bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling low frequency scattering from small schools of fish
Authors: Feuillade C. , Nero R. W. , Love R. H.
Published: October 2005

A low-frequency scattering model for small to moderately sized fish schools has been developed. The model uses a mathematical formalism based upon the harmonic solution of sets of coupled differential equations, and incorporates a verified swimbladder scattering ‘‘kernel’’ for an individual fish. All orders of multiple scattering interactions between the fish are included, and the aggregate scattering field calculated by coherent summation. Application to ensembles of closely spaced fish indicates significant deviations from the returns expected when incoherent scattering is dominant. The peak target strength is reduced and the resonance frequency is shifted due to multiple scattering. The target strength also varies strongly with frequency as a result of interference effects. For widely dispersed ensembles, the model reproduces the results of incoherent scattering. For larger ensembles the model predicts target strength values near the main resonance which diminish sharply with depth. The effects of a school on the scattering of any single individual within it become greater as the school size increases. By reducing the viscous damping in the scattering kernel, the model can also describe scattering from small bubble clouds.
A generalized wave-number method for solving waveguide scattering problems
Authors: Fawcett John A.
Published: October 2005

A general plane-wave decomposition method for solving scattering problems for objects in a possibly range-dependent oceanic waveguide is presented. The waveguide’s interfaces and objects within the waveguide are characterized by plane-wave scattering matrices. The total response of the medium can be computed by combining these matrices using an invariant embedding approach. This operator formalism is independent of the method used to solve the individual free-space objector interface scattering problems. The method is derived from the theory of generalized reflection operators [B. L. N. Kennett, Wave Motion 6, 419–429 (1984)] and is also closely related to some T-matrix formulations [G. Kristensson and S. Ström, 917–936 (1978)]. The generalized wave-number method is used to compute scattering from a cylinder in perfect and penetrable waveguides. The case of a bottom sloping interface is also considered. For some of the examples, a comparison is made with the results from other computational techniques.
Sound scattering by a fluid-filled cylindrical shell in water
Authors: Kaduchak Gregory , Loeffler Charles M.
Published: October 2005

Previous calculations and observations of backscattering by cylindrical shells in water usually involve shells which are either empty or subject to extremely light interior loading conditions such as air. Typical echo signatures display distinct contributions described by specular reflection and guided waves launched along the shell structure. The present research analyzes the backscattering effects as a consequence of filling the interior cavity with a higher impedance fluid such as water. Energy transferred into the cavity couples into radiation mechanisms which drastically increase the fine structure in the backscattering form function. Dispersion curves derived from full 3-D elasticity theory via the Watson transform methodology display a complicated mode structure which is a combination of the guided waves found on a cylindrical shell in vacuum and the normal modes of a fluid-filled cylindrical cavity satisfying rigid boundary conditions. The radiation damping of the associated curves yields insight into mechanisms of energy transfer to and from the internal cavity through the guided Lamb waves traveling along the shell. The cylindrical shells studied are excited by plane waves at normal incidence and have radius to thickness ratios of 5% and 10%.
A perturbative technique to compute scattering of interface waves from pointlike obstacles
Authors: Smith Eric
Published: October 2005

A technique is presented to compute a scattering amplitude for waves from a pointlike inhomogeneity in an elastic medium with boundary, into interface as well as bulk modes. The particular system considered is a half-space of fluid overlying a half-space of a liner elastic solid, with the obstacle placed in the solid very near the boundary. The object of the calculation is to construct a perturbation theory in layered media in which the scattered wave respects the boundary conditions at each perturbative order. This can then be used to estimate and qualitatively analyze the significant features of such scattering, and to produce a well-defined yet simple algorithm for approximating exact solutions. [Work supported by the U.S. Navy, Office of Naval Research.]
Modeling of backscattering by bottom volumetric inhomogeneities
Authors: Tang Dajun
Published: October 2005

It has been recognized that when a sound wave encounters the ocean bottom, part of the energy will be scattered by volumetric inhomogeneities in the bottom. To simplify the mathematics, previous efforts in modeling the volumetric scattering process invoke some forms of plane-wave approximation to either or both of the forward and backward propagating fields. Since the ocean bottom has different acoustic properties from that of the water column, particularly since it often has a more complicated structure, introduction of the plane-wave approximation casts clouds on the validity of the modeling results. Here an approach is presented that uses the exact forward and backward propagating fields and calculates the backscattering strength numerically in the spatial domain. The bottom is assumed to be generally layered with superimposed random scatterers which have given correlation functions. Finally the validity of this model and its range of applicability will be discussed.
Using matched-field processing technique to map the forward-scattered signal
Authors: Lee Yung P.
Published: October 2005

Matched-field processing combines an acoustic propagation model with matched-filter processing to localize a source in three-dimensional space. It has been shown to be effective in discriminating passive sources both in range and depth by exploiting the vertical structure of the signal. Reverberation, especially the surface-scattered energy, is the primary concern for active systems. Surface scattering occurs near the ocean surface. Since matched-field processing can discriminate in depth, it may potentially provide significant clutter suppression for active systems. In a sea test, a vertical array was deployed and a cw source was moored from a stationary platform approximately 18.6 km away from the array. The forward-scattered energy was spectrally separated from the carrier and then MFP was performed to examine the spatial distribution of the scattered energy. MFP successfully maps the scattered energy near the surface. Simulations was done by generating realization of an ocean surface with randomly distributed surface waves and a modified FEPE was used to propagate signals to a vertical array. Results of this simulation show that MFP also successfully maps the simulated scattered energy near the surface. [Work supported by U.S. Navy.]
On automated language acquisition
Authors: Gorin Allen
Published: October 2005

The purpose of this paper is to review our investigation into devices which automatically acquire spoken language. The principles and mechanisms underlying this research are described and then experimental evaluations for several tasks are reported, involving both spoken and keyboard input. The generic mechanism in these experiments is an information-theoretic connectionist network embedded in a feedback control system.
A note on the effect of wall compliance on lowest-order mode propagation in fluid-filled/submerged impedance tubes
Authors: Easwaran V. , Munjal M. L.
Published: October 2005

Wave propagation in fluid-filled/submerged tubes is of interest in large HVAC ducts, and also in understanding and interpreting the experimental results obtained from fluid-filled impedance tubes. Based on the closed form analytical solution of the coupled wave equations, an eigenequation, which is the determinant of an 8×8 matrix, is derived and solved to obtain the axial wave number of the lowest-order longitudinal modes for cylindrical ducts of various diameter and wall thickness. The dispersion behavior of the wave motion is analyzed. It is observed that the larger the diameter of the duct and/or the smaller its wall thickness, the more flexible the impedance tube leading to more coupling between the waves in the elastic media. Also, it is shown that the wave motion in water-filled ducts submerged in water exhibits anomalous dispersion behavior. The axial attenuation characteristics of plane waves along water-filled tubes submerged in water or air are also investigated. Finally, investigations on the sound intensity level difference characteristics of the wall of the air-filled tubes are reported.
The nonlinear pressure field of plane, rectangular apertures: Experimental and theoretical results
Authors: Baker Andrew C. , Berg Aina M. , Sahin Ali , Tjo/tta Jacqueline Naze
Published: October 2005

The nonlinear sound pressure field from finite amplitude, plane, rectangular apertures, is considered. Experimental measurements on a 2.25-MHz transducer are presented for various source geometries and excitation levels. These results are compared with simulations based on the transformed beam equation, using a new algorithm which generalizes the Bergen code to treat the case of nonaxisymmetric on-source boundary conditions.
A numerical study of seafloor scattering
Authors: Robertsson Johan O. A. , Levander Alan
Published: October 2005

The processes which result in backscattered acoustic energy from the seafloor are of primary interest for interpreting sonar signals measured in the deep ocean basins. This complex problem can be approached from a realistic perspective with the employment of modern high-resolution seafloor bathymetry measurements and viscoelastic wave simulation techniques capable of modeling highly heterogeneous anelastic media. A numerical study of low-frequency (100–200 Hz) backscattering processes from rough seafloor models is presented and several scattering hypotheses are proposed. In particular the effects that low-Q sediments have on the backscattered field from a rough seafloor and the effects that perturbations in the different material properties have on the backscattered energy are investigated. The principal conclusions reached are that anelastic sediments on the seafloor can have a significant impact on the backscattered field from low grazing angle scattering experiments, and that small perturbations in the compressional sediment velocity can dramatically alter the backscattered field.
Perceptual normalization of synthesized vowels following natural speech and breath sounds
Authors: Sheffert Sonya M. , Whalen D. H.
Published: October 2005

The identification of synthetic vowels relies in part on a precursor phrase, suggesting that normalization is taking place. Breath intake sounds, which can also precede speech, may also give information. This study examines both speech and breath precursors. Two adult speakers (one male, one female) produced the phrase ‘‘The next one is.’’ They also produced audible breath sounds before saying the words ‘‘bead,’’ ‘‘bad,’’ or ‘‘bud.’’ Two 5-member continua were created, one from ‘‘bid’’ to ‘‘bed,’’ another from ‘‘bad’’ to ‘‘bud,’’ based on these words produced by each speaker. Formants were averages (across the two speakers) for the natural productions; F0 was 160, resulting in gender neutral tokens. The gender of precursor speech and breath before each continuum item were varied. The vowel information in the breaths also favored one end of the continuum or the other. Two results suggest that, under some circumstances, vowel identification was affected by breath precursors: (1) There were more /i/ responses on the ‘‘bid-bed’’ continuum following the female breaths; (2) there were more /æ/ responses following the male and female æ-breath. Paradoxically, natural speech precursors shifted identification toward the opposite gender’s formant space. Another test suggests that these vowels identification shifts did not arise postperceptually.
Intersyllabic regulation of F0 and SPL with and without auditory feedback
Authors: Wozniak Jane , Lane Harlan , Manzella Joyce , Perkell Joseph , Matthies Melanie , Svirsky Mario , O’Connell Michael , Mitchell Clay
Published: October 2005

Syllable-to-syllable fluctuation of F0 and SPL were measured in readings of a passage by 4 post-lingually deafened adults, recorded before and after they received cochlear implants, and one adult with neurofibromatosis-2 (NF2), who was initially profoundly deaf in one ear and had a mild to moderate hearing loss in the other (aided). Three of the 4 cochlear implant users reliably reduced syllable-to-syllable fluctuation in F0 and SPL following the activation of their speech processors. The fourth speaker began with and maintained the regularity achieved by the others post-activation. In recordings made following the onset of bilateral profound deafness, the NF2 subject showed increased syllable-to-syllable fluctuation in F0 and SPL. Results from another experiment [M. A. Svirsky etal., 1284–1300 (1992)], in which multiple repetitions of vowels in an /hVd/ context were produced by cochlear implant users with their processors turned off and on, suggest that some subjects showed less token-to-token variability in F0 and SPL with their processors turned on. The present results indicate that auditory feedback may also constrain the syllable-to-syllable variability of F0 and SPL contours. [Work supported by NIDCD.]
Measuring speaker normalization of fricatives using three methods
Authors: Johnson Keith , Peng Shuhui , Strand Elizabeth
Published: October 2005

Speaker normalization effects using continua from ‘‘sue’’ to ‘‘shoe’’ and three experimental tasks: Identification, goodness ratings, and direct prototype estimation are compared. The continua were formed by concatenating synthetic fricative noises ranging from [s] to [sh] with the vowel portion of ‘‘sue’’ or ‘‘shoe’’ produced by a male and a female speaker. Speaker normalization was measured in the identification task as a boundary shift between responses to the ‘‘male’’ stimuli and the ‘‘female’’ stimuli. Comparison of category boundaries was also used to measure the speaker normalization effect in the goodness rating paradigm, where a stimulus was considered to be in the ‘‘s’’ category when the ‘‘goodness as [s]’’ rating was higher than the ‘‘goodness as [sh]’’ rating. Speaking normalization in the prototype estimation procedure was measured as the shift in the average estimate of the [s] or [sh] prototype. Both measures of category boundary shift showed substantial speaker normalization effects, while the magnitude of the effect in the prototype estimation task, though significant, was three to four times smaller. However, this smaller effect closely mirrors the magnitude of the acoustic difference usually found between male and female fricative. [Work supported by NIH.]
Testing the importance of talker variability in non-native speech contrast training
Authors: Magnuson James S. , Yamada Reiko A. , Tohkura Yoh’ichi , Bradlow Ann R.
Published: October 2005

In contrast to results of training with stimuli produced by 5 talkers, Lively etal. [ 1242–1255 (1993)] reported that Japanese adults trained to perceive English /r/ and /l/ with stimuli produced by a single talker failed to improve from pretest to post-test, or to generalize to novel stimuli. That study was extended by training 5 groups of subjects each with a different talker, and by examining the retention of learning after 3 and 6 months. The previous results were partially replicated: Although all subjects showed significant learning during training, subjects in 3 of the 5 groups did not show significant improvement in a pretest–post-test comparison, did not generalize well to new stimuli, and did not show good retention in 3- and 6-month follow-up tests. Subjects in two of the five groups improved significantly from pretest to post-test, generalized well to new stimuli, and showed retention comparable to that of subjects trained with multiple talkers. The results indicate that while multiple-talker training leads to consistently good results, training with stimuli produced by only one talker may fail to promote generalization to new stimuli and talkers under certain conditions.
Perceptual training on Hindi dental and retroflex consonants by native English and Japanese speakers
Authors: Pruitt John S.
Published: October 2005

Previous research has shown that both native English and native Japanese speakers have great difficulty distinguishing the dental and retroflex stop-consonants of the Hindi language. However, Japanese speakers perform much better than English speakers—particularly on voiced-unaspirated consonants. This differential performance is thought to be due to contrastive experience that Japanese have with /d/ versus flapped /r/. (While English does contain a flapped /r/, it is not contrasted with /d/.) This research further compared English and Japanese speakers’ ability to distinguish the Hindi contrast by providing laboratory training and generalization tests for both language groups. Twenty native speakers from each language group were pretested and post-tested on voiced-aspirated, voiced-unaspirated, voiceless-aspirated, and voiceless-unaspirated dental and retroflex consonant-vowel syllables produced by 2 native Hindi speakers in 3 vowel contexts (/a/, /e/, /o/). Training consisted of 12, 30-min sessions in which only voiced-aspirated tokens produced by 6 Hindi speakers in 2 vowel contexts (/a/ and /o/) were presented in a self-paced, self-selected fashion. While Japanese speakers performed at much higher levels than English speakers, both groups improved markedly and showed generalization to new speakers, new vowel contexts, and new voicing/manner contexts. [Work supported by NIDCD and Applied Telecommunications Research, Kyoto, Japan.]
Visual feedback training for a nasal/non-nasal distinction
Authors: Schmidt Anna Marie
Published: October 2005

Native speakers of some Chinese dialects do not make a distinction between /n/ and /l/. This lack of a phonemic distinction may be a problem when these speakers learn English and the distinction is often difficult to teach. Three native Chinese speakers from Shanghai who had been in the US less than 2 years participated in a training experiment using a nasometer to provide visual feedback. Production was trained in initial position in minimal pairs using initial /n/–/l/ and /sn/–/sl/ pairs. Subjects’ perception of the distinction in English minimal pairs was tested prior to training and post-training using both same/different and categorization tasks.
Effects of perceptual learning on the production of a non-native contrast
Authors: Yamada Reiko A. , Tohkura Yoh’ichi , Bradlow Ann R. , Pisoni David B.
Published: October 2005

Previous research has shown a significant correlation between the perception and production of English /r/ and /l/ by Japanese speakers [Yamada etal., Proc. ICSLP94, 2023–2026 (1994)]. The present study further investigated this perception-production link by examining the transfer of training in perception to production of a non-native contrast. Twelve monolingual Japanese speakers were trained to perceive the English /r/–/l/ contrast using a high-variability training program [Lively etal., 2076–2087]. Recordings were also made of the trainees’ productions of English /r/-/l/ minimal pairs before and after the perceptual training. These pretest and post-test recordings were then evaluated perceptually by American listeners who were presented with pairs of tokens in an A-B test format. As expected, subjects’ accuracy on the perceptual task improved by about 16% after 45 training sessions. More importantly, subjects’ productions at pretest and at post-test were distinguishable by American listeners. More post-test productions were judged as ‘‘better’’ tokens of English /r/ and /l/ than pretest productions. Implications for the perception-production link in the acquisition of novel phonetic contrasts will be discussed. [Work supported by NIH and ATR.]
Acoustic analysis of Italian [r] and [l]
Authors: Argiolas Francesca , Macrì Federico , Di Benedetto Maria-Gabriella
Published: October 2005

Acoustic analysis of Italian [r] and [l] was carried out. Speech materials consisting of prestressed VCV syllables produced by 3 male and 3 female native speakers of Italian formed the basis of the present study. Each syllable was repeated 3 times by each speaker. The vowel in the syllable was [i,a,u] and the consonant was [r] or [l] in geminated and nongeminated form, leading to 216 syllables. Confirming the results of a previous study on Italian stop consonants [R. Rossetti, 2874 (1994)] results of the present analysis showed that the first vowel duration was systematically shortened in the geminated consonants. The data also showed that in the present case the duration of the consonant as well as, in most cases, of the VC and CV transitions were lengthened in the geminated form. Spectral analysis showed that there is little or no effect on the spectral properties of the consonants due to the presence of gemination. However, [r] in geminated form is in a few cases devoiced. Informal perceptual tests indicate that [r] can be automatically generated from [l] by introducing a silent portion within the stationary portion of [l].
A connection between coarticulation and variable rule application: Coda r’s in Brooklyn English
Authors: de Jong Kenneth , Zsiga Elizabeth C.
Published: October 2005

Ohala (1975, 1981) has proposed that sound changes are caused by listeners misperceiving coarticulatory effects. This paper examines variable ‘‘r-dropping’’ in Brooklyn English, and discusses the coarticulatory exigencies that may encourage speakers toward weakened forms. It is argued that production strategies do play a role in driving sound change apart from creating misperceptions. Recordings were made of speakers of Brooklyn and other dialects as part of the development of a larger multidialect database (Hertz etal., 1994). Analyses of nuclear r’s (as in bird, and burl) show that neighboring l’s both lower the second formant and raise the third formant, obscuring the r. Analyses of coda r’s in ‘‘r-ful’’ speakers also show following coronals raise the r’s third formant. Analyses of three Brooklyn speakers show one consistently produces coda r’s, one never does, and a third does so variably as evident in a bimodal distribution of formant patterns. The variable speaker produced r-less tokens particularly in codas which contained coronals, especially l. This pattern suggests that coarticulatory influences affect the application of variable rules. Thus coarticulation seems to exert pressure within a speaker toward a changed form. [Work supported by the NIDCD.]
Time-variation in Mandarin voiceless sibilant spectra
Authors: Xu Yi
Published: October 2005

The three Mandarin sibilant fricatives, [s], [hooked ess], and [looped cee], were studied using a combination of time averaging and ensemble averaging as described by Xu and Wilde [ 3230 (A) (1994)]. Ten native speakers of Beijing Mandarin (5 male and 5 female) produced these fricatives followed by both unrounded and rounded high vowels. Time-averaged spectra were obtained by averaging 13 consecutive 8-ms FFT windows over 20-ms intervals. Token-ensemble-averaged spectra were then obtained by averaging over the time-averaged spectra of 10 repetitions of each sentence produced by each speaker at time-normalized locations in the utterances. Further ensemble-averaging was also performed over the male and female speakers separately to obtain group-ensemble-averaged spectra. Preliminary examination of both token-ensemble-averaged and group-ensemble-averaged spectra reveals that (a) Mandarin sibilants have substantial time variation in their noise spectra, indicating continuous articulatory movement throughout the production of the frication; and (b) all three sibilants manifest substantial spectral variation due to anticipatory coarticulation with the following vowel. This kind of variation is evident from the very beginning of the frication noise, indicating that the extent of the anticipatory coarticulation may go beyond the beginning of the frication. [Work supported by NIH.]
Perception of vowel length in Arabic
Authors: Al-Bannai Abdulla A.
Published: October 2005

This study investigates the acoustic correlates of distinctive vowel length in Arabic, and examines the extent to which these cues might figure in the phonological distinction of vowel length in Arabic. The perceptual experiment determines the accuracy with which vowel duration contrast in spoken Arabic can be auditorily represented. The method was to create sets of stimuli by adding or removing a variable numbers of the excised vowel pitch period in the data selected. These stimuli were presented to native speakers of Arabic in a word identification task. The perceptual accuracy of vowel duration as determined from the slopes of the identification curves revealed that relative vowel duration is the dominant acoustic cue in the phonological distinction of vowel length in Arabic. But spectral cues such as steady-state formant frequency, level of intensity play a significant secondary role in the discrimination of vowel contrast when the relative duration is maximally ambiguous between short versus long vowels. a)Send notice to: P.O. Box 5837, Sharjah, U.A.E.
Waveform dynamics and the perceptual segregation of concurrent vowels
Authors: Assmann Peter
Published: October 2005

When two synthetic vowels are presented concurrently, listeners identify the vowels more accurately if they differ in fundamental frequency (F0) or if one of them is preceded/followed by a gliding (versus static) formant pattern. Previous experiments have shown that gliding formants generally do not help listeners identify the vowel to which they are linked; instead, they make the vowel without transitions easier to identify. One explanation is that the formant transition region provides a brief interval during which the competing steady-state vowel is perceptually more prominent. This interpretation is supported by two computational models that perform a filter bank analysis, process the waveform in each filter channel using a sliding temporal window, and determine which region of the signal provides the strongest evidence of each vowel. Model A computed the energy in each channel at successive time intervals to generate runningexcitationpatterns. Model B used a temporal analysis to generate runningautocorrelationfunctions, and included a further stage to partition the channels based on periodicity cues. Both models predicted effects of F0 and gliding formants, but model B provided better predictions of the pattern of listeners’ identification responses. Identification of concurrent vowels appears to benefit from an analysis of the composite waveform using a sliding temporal window, combined with a form of F0-guided source segregation.
Does the perceptual magnet effect hold for the [i] category?
Authors: Sussman Joan E. , Gekas Brian S.
Published: October 2005

Recent speech perception investigations [J. E. Sussman and V. J. Lauckner-Morano, 539–562 (1995); P. Iverson and P. K. Kuhl, 563–572 (1995)] support a ‘‘perceptual magnet effect’’ [P. K. Kuhl, Percept. Psychophys. 50, 93–107 (1991)], i.e., poor discrimination around a best exemplar compared with discrimination around a poor example of the category. To date, the magnet effect has been observed using the vowel [i] or consonant categories. A magnet effect might be expected because a range of good [i] tokens around a ‘‘best’’ exemplar would exist. However, a magnet effect may not occur for vowels with smaller and more variable categories. Each of 10 listeners rated [ib] stimuli as the [i] in ‘‘bib’’ or not the [i] in ‘‘bib.’’ Then, each listener heard the tokens he/she had labeled as [i] at least 50% of the time and chose a ‘‘best [i].’’ Results show that [i] has a smaller range (45–60 mels) around a best exemplar than [i]. Subjects chose different tokens as their ‘‘best’’ exemplar and varied in the number of tokens located in their [i] categories. Finally, results were compared to two sessions of a Change/No-change discrimination task: One with the ‘‘best [i]’’ s the fixed standard, the other with a poorer example of [i] as the fixed standard for measurement of a magnet effect.
Generalization in the vowel space
Authors: Aldridge Michelle
Published: October 2005

Vowels may be represented by a three-dimensional volume of space. The axes of the volume may be defined in articulatory terms (front–back, high–low, rounded–unrounded) or in physical terms (F1, F2, F3). Shepard [Science 237, 1317–1323 (1987)] plotted data of Peterson and Barney [ 175–184 (1952)] to show that generalization in the vowel space is an instance of his universal law of generalization, an exponential decay function with physical measures on the x axis. This theory is contradicted by the magnet effect [P. Kuhl, Percept. Psychophys. 50, 93–107 (1991)] which indicates that some areas of the vowel space are perceptually shrunken. Experiments with naive adult subjects were executed. Generalization, ABX, and discrimination experiments were performed using eight cardinal vowels plus intermediate steps between selected vowels. Results, indicating both Shepard and Kuhl are partially correct, are best represented by Gluck’s scheme [Psych. Sci. 2, 50–55 (1991)] with the data indicating that it is the distinctive features of vowels that are perceived categorically. There was little evidence of language-specific effects for adults. Pilot work with newborns indicate that they organize the vowel space like adults.
Psychophysical procedure and the perceptual magnet effect: Comparisons of fixed and roving AX discrimination of /i/
Authors: Iverson Paul , Kuhl Patricia K.
Published: October 2005

Recent experiments by Iverson and Kuhl [ 553–562 (1995)] have demonstrated that the perception of /i/ is influenced by category goodness. Listeners exhibit a perceptualmagneteffect characterized by high sensitivity to acoustic differences near poor exemplars of /i/ and low sensitivity near excellent exemplars of /i/. The present study examines whether this effect is influenced by psychophysical procedures. Listeners were asked to discriminate pairs of stimuli from an /i/ to /e/ continuum, and the task was varied in two ways: (1) Each block of trials had either one pair of tokens (fixed discrimination) or pairs of tokens from the entire stimulus range (roving discrimination), and (2) the acoustic difference between each pair of tokens was either 30 or 60 mels. The results demonstrated that the peak in discrimination at the /i/-/e/ boundary diminished with fixed discrimination tasks and 30-mel differences between tokens, supporting previous findings [Macmillan etal., 1262–1280 (1988)]. However, the magnitude of the perceptual magnet effect seemed less influenced by these manipulations. The results suggest that distortions of sensitivity at boundaries and within phonetic categories may arise from different mental processes.
An investigation of the perceptual magnet effect in adults
Authors: Renda Susan C. , Hawks John W. , Klich Richard
Published: October 2005

Three experiments were undertaken to investigate the validity and strength of the perceptual magnet effect in adults. First, the original perceptual magnet experiment [P. K. Kuhl, Percept. Psychophys. 50, 93–107 (1991)] was directly replicated with adults, using Kuhl’s stimulus parameters. These subjects were then tested with the AAXX protocol used to test monkeys in Kuhl (1991). Generalization scores were computed for subjects under both conditions and compared. A second group of subjects rated a large number of /KY/ vowel tokens in the next experiment. Average ratings were computed and a prototype (P) and nonprototype (NP) were chosen based on them. Variants of each were synthesized as in Kuhl (1991). Subjects rated the goodness of each variant on a scale from 1 to 7. In addition they assigned a 0 to any token perceived as not belonging to the /i/ category. The subjects then participated in the perceptual magnet experiment. Data from trials containing stimuli assigned 0 were excluded from analysis. In the third experiment, a large number of /EH/ vowel tokens were rated and P and NP were chosen. Variants were synthesized and rated and the perceptual magnet effect experiment was again conducted using these tokens. Results and implications of these experiments will be discussed.
Average response of an infinite plate on a random elastic foundation
Authors: Turner Joseph A. , Weaver Richard L.
Published: October 2005

The average response of infinite thin plates with attached random impedances is examined. The added impedance, which represents typical heterogeneities that might occur on complex shells, provides light coupling between the three propagation modes. The problem is formulated in terms of the Dyson equation which governs the mean plate response. It is solved within the assumptions of the Keller (smoothing) approximation which is valid when the heterogeneities are weak. Scattering attenuations are derived for each propagation mode. The specific case of delta-correlated springs provides a simple intuitive result for a statistically homogeneous plate. The attenuation of one wave type due to coupling to another is shown to be proportional to the modal density of the other wave type. Thus the attenuation of extensional and shear waves is predominantly due to mode conversion into flexural waves and is proportional to the large modal density of flexural waves. The flexural degrees of freedom serve as a sink for the energy of the membrane modes and constitute for them an effective fuzzy structure. A similar result is expected for the more complicated submerged shell case. A discussion of diffuse energy transport on such a plate will also be presented. [Work supported by ONR.]
Vibrational response of a simple oscillator attached to an elastic structure
Authors: Photiadis Douglas M. , Bucaro J. A. , Houston Brian H.
Published: October 2005

The effect of many internal degrees of freedom on the vibration of elastic structures has been of great recent interest; several theories have predicted damping effects arising from associated internal resonances. As an initial effort to explore this phenomena experimentally, the behavior of a single such oscillator attached to ribbed cylindrical shell section has been measured. The single oscillator has been found to give rise to a fairly broadband resonance structure, with a bandwidth that paradoxically increases with decreasing frequency. These results, along with the physical interpretation and modeling, will be discussed.
Response of a fuzzy structure in terms of the impulse response function
Authors: Maidanik G. , Dickey J.
Published: October 2005

A masterstructure is defined in terms of a known and proper impulse response function g∞(x‖x’,ω), where x is the spatial variable that spans the master structure and ω is the frequency variable. The response v∞(x,ω) of the master structure to the external drive pe(x,ω) is stated in the form v∞(x,ω)=∫g∞(x‖x’, ω)dx’ pe(x’,ω), where dx is an elemental ‘‘volume’’ in the x domain. An ensemble of appendages is attached to the master structure. The ensemble and its attachment configures an appendedmasterstructure. The response v(x,ω) of the appended master structure is stated in the form v(x,ω)=∫g∞S(x‖x’,ω)dx’ pe(x’,ω), where g∞S(x‖x’,ω) is the impulse response function of the appended master structure and it is assumed that the external drive remains unchanged. In the preceding equation it is implied that g∞S(x‖x’,ω) is properly derived; indeed, without this propriety the equation is meaningless. An ensemble of configurations defines a master structure that is variously appendaged. When the ensemble of configurations is statisticalized, a fuzzystructure is defined. Using this equation and designating statistical averaging over configurations by angular brackets, one obtains the response 〈v(x,ω)〉 of a fuzzy structure in the form 〈v(x,ω)〉=∫〈g∞S(x‖x’, ω)〉dx’ pe(x’,ω). In 〈g∞S(x‖x’,ω)〉 only statistical variations in the properties of the appendages and their attachments are involved; a proper g∞S(x‖x’,ω) is not committed to v(x,ω) and pe(x,ω). Thus it is argued that the last equation is an acceptable solution to the response 〈v(x,ω)〉 of a fuzzy structure.
Prediction of scattering cross sections using averaged models
Authors: Photiadis Douglas M. , Hughes David
Published: October 2005

The presence of internal structure can greatly alter the acoustic behavior of elastic structures. Even in relatively simple systems, it is necessary to employ approximate models, effectively averaging out unwanted detail. Some phenomenological aspects can be easily obtained in this way provided the ‘‘base’’ structure is not too complicated. For example, the locus of peaks in the scattering cross section as a function of frequency and angle can often be predicted in a deterministic manner, but estimating the actual scattering levels requires more sophisticated modeling. One approach to this modeling problem is to employ a ‘‘fuzzy’’ structures paradigm in which a Neumann series involving the random aspects of the internal structure is averaged. A more sophisticated approach involves directly constructing and approximating equations for the desired averages; employing the Dyson and Bethe-Salpeter equations of random media theory. These techniques have been applied to predict the scattering cross section from an irregular ribbed structure. The results will be discussed and compared.
Electrodynamic reciprocity method for vibration standards
Authors: Ge Li-Feng
Published: October 2005

In a previous paper, a reciprocity calibration formula different from the Levy–Bouche’s is derived [L.-F. Ge, Proceedings of the XIII IMEKO World Congress, 2606–2610 (1994)]; the latter has been regarded as a standard method [ISO 5347-0, 1987; ISO/DIS 5347-20, 1990]. The new formula is S=(RT/jω)1/2 (V/ms−2), where T is the mean of the transfer admittance ratio, Tn=Mn/(Yn−Yo) and R is the voltage ratio for the typical three-transducer-two-experiment procedure, in which an electrodynamic transducer serves as reciprocal one. This method is suited to the low- and mid-frequency ranges, and most accurate at 100–1000 Hz. This paper reveals that a coefficient of variation, i.e., ratio of standard deviation of Tn to its mean value, can be viewed as a reciprocity index of such an electrodynamic calibration system including two transducers and a solid mass medium. An index smaller than 0.5% indicates that the system is better reciprocal, and can be calibrated more accurately. At frequencies higher than about 3000 Hz, nonlinear problems, such as stress wave effect and resonance, become pronounced, and should be considered; a better way would be to apply other more available methods, such as the laser interferometry and piezoelectric reciprocity method.
Free vibration of liquid-filled composite shells of revolution
Authors: Xi Z. C. , Yam L. H. , Leung T. P.
Published: October 2005

As composite materials are increasingly used in aerospace, marine, civil power generating, petrochemical, and chemical industries, the interaction of fluid and composite shells of revolution has been an active subject in the area of structural dynamics. In this paper, a semianalytical procedure was presented for predicting free vibration characteristics of liquid-filled composite shells of revolution. A new unaxisymmetric conical frustum element was derived based on the first-order shear deformation theory. The element considers both the displacement in the circumferential direction and the rotation around the meridian of the shell. The coupling between symmetric and antisymmetric modes is taken into account in the formulation. Reduced integration was employed to avoid ‘‘shear locking.’’ Numerical examples were given for free vibrations of liquid-filled laminated shells of revolution with various types of boundary conditions. Comparisons of the results predicted by the present paper with those available in the literature were made. The effects of the liquid depth, the ratio of mass density of the liquid to that of the shell, circumferential wave number, thickness to radius ratio, ply angle, and stacking sequence on natural frequency of wet shells were discussed. [Work supported by RC, HK Poly U.]
Prediction of obstruent spectra from the slope of preceding and following second formant transitions
Authors: Weismer Gary , Guhan Vidya , Kent Ray D.
Published: October 2005

There is evidence that the slope of second formant (F2) transitions provides an index of the severity of speech mechanism involvement in motor speech disorders [Weismer etal., 1085–1098 (1992)]. From an articulatory perspective, the slope of the F2 transition is an ordinal index of the rate of change in vocal tract configuration. It was hypothesized that, for single words, these F2 slopes would predict quantitative spectral characteristics of adjacent obstruents, under the assumption that the rate of change in vocal tract configuration during a vocalic segment would influence the articulation of a preceding or following obstruent. Quantification of obstruent spectra was achieved by means of spectral moments, which were regressed on F2 transition slopes for a group of normally articulating men and a group with amyotrophic lateral sclerosis, a degenerative motoneuron disease typically associated with dysarthria. Results partially confirmed the hypothesis for both groups of subjects; the findings will be discussed in terms of separate treatment of vocalic and obstruent segments in a model of speech intelligibility. [Work supported by NIH.]
Acoustic-to-articulatory mapping of fricatives
Authors: Riegelsberger Edward L. , Krishnamurthy Ashok K.
Published: October 2005

This research considers the acoustic-to-articulatory mapping of fricative speech. By incorporating additional knowledge about fricative production, perception, and dynamics into the mapping scheme, improved performance may be achieved over standard acoustic-to-articulatory mapping techniques. A hybrid time-frequency domain articulatory synthesizer and numerical optimization techniques are applied to steady-state, unvoiced fricatives. The work differs from the fricative inverse mapping experiments of Sorokin [V. Sorokin, Speech Commun. 14, 249–262 (1994)] and Shirai [K. Shirai and S. Masaki, Speech Commun. 2, 111–114 (1983)] in that a fricative-specific linked codebook is used to initialize optimization and amplitude sensitive distance measures are used. The fricative codebook produces starting configurations for numerical optimization based on their spectral characteristics and their ability to match frication source characteristics for a given lung pressure and glottal configuration. The use of amplitude sensitive spectral distance measures is necessary to account for the interaction between the tract and the flow-dependent frication source. Examples of acoustic-to-articulatory mapping are given that compare fricative articulatory models and fricative spectral distance measures for the inverse mapping scheme. Acoustic-to-articulatory performance is evaluated in terms of spectral distance and clustering ability. [Work supported by the AFOSR.]
Modeling of optical microphone performance
Authors: Bilaniuk Nykolai , Delâge André
Published: October 2005

A number of modulation principles and an even larger variety of specific implementations may be considered for all-optical microphones. The procedures for designing optical microphones described in this paper include three principal steps. First the mechanical response of a membrane to an acoustic field is modeled by an analytical technique [A. Hu etal., 3049–3056 (1992)], and is used to obtain the magnitude of the membrane deformation and its frequency response. Next the behavior of the optical path under this flexure is studied using the beam propagation method. Predictions of the optical sensitivity (depth of modulation versus membrane displacement), and optical insertion loss are thus obtained. Third the signal-to-noise performance of the device is evaluated by representing all noise sources as equivalent acoustic noise fields at the microphone input. Applications of this methodology to optical microphone designs under consideration are described.
Signal-to-noise ratio of thermoacoustic enhanced photoacoustic spectrometers
Authors: Arnott W. Patrick , Moosmüller Hans , Abbott Robert E. , Ossofsky Michael
Published: October 2005

The quality factor, Q, of plane or radial wave resonators can be increased and controlled using thermoacoustics. When such a resonator is used in photoacoustics, a laser beam passes through it and sound is produced when light absorption occurs. Sound amplitude is proportional to the coefficient for light absorption, to the resonator Q, and to the laser beam power. Traditionally, resonator dimensions have determined both the coupling strength of the laser beam to a particular mode and the quality factor. High coupling strength is desirable, but implies use of a narrow resonator where most of the interior is filled with laser. On the other hand, high Q traditionally implied need for a wide resonator. Thermoacoustics can be used to increase the Q of the narrow resonator to optimize the acoustic signal. Our theory and measurements show that the thermoacoustically enhanced photoacoustic spectrometer can be viewed as an analog narrow-band amplifier for sound where the resonance frequency is f0, the bandwidth is f0/Q, the gain is Q, and the signal-to-noise ratio for discrimination against Gaussian acoustic noise in the resonator is Q1/2. [Work supported by the EPA, ONR.]
Visualization of oscillating temperature and flow fields in the stack region of a thermoacoustic refrigerator model
Authors: Herman C. , Wetzel M. , Volejnik M.
Published: October 2005

In order to study the oscillating temperature and flow fields in the stack region, a model of a thermoacoustic refrigerator is built. The model allows the application of visualization techniques such as holographic interferometry, thermochromatic liquid crystals, and smoke injection. In the first experiments, the correct operation of the thermoacoustic refrigerator is verified. Using the Kundt’s dust tube method, the propagation of longitudinal plane-wave fronts is analyzed. Furthermore, the distortion due to the presence of higher harmonics in the resonance tube is kept small. This is verified by applying the Fourier transform to a pressure signal at several positions within the resonance tube. The focus of current investigations is to apply the above visualization techniques in the stack region and its neighborhood. These measurements provide information which can be used to determine requirements for the design of heat exchangers. An improved design of the heat exchangers and a better understanding of heat transfer processes and flow phenomena are key issues to improve the efficiency of thermoacoustic refrigerators. [Work supported by the Office of Naval Research; Martin Wetzel is also supported by a scholarship from DAAD.]
Plane- and radial wave thermoacoustic engines with variable plate separation
Authors: Lightfoot Jay A. , Raspet Richard , Bass Henry E. , Arnott W. Patrick
Published: October 2005

Rott developed the theory of thermally driven acoustic oscillations in tubes with variable cross section. Bennett, in her dissertation, considered plane-wave thermoacoustic refrigerators with variable plate separation and found them to have higher COP’s than those with parallel plates. This principle has application to the work in radial wave thermoacoustics, since variable plate separation is a natural product of radial vertical-plate engines with constant plate thickness. Bennett appears to have overlooked a term in the wave equation. An analysis is presented including this term to study two important questions: What is the optimal slope, and even more basic, which side (hot or cold) should have the greater plate separation? [This work was supported by the Office of Naval Research.]