bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of intensity decrements by the chinchilla
Authors: Graf Christine J. , Saunders Samuel S. , Salvi Richard J.
Published: October 2005

Three monaural chinchillas were trained to detect intensity decrements in broadband noise (20 kHz) using a shock-avoidance conditioning procedure. The intensity decrements were presented at one of nine different durations between 2 and 35 ms at noise levels of 25, 45, and 65 dB SPL. At each intensity-duration combination, the level of the decrement was varied to obtain a decrement threshold. The minimal detectable decrement decreased from approximately 20 dB at the shortest duration to an asymptote of roughly 4 dB at approximately 30 ms. The data were modeled by a low-pass filter with an 11-ms time constant. The decrement detection function of the chinchilla is similar to that of humans. However, long-duration decrement thresholds are larger in the chinchilla, as would be predicted from the large intensity difference limen of the chinchilla. In general, there was little change in the decrement function across background intensities except that 2-ms decrements were not detected at the 25-dB SPL background intensity.
The detection of temporal gaps as a function of frequency region and absolute noise bandwidth
Authors: Eddins David A. , Hall Joseph W. , Grose John H.
Published: October 2005

Temporal gap detection was measured as a function of absolute signal bandwidth at a low-, a mid-, and a high-frequency region in six listeners with normal hearing sensitivity. Gap detection threshold decreased monotonically with increasing stimulus bandwidth at each of the three frequency regions. Given conditions of equivalent absolute bandwidth, gap detection thresholds were not significantly different for upper cutoff frequencies ranging from 600 to 4400 Hz. A second experiment investigated gap detection thresholds at two pressure–spectrum levels, conditions typically resulting in substantially different estimates of frequency selectivity. Estimates of frequency selectivity were collected at the two levels using a notched-noise masker technique. The gap threshold-signal bandwidth functions were almost identical at pressure–spectrum levels of 70 dB and 40 dB for the two subjects in experiment II, while estimates of frequency selectivity showed poorer frequency selectivity at the 70-dB level than at 40 dB. Data from both experiments indicated that gap detection in bandlimited noise was inversely related to signal bandwidth and that gap detection did not vary significantly with changes in signal frequency over the range of 600 to 4400 Hz. Over the range of frequencies investigated, the results indicated no clear relation between gap detection for noise stimuli and peripheral auditory filtering.
Binaural suppression of nonechoes
Authors: Divenyi Pierre L.
Published: October 2005

A brief diotic conditioner has been shown to effectively disrupt lateralization of a brief dichotic probe presented after a short interval (4–10 ms, onset to onset) with an interaural time delay that is clearly discriminable in the absence of the conditioner [e.g., P. M. Zurek, J. Acoust. Soc. Am. 66, 1750–1757 (1980)], even when the conditioner and the probe are different sounds [P. L. Divenyi and J. Blauert, in Auditory Processing of Complex Sounds, edited by W. A. Yost and C. S. Watson (Erlbaum, Hillsdale, NJ, 1987), pp. 146–155]. The present experiments investigated lateralization suppression of a narrow-band dichotic probe centered at 2 kHz by a narrow-band diotic conditioner, in situations in which the probe could not be regarded as an echo of the conditioner. In one case, the conditioner was identical to the probe but was presented in opposite phase; in other conditions, the center frequency of the conditioner was different, with the center frequency to bandwidth ratio remaining constant. The effects of frequency and temporal separation between the conditioner and the probe on the suppression of the lateralization of the probe were explored. Suppression of lateralization was measured as the increase in the just-noticeable interaural time difference (jnd), with respect to the interaural time jnd obtained for the probe alone. Low-frequency (0.5 to 1.5 kHz) conditioners were more effective in suppressing the lateralization of the probe than those at or above the probe frequency. The results suggest that a diotic stimulus with a relatively high localization strength (i.e., one that yields low interaural time jnd’s when presented in isolation) could ‘‘mask’’ the localization of a subsequent dichotic stimulus having a lower localization strength.
Formant trajectory characteristics of males with amyotrophic lateral sclerosis
Authors: Weismer Gary , Martin Ruth , Kent Ray D. , Kent Jane F.
Published: October 2005

The purpose of this study was to describe the formant trajectories produced by males with amyotrophic lateral sclerosis (ALS), a degenerative neuromuscular disease that is typically associated with dysarthria. Formant trajectories of 25 males with ALS and 15 neurologically normal geriatric males were compared for 12 words selected from the speech intelligibility task developed by Kent et al. [J. Speech. Hear. Disord. 54, 482–499 (1989)]. The results indicated that speakers with ALS (1) produced formant transitions having shallower slopes than transitions of normal speakers, (2) tended to produce exaggerations of formant trajectories at the onset of vocalic nuclei, and (3) had greater interspeaker variability of formant transition characteristics than normal speakers. Within the group of ALS speakers, those subjects who were less than 70% intelligible produced distinctly more aberrant trajectory characteristics than subjects who were more than 70% intelligible. ALS subjects who were less than 70% intelligible produced many trajectories that were essentially flat, or that had very shallow slopes. These results are discussed in terms of the speech production deficit in the dysarthria associated with ALS, and with respect to the potential influence of aberrant trajectories on speech intelligibility.
Ultrasonic wave propagation in cancellous and cortical bone: Prediction of some experimental results by Biot’s theory
Authors: Williams John L.
Published: October 2005

Pulse transmission ultrasound was used to determine the longitudinal wave speed along the direction of trabecular alignment in 32 water-saturated anisotropic tibial bovine cancellous bone samples and in one cortical bone sample also from the bovine tibia. These results are compared to published ultrasound wave-speed data obtained from bovine femoral specimens. Nonlinear regression was used to fit Biot’s theory to the data. The correlation coefficient for regression analysis between the experimental ultrasound velocities and the velocities predicted by Biot’s theory was r=0.78.
Stabilization of perceived echo amplitudes in echolocating bats. II. The acoustic behavior of the big brown bat, E
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s, when tracking moving prey
Authors: Hartley David J.
Published: October 2005

Big brown bats, Eptesicus fuscus, can be trained to use echolocation to track a small microphone with a food reward attached when it is moved rapidly toward them. This situation mimics prey interception in the wild while allowing very precise recording of the sonar pulses emitted during tracking behavior. The results show that E. fuscus intensity compensates, reducing emitted intensity by 6 dB per halving of target range so that the intensity incident upon the target is constant and echo intensity increases by 6 dB per halving of range. This increase in echo intensity is effectively canceled by the reduction in auditory sensitivity due to automatic gain control (AGC) of 6 to 7 dB per halving of range. Intensity compensation behavior and AGC therefore form a dual-component, symmetrical system that stabilizes perceived echo amplitudes during target approach. The same system is present in the fishing bat, Noctilio leporinus, suggesting that it may be widespread in echolocating bats. Correlation analysis shows that, despite large changes in the duration of the pulses emitted by E. fuscus during an approach, the pulse frequency structure is such that the spatial image of the target perceived along the range axis is highly stable. Pulse duration is not reduced in the manner theoretically necessary to eliminate potential echo distortion effects due to AGC, but is reduced in such a way that this distortion is insignificant. During the terminal buzz, a high degree of temporal overlap (relative to pulse duration) occurs between emitted pulse and returning echo.
On the asymptotic solution of scattering from slender bodies by the two-variable technique
Authors: Tran-Van-Nhieu Michel
Published: October 2005

A formal construction of an approximate solution of scattering from rigid slender bodies by the two-variable expansions method is presented. The determination of the solution is obtained by modifying the usual concept of secular term which is not appropriate to singular perturbation problems. It is proved that matched asymptotic and two-variable solutions are asymptotically equivalent in the near and intermediate fields.
Relative ear advantage and element duration
Authors: Speaks Charles , Clay John L. , Niccum Nancy , McLaughlin Colleen , Faller Lisa
Published: October 2005

Lauter [J. Acoust. Soc. Am. 71, 701–707 (1982)] reported that although the magnitude and direction of the absolute ear advantage for speech and nonspeech sound sets presented dichotically varies considerably among listeners, consistent patterns of a relative ear advantage (EArel) across sound sets are preserved from listener to listener. She further claimed that EArel appeared to be related to the duration of elements that composed a sequence. The existence of EArel is investigated for four sound sets: CV nonsense syllables and pitch patterns that were composed of 50-, 80-, or 120-ms tones. The paradigm was target monitoring, a Yes/No task in which listeners attended to only one ear and listened for the presence of a target signal. The results failed to confirm that listeners have a consistent relative ear advantage related to element duration for nonspeech sound sets.
Acoustic wave propagation through periodic bubbly liquids
Authors: Ruffa Anthony A.
Published: October 2005

A three-dimensional finite-element analysis is used to determine the acoustic behavior of plane waves propagating through bubbly liquids having periodic bubble distributions. The results obtained from the model include the effective phase speed and attenuation of the medium, the acoustic field in the region of each bubble, and the virtual mass for both the monopole and dipole modes of bubble oscillation. The results are in agreement with both experimental data and previous analytical results.
Seasonal variations of the sediment compressional wave-speed profile in the Gulf of Mexico
Authors: Rajan Subramaniam D. , Frisk George V.
Published: October 2005

The seasonal variation of the sediment compressional wave-speed profile due to temperature variability in the water column is investigated for shallow-water regions, where large temperature fluctuations can occur during the course of a year. For example, in water depths of less than 30 m in the Gulf of Mexico, field observations indicate that the annual fluctuation of the ocean bottom temperature is approximately sinusoidal with a peak-to-trough value of about 15 °C. The heat flow across the water/sediment interface results in the variation of the pore water temperature with season. It is shown that the compressional wave speed varies approximately linearly with pore water temperature, an effect which is, to first order, independent of both the porosity and given sediment type. Further, the velocity ratio (ratio of sound speeds in the water and the sediment at the water/sediment interface) is shown to be independent of temperature but dependent on sediment type. The effect of variations in water column temperature on sediment compressional wave speed is demonstrated by inversions of two data sets. The data were obtained at the same location in the Gulf of Mexico but at different seasons. Finally, the importance of these variations is studied by considering their effect on (a) the prediction of the pressure field in the water column and (b) the errors introduced in source localization by matched-field processing.
On the possibility of monitoring El Niño by using modal ocean acoustic tomography
Authors: Shang E. C. , Wang Y. Y.
Published: October 2005

The possibility of monitoring El Niño by using the modal acoustic tomography (MOAT) is discussed. It is found that the inversion of El Niño profile with linear inversion scheme is less successful than the mid-ocean eddy case indicated by the condition number of the kernel matrix. However, based on a simple yet realistic acoustic model of El Niño, it appears that it might be possible to detect temperature fluctuations associated with El Niño’s by examining a proper set of modal features of the acoustic field. Numerical simulation illustrated that a fair reconstructed El Niño profile could be obtained by using the ‘‘damped least-squares’’ inversion incorporating the singular value decomposition (SVD) analysis.
Contributions to the vibratory excitation of gear systems from periodic undulations on tooth running surfaces
Authors: Mark William D.
Published: October 2005

The transmission error is widely recognized to be the principal source of vibratory excitation arising from meshing gear pairs. Periodic machining errors (undulation errors) on gear teeth can provide an important contribution to the transmission error of wide-face helical gears. A method is described for using complex sinusoids to represent such periodic errors on individual gear teeth. Expressions are derived for the Fourier series expansion coefficients of the contributions from such errors to the transmission error. A model describing the relative phase relation on successive teeth of the individual sinusoidal components of such errors is postulated which is believed to provide a valid representation of the phase of most, if not all, such errors generated by imperfections in the rotating elements of gear manufacturing apparatus. For particular parameter values of the phase model, it is shown that such periodic errors can contribute to: (1) tooth meshing harmonics only, (2) rotational harmonics only, or (3) both tooth meshing and rotational harmonics. Two cases of practical interest are analyzed in detail—namely, periodic errors caused by imperfections in worktable rotational and translational drives. The rotational drive imperfections give rise to one dominant rotational harmonic in the transmission error spectrum; whereas, the translational drive imperfections contribute, primarily, to the tooth meshing harmonics of the transmission error spectrum.
Detection of across-frequency differences in fundamental frequency
Authors: Carlyon Robert P. , Demany Laurent , Semal Catherine
Published: October 2005

Listeners discriminated between pairs of complex sounds, each consisting of two groups of components. Two harmonic complexes were played out through separate channels, and each filtered to obtain a ‘‘lower’’ and a ‘‘higher’’ group. The ‘‘carrier fundamental frequencies (F0s)’’ of both groups were usually 125 Hz; only those components in the lower group were resolvable by the peripheral auditory system. For the standard stimulus, the F0s of the two groups were frequency modulated coherently with each other, so that they were always equal. For the signal, the F0s of the two groups were modulated incoherently (π modulator delay), so that they differed by an amount that varied sinusoidally between values proportional to the depth of FM (the dependent variable). Stimuli were usually presented in continuous pink noise. The results showed that (i) when the components were added in sine or cosine phase, the mean threshold across listeners corresponded to a zero-peak modulation depth of 6%–7% (rms mistuning=8.5%–10%); (ii) performance dropped to chance when the upper components were added in alternating sine–cosine phase, but was only moderately affected by the phase of the lower components; (iii) threshold for sine-phase stimuli improved by a factor of 1.6 when noise in the frequency region of the two component groups was removed; (iv) threshold increased moderately with increases in the frequency separation between the two component groups; (v) threshold dropped markedly when the F0s of both groups of components were increased so as to be resolvable by the peripheral auditory system; and (vi) performance dropped to chance when the nominal carrier F0s of the two groups of components differed from each other. It is concluded that listeners can perform simultaneous comparisons of F0s derived from resolved and unresolved harmonics, and that their performance on this task is fairly robust. Implications for the perceptual segregation of concurrent complex sounds, and for models of pitch perception, are discussed.
Fundamental frequency declination is not unique to human speech: Evidence from nonhuman primates
Authors: Hauser Marc D. , Fowler Carol A.
Published: October 2005

In human speech, declination of the fundamental frequency (F0) of the voice spans coherent units of an utterance and, therefore, signals where units begin and end. A rapid final fall at the end of an utterance provides a further indication of an utterance’s ending. The occurrence of declination is sufficiently widespread across languages that several investigators have suggested it as a language universal. Language universals may be universal because they are part of a species-specific specialization for language or, alternatively, they may constitute conventionalizations of natural dispositions of the vocal tract that may serve a communicative function. Evidence is offered favoring the latter account for declination and the final fall by showing that vocal productions of vervet monkeys (Cercopithecus aethiops) and rhesus macaques (Macaca mulatta) show declination, and vervets show clear evidence of a final fall. Interestingly, the fall in F0 may serve some communicative role in the vocal exchanges of vervets and rhesus, analogous to its signalling function in human language.
Talker and listener effects on degree of perceived foreign accent
Authors: Flege James Emil , Fletcher Kathryn L.
Published: October 2005

Four experiments were carried out to examine listener- and talker-related factors that may influence degree of perceived foreign accent. In each, native English listeners rated English sentences for degree of accent. It was found that degree of accent is influenced by range effects. The larger the proportion of native (or near-native) speakers included in a set of sentences being evaluated, the more strongly accented listeners judged sentences spoken by non-native speakers to be. Foreign accent ratings were not stable. Listeners judged a set of non-native-produced sentences to be more strongly accented after, as compared to before, they became familiar with those sentences. One talker-related effect noted in the study was the finding that adults’ pronunciation of an L2 may improve over time. Late L2 learners who had lived in the United States for an average of 14.3 years received significantly higher scores than late learners who had resided in the United States for 0.7 years. Another talker-related effect pertained to the age of L2 learning (AOL). Native Spanish subjects with an AOL of five to six years were not found to have an accent (i.e., to receive significantly lower scores than native English speakers), whereas native Chinese subjects with an average AOL of 7.6 year did have a measurable accent. The paper concludes with the presentation of several hypotheses concerning the relationship between AOL and degree of foreign accent.
Acoustic impedance of a finite length duct with dynamic termination
Authors: Kim W. S. , Prasad M. G.
Published: October 2005

The acoustic impedance studies in duct systems are important for a complete analysis and design in acoustical transmission lines and filters such as mufflers and silencers. The analysis of standing waves in a duct with passive termination is well known. In this paper, the formulation for acoustic impedance in a finite length duct with dynamic termination is presented. The boundary-element method was used to verify the formulation. The studies can be applied to source characterization and active noise control in duct systems.
Experiments on active control of structurally radiated sound using multiple piezoceramic actuators
Authors: Clark Robert L. , Fuller Chris R.
Published: October 2005

Active control of sound radiation from a vibrating rectangular plate excited by a steady-state harmonic point force disturbance is experimentally studied. Control structural inputs are achieved by three piezoceramic actuators bonded to the surface of the panel. Microphones were implemented as error sensors in the radiated field, while the control approach was based upon a filtered-X version of the adaptive least-mean-squares (lms)algorithm. Both position and number of piezoceramic actuators were varied during the test to determine the effects on control authority. A variety of test cases were studied for controlling sound radiation due to a disturbance both on and off resonance. Results from these experiments indicate that piezoceramic elements provide an efficient method for distributed modification of structural response to attenuate sound radiation. In addition, the adaptive lms algorithm is shown to be an effective narrow-band controller, which in contrast to feedback approaches, requires little system modeling.
Modal sensing of efficient acoustic radiators with polyvinylidene fluoride distributed sensors in active structural acoustic control approaches
Authors: Clark Robert L. , Fuller Chris R.
Published: October 2005

An experimental investigation was performed to determine the feasibility of implementing polyvinylidene fluoride (PVDF) piezoelectric distributed sensors on the surface of a structure as error sensors in an adaptive least-mean-squares (lms) control approach to minimize acoustic radiation. While much research has been devoted to controlling vibration of structures with these sensors, they have yet to be implemented in structural acoustic control. To this end, two narrow strip PVDF sensors were positioned on a simply supported plate such that the dominant observed response was due to the odd–odd modes of the plate (i.e., the more efficient acoustic radiators). The error sensors in effect act as spatial wave-number filters and only observe those components that contribute significantly to far-field sound radiation. A variety of test cases were studied for controlling sound radiation due to a disturbance both on and off resonance. Results from these experiments indicate that PVDF sensors and piezoceramic actuators show much promise for controlling acoustic radiation from structures, to a large degree overcoming the need for error microphones in the far field.
Grouping in pitch perception: Effects of onset asynchrony and ear of presentation of a mistuned component
Authors: Darwin C. J. , Ciocca Valter
Published: October 2005

Three experiments investigated how the onset asynchrony and ear of presentation of a single mistuned frequency component influence its contribution to the pitch of an otherwise harmonic complex tone. Subjects matched the pitch of the target complex by adjusting the pitch of a second similar but strictly periodic complex tone. When the mistuned component (the 4th harmonic of a 155 Hz fundamental) started 160 ms or more before the remaining harmonics but stopped simultaneously with them, it made a reduced contribution to the pitch of the complex. It made no contribution if it started more than 300 ms before. Pitch shifts and their reduction with onset time were larger for short (90 ms) sounds than for long (410 ms). Pitch shifts were slightly larger when the mistuned component was presented to the same ear as the remaining 11 in-tune harmonics than to the opposite ear. Adding a ‘‘captor’’ complex tone with a fundamental of 200 Hz and a missing 3rd harmonic to the contralateral ear did not augment the effect of onset time, even though the captor was synchronous with the mistuned harmonic, the mistuned component was equal in frequency to the missing 3rd harmonic of the captor complex tone and it was played to the same ear as the captor. The results show that a difference in onset time can prevent a resolved frequency component from contributing to the pitch of a complex tone even though it is present throughout that complex tone.
Accuracy of pitch matching for pure tones and for complex tones with overlapping or nonoverlapping harmonics
Authors: Moore Brian C. J. , Glasberg Brian R. , Proctor Gillian M.
Published: October 2005

The discrimination of the fundamental frequency (f0) of pairs of complex tones with no common harmonics is worse than the discrimination of f0 for tones with all harmonics in common. These experiments were conducted to assess whether this effect is a result of pitch shifts between pairs of tones without common harmonics or whether it reflects influences of spectral differences (timbre) on the accuracy of pitch perception. In experiment 1, pitch matches were obtained between sounds drawn from the following types: (1) pure tones (P) with frequencies 100, 200, or 400 Hz; (2) a multiple-component complex tone, designated A, with harmonics 3, 4, 8, 9, 10, 14, 15, and f0=100, 200 or 400 Hz; (3) A multiple-component complex tone, designated B, with harmonics 5, 6, 7, 11, 12, 13, 16, and with f0=100, 200 or 400 Hz. The following matches were made; A vs A, B vs B, A vs B, A vs P, B vs P and P vs P. Pitch shifts were found between the pure tones and the complex tones (A vs P and B vs P), but not between the A and B tones (A vs B). However, the variability of the A vs B matches was significantly greater than that of the A vs A or B vs B matches. Also, the variability of the A vs P and B vs P matches was greater than that for the A vs B matches. In a second experiment, frequency difference limens (DLCs) were measured for the A vs A, B vs B, and A vs B pairs of sounds. The DLCs were larger for the A vs B pair than for A vs A or B vs B. The results suggest that the poor frequency discrimination of tones with no common harmonics does not result from pitch shifts between the tones. Rather, it seems that spectral differences between tones interfere with judgements of their relative pitch.
Fringe effects in modulation masking
Authors: Bacon Sid P. , Grantham D. Wesley
Published: October 2005

Modulation detection thresholds (20 log ms) for a sinusoidally amplitude-modulated (SAM) noise were measured in the presence of a SAM noise masker with a modulation depth (mm) of 1.0 and a modulation frequency of 16 or 64 Hz. The signal and masker carriers were presented continuously, and the signal was modulated during one of the two 500-ms observation intervals. The masker was modulated during both observation intervals and, in some conditions, for a certain amount of time before and after signal modulation. The duration of this ‘‘fringe’’ ranged from 62.5 ms to continuous (masker modulated throughout the threshold estimate). The first experiment showed that a 500-ms fringe could reduce masked thresholds by 4–6 dB, but only at low signal modulation frequencies (2–8 Hz). In the second and third experiments, it was found that the fringe had to have a duration of 500 ms and a depth of about 0.75 to be maximally effective. A final, supplementary experiment indicated that the fringe effect is not due solely to the fringe that occurs prior to the observation intervals. The results are discussed in terms of both peripheral and central auditory processing.
Young cochlear implant users’ response to delayed auditory feedback
Authors: Tye-Murray Nancy
Published: October 2005

This investigation determined whether the signal provided by the Cochlear Corporation Nucleus cochlear implant can convey enough speech information to induce a response to delayed auditory feedback (DAF), and whether prelingually deafened children who receive a cochlear implant relatively late in their speech development are susceptible. Ten children with the Nucleus cochlear implant spoke simple phrases, first without and then with DAF. Three prelingually deafened subjects and the only two postlingually deafened subjects demonstrated longer phrase durations when speaking with DAF than without it. Two of the prelingually deafened subjects who demonstrated a response received their cochlear implants at the age of 5 years.
The use of static and dynamic vowel cues by multichannel cochlear implant users
Authors: Kirk Karen Iler , Tye-Murray Nancy , Hurtig Richard R.
Published: October 2005

Multichannel cochlear implant users vary greatly in their word-recognition abilities. This study examined whether their word recognition was related to the use of either highly dynamic or relatively steady-state vowel cues contained in /bVb/ and /wVb/ syllables. Nine conditions were created containing different combinations of formant transition, steady-state, and duration cues. Because processor strategies differ, the ability to perceive static and dynamic information may depend on the type of cochlear implant used. Ten Nucleus and ten Ineraid subjects participated, along with 12 normal-hearing control subjects. Vowel identification did not differ between implanted groups, but both were significantly poorer at identifying vowels than the normal-hearing group. Vowel identification was best when at least two kinds of cues were available. Using only one type of cue, performance was better with excised vowels containing steady-state formants than in ‘‘vowelless’’ syllables, where the center vocalic portion was deleted and transitions were joined. In the latter syllable type, Nucleus subjects identified vowels significantly better when /b/ was the initial consonant; the other two groups were not affected by specific consonantal context. Cochlear implant subjects’ word-recognition was positively correlated with the use of dynamic vowel cues, but not with steady-state cues.
Pitch and voiced/unvoiced determination with an auditory model
Authors: Van Immerseel Luc M. , Martens Jean-Pierre
Published: October 2005

In this paper, an accurate pitch and voiced/unvoiced determination algorithm for speech analysis is described. The algorithm is called AMPEX (auditory model-based pitch extractor) and it performs a temporal analysis of the outputs emerging from a new auditory model. However, in spite of its use of an auditory model, AMPEX should not be regarded as a substitute for any psychophysical theory of human auditory pitch perception. What is mainly described is the design of a computationally efficient auditory model, the perceptually motivated determination of the model parameters, the conception of a reliable pitch extractor for speech analysis, and the elaboration of an experimental procedure for evaluating the performance of such a pitch extractor. In the course of the evaluation experiment several kinds of speech stimuli including clean speech, bandpass-filtered speech, and noisy speech were presented to three different pitch extractors. The experimental results clearly indicate that AMPEX outperforms the best algorithms available.
Acoustic reflectometry with an arbitrarily short source tube
Authors: Marshall Ian
Published: October 2005

In acoustic reflectometry, the input impulse response (reflectance) of an object is measured, from which its internal area profile can be deduced. Unwanted multiple reflections are normally avoided by using a source tube that is longer than the object, thus making the source appear nonreflecting. If the source tube is shorter than the object, the required reflectance is obscured by multiple reflections, which cannot be removed by conventional dereverberation. A new analysis of the acoustic reflectometry technique reveals a method by which the source tube may be made arbitrarily short. Such a novel reflectometer is implemented and used to measure objects up to three times the source tube length. Reconstructed areas have accuracies of typically 10%.
Double through-transmission bulk wave method for ultrasonic phase velocity measurement and determination of elastic constants of composite materials
Authors: Rokhlin S. I. , Wang W.
Published: October 2005

This paper describes a modification of a nondestructive ultrasonic method for measurements of the phase velocity of bulk waves in arbitrary directions in generally anisotropic materials. In the conventional method the through-transmission technique is used for velocity measurements at a specified angle of incidence. When this angle is changed by rotation of the sample, the transmitted beam changes position, and so the position of the receiving transducer must be changed. This leads to experimental difficulties and loss of precision. In the double-transmission technique, the ultrasonic wave is reflected from reflector plates behind the sample and returns via the same path to the same position on the transmitter/receiver working in pulse-echo mode, which eliminates the necessity of readjusting the receiver position. It is also shown that for arbitrary direction of measurement in anisotropic materials, time-delay measurements give phase velocity regardless of the angle of deviation between phase and group velocities. The physical basis of this phenomenon is explained. An example of velocity measurement and elastic-constant determination is given for unidirectional graphite–epoxy composite. Stability of the nonlinear least-square algorithm used for reconstruction of the elastic constants from the velocity data is demonstrated by computer simulation on a synthetic set of data.
Acoustic scattering by a rigid sphere in the field of waves emanating from a circular concave radiator
Authors: Hasegawa Takahi , Noda Hideki , Hino Yasutaka , Annou Akio , Kato Masahiko , Inoue Naoki
Published: October 2005

This paper presents a new method for calculating the velocity potential Φ of scattered ultrasonic waves from a rigid sphere placed in the field of waves emanating from a circular concave radiator in an infinite baffle. The solution Φ is given in the form of an infinite series of spherical surface harmonics as a function of reduced quantities ka, krc, kb, kz0, etc., where k is the wave number, a is the radius of the circular concave vibrator, rc is the radius of curvature of it, b is the radius of the sphere, and z0 is the distance from the piston to the center of the sphere. The present theoretical framework has the advantages that it includes no numerical integrations and that it is applicable to elastic or compressible sphere cases with slight modifications of the boundary conditions.
The effect of a viscous fluid on Love waves in a layered medium
Authors: Kim Jin O.
Published: October 2005

This paper describes a theoretical study pertaining to the effect of the viscosity and density of an adjacent viscous fluid on the characteristics of Love waves propagating in a layered half-space medium. Expressions for the Love wave velocity and attenuation are obtained as functions of the viscosity and density of the fluid by exact and asymptotic analyses. The valid range of the asymptotic solution is identified by comparing it with the exact solution.
On multidimensional ultrasonic scattering in an inhomogeneous elastic background
Authors: Aymé-Bellegarda Eveline J. , Habashy Tarek M.
Published: October 2005

This work is concerned with the modeling of elastic wave scattering by solid or fluid-filled objects embedded in an inhomogeneous elastic background. The medium is probed by a monochromatic force and the scattered field is computed (forward problem) or observed (inverse problem) at some known receiver locations. Based on vector integral equations for elastic scattering, a general framework is developed, independent of both the problem geometry and the transmitter–receiver characteristics. This framework encompasses both forward and inverse modeling. In the forward model, a Born approximation for an inhomogeneous background is applied to obtain a closed form expression for the scattered field. In the inverse model, this approximation is also invoked to linearize for the mutliparameter characteristic of the object. Finally, an iterative inversion scheme alternating forward and inverse modeling is proposed to improve the resolution and accuracy of the reconstruction algorithm.
Pitch discrimination and phase sensitivity in young and elderly subjects and its relationship to frequency selectivity
Authors: Moore Brian C. J. , Peters Robert W.
Published: October 2005

Frequency difference limens for pure tones (DLFs) and for complex tones (DLCs) were measured for four groups of subjects: young normal hearing, young hearing impaired, elderly with near-normal hearing, and elderly hearing impaired. The auditory filters of the subjects had been measured in earlier experiments using the notched-noise method, for center frequencies ( fc) of 100, 200, 400, and 800 Hz. The DLFs for both impaired groups were higher than for the young normal group at all fc ’s (50–4000 Hz). The DLFs at a given fc were generally only weakly correlated with the sharpness of the auditory filter at that fc, and some subjects with broad filters had near-normal DLFs at low frequencies. Some subjects in the elderly normal group had very large DLFs at low frequencies in spite of near-normal auditory filters. These results suggest a partial dissociation of frequency selectivity and frequency discrimination of pure tones. The DLCs for the two impaired groups were higher than those for the young normal group at all fundamental frequencies ( f0) tested (50, 100, 200, and 400 Hz); the DLCs for the elderly normal group were intermediate. At f0=50 Hz, DLCs for a complex tone containing only low harmonics (1–5) were markedly higher than for complex tones containing higher harmonics, for all subject groups, suggesting that pitch was conveyed largely by the higher, unresolved harmonics. For the elderly impaired group, and some subjects in the elderly normal group, DLCs were larger for a complex tone with lower harmonics (1–12) than for tones without lower harmonics (4–12 and 6–12) for f0’s up to 200 Hz. Some elderly normal subjects had markedly larger-than-normal DLCs in spite of near-normal auditory filters. The DLCs tended to be larger for complexes with components added in alternating sine/cosine phase than for complexes with components added in cosine phase. Phase effects were significant for all groups, but were small for the young normal group. The results are not consistent with place-based models of the pitch perception of complex tones; rather, they suggest that pitch is at least partly determined by temporal mechanisms.
Vocal intensity in speakers and singers
Authors: Titze Ingo R. , Sundberg Johan
Published: October 2005

Vocal intensity is studied as a function of fundamental frequency and lung pressure. A combination of analytical and empirical models is used to predict sound pressure levels from glottal waveforms of five professional tenors and twenty five normal control subjects. The glottal waveforms were obtained by inverse filtering the mouth flow. Empirical models describe features of the glottal flow waveform (peak flow, peak flow derivative, open quotient, and speed quotient) in terms of lung pressure and phonation threshold pressure, a key variable that incorporates the F0 dependence of many of the features of the glottal flow. The analytical model describes the contributions to sound pressure levels SPL by the vocal tract. Results show that SPL increases with F0 at a rate of 8–9 dB/octave provided that lung pressure is raised proportional to phonation threshold pressure. The SPL also increases at a rate of 8–9 dB per doubling of excess pressure over threshold, a new quantity that assumes considerable importance in vocal intensity calculations. For the same excess pressure over threshold, the professional tenors produced 10–12 dB greater intensity than the male nonsingers, primarily because their peak airflow was much higher for the same pressures. A simple set of rules is devised for predicting SPL from source waveforms.
Acoustic and perceptual characteristics of voicing in fricatives and fricative clusters
Authors: Stevens Kenneth N. , Blumstein Sheila E. , Glicksman Laura , Burton Martha , Kurowski Kathleen
Published: October 2005

Several types of measurements were made to determine the acoustic characteristics that distinguish between voiced and voiceless fricatives in various phonetic environments. The selection of measurements was based on a theoretical analysis that indicated the acoustic and aerodynamic attributes at the boundaries between fricatives and vowels. As expected, glottal vibration extended over a longer time in the obstruent interval for voiced fricatives than for voiceless fricatives, and there were more extensive transitions of the first formant adjacent to voiced fricatives than for the voiceless cognates. When two fricatives with different voicing were adjacent, there were substantial modifications of these acoustic attributes, particularly for the syllable-final fricative. In some cases, these modifications leads to complete assimilation of the voicing feature. Several perceptual studies with synthetic vowel-consonant-vowel stimuli and with edited natural stimuli examined the role of consonant duration, extent and location of glottal vibration, and extent of formant transitions on the identification of the voicing characteristics of fricatives. The perceptual results were in general consistent with the acoustic observations and with expectations based on the theoretical model. The results suggest that listeners base their voicing judgments of intervocalic fricatives on an assessment of the time interval in the fricative during which there is no glottal vibration. This time interval must exceed about 60 ms if the fricative is to be judged as voiceless, except that a small correction to this threshold is applied depending on the extent to which the first-formant transitions are truncated at the consonant boundaries.
Calculating acoustical properties of cells: Influence of surface topography and liquid layer between cell and substrate
Authors: Kundu T. , Bereiter-Hahn J. , Hillmann K.
Published: October 2005

In this paper, a mathematical formulation is presented to compute the V(z) of a tapering layered solid and applying this formulation to the determination of acoustic properties of biological cells and tissues. The formulation is adopted in the simplex inversion algorithm to obtain the acoustic properties of a tapering cell from its V(z) values. The influence of two parameters had been considered: The tapering angle and the presence of a thin liquid layer present between cells and the substratum to which they adhere. Up to a tapering angle less than 10°, it can be safely neglected. However, if a larger angle is neglected, then the acoustic wave velocity in the cell is overestimated. Cell thickness estimation is not affected significantly when the tapering angle is ignored. The calculations of acoustic properties of cells are considerably influenced by the introduction of a thin fluid layer between the solid substratum and the overlying cell, neglecting the presence of at least a very thin layer (20–30 nm), in general, results in a considerable overestimation of sound velocity. The reliability of the data calculated from V(z) values was ascertained using an independent method to determine cell thickness by calculating it from the interference fringe pattern obtained with the reflection-interference light microscope. The shape of the glutaraldehyde-fixed cells was similar to fried eggs. The highest sound velocities were found close to the periphery of the dome-shaped cell center. In the very center and over most of the area of the thin periphery, sound velocity was close to that in saline.
Effect of spectral envelope smearing on speech reception. I
Authors: ter Keurs Mariken , Festen Joost M. , Plomp Reinier
Published: October 2005

The effect of reduced spectral contrast on the speech-reception threshold (SRT) for sentences in noise and on phoneme identification, was investigated with 16 normal-hearing subjects. Signal processing was performed by smoothing the envelope of the squared short-time fast Fourier transform (FFT) by convolving it with a Gaussian-shaped filter, and overlapping additions to reconstruct a continuous signal. Spectral energy in the frequency region from 100 to 8000 Hz was smeared over bandwidths of 1/8, 1/4, 1/3, 1/2, 1, 2, and 4 oct for the SRT experiment. Vowel and consonant identification was studied for smearing bandwidths of 1/8, 1/2, and 2 oct. Results showed the SRT in noise to increase as the spectral energy was smeared over bandwidths exceeding the ear’s critical bandwidth. Vowel identification suffered more from this type of processing than consonant identification. Vowels were primarily confused with the back vowels /c,u/, and consonants were confused where place of articulation is concerned.
A systematical study for psychological impression caused by fluctuating random noise based on fuzzy set theory
Authors: Kato Yuichi , Yamaguchi Shizuma
Published: October 2005

An opinion that the psychological impression caused by noise exposure can be regarded as a fuzzy event is first shown, based on the information obtained from an actual psychological experiment. That is, the psychological impression is essentially subjective and originally includes fuzziness. The above subjective psychological impression is grasped quantitatively by using the so-called membership function in the field of fuzzy set theory. Next, a new systematical method for estimating and/or predicting the psychological impression is proposed, in the case when the persons are exposed to the fluctuating random noise of arbitrary probability distribution type. Finally, the validity and usefulness of the proposed method are confirmed experimentally by applying it to the actually observed data for road traffic noise.
Detection of oscillatory and impulsive transients using higher-order correlations and spectra
Authors: Pflug Lisa A. , Ioup George E. , Ioup Juliette W. , Barnes Kenneth H. , Field Robert L. , Rayborn Grayson H.
Published: October 2005

Higher-order cross and ordinary correlation detectors are applied to four deterministic transients contaminated by uncorrelated Gaussian noise only. Histograms and moments are used to examine the properties of the signals and their effect on detector performance. Receiver operating characteristic (ROC) curve analysis and limiting signal-to-noise ratios for ‘‘good’’ detection provide comparative measures for different detectors. Probability density functions of detection ordinate values of signal-present and noise-only correlations are used to explain ROC curve behavior. Using a known source, the cross-correlation detector performs better than the higher-order correlation detectors for each transient studied. However, for an unknown narrow pulse source signal, the bicorrelation and tricorrelation detectors outperform the cross-correlation detector. In contrast, the bicorrelation detector performs very poorly for low-frequency narrow-band signals with a small third moment embedded in uncorrelated Gaussian noise. Rectification as part of the detection process improves the performance of the bicorrelation detector and also places the peak of maximum magnitude at the origin. This eliminates the problem in detection or time delay estimation that the existence of multiple peaks due to symmetries in the auto-bicorrelation or the bicorrelation of repeated signals may cause. The tricorrelation detector also performs better with rectification than without. For an unknown source, the bicorrelation and tricorrelation detectors with rectification perform on a level comparable to the cross-correlation detector for certain signals. Comparisons are made between repeating a known source and repeating noisy received signals in the bicorrelation.