bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of short-term auditory deprivation on speech production in adult cochlear implant users
Authors: Svirsky Mario A. , Lane Harlan , Perkell Joseph S. , Wozniak Jane
Published: October 2005

Speech production parameters of three postlingually deafened adults who use cochlear implants were measured: after 24 h of auditory deprivation (which was achieved by turning the subject’s speech processor off); after turning the speech processor back on; and after turning the speech processor off again. The measured parameters included vowel acoustics [F1, F2, F0, sound-pressure level (SPL), duration and H1–H2, the amplitude difference between the first two spectral harmonics, a correlate of breathiness] while reading word lists, and average airflow during the reading of passages. Changes in speech processor state (on-to-off or vice versa) were accompanied by numerous changes in speech production parameters. Many changes were in the direction of normalcy, and most were consistent with long-term speech production changes in the same subjects following activation of the processors of their cochlear implants [Perkell et al., J. Acoust. Soc. Am. 91, 2961–2978 (1992)]. Changes in mean airflow were always accompanied by H1–H2 (breathiness) changes in the same direction, probably due to underlying changes in laryngeal posture. Some parameters (different combinations of SPL, F0, H1–H2 and formants for different subjects) showed very rapid changes when turning the speech processor on or off. Parameter changes were faster and more pronounced, however, when the speech processor was turned on than when it was turned off. The picture that emerges from the present study is consistent with a dual role for auditory feedback in speech production: long-term calibration of articulatory parameters as well as feedback mechanisms with relatively short time constants.
Target detection, shape discrimination, and signal characteristics of an echolocating false killer whale (P
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Authors: Brill Randall L. , Pawloski Jeffrey L. , Helweg David A. , Au Whitlow W. , Moore Patrick W. B.
Published: October 2005

This study demonstrated the ability of a false killer whale (Pseudorca crassidens) to discriminate between two targets and investigated the parameters of the whale’s emitted signals for changes related to test conditions. Target detection performance comparable to the bottlenose dolphin’s (Tursiops truncatus) has previously been reported for echolocating false killer whales. No other echolocation capabilities have been reported. A false killer whale, naive to conditioned echolocation tasks, was initially trained to detect a cylinder in a ‘‘go/no-go’’ procedure over ranges of 3 to 8 m. The transition from a detection task to a discrimination task was readily achieved by introducing a spherical comparison target. Finally, the cylinder was successfully compared to spheres of two different sizes and target strengths. Multivariate analyses were used to evaluate the parameters of emitted signals. Duncan’s multiple range tests showed significant decreases (df=185, p<0.05) in both source level and bandwidth in the transition from detection to discrimination. Analysis of variance revealed a significant decrease in the number of clicks over test conditions [F(5,26)=5.23, p<0.0001]. These data suggest that the whale relied on cues relevant to target shape as well as target strength, that changes in source level and bandwidth were task-related, that the decrease in clicks was associated with learning experience, and that Pseudorca’s ability to discriminate shapes using echolocation may be comparable to that of Tursiops truncatus.
Analyzing reverse middle-ear transmission: Noninvasive Gedankenexperiments
Authors: Shera Christopher A. , Zweig George
Published: October 2005

The phenomenological framework outlined in the companion paper [Shera and Zweig, J. Acoust. Soc. Am. 92, ▪▪–▪▪ (1992)] characterizes both forward and reverse transmission through the middle ear. This paper illustrates its use in the analysis of noninvasive measurements of middle-ear and cochlear mechanics. A cochlear scattering framework is developed for the analysis of combination-tone and other experiments in which acoustic distortion products are used to drive the middle ear ‘‘in reverse.’’ The framework is illustrated with a simple psychophysical Gedankenexperiment analogous to the neurophysiological experiments of Fahey and Allen [J. Acoust. Soc. Am. 77, 599–612 (1985)].
Matched-field minimum variance beamforming in a random ocean channel
Authors: Krolik Jeffrey L.
Published: October 2005

Matched-field source localization methods that employ deterministic full-wave acoustic propagation models can be seriously degraded due to the presence of random inhomogeneities in the ocean channel. In this paper, a minimum variance (MV) matched-field beamformer is presented that achieves greater robustness to random inhomogeneities in the sound-speed profile between the source and receiver. The proposed modification of the MV beamformer consists of employing multiple linear constraints derived from predicted pressure fields obtained using a set of perturbed sound-speed profiles. In order to investigate the nature of wave-front variations due to random sound-speed perturbations, a normal mode model based on adiabatic and first-order perturbation approximations is examined. The signal wave-front spatial correlation implied by this model suggests that the coherence among modes can remain high even in a fluctuating ocean environment. This in turn implies that the dimension of the signal perturbation constraint space for the MV beamformer can be small for typical sound-speed variations at moderate source ranges. Given the signal constraint space, design of the MV beamformer with sound-speed perturbation constraints is achieved by selecting its quiescent response to maximize the average signal-to-noise ratio gain against spatially uncorrelated noise. This leads to a computationally efficient realization of the beamformer that avoids the need to repeatedly compute perturbed pressure fields. Simulation experiments using a realistic deep-water Pacific Ocean environment are presented, which suggest that robust unambiguous low-frequency source location estimates can be achieved in the presence of mesoscale inhomogeneities given only knowledge of the second-order statistics of the random range-dependent sound-speed profile plus a single environmental measurement at the receiving array.
Sound transmission through two kinds of porous concrete blocks with attached drywall
Authors: Warnock A. C. C.
Published: October 2005

The airflow resistance of concrete blocks plays a significant role in determining sound transmission losses for block walls with drywall added on furring. Two block types were tested. One was so porous that sound passed easily through it and there was no sign of a mass–air–mass resonance behind the added drywall. Such blocks must be plastered or else their contribution to the attenuation of sound is very small. Once plastered, the low porosity increased the effective depth of the air cavity behind the added drywall on the unplastered side with attendant increases in sound transmission loss. The mass–air–mass resonance occurred at a lower frequency corresponding to the distance from the drywall through the block to the plaster. The other block type tested had a higher airflow resistance that added a loss mechanism to the wall systems; the mass–air–mass resonance was damped and transmission loss was not reduced by the resonance. The benefits of having drywall added on furring were still obtained with these blocks. Their sound transmission losses were increased when plaster was applied on one face but the increase was not so great as for the very porous blocks. Airflow resistance is an important parameter that should be considered when designing block walls.
Active control of low-frequency sound transmission between rooms
Authors: Jo C. H. , Elliott S. J.
Published: October 2005

The sound insulation properties of many structures mounted between adjacent rooms are known to be poor at low frequencies. The feasibility of using acoustic secondary sources in either the source room, or in the receiving room, to actively control the sound transmitted from one room to the other via a common panel has been investigated. A theoretical formulation for such low-frequency sound transmission was first developed. The effects of three different active control strategies were then investigated, using computer simulations with a pure-tone primary source, for a number of different room and panel arrangements. The first strategy involved minimizing the total acoustic potential energy in the source room using a secondary source in the source room. It was found that this could cause increases in the acoustic energy transmitted into the receiving room at some excitation frequencies. Second, the total acoustic potential energy in the receiving room was minimized using a secondary source in the receiving room. This strategy generally produced rather small reductions of sound energy in the receiving room. Finally, the approach of minimizing the total acoustic potential energy in the receiving room using a secondary acoustic source in the source room was investigated. This turned out to be the most successful strategy, giving significant reductions in transmitted sound energy, particularly for excitation frequencies at which only a few acoustic modes of the source room or structural modes of the panel were excited. These reductions in transmitted sound energy may, however, be accompanied by increases in the sound energy in the source room.
On the consistency of tapping to repeated noise
Authors: Kaernbach Christian
Published: October 2005

Repeated noise at 1–4 cycles per second evokes an effortless heard rhythmic sensation which is often heard as ‘‘clanks’’ and ‘‘rasping.’’ Tapping in synchrony with the period of the perceived structure is easy and consistent within one presentation. The present study addresses the question of whether the tapping to presentations at different times is consistent across presentations and across subjects. Nine listeners from three countries were presented with repeated Gaussian noise samples in 300 separate cyclical presentations. Nine samples of Gaussian noise with sample lengths ranging from 500 to 700 ms were used. In each of the presentations, one of these samples was selected at random and presented cyclically with transientless juxtapositions. The listeners were instructed to tap in synchrony with the perceived structure (i.e., once per period). Tapping to later presentations of a given sample was found to be consistent with prior tapping to the same sample: In most cases, one or two different tapping points per noise sample could be reproduced in different presentations. In the case of two possible tapping points in different presentations, the two points are usually far away from each other (most likely half a period away). The correlation between subjects is noticeable, although not perfect. The correlation between subjects of the same country is not significantly higher. The noise generating algorithm is given explicitly to allow subsequent studies to use exactly the same noises.
An experimental study of the active control of multiple-wave types in an elastic beam
Authors: Clark R. L. , Pan Jie , Hansen Colin H.
Published: October 2005

In many practical situations, different types of waves may coexist within a structure. If control is limited to a single wave type, other kinds of waves may be generated unintentionally by the action of the control forces. In this paper an experimental study of the simultaneous control of multiple wave types in a semi-infinite beam has been undertaken. The ability of the piezoelectric control sources to provide adequate system control and the ability of the accelerometer error sensors to provide adequate observability of the power flow associated with each wave type was also evaluated.
High-frequency bottom backscattering: Roughness versus sediment volume scattering
Authors: Jackson Darrell R. , Briggs Kevin B.
Published: October 2005

High-frequency bottom acoustic and geoacoustic data from three well-characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy.
Attenuation of sound by schooling fish
Authors: Furusawa Masahiko , Ishii Ken , Miyanohana Youichi
Published: October 2005

Attenuation of sound by schooling fish was measured or estimated for yellowtail (Seriola quinqueradiata), sea bream (Pagrus major), and spotted mackerel (Scomber australasicus) in culture nets and a net cage. The results, along with those of other researchers, are normalized to obtain extinction cross sections per 2/3 power of the body weight. In the normalized cross sections there are no large differences among fish species, sizes, and measuring methods. The attenuation increases slightly with the frequency. Attenuations to be encountered in field observations by echo sounders are estimated and the results reveal that ordinary fish schools do not attenuate sound significantly.
Acoustic tracking system for monitoring under-ice movements of polar seals
Authors: Wartzok Douglas , Sayegh Samir , Stone Henry , Barchak John , Barnes Warren
Published: October 2005

An acoustic tracking system is described that has been used to track Weddell seals in Antarctica and ringed and spotted seals in the arctic. The seals are released with a small, depth-modulated acoustic transmitter attached. They are tracked in real time based on the time difference of arrival at four hydrophones of the pulse from the acoustic transmitter. Working ranges are approximately those predicted by acoustic equations. Closed-form solutions of the tracking algorithm allow rapid calculation of position. The effect of different array geometries on accuracy of tracking is explored analytically.
Horizontal refraction of low-frequency acoustic waves in the Barents Sea stationary acoustic track experiment
Authors: Shmelerv A. Yu. , Migulin A. A. , Petnikov V. G.
Published: October 2005

In this paper, data from the Barents Sea stationary acoustic range experiment carried out in October 1983 are analyzed. The experiment used a tonal acoustic source at 100 Hz and a horizontal array that consisted of 48 hydrophones extending over 450 m, mounted on the bottom. From the measured phase difference between a reference signal and the signal received by the individual hydrophones, phase front fluctuations have been obtained. Continuous measurements of the sound-speed profile showed fluctuations of the thermocline boundary caused by long period (3.5 h) internal waves with 10-m amplitude. Simultaneously, acoustic measurements were made of the deviations from linearity of the phase front along the array. Using spatial Fourier analysis, it was seen that the variability of the phase front showed several scales. To explain the spatial phase fluctuations we used results from a horizontal refraction theory for shallow water and a theory of phase dislocation in a waveguide [Kravtsov et al., Sov. Phys. Acoust. 30, 45–47 (1984); Sov. Phys. Acoust. 35, 156–159 (1989)]. Calculations showed that long period phase fluctuations were produced by long period internal waves and short period fluctuations were produced by the interference of direct waves and waves reflected from the shore. It was also possible to account for some of the parameters of the internal waves and the reflected waves.
Improved perturbation method for scattering from a fluid cylinder
Authors: Chandra Kavitha , Thompson Charles
Published: October 2005

The scattering of sound from a fluid cylinder having strong compressibility contrast is considered. For such a problem, direct application of the Neumann solution results in a divergent series for the pressure. The divergence of the aforementioned series is shown to be the result of an inadequate choice of gauge functions for the expansion. Asymptotic representations equivalent to the Neumann series are obtained using the method of Padé approximants. The method of Padé approximants is shown to extend the range of contrast as well as accelerate the convergence of the Neumann series. Optimal truncation of the Neumann series is shown to yield low-order approximations for the pressure at moderate values of contrast and wavelength. Numerical results using the method of Padé approximants are shown to agree favorably with analytical solutions for scattered pressure from a fluid cylinder.
Characterization of external ear impulse responses using Golay codes
Authors: Zhou Bin , Green David M. , Middlebrooks John C.
Published: October 2005

This report explains the use of a complementary series, Golay codes, for probing the impulse response of the external ear. The codes are used to measure both the resonance of the human ear canal, using a sealed sound-delivery system, and to measure the transfer function of the pinna, using a free-field source. With two series of 512 binary numbers, the improvement in signal-to-noise ratio over a single impulse approaches the theoretical value of 30.1 dB [10 log(2⋅512)]. This technique has many of the same properties as maximal-length sequences [M. R. Schroeder, J. Acoust. Soc. Am. 66, 497–500 (1979)], but it has the added advantage that the sequence length is an integer power of two and is, therefore, particularly convenient to use with modern Fourier transform techniques.
Annular array imaging with full-aperture resolution
Authors: Norton Stephen J.
Published: October 2005

The problem of imaging with an annular array of transducers by employing all pairs of transducer elements around the circumference of the annulus as transmitters and receivers is considered. If θt and θr are, respectively, the angular locations of a pair of transmitting and receiving elements, then weighting the received signal with the positive weight 2‖sin(θt−θr)‖ before coherent summation results in an image point spread function of the form J1(R)/R. This corresponds to the point spread function of a full circular (area) aperture. Moreover, it is shown that the diameter of this synthetic aperture is twice that of the annulus. A more general weighting function is also derived that results in a point spread function of the form Jn(R)/Rn, n=1,2,..., which is shown to correspond to an apodized circular aperture of diameter twice that of the annulus.
Use of Lanczos vectors in fluid/structure interaction problems
Authors: Jeans R. , Mathews I. C.
Published: October 2005

The goals of any numerical computational technique used for the solution of structural acoustics problems in the exterior infinite domain should be ones of accuracy with rapid convergence, robustness, and computational efficiency. A computer program has recently been developed to achieve each of these three goals. Accuracy and robustness in the numerical representation of the integral equations used to represent the infinite fluid was attained through the use of boundary element implementations of the surface Helmholtz integral equations. The computational efficiency was resolved through the use of Lanczos vectors to model the deformation characteristics of the structure. The difficulty hindering the use of the boundary element formulation has been in finding a suitable numerical representation of the hypersingular integral operator contained in the differentiated form of the Helmholtz integral equations. This difficulty has hampered the convergence, accuracy, and robustness of many previous numerical integral equation implementations used for the modeling of the infinite fluid field. The authors have recently developed both collocation and variational techniques to overcome the difficulties previously encountered in the numerical implementation of the hypersingular integral operator.

The Cauchy singularity present in the integral formulation is made numerically amenable through the use of tangential derivatives in both the collocation and variational techniques. The variational approach has the advantage that the resulting added fluid mass term is symmetric and combines efficiently with a finite element approximation of the structural elastic response. Several different strategies making use of the Lanczos vectors have been investigated. The first involved the use of Lanczos vectors solely to characterize the structural response. This reduced form of the structural dynamical matrix was then substituted back into a Burton and Miller formulation of the acoustic problem, from which the normal surface pressure was obtained. The second strategy investigated involved forming the complex Lanzcos vectors of the dynamical matrix formed from the addition of a symmetrical added fluid matrix to the structural mass matrix. The size of resultant matrix equation set solved at each frequency for this strategy is determined by the number of Lanczos vectors used.
Application of a diffraction-corrected ray theory to the slot lens in acoustic microscopy
Authors: Chizhik Dmitry , Davids Douglas A.
Published: October 2005

A modified ray approach is used to model the slot lens for determining V(z) and the results are compared with experiment for several materials. The slot lens is also used to obtain V(z) of y-cut quartz for a number of slot orientations relative to the crystalline x axis. The Rayleigh wave velocity as a function of propagation direction is then deduced from these measurements and compared with accepted values. It is shown that although the angular restriction of the slot lens is introduced in the lens aperture plane in contrast to shaped electrodes in the transducer plane, it is still necessary to account for diffraction in the lens rod in order to provide agreement with experiment. The application of the slot lens to crack detection is also examined and an analysis provided that yields substantial agreement with experiment. A simple yet effective method for extracting the surface wave reflection coefficient of a crack from measurements is proposed and demonstrated.
Acoustic scattering by an open-ended hard circular tube of finite length
Authors: Scharstein Robert W.
Published: October 2005

A boundary value problem for the time-harmonic acoustic field scattered by an open-ended circular tube of finite length is solved by a Galerkin method. The Neumann boundary condition applies on the infinitesimally thin, cylindrical surface of the acoustically hard scatterer. The circular symmetry of this surface of revolution preserves the orthogonality of the azimuthal modes of the obliquely incident plane wave, which serve as the basis for a trigonometric Fourier series in the φ coordinate. Spatial Fourier integrals (plane wave spectra) for the scattered field are expressed in terms of the Galerkin coefficients of a Chebyshev series expansion for the discontinuity in surface pressure. Resultant graphs of the interior and near pressure field on the cylinder axis are presented and qualitatively interpreted in terms of traveling wave components that are reflected from the tube ends. An asymptotic evaluation of the far scattered field yields the angular variation of the obstacle scatter diagram, which is compared to a Kirchhoff approximation. Numerical implementation of this finite-dimensional Galerkin projection precludes the practical extension to very high-frequency scattering, but low and intermediate (resonance region) frequencies are efficiently and accurately accommodated.
Effect of spatial sampling in the calculation of ultrasonic fields generated by piston radiators
Authors: Hah Zae G. , Sung Koeng M.
Published: October 2005

The effect of spatial sampling in the calculation of sound fields generated by piston radiators mounted in an infinite baffle was analyzed, and quantitative analysis was performed for the case of rectangular pistons. The source function is modified with spatial sampling and the efficient sampling is found to be such that the source size divided by sampling interval should be odd integers. The aliasing error in the field calculation is defined as the ratio of the power radiated by the original source to the power radiated by the replicated sources that are generated in the wave-number domain by the sampling process. The aliasing error decreases as sampling frequency and source size increase. The results can be used as a reference when calculating sound fields by the spatial sampling method in that, once the source size and desired aliasing error are fixed, appropriate sampling frequency can be obtained.
Flow noise reduction techniques for a planar array of hydrophones
Authors: Ko Sung H. , Schloemer Howard H.
Published: October 2005

This paper presents techniques for reducing turbulent boundary layer pressure fluctuations using wave-number filters. Reduction of flow noise can be achieved by filtering wave numbers using a finite hydrophone or an array of hydrophones, or by filtering wave numbers using a layer of elastomer. The baseline turbulent wall pressure spectrum that represents the flow excitation function is based on the Corcos model modified to fit a realistic estimate at the low wave-number region. The occurrence of the convective ridge wave number is estimated by using a convective flow speed that is a function of frequency. Major results presented are numerically calculated noise reductions compared to the calculated noise level for a flush-mounted point hydrophone.
Place specific influences on the wave I to V interpeak latency of the auditory brain-stem response
Authors: Zapala David A. , Gould Herbert J. , Mendel Maurice I.
Published: October 2005

There is controversy over whether the wave I to V interpeak latency (I–V IPL) of the auditory brain-stem response can be manipulated by cochlear processing. In this study, a forward masking paradigm was used to test the predictions of two contrasting models of I–V IPL generation. The paradigm was designed to determine if the I–V IPL can be affected by masking selected portions of the cochlear response region. The results from ten normal hearing subjects suggest that: (1) waves I and V can be masked semi-independent of each other, and (2) the I–V IPL can be shortened or prolonged by masking the basal or apical portion of the cochlear response region respectively. These findings support the hypothesis that, at least in normal hearing subjects, wave V is biased to reflect more apical cochlear events than wave I. Additionally, they offer tentative support for anecdotal reports of shortened I–V IPLs in the presence of high-frequency hearing loss.
Intensity discrimination under backward masking
Authors: Plack Christopher J. , Viemeister Neal F.
Published: October 2005

The Weber fraction was measured for a 25-ms sinusoidal pedestal presented 100 ms before, or 100 ms after, an intense narrow-band noise. Consistent with the finding of Zeng et al. [Hear. Res. 55, 223–230 (1991)], the forward masker caused an elevation in the Weber fraction at medium pedestal levels. Surprisingly, however, a much larger midlevel elevation was observed in the backward masking conditions; in some cases, the Weber fraction was increased by over 20 dB by the backward masker. In both masking conditions, presenting a notched noise simultaneously with the pedestal reduced the magnitude of the midlevel elevation. These results indicate that it is possible to produce large masking effects on intensity discrimination in conditions where there is no possibility of the masker affecting the representation of the pedestal at the level of the auditory nerve. This suggests that there may be ‘‘central’’ processes underlying the original finding of Zeng et al. Despite the similarities in the results, however, it is not certain that the elevations seen in the forward and backward masking conditions were caused by the same mechanisms.
Listening for climatic temperature change in the northeast Pacific: 1983–1989
Authors: Spiesberger John L. , Metzger Kurt , Furgerson John A.
Published: October 2005

Data are presented from an acoustic experiment designed to detect climatic trends of temperature in the ocean with basin-scale resolution. These data are presented as an intriguing new way to recognize changes in spatially averaged temperature. In 1983, travel times of acoustic signals (133 Hz, 60-ms resolution) were measured over 4000 km between a source and receiver mounted near Oahu and northern California, respectively. In 1987, measurement was begun on the travel times along six additional sections in the northeast Pacific, each at a distance of 3000 to 4000 km. Travel times changed by about ±0.2 s at each receiver at interannual periods. Changes in acoustic travel time exceeding about ±0.03 s are due to changes in the spatially averaged temperature along each section. A change of ±0.03 s is equivalent to a change in spatially averaged temperature of only about ∓0.02 °C in the upper kilometer of the ocean. The dynamical processes responsible for the temperature variability along the acoustic sections are not yet identified. No evidence is seen for a long term change in climate from intermittent data between 1983 and 1989 along a 4000-km section.
New approaches to model-based ultrasonic flaw sizing
Authors: Chiou Chien-Ping , Schmerr Lester W.
Published: October 2005

Ultrasonic equivalent flaw sizing methods have been recently used to size a flaw in a material by obtaining a best-fit simple equivalent shape that matches the ultrasonic scattering data. However, current ultrasonic equivalent flaw sizing methods have a number of important limitations: (1) they are both iterative and highly nonlinear in nature, and (2) they require the availability of flaw classification information. Here, a series of approaches are outlined that address both of the above problems. Both numerical and experimental results that validate these new approaches are also given. First, when the flaw shape is determined in terms of a best-fit equivalent ellipsoid, a new linear least-squares/eigenvalue method is described that can replace existing nonliner routines and provide a computationally fast and robust sizing procedure. Second, it is shown that if the shape is determined instead in terms of an expansion in spherical harmonics, the sizing problem again reduces to a simpler linear least-squares/differentiation process. Third, a way to do equivalent flaw sizing even when flaw classification information is not present is demonstrated. When such classification information is available, however, one can see how it can be used to improve sizing estimates for cracks, by the elimination of systematic measurement errors due to finite transducer bandwidth effects.
Normal mode expansions in dynamic electroelasticity and their application to electromechanical energy conversion
Authors: Zharii Oleg Yu.
Published: October 2005

A method of eigenfunction expansions is extended to transient problems of dynamics of piezoelectric bodies. After investigation of the eigenfunctions’ properties, the general solution of an initial boundary-value problem is constructed in the form of a series of eigenfunctions. Considerable differences between the structure of expansions obtained in this paper and that for a purely elastic case are discussed. The method derived is shown to be a convenient mathematical and physical basis of the theory of electromechanical energy conversion grounded on the concept of the electromechanical coupling factor. It allows one to present this important nonlinear integral characteristic of electroelastic field in the form of a combination of factors corresponding to normal modes of vibrations. The latter quantities are approximately equal to effective coupling factors. These factors can be easily calculated from experimental data by means of the Mason formula instead of Ulitko’s energy-related definition used in the paper. In practical problems, this circumstance enables one to simplify calculation of maximal values of the coupling factor and corresponding distributions of displacement with the formulas derived. In general, a consistent theory suggested in this paper gives one an opportunity to understand better the nature of dynamical behavior of piezoelectric bodies and of electromechanical energy conversion.
Preliminary results on speaker-dependent variation in the TIMIT database
Authors: Byrd Dani
Published: October 2005

A set of phonetic studies based on analysis of the TIMIT speech database is presented. Using a database methodological approach, these studies detail new results in speaker-dependent variation due to sex and dialect region of the talker including effects on stop release frequency, speaking rate, vowel reduction, flapping, and the use of glottal stop. TIMIT was found to be fertile ground for gathering acoustic–phonetic knowledge having relevance to the phonetic classification and recognition goals for which TIMIT was designed, as well as to the linguist attempting to describe regularity and variability in the pronunciation of read English speech.
Production of the word-final English /t/–/d/ contrast by native speakers of English, Mandarin, and Spanish
Authors: Flege James Emil , Munro Murray J. , Skelton Laurie
Published: October 2005

The primary aim of this study was to determine if adults whose native language permits neither voiced nor voiceless stops to occur in word-final position can master the English word-final /t/–/d/ contrast. Native English-speaking listeners identified the voicing feature in word-final stops produced by talkers in five groups: native speakers of English, experienced and inexperienced native Spanish speakers of English, and experienced and inexperienced native Mandarin speakers of English. Contrary to hypothesis, the experienced second language (L2) learners’ stops were not identified significantly better than stops produced by the inexperienced L2 learners; and their stops were correctly identified significantly less often than stops produced by the native English speakers. Acoustic analyses revealed that the native English speakers made vowels significantly longer before /d/ than /t/, produced /t/-final words with a higher F1 offset frequency than /d/-final words, produced more closure voicing in /d/ than /t/, and sustained closure longer for /t/ than /d/. The L2 learners produced the same kinds of acoustic differences between /t/ and /d/, but theirs were usually of significantly smaller magnitude. Taken together, the results suggest that only a few of the 40 L2 learners examined in the present study had mastered the English word-final /t/–/d/ contrast. Several possible explanations for this negative finding are presented. Multiple regression analyses revealed that the native English listeners made perceptual use of the small, albeit significant, vowel duration differences produced in minimal pairs by the nonnative speakers. A significantly stronger correlation existed between vowel duration differences and the listeners’ identifications of final stops in minimal pairs when the perceptual judgments were obtained in an ‘‘edited’’ condition (where post-vocalic cues were removed) than in a ‘‘full cue’’ condition. This suggested that listeners may modify their identification of stops based on the availability of acoustic cues.
Temporal decline of masking and comodulation masking release
Authors: McFadden Dennis , Wright Beverly A.
Published: October 2005

Masking sounds can be continuously present, gated simultaneously with the signal, or gated somewhat prior to the signal. This continuum of relative onset times was explored using waveforms of the sort commonly employed in studies of comodulation masking release (CMR). There was a 50-Hz masker band centered on the 1250-Hz tonal signal, and four 50-Hz flanker bands centered at 850, 1050, 1450, and 1650 Hz. In some conditions, all four flanker bands had the same temporal envelope, and the masker band either had that same envelope (correlated presentations) or a different envelope (uncorrelated presentations). In other conditions, all five bands had different temporal envelopes (all-uncorrelated presentations). The masker band and/or the four flanker bands were either gated nearly simultaneously with the signal (burst conditions) or were gated prior to the signal by a duration that was systematically varied (fringed conditions). The eight listeners could be partitioned into three groups on the basis of their response to these fringing manipulations. Two listeners (the large fringers) showed a gradual improvement in detectability with increasing fringe duration (called a temporal decline of masking), while three others (the small fringers) showed little improvement in detectability. For the remaining three subjects, there was evidence of a ‘‘learning’’ effect that changed them from large fringers to small fringers over a 10-week period of listening. When present, the temporal decline of masking was greater for the correlated than for the uncorrelated comodulation condition; as a consequence, the difference in detectability between them (the comodulation masking release or CMR) increased with fringe duration. By fringing the masker and flanker bands separately and in combination, it was revealed that the temporal declines of masking were primarily attributable to the fringing of the flanker bands. In contrast, large CMRs required long fringes on both the masker and flanker bands. The above results were obtained with 50-ms signals, but generally similar data were obtained with a signal duration of 240 ms. The difficulties raised for experimentalists and theorists by such long-term practice effects are discussed.
Psychometric functions for level discrimination and the effects of signal duration in the goldfish (C
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Authors: Fay Richard R. , Coombs Sheryl L.
Published: October 2005

Classical conditioning of respiration was used to obtain psychometric functions for pulsed tone level discrimination in the goldfish (Carassius auratus). Conditioned respiratory suppression is a graded response that has some properties of a confidence rating measure. These properties were used to obtain receiver operating characteristics (ROC) and psychometric functions using a blocked method of constant stimuli. Empirical ROCs and neurometric functions were also obtained for single auditory-nerve fibers using spike count as the decision variable in order to evaluate a simple rate code for level discrimination. Psychometric and neurometric functions for level discrimination are similar in showing the same general form (summarized by Weibull functions) that is independent of signal duration. The lower slope of neurometric functions compared with behavioral functions for level discrimination is in accord with similar data on sound detection and vision in nonhuman mammals. Both neural and psychophysical level discrimination thresholds decline with increasing duration (20 to 320 ms), with similar slopes except at short signal durations (20 to 50 ms). At these durations, the animal’s use of a channel-selection strategy and neural information following stimulus offset could reduce the difference between neural and psychophysical thresholds. The slopes of the neural and psychophysical duration functions are similar to those for human observers, but the majority of auditory-nerve fibers sampled have lower level discrimination thresholds than the behaving animal. Since human observers perform better than the majority of neurons in level discrimination, well-trained human listeners may be able to select channels with superior information, or to combine information across channels in ways that the goldfish and other animals do not. In general, one is encouraged to believe that neural mechanisms need not be more complex or sensitive than those considered here to account for pure-tone level discrimination in fishes, humans, and other vertebrates.
Analytical solution of the laminar mean flow wave equation in a lined or unlined two-dimensional rectangular duct
Authors: Gogate G. R. , Munjal M. L.
Published: October 2005

The prediction of the sound attenuation in lined ducts with sheared mean flow has been a topic of research for many years. This involves solving the sheared mean flow wave equation, satisfying the relevant boundary condition. As far as the authors’ knowledge goes, this has always been done using numerical techniques. Here, an analytical solution is presented for the wave propagation in two-dimensional rectangular lined ducts with laminar mean flow. The effect of laminar mean flow is studied for both the downstream and the upstream wave propagation. The attenuation values predicted for the laminar mean flow case are compared with those for the case of uniform mean flow. Analytical expressions are derived for the transfer matrices.
Error analysis for the four-load method used to measure the source impedance in ducts
Authors: Sridhara B. S. , Crocker Malcolm J.
Published: October 2005

The impedance of a sound source can be measured using direct approaches such as the standing wave and transfer function methods or indirect approaches such as two-load, three-load, and four-load methods. Unlike the direct and two-load methods, the three-load and four-load methods do not require the measurement of a complex quantity such as the acoustic transfer function. Therefore, a single-channel signal analyzer can be used to measure the autospectra needed in the case of the three-load and four-load methods. The formulation for the source impedance gives two and three second-order, nonlinear algebraic equations for the three-load and four-load methods. The unknowns in these equations are the real and imaginary parts of the source impedance. The two nonlinear equations in the three-load method can be solved graphically for each frequency of interest or by using well-known mathematical methods. However, in the four-load method, there are three nonlinear equations in terms of two unknowns which means one of the equations is redundant. The three nonlinear equations could also be reduced to two linear equations and the two equations could be solved for the real and imaginary parts of the source impedance. The accuracy of the solutions depends on how accurately the original (nonlinear) equations are satisfied when the real and imaginary parts are substituted into these equations. An error analysis of the formulation in the four-load method of source impedance measurement was done. It was found that the error due to apparent reduction of the nonlinear equations to linear equations was very large. The source impedance values computed using the four-load method were compared with those obtained from the direct (transfer function) method. Although the formulation of the four-load method satisfies the mathematical procedure, the error due to computation could be large, and further work is needed in the application of the three-load and the four-load methods.
On the calculation of acoustic radiation impedance of polygonal-shaped apertures
Authors: Rowlands G.
Published: October 2005

The analogy that exists between the calculation of low-frequency acoustic impedances and of electrostatic energies is used to obtain analytic expressions for the impedance for a range of aperture shapes.
Linear dependencies of electroelastic equations for extensional mode resonators
Authors: Kittinger E.
Published: October 2005

In this Letter a very compact formulation of the theory of the electroelastic effect of extensional mode resonators is presented. The expression derived is quite general insofar as no special assumptions concerning the orientation of the resonator are made. It is applicable to arbitrary piezoelectric materials and is not restricted to any particular material symmetry properties. On the basis of this general result, the source of linear dependencies encountered in the interpretation of experimental work find an explicit and direct explanation.
Scattering by an isotropic noncentrosymmetric solid sphere immersed in a fluid
Authors: Lakhtakia Akhlesh , Ma Yushieh
Published: October 2005

A formulation for the time-harmonic scattering response of an isotropic noncentrosymmetric (chiral) solid sphere immersed in a fluid is obtained, and the effect of chirality on the scattering response is numerically explored.
Transverse cusp diffraction catastrophes produced by the reflection of ultrasonic tone bursts from a curved surface in water: Observations
Authors: Frederickson Carl K. , Marston Philip L.
Published: October 2005

An experiment was performed to image the acoustical diffraction pattern decorating the transverse cusp caustic. In the vicinity of the cusp point, the wave field is described by the Pearcey function P(w2,w1). The wave field was formed by reflecting sound from a curved surface with the generic local shape h(x,y)=h1x2+h1xy2+h3y2. Images of the reflected wave field were formed by relating the pressure amplitude of points in the observation plane to the gray levels of pixels on a computer screen building a gray-scale picture of the wave field in the observation plane. When the source was replaced by a light source, the optical intensity was recorded for the same geometry. The optical experiment produced images of the caustic curve of the form d(u−uc)3=(v−vc)2 that were used to locate the cusp point in comparisons of imaged acoustical diffraction patterns to calculated patterns. In the region near the cusp point, the imaged and calculated patterns compare very well. There were no adjustable parameters used in the comparison; the calculated patterns were completely determined by the experimental setup. The general agreement between the imaged and calculated patterns supports the use of the paraxial approximation used to calculate the caustic and diffraction pattern.
Intensity measurements in the presence of standing waves
Authors: Guy R. W. , Li J.
Published: October 2005

A sound power measurement employing the point-to-point (p–p) measurement procedure within a semi-anechoic chamber resulted in a negative primary indicator (F2) due to weak standing waves in association with reflection surface proximity. An expression detailing errors inherent to a p–p measurement within standing waves was then developed and examined. Negative indicator F2 was found generally acceptable with regards to overall accuracy and infact may signal reduced measurement error, however, the presence of strong standing waves and reflection surface proximity can lead to exacerbated errors which may have consequences for measures of sound transmission loss or surface intensity profile; remedial actions are discussed.
Spectral parametrization of scattering from a random ocean bottom
Authors: Tang Dajun , Frisk George V.
Published: October 2005

This paper concerns the development of a concept in bottom scattering theory, in which a key ingredient is the introduction of a quantity called the scattering correlation coefficient (SCC), to characterize low-frequency sound scattering from a random ocean bottom. The conventional quantities used to characterize bottom scattering are the surface and volume scattering coefficients, which are not suitable either when scattering at small grazing angles is concerned (when interface wave will be involved in the scattering but the conventional scattering coefficients do not consider this effect), or when sub-bottom structures take part in the scattering process, which is often the case for low-frequency sound scattering problems. Because the SCC is defined in the wave-number domain, it does not have the ambiguity that the scattering coefficients have. An analogy can be made between the role played by the plane-wave reflection coefficient in the problem of reflection from a horizontally stratified medium and the role played by the SCC in the problem of scattering from a random medium. In the reflection problem, when the reflection coefficient at all frequencies and angles, including complex angles, is given, the influence of the stratified medium on the reflected wave is completely known; similarly in the scattering problem, when the SCC at all frequencies and wave numbers is given, the influence of the random medium on the scattered wave is completely known.