coordinate.
Exact free-vibration analysis of laminated plates with embedded piezoelectric layers
Authors: Heyliger Paul , Saravanos D. A.
Published: October 2005

Exact solutions are developed for predicting the coupled electromechanical vibration characteristics of simply supported laminated piezoelectric plates composed of orthorhombic layers. The three-dimensional equations of motion and the charge equation are solved using the assumptions of the linear theory of piezoelectricity. The through-thickness distributions for the displacements and electrostatic potential are functions of eight constants for each layer of the laminate. Enforcing the continuity and surface conditions results in a linear system of equations representing the behavior of the complete laminate. The determinant of this system must be zero at a resonant frequency. The natural frequencies are found numerically by first incrementally stepping through the frequency spectrum and refining the final frequencies using bisection. Representative frequencies and mode shapes are presented for a variety of lamination schemes and aspect ratios.
The radiation modes of baffled finite plates
Authors: Currey M. Noelle , Cunefare Kenneth A.
Published: October 2005

The modal-style approach for representing the exterior radiation characteristics of structures generally seeks to find a set of orthogonal functions, or radiation modes, that diagonalize a discretized radiation operator in the exterior domain of the structure. The choice of basis functions for the modal representation is arbitrary, though use of the structural modes of vibration tends to provide some physical insight. The radiation modes are found through an eigenanalysis or singular-value decomposition analysis of the radiation operator. The eigenvalue or singular value associated with a given radiation mode is directly proportional to the radiation efficiency of that radiation mode. In this paper, the dependency of the radiation efficiencies and radiation mode shapes on the number of degrees of freedom permitted in the derivation of the radiation operator is investigated for a baffled finite rectangular plate. The accuracy of the acoustic modal representation depends on the number of degrees of freedom in the radiation operator, with the least efficient radiation modes converging slowest. Further, the rate of convergence is dependent on the particular basis function selection. The convergence behavior has significant impact on those applications of the exterior acoustic modal approach that seek to exploit the least efficient radiation modes.
The influence of curvature on the sound radiated by vibrating panels
Authors: Graham W. R.
Published: October 2005

The influence of curvature on sound radiation by a rectangular panel is investigated by considering the situation where the panel is set in an infinite cylinder. As in the flat panel case, acoustic effects may be characterized by a set of modal impedances, whose relationship to the corresponding flat panel terms is calculated for large cylinder radius. It is found that the impedances arising from the external acoustic field tend to their flat panel counterparts, but those associated with the internal field only do so under suitable conditions on the cylinder internal acoustic damping. Specifically, the interior wall must be sufficiently hard that it effectively appears rigid around the panel, but sufficiently dissipative that reflected ray and near-field line-of-sight contributions to the impedance are negligible. The conditions are investigated in detail for parameters appropriate to a wide-body civil aircraft, and curvature is found to be potentially important for the mode classes of interest.
Analysis of harmonic distortion in electroacoustic transducers
Authors: Sherman Charles H. , Butler John L.
Published: October 2005

Nonlinear transducer equations are formulated for the six major types of electroacoustic transducers (electrostatic, variable reluctance, moving coil, piezoelectric, electrostrictive, and magnetostrictive) in a common form using the various physical and mathematical similarities among the transduction mechanisms. The common nonlinear equation is solved approximately by perturbation analysis giving simple expressions and graphs for harmonic amplitudes caused by all the frequently occurring nonlinear mechanisms. The expressions and graphs can be applied to all the transducer types by using nonlinear parameters tabulated for each type. These results can facilitate diagnosis of the cause of measured harmonics, prediction of harmonics during design, and development of electrical drives to suppress harmonics.
Acoustic dispersion and attenuation relations in bubbly mixture
Authors: Ye Zhen , Ding Li
Published: October 2005

Multiple scattering in bubbly mixture can be studied using a many-body theory, which in principle is able to include any order interactions in a many-body system. In this paper, the theory is first described in an illustrative manner, and then applied to the case of a bubbly mixture. As an initial step, consideration is given to up to second-order interactions of bubbles, and the effective wave number of the average scattered field is derived. The result provides a higher-order correction to previous results that have generally neglected mutual interactions of bubbles. The phase speed and amplitude attenuation of acoustic waves in the mixture are calculated from the effective wave number. Numerical results show that the higher-order correction can be rather significant under certain circumstances. The primary purpose of this paper is to present a relatively simple and systematic approach to such problems as described here. The work can also be extended to include higher-than-second-order interactions, which remains to be the subject of future research.
Measurement of seismo-acoustic ocean-bottom properties in the high Arctic
Authors: Dosso S. E. , Brooke G. H.
Published: October 2005

This paper describes a high-resolution seismic experiment designed to measure compressional and shear properties of the ocean bottom in the Lincoln Sea, north of Ellesmere Island, Canada. A three-component ocean-bottom seismometer (OBS) was deployed through 4 m of multiyear sea ice in 540 m of water, and used to record broadband signals from explosive sources detonated on the seafloor at ranges from 35 to 900 m. Subsequently, a layered compressional-speed model was determined from a travel-time analysis of refracted compressional waves, and a shear-speed model was determined by matching the observed dispersion characteristics of Scholte and shear waves using the full-wave numerical propagation model SAFARI. Compressional and shear attenuation coefficients were estimated from an analysis of the decay of signal amplitude with range; an approximately linear increase in attenuation with frequency was observed for both wave types. The sensitivity of acoustic propagation in the ocean to the various geoacoustic parameters was investigated using the propagation model.