bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of frequency transposition on the discrimination of amplitude envelope patterns
Authors: Takeuchi Annie H. , Braida Louis D.
Published: October 2005

The effects of systematic training on listeners’ ability to compare the amplitude envelopes of signals differing in frequency was tested. Listeners indicated which of two comparison signals had the same amplitude envelope as the target signal. During training, center frequencies of comparison signals were gradually increased or decreased relative to target signal center frequencies of 500, 1600, and 3160 Hz. After training, performance was still worse when target and comparison signals were at different frequencies rather than at the same frequency, except possibly when comparison signals were higher in frequency than the 1600-Hz target. Thus the amplitude envelopes of signals do not appear to be perceived independently of the signal itself. Listeners who received no training performed similarly to the trained listeners, except that their performances declined when comparison signals were higher in frequency than the 1600-Hz target. Training did not reduce interlistener differences in overall performance or in the extent of the decline in performance when frequency differences between the target and comparison signals were introduced. The effects of frequency lowering on amplitude envelope discrimination do not appear to be related to the reduced efficacy of frequency-lowered speech-derived amplitude envelopes in supplementing speechreading.
The supraglottal articulation of prominence in English: Linguistic stress as localized hyperarticulation
Authors: de Jong Kenneth J.
Published: October 2005

The results of an articulatory investigation of the supraglottal correlates of linguistic prominence in English, and a proposal of a unified description of linguistic stress are reported. Three models of stress are evaluated: that prominence expands jaw movement, that stress expands an abstract articulatory scale involving the opening and closing of the vocal tract, and that stress involves a localized shift toward hyperarticulate speech. A corpus of x-ray microbeam records of sensible speech is studied, within which the stress pattern is controlled and is checked by means of an intonational analysis. Jaw movement data yield similar results to earlier studies, but kinematic differences interpreted with reference to a gestural theory suggest that different subjects use different articulatory strategies to articulate stress contrasts. In addition, the jaw, lip, and tongue interact in the articulation of stress in subject dependent ways. Thus the articulation of stress should be formulated in terms of abstract articulatory goals, rather than in terms of individual articulator positioning. Finally, the data show that stress affects the articulation of nonsonority distinctions such as backness in vowels and point of articulation in consonants. A hyperarticulation model of stress is discussed in terms of these results.
Children learn separate aspects of speech production at different rates: Evidence from spectral moments
Authors: Nittrouer Susan
Published: October 2005

One theoretical perspective on speech development holds that segmental structure gradually emerges in the utterances of children as their first words, realized as roughly specified patterns of gesture, are differentiated into patterns of precisely specified and carefully coordinated gestures. The purpose of the present study was to test one aspect of this theoretical position, namely that children’s articulatory gestures are not as precisely specified as are those of adults. In addition, a related hypothesis was tested, namely that some patterns of gesture achieve adultlike precision sooner than others. To test these hypotheses, the first, third, and fourth spectral moments were derived for fricative (/s/ and /∫) and for stop-burst (/t/ and /k/) noises in the speech samples of children (3 to 7 years of age) and of adults. First spectral moments for fricatives showed stronger consonant effects (i.e., /s/ vs /∫/) for adults’ than for children’s samples. This acoustic finding replicated a previous result [Nittrouer et al., J. Speech Hear. Res. 32, 120–132 (1989)], and provided support for the hypothesis that some articulatory gestures are not as precisely specified in children’s speech as in that of adults. First spectral moments for /t/ and /k/ revealed no age-related differences in the magnitude of the consonant effect, providing support for the hypothesis that some gestures achieve mature status sooner than others. Although not a focus of the present study, it was also found that children’s /k/ first moments varied more than adults’ as a function of vowel environment (/i/, /ɑ/, or /u/). Thus further support was obtained for a finding described elsewhere: For at least some articulatory gestures, there is greater influence of one on another for children’s than for adults’ speech [e.g., Nittrouer et al., J. Speech Hear. Res. 32, 120–132 (1989); S. Nittrouer, J. Speech Hear. Res. 36, 959–971 (1993)].
Mapping the perceptual magnet effect for speech using signal detection theory and multidimensional scaling
Authors: Iverson Paul , Kuhl Patricia K.
Published: October 2005

Recent experiments have demonstrated that the category goodness of speech sounds strongly influences perception in both adults and infants [Kuhl, Percept. Psychophys. 50, 93–107 (1991); Kuhl et al., Science 255, 606–608 (1992)]. Stimuli judged as exceptionally good instances of phonetic categories (prototypes) make neighboring tokens in the vowel space seem more similar, exhibiting a perceptual magnet effect. Three experiments further examined the perceptual magnet effect in adults. Experiment 1 collected goodness and identification judgments for 13 variants of the vowel /i/. Experiment 2 used signal detection theory to assess the discrimination of these tokens using a bias-free measure (d′). Experiment 3 employed multidimensional scaling (MDS) to geometrically model the distortion of the perceptual space due to the magnet effect. The results demonstrated a strong relationship between category goodness and discrimination. Vowel tokens receiving high goodness ratings in experiment 1 were more difficult to discriminate in experiment 2 and were more tightly clustered in the MDS solutions of experiment 3. These findings support the existence of a perceptual magnet effect, and may help explain some aspects of first language learning in infants and second language learning in adults.
The role of formant transitions in the perception of concurrent vowels
Authors: Assmann Peter F.
Published: October 2005

When two voices compete for the attention of the listener, the spectral peaks that define the formants of one voice can be intermittently obscured or distorted by formants of the other voice. However, formant peaks vary slowly and continuously in frequency and time, providing a basis for tracking through regions of overlap. Three experiments investigated the ability of listeners to exploit formant-pattern continuity to segregate pairs of synthesized vowels that were presented simultaneously and monaurally. Experiments 1 and 2 examined the effects of introducing one member of the pair with formant-frequency transitions that specified syllable-initial glides /w/ or /j/. Identification accuracy was generally higher in conditions where glides were present. Gliding formants provided smaller benefits than a two-semitone difference in fundamental frequency between the vowels. Experiment 3 found larger effects of formant transitions specifying initial or final /l/. Overall, formant transitions did not make it easier to identify the vowel to which they were linked; instead, they helped by making the competing vowel more identifiable. One explanation for improvement in the glide conditions is a formant-tracking process which groups together the formants of each voice using the Gestalt principle of good continuation. However, this account predicts improvement for both vowels which was generally not observed. An alternative explanation is suggested by models that apply a brief, sliding temporal window to determine which region of the signal provides the strongest evidence of each vowel constituent. The formant transition region may provide a time interval during which the competing steady-state vowel is perceptually more prominent.
How young and old adults listen to and remember speech in noise
Authors: Pichora-Fuller M. Kathleen , Schneider Bruce A. , Daneman Meredyth
Published: October 2005

Two experiments using the materials of the Revised Speech Perception in Noise (SPIN-R) Test [Bilger et al., J. Speech Hear. Res. 27, 32–48 (1984)] were conducted to investigate age-related differences in the identification and the recall of sentence-final words heard in a babble background. In experiment 1, the level of the babble was varied to determine psychometric functions (percent correct word identification as a function of S/N ratio) for presbycusics, old adults with near-normal hearing, and young normal-hearing adults, when the sentence-final words were either predictable (high context) or unpredictable (low context). Differences between the psychometric functions for high- and low-context conditions were used to show that both groups of old listeners derived more benefit from supportive context than did young listeners. In experiment 2, a working memory task [Daneman and Carpenter, J. Verb. Learn. Verb. Behav. 19, 450–466 (1980)] was added to the SPIN task for young and old adults. Specifically, after listening to and identifying the sentence-final words for a block of n sentences, the subjects were asked to recall the last n words that they had identified. Old subjects recalled fewer of the items they had perceived than did young subjects in all S/N conditions, even though there was no difference in the recall ability of the two age groups when sentences were read. Furthermore, the number of items recalled by both age groups was reduced in adverse S/N conditions. The results were interpreted as supporting a processing model in which reallocable processing resources are used to support auditory processing when listening becomes difficult either because of noise, or because of age-related deterioration in the auditory system. Because of this reallocation, these resources are unavailable to more central cognitive processes such as the storage and retrieval functions of working memory, so that ‘‘upstream’’ processing of auditory information is adversely affected.
Objective speech quality assessment and the RPE-LTP coding algorithm in different noise and language conditions
Authors: Hansen John H. L. , Nandkumar S.
Published: October 2005

The formulation of reliable signal processing algorithms for speech coding and synthesis require the selection of a prior criterion of performance. Though coding efficiency (bits/second) or computational requirements can be used, a final performance measure must always include speech quality. In this paper, three objective speech quality measures are considered with respect to quality assessment for American English, noisy American English, and noise-free versions of seven languages. The purpose is to determine whether objective quality measures can be used to quantify changes in quality for a given voice coding method, with a known subjective performance level, as background noise or language conditions are changed. The speech coding algorithm chosen is regular-pulse excitation with long-term prediction (RPE-LTP), which has been chosen as the standard voice compression algorithm for the European Digital Mobile Radio system. Three areas are considered for objective quality assessment which include: (i) vocoder performance for American English in a noise-free environment, (ii) speech quality variation for three additive background noise sources, and (iii) noise-free performance for seven languages which include English, Japanese, Finnish, German, Hindi, Spanish, and French. It is suggested that although existing objective quality measures will never replace subjective testing, they can be a useful means of assessing changes in performance, identifying areas for improvement in algorithm design, and augmenting subjective quality tests for voice coding/compression algorithms in noise-free, noisy, and/or non-English applications.
Speech intelligibility assessment in a helium environment
Authors: Mendel Lisa Lucks , Hamill Bruce W. , Crepeau Loring J. , Fallon Eric
Published: October 2005

The purpose of this study was to compare the appropriateness and effectiveness of the speech perception in noise (SPIN) test and the Griffiths version of the modified rhyme test (GMRT) in assessing Navy divers’ speech understanding using communication systems containing different helium speech unscramblers (HSUs), one of which produces, by subjective observations, more intelligible output than the other. Divers participating in a saturation deep dive and a group of nondivers using digital audio tape recordings of the stimuli used by the divers were tested. Mean percent correct scores on the SPIN and GMRT lists within two listening conditions (taped, topside–diver and live-voice, diver–diver) were almost identical. Listeners scored better on both tests in the topside–diver condition than in the diver–diver condition. The majority of the SPIN errors were on low-predictability items that are void of context. Context clearly played a role in measuring the performance of these subjects, at least for the SPIN test. No significant differences were measured between the two HSUs, although a trend was seen favoring one HSU over the other for the divers. These results have theoretical as well as practical value for measuring the quality and intelligibility of helium speech enhancement systems.
A study on minimum error discriminative training for speaker recognition
Authors: Liu Chi-Shi , Lee Chin-Hui , Chou Wu , Juang Biing-Hwang , Rosenberg Aaron E.
Published: October 2005

The use of discriminative training to construct hidden Markov models of speakers for verification and identification is studied. As opposed to conventional maximum likelihood training which estimates a speaker’s model based only on the training utterances from the same speaker, a discriminative training approach is used which takes into account the models of other competing speakers and formulates the optimization criterion such that speaker separation is enhanced and speaker recognition error rate on the training data is directly minimized. The optimization solution is obtained with a probabilistic descent algorithm. For all experiments an isolated digit database consisting of 100 speakers is used. For speaker identification, the resulting discriminative speaker models reduce the identification error rate by more than 25% over the results obtained with the conventional training algorithm. A new normalized score function is proposed which makes the verification formulation consistent with the minimum error training objective. When combining the proposed verification score function with discriminative training, an average equal error rate of 0.8% is achieved using only one-digit test utterances. This represents an error rate reduction of over 80% from an average equal error rate of 6.1% when using the conventional algorithm for training and the unnormalized score function for testing.
Modeling acoustic backscatter from kidney microstructure using an anisotropic correlation function
Authors: Insana Michael F.
Published: October 2005

Techniques for investigating acoustic backscatter from anisotropic biological tissues are examined. This empirical study combines single-scatter theory with the known elastic properties and histology of the renal cortex to predict the backscatter coefficient from kidney parenchyma. A transverse isotropic correlation model is developed to explain how backscattered energy, which varies with the incident sound wave direction, is related to the anisotropic structure of the tissue. From the results we conclude that renal morphology scatters sound incoherently, and that complex mixtures of scattering structures of different sizes, number densities, and scattering strengths can be distinguished by analyzing backscatter in specific frequency channels—a spectroscopic approach. A K-space description of backscatter measurements from kidney cortex, including the effects of anisotopy, provides further support of our hypothesis regarding sources of acoustic scattering.
Acoustic scattering from elemental Arctic ice features: Experimental results
Authors: Fricke J. Robert , Unger Gladys L.
Published: October 2005

It has been conjectured that young keels should be modeled as fluid structures while old keels should be modeled as elastic structures. If this conjecture is true, it has been shown that young keels scatter in a dipolar field and old keels scatter in a quadrupolar field. The experiment described in this paper tests the conjecture. Polypropylene chips were used to build a young keel model and a polypropylene half cylinder was used to build an old keel model. Both models were insonified in a laboratory tank with a pulse centered near 60 kHz; the experiment was nominally at a scale of 1000:1 relative to full scale Arctic experiments. Measurements of the scattered field from the two models clearly shows a dipolar field for the chips, or young, keel model. This result supports the young, fluid keel conjecture, which opens the door to relatively simple analytical modeling.
Fundamental limits on acoustic source range estimation performance in uncertain ocean channels
Authors: Narasimhan Sunil , Krolik Jeffrey L.
Published: October 2005

Matched-field methods which exploit complex multipath propagation models to localize underwater acoustic sources are particularly sensitive to errors in the assumed environmental parameters. In this paper, the Cramer–Rao lower bound (CRLB) is used to determine fundamental limits on the accuracy of range estimates obtained in the presence of uncertain environmental parameters. Theoretical results obtained using an adiabatic normal mode propagation model and a realistic model of sound-speed profile uncertainty indicate that without prior statistical knowledge of the environmental parameters, the CRLB may diverge even when the number of unknowns is less than the number of acoustic modes. When the prior probability distribution of the environmental parameters is available, however, the CRLB indicates a significant improvement in range estimation performance is possible. Numerical evaluation of the bound on range estimation in the presence of sound-speed profile uncertainty is performed both for an ideal waveguide and a realistic shallow-water channel using environmental data collected off the New England coast.
The multivalued Bartlett processor and source tracking
Authors: Collins Michael D. , Fialkowski Laurie T. , Kuperman W. A. , Perkins John S.
Published: October 2005

A matched-field processing algorithm based on the eigenvectors of the covariance matrix is developed for localization problems involving interference from multiple sources and ambient noise. Since the multivalued Bartlett processor is related to the Bartlett processor, it should be more robust in practice than eigenprocessors that are related to the maximum likelihood processor. This eigenprocessor also has the advantage that it provides well-defined estimates of the locations of multiple sources. An example involving moving sources and ambient noise illustrates that matched-field eigenprocessing requires source motion in order to be reliable when there are multiple sources.
Decomposition theorem of sound intensity with application
Authors: Zhe Jiang
Published: October 2005

The sound intensity I is rotational and may be decomposed into an irrotational component expressed by a gradient of potential function and a rotational component expressed by a curl of potential vector. It is proven that the decomposition is unique. It is shown that the rotational and irrotational components are orthogonal in the form of the inner product in the sound field and that in the far field the constant potential surfaces of the potential function are spherical surfaces. It is the irrotational component of sound intensity that transfers sound energy into the far field. The sound energies transferred by the rotational components cancel out each other. The effect of the rotational component on the results measured by the two-microphone technique is discussed.
Attenuation of helical wave radiation from cylindrical shells by viscoelastic layer
Authors: Guo Y. P.
Published: October 2005

This paper studies the attenuation of helical wave radiation from cylindrical shells by a viscoelastic layer through the problem of sound scattering from a three-layered shell with its core layer being made of viscoelastic material. An asymptotic method is used to derive the helical wave numbers for compressional and shear waves which are the main contributors to the scattered field in the midfrequency domain. These helical wave numbers are derived in explicit analytical forms so that the dominant material parameters that control the dissipation are identified. The technique of ray acoustics is used to find contributions to the scattered field due to compressional and shear waves, as well as the specularly reflected field, and the dissipative effects of the viscoelastic layer on each of the components are discussed.
Evaluation of the performance of suspended baffle arrays in typical industrial sound fields. Part II. Prediction
Authors: Hodgson Murray , Eldada Mazen Victor , Simard Louis-Philippe
Published: October 2005

A recent paper investigated the performance of suspended-baffle arrays experimentally using a 1:8 scale model. Early-decay times and steady-state noise levels were measured for various baffle-arrays in empty and fitted scale-model workroom configurations and in a scale-model reverberation room. In order to quantify the performance of the baffles, and to develop a simple model for predicting that performance, the experimental results were predicted using Eyring and ray-tracing prediction models, with the input parameters describing the baffle array varied in order to obtain a best fit; the baffle-array parameter value which gives a best fit describes the effective performance in that case. The performance of baffle arrays was quantified by increased octave-band ceiling absorption coefficients. The results of the prediction work were that the performance is significantly lower in workroom configurations than in a reverberation room; the performance is generally significantly higher in empty rooms than in fitted rooms; with respect to early-decay time, the effective absorption coefficients are often greater than 1.0 in the empty workroom; the performance is generally significantly higher with respect to early-decay time than with respect to steady-state noise levels; the performance depends on room geometry and contents. Since the effective baffle-array performance usually did not vary monotonically with the room and baffle-array parameters studied, the development of empirical models is not feasible at this time.
Ultrasonic measurement of density of liquids
Authors: Adamowski Julio C. , Buiochi Flávio , Simon Claudio , Silva Emílio C. N. , Sigelmann Rubens A.
Published: October 2005

This paper presents two methods to measure the density of liquids based on the measurement of the reflection coefficient and propagation velocity, using a novel double-element transducer. The measurements can be made in liquids, stationary or in motion. The main factors that affect the precision of the measurements are analyzed. The effect of acoustic diffraction is eliminated by using the double-element transducer, where the receiver is somewhat larger in diameter than the emitter. The effect of short- and long-term stability of the electronics and piezoelectric ceramics employed in the system is also eliminated. A system was implemented and measurements of several liquids, stationary and in motion, were conducted.
A fast Fourier transformation algorithm for the Kirchhoff integral formulation
Authors: Wu Sean F. , Wang Zhaoxi
Published: October 2005

A fast Fourier transformation-based Kirchhoff integral formulation is developed for calculating sound radiation from finite objects. This formulation is applicable to both transient and steady-state radiation in both near and far fields. The radiated acoustic pressure is solved in the frequency domain first and then converted to the time domain by taking a discrete inverse Fourier transformation. Since the spatial domain is decoupled from the temporal domain in numerical computations, and since commercially available fast Fourier transformation software packages are utilized directly, numerical computations are highly efficient and accurate. Another advantage of using this formulation is that it always yields unique solutions for sound radiation from an object vibrating at a constant frequency.
Optimal estimation of acoustic intensity from pressure in the presence of mean flow
Authors: Strait Stewart , Stoughton Roland
Published: October 2005

Bayesian minimum mean-squared error (MMSE) estimators are constructed for obtaining pressure, velocity, and intensity in the near- or far-field of an extended acoustic source from near-field pressure measurements alone, in the presence of noise and mean flow. In the absence of mean flow, there is a unique relation between the local pressure gradient and the local velocity, but in the presence of mean flow this uniqueness is destroyed [D. Munro and K. Ingard, ‘‘On acoustic intensity measurements in the presence of mean flow,’’ J. Acoust. Soc. Am. 65, 1402–1406 (1979)]. This nonuniqueness makes an exact reconstruction of the velocity and intensity fields impossible, even in the absence of noise; however, accurate approximate reconstruction may be accomplished with a sufficient array of receivers. The MMSE estimation framework provides a prediction of the estimation accuracy which may be used to assess the sufficiency of a given pressure sensor array. Numerical examples of array performance assessment are presented for intensity estimation in the near field of an extended source in mean flows of Mach 0 to 0.8.
Response on a cylindrical surface due to an incident plane wave. I. Pressure-release surface
Authors: Rumerman M. L.
Published: October 2005

Because the Debye approximation to the Hankel function is not applicable at points in or near the shadow zone of a cylinder insonified by an incident plane wave, it cannot be used to obtain asymptotic representations of the surface response at arbitrary locations. This paper proposes the use of an Airy function approximation to the Hankel function, as is done in electromagnetic problems. Solutions to the latter are sometimes approximated in terms of an integral of the Airy function called the Fock function, which is calculated by series expansions. The departure here is the evaluation of the integral by a saddle point approximation, and it is shown that this approximation to the Fock function agrees well with tabulated values. The method is applied to calculating the radial velocity on the surface of a pressure-release cylinder, and the approximate solution is shown to agree well with the modal solution, for ka above 2. The relevance to structural acoustics is that it may be possible to estimate the surface response of a structural shell at arbitrary locations by using the saddle point of the Airy function integral to describe the admittance properties of a shell and the acoustic medium.
Response on a cylindrical surface due to an incident plane wave. II. Uniformly point-reacting surface
Authors: Rumerman M. L.
Published: October 2005

Asymptotic estimates of the response in the radial direction, at arbitrary locations in the shadow and transition zones, of a cylindrical surface due to an incident plane wave can be obtained through an integral that includes an Airy function representation of the Hankel function. A previous paper [J. Acoust. Soc. Am. 97, 128–133 (1995)] showed that, for a pressure-release surface, the relevant integral could be estimated through a saddle point evaluation. The motivation was the hope that, when applied to the response of an elastic shell, the saddle point would have significance in quantifying the shell admittance and the surface acoustic admittance. The present paper applies the method to the intermediate case of a point-reacting surface, which introduces the complication of a creeping wave that must be accounted for in the saddle point evaluation. Results are presented for the radial velocity of a surface having a masslike surface admittance equivalent to the mass per unit wall area of a steel shell with a wall thickness that is 1% of the radius. The ambient acoustic medium is water. Good agreement with the modal solution is obtained for ka greater than 2.
The effect of supersonic aircraft speed on the penetration of sonic boom noise into the ocean
Authors: Sparrow Victor W.
Published: October 2005

In 1968 Sawyers presented a theory which predicts the acoustic pressure underwater due to a supersonic aircraft’s sonic boom in the air. The theory has since been validated in laboratory experiments. In the present paper Sawyers’ theory is utilized to predict the effect of a supersonic aircraft’s speed on the penetration of the sonic boom into the water. By taking into account the variation in a sonic boom’s duration as a function of the aircraft Mach number, it is shown that higher aircraft speeds are associated with higher acoustic pressures in the water. For fixed depths of 10 m or less the peak SPL varies less than 6 dB over a wide range of Mach numbers. For greater depths, 100 m for example, increased Mach numbers may increase the SPL by 15 dB or more. The actual levels are always diminished for deeper depths. These observations may be important for evaluating the possible effects of sonic boom noise on marine mammals.
Classification of prosthetic heart valve sounds: A parametric approach
Authors: Candy J. V. , Jones H. E.
Published: October 2005

People with heart problems have had their lives extended considerably with the development of the prosthetic heart valve. Great strides have been made in the development of the valves through the use of improved materials as well as efficient mechanical designs. However, since the valves operate continuously over a long period, structural failures can occur—even though they are relatively uncommon. Here the development of techniques to classify the valve either as having intact struts or as having a separated strut, commonly called single leg separation, is discussed. In this paper the signal processing techniques employed to extract the required signals/parameters are briefly reviewed and then it is shown how they can be used to simulate a synthetic heart valve database for eventual Monte Carlo testing. Next, the optimal classifier is developed under assumed conditions and its performance is compared to that of an adaptive-type classifier implemented with a probabilistic neural network. Finally, the adaptive classifier is applied to a data set and its performance is analyzed. Based on synthetic data it is shown that excellent performance of the classifiers can be achieved implying a potentially robust solution to this classification problem.
Relaxation dynamics of spontaneous otoacoustic emissions perturbed by external tones. I. Response to pulsed single-tone suppressors
Authors: Murphy W. J. , Talmadge C. L. , Tubis A. , Long G. R.
Published: October 2005

The dynamic aspects of the suppression of spontaneous otoacoustic emissions by external tones are evaluated. A Van der Pol oscillator driven by an external tone is used as an interpretive model for data on the pulsed suppression of spontaneous emissions obtained from six female subjects. Typical results for both the onset of, and recovery from suppression yield 1/r1 (where −r1 is the negative linear component of the damping function) in the range of 2–25 ms. In accordance with the predictions of the model, (a) the relaxation time for the onset of suppression increases with the amount of suppression induced by the external tone, (b) the values of r1 and the amplitudes of the unsuppressed emissions exhibit an inverse correlation, (c) the values inferred for r1 are not significantly dependent on the frequency of the pulsed suppressor tone, and (d) the inferred r1 values are not significantly dependent upon the amount of suppression.
Relaxation dynamics of spontaneous otoacoustic emissions perturbed by external tones. II. Suppression of interacting emissions
Authors: Murphy W. J. , Tubis A. , Talmadge C. L. , Long G. R.
Published: October 2005

The level of a spontaneous otoacoustic emission (SOAE) during recovery from suppression by an external tone sometimes exhibits a prominent overshoot before reaching its normal level. At the onset of suppression, a less prominent undershoot is sometimes observed before the emission level stabilizes. The overshoot and undershoot are described in terms of the variable amount suppression produced by a neighboring higher-frequency SOAE which is responding more slowly to the modulation of the external tone. The variation of the SOAE amplitude during pulsed suppression is modeled by a pair of Van der Pol limit-cycle oscillators with the primary oscillator linearly coupled to the displacement of the secondary high-frequency one. We have found relaxation time constants for the onset of suppression of the order of 4.5 and 7.4 ms for the primary and secondary SOAEs, respectively, and for the recovery from suppression 4.8 and 10.48 ms for the primary and secondary SOAEs, respectively. The same model is also successful in describing the release from suppression of the primary SOAE by the secondary SOAE when the latter is partially suppressed by the external tone. Aspirin administration reduces the magnitude of the overshoot by reducing the level of the higher-frequency SOAE and thereby eliminating the suppression of the lower-frequency one.
Maximum-likelihood procedures and the inattentive observer
Authors: Green David M.
Published: October 2005

In most experimental situations, it is expected that observers will achieve perfect detection at extremely high signal levels. Technically, it is assumed that the asymptote of the psychometric function is unity. In many practical psychophysical tests, such as those involving children, patients, or nonhuman animals, the observers are occasionally inattentive. Using computer simulations, it was assumed that inattention can be modeled as a stationary stochastic process whose major effect is to produce a psychometric function having an asymptote less than unity. A maximum-likelihood procedure was used to estimate threshold, because it has been shown to provide reasonably stable threshold estimates using very few observations. Inattention increases the variability of the threshold estimate, as would be expected, because inattention reduces the slope of the psychometric function. The simulations also show that the maximum-likelihood procedure poorly estimates the amount of inattention, and can, thereby, produce a strong bias in the threshold estimates, overestimating or underestimating the true values under different circumstances. Inattention appears to affect the two-alternative forced-choice procedure more strongly than the yes–no (go/nogo) procedure.
Obtaining equal loudness contours from Weber fractions
Authors: Wong Willy , Norwich Kenneth H.
Published: October 2005

An empirical equation from Riesz’s classic study on difference thresholds is treated in a new manner. Reformulating the expression for the Weber fraction allows one to account for the shape of the loudness function at different frequencies. Furthermore, the emerging loudness function unifies both the commonly used power and logarithmic laws of sensation. In principle, equal loudness contours can be derived from Riesz’s data. While the derived contours are imperfect, the theoretical method provides a basis for further experimental work.
A developmental study of the perception of onset spectra for stop consonants in different vowel environments
Authors: Ohde Ralph N. , Haley Katarina L. , Vorperian Houri K. , McMahon Christine W.
Published: October 2005

The importance of different acoustic properties for the perception of place of articulation in prevocalic stop consonants was investigated from a developmental perspective. Eight adults and eight children in each of the age groups, 5, 6, 7, 9, and 11 years, listened to synthesized syllables comprised of all combinations of [b d g] and [i open aye]. The synthesis parameters were adapted from Blumstein and Stevens [J. Acoust. Soc. Am. 67, 648–662 (1980)], and included manipulations of the following stimulus variables: formant transitions (moving or straight), noise burst (present or absent), and voicing duration (10 or 46 ms). Identification performance was high for all age groups across most stimulus types. Formant transition motion generally was not necessary for accurate identification, and there was no difference between age groups in terms of the perceptual weight placed on this cue. Furthermore, the results did not support the salience of duration as a developmental cue to place of articulation. The presence of a burst improved identification for the velar and alveolar places of articulation for all age groups, but was particularly important for the 11-year-olds and adults. These findings indicate that children, by age 5, do not rely on dynamic formant motion any more than adults do, and that the ability to integrate acoustic cues across regions of spectral change shows developmental patterns.
The identification of vowel-like harmonic complexes: Effects of component phase, level, and fundamental frequency
Authors: Alcántara Joseph I. , Moore Brian C. J.
Published: October 2005

These experiments investigate how the identification of vowel-like harmonic complexes, similar to those used by Leek et al. [J. Acoust. Soc. Am. 81, 148–154 (1987)], is affected by spectral contrast, overall level, component phase, and fundamental frequency (F0). Four normally hearing subjects were required to identify which of six vowel-like harmonic complexes was presented on each trial. The test stimuli were complex tones containing the first 35 harmonics of a 100-Hz fundamental or the first 70 harmonics of a 50-Hz fundamental. All of the harmonics with frequencies below 3000 Hz were equal in amplitude except for three pairs of successive harmonics which were located at the first, second, and third formant frequency values, and incremented in level by 1, 2, 4, 8, and 16 dB relative to the other components. Three overall levels were used, 85, 65, and 45 dB SPL, and harmonics were added in either cosine or random phase. The results indicated that identification was better for cosine phase than for random phase, except for the 100-Hz fundamental at 45 dB SPL. The difference between the two phase conditions increased with increasing presentation level and with decreasing fundamental frequency. The results are explained in terms of the waveforms that would occur at the outputs of different auditory filters. It does not appear necessary to invoke nonlinear enhancement mechanisms to explain the results, although an influence of such mechanisms cannot be ruled out.
Sonoelasticity imaging: Theory and experimental verification
Authors: Gao L. , Parker K. J. , Alam S. K. , Lerner R. M.
Published: October 2005

Sonoelasticity is a rapidly evolving medical imaging technique for visualizing hard tumors in tissues. In this novel diagnostic technique, a low-frequency vibration is externally applied to excite internal vibrations within the tissue under inspection. A small stiff inhomogeneity in a surrounding tissue appears as a disturbance in the normal vibration eigenmode pattern. By employing a properly designed Doppler detection algorithm, a real-time vibration image can be made. A theory for vibrations, or shear wave propagation in inhomogeneous tissue has been developed. A tumor is modeled as an elastic inhomogeneity inside a lossy homogeneous elastic medium. A vibration source is applied at a boundary. The solutions for the shear wave equation have been found both for the cases with tumor (inhomogeneous case) and without tumor (homogenous case). The solutions take into account varying parameters such as tumor size, tumor stiffness, shape of vibration source, lossy factor of the material, and vibration frequency. The problem of the lowest detectable change in stiffness is addressed using the theory, answering one of the most critical questions in this diagnostic technique. Some experiments were conducted to check the validity of the theory, and the results showed a good correspondence to the theoretical predictions. These studies provide basic understanding of the phenomena observed in the growing field of clinical Sonoelasticity imaging for tumor detection.
Dimensions and units of underwater acoustic parameters
Authors: Hall Marshall V.
Published: October 2005

The dimensions and units of certain parameters used in underwater acoustics should be modified to take account of the physical phenomena they represent and to conform with accepted practice in other branches of physics. These parameters are source strength, transmission loss, target strength, surface scattering strength, and volume scattering strength. In particular, the SI units for these parameters should be as follows: source strength, W sr−1 (for a steady source) or J sr−1 (for a transient source); transmission loss and target strength, m2 sr−1; surface scattering strength, sr−1, and volume scattering strength, m−1 sr−1.
Comments on ‘‘Acoustic scattering by elastic spherical shells that have multiple massive internal components attached by compliant mounts’’ [J. Acoust. Soc. Am. 94, 2924–2935 (1993)] and a simple method for calculating the response from internally loaded spherical shells
Authors: Titterton Paul J.
Published: October 2005

Gaunaurd et al. [J. Acoust. Soc. Am. 94, 2924–2935 (1993)] provide a method for computing the scattering from a submerged spherical shell with internal structure. Some of the graphed results in that paper are in error: The form function peaks associated with the internal structure are missing or misplaced. To support this conclusion, the Gaunaurd et al. method and an equivalent impedance-based formulation have been independently programmed. The computed results match to numerical precision. The results do not match the published paper’s graphed data.
Response to ‘‘Comments on ‘Acoustic scattering by elastic spherical shells that have multiple massive internal components attached by compliant mounts’ [J. Acoust. Soc. Am. 94, 2924–2935 (1993)] and a simple method for calculating the response from internally loaded spherical shells’’ [J. Acoust. Soc. Am. 97, 3890 (1995)]
Authors: Gaunaurd G. C. , Huang H. , Wertman W.
Published: October 2005

The authors respond to some comments made by P. J. Titterton, Jr., in a recent letter.
Comments on ‘‘Transient sound radiation from impulsively accelerated bodies’’ [J. Acoust. Soc. Am. 94, 542–553 (1993)]
Authors: Ochmann Martin
Published: October 2005

Two comments are given on a method for predicting the transient sound radiation of impulsively accelerated bodies which was recently developed by Wu [J. Acoust. Soc. Am. 94, 542–553 (1993)]. The former concerns the author’s assumption that the surface impedance of the radiator would be constant along the boundary if the surface velocity is constant (in the case of a movable solid body). In the latter, the proof of uniqueness of the solutions (Sec. III of Wu’s paper) is checked. Contradictions to classical results are found, and an explicit counterexample is presented showing that the proof seems to be incorrect since nonuniqueness appears at critical frequencies.
Response to: ‘‘Comments on ‘Transient Sound Radiation from Impulsively Accelerated Bodies’ [J. Acoust. Soc. Am. 97, 3895 (1995)]’’
Authors: Wu Sean F.
Published: October 2005

The author replies to the comments of Ochmann.
A simple example of a trapped mode in an unbounded waveguide
Authors: Kaplunov Julii D. , Sorokin Sergey V.
Published: October 2005

This letter presents concerns on analysis of a trapped mode in a simple one-dimensional waveguide. The chosen system is an unbounded elastic string lying on a Winkler elastic foundation. It is shown that in such a system there is the single eigenfrequency corresponding to a trapped mode.
Mechanical impedance of a cracked cantilever beam
Authors: Bamnios G. , Trochidis A.
Published: October 2005

In this paper the influence of a transverse surface crack on the mechanical impedance of a cantilever beam is investigated both analytically and experimentally. Modeling the flexibility induced by the crack by a linear spring constant, relations linking the changes of the mechanical impedance to the location and size of the crack are obtained for both longitudinal and flexural vibrations. The results show that the mechanical impedance changes substantially due to the presence of the crack in case of flexural vibrations. The changes follow definite trends depending upon the location and size of the crack and consequently the impedance can be used as an additional defect information carrier for crack appearance and possible estimation of crack location.
Choice of frequency weighting for the evaluation of weapon noise
Authors: Meloni Tommaso , Rosenheck Allan
Published: October 2005

This paper describes a laboratory study to choose an appropriate frequency weighting network for predicting the annoyance caused by the noise from small, medium, and large weapons. The results indicate that the annoyance of all three weapon types is the same if the blasts are heard at identical A-weighted SEL’s. On the other hand, equal C-weighted SEL’s result in large differences in annoyance between the weapon types. The implications of these results for outdoor noise criteria depend on the assumption concerning window condition. If one assumes that people hear the blasts predominantly through open windows, then A-weighted criteria should be appropriate for all the weapon types without any correction (penalty or bonus) for weapon type. On the other hand, if the blasts are heard predominantly through closed windows a penalty of about 5 dB should be applied to the outdoor levels of the large weapons to account for the poorer low-frequency attenuation of the windows.
Mechanical modeling of palatal snoring
Authors: Huang Lixi
Published: October 2005

The mechanism of human snoring caused by vibration of the soft palate and the characteristics of the noise are investigated. The soft palate becomes unstable and vibrates violently once the inspiratory flow exceeds a critical speed. The physiological phenomenon is modeled by studying flow over a flexible plate. In determining the stability of this flow, the trailing edge conditions are crucial. It is found that the noise generated in the simple experimental configuration has distinct characteristics found in human snores. For example, there is an antiphase relation between unsteady pressures from the oral and nasal channels and this provides a feature that distinguishes snoring by vibration of the soft palate from that caused by other parts of the human airway.
Identification and synthesis of acoustic scattering components via the wavelet transform
Authors: Drumheller D. M. , Hughes D. H. , O’Connor B. T. , Gaumond C. F.
Published: October 2005

An acoustic scatterer can be described in the time domain by its impulse response function, or in the frequency domain by its form function. Both functions will contain several complementary and distinct components, none of which is fully separable in either the time or frequency domain. This renders Fourier based methods ineffective in identifying and extracting one component from all the others. However, it is possible to do this using the wavelet transform, a transform that yields a two-dimensional (two-parameter) representation of a signal. In this paper, this transform is used to identify and extract the acoustic components from physical model data.