bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple scattering from a randomly distributed cloud of bubbles
Authors: Wang Lintao , Gilbert Kenneth E.
Published: October 2005

Exact multiple scattering calculations are presented for scattering from a randomly distributed cloud of bubbles. The conditions under which a single scattering (Born) approximation holds are discussed. In addition, numerical calculations are presented that show the relative contributions of coherent and incoherent scatter. The multiple scattering calculations are compared to scattering from an “effective fluid” model of a bubble cloud. It is shown that while the fluid model is adequate for predicting forward scatter, it cannot accurately predict backscatter when the acoustic wavelength is comparable to the dimensions of the bubble cloud. Some alternative approaches are discussed for accurately predicting backscatter from a randomly distributed cloud of bubbles. [Work supported by ONR.]
Dynamics of air bubbles entrapped by capillary waves
Authors: Oguz Hasan N. , Longuet-Higgins Michael S.
Published: October 2005

It is well known that entrapment of air bubbles near the sea surface contributes substantially to the underwater noise levels. The collapse of air pockets created by steep capillary waves is a possible mechanism of bubble formation. A boundary integral formulation is employed to simulate the bubble behavior after detachment from these air pockets. The initial profile of the trapped bubble, approximated from the form of the capillary waves, suggests a high elongated bubble relatively far from the sea surface. A sequence of initial bubble shapes is generated from successively closer approximations to the bubble shape. Depending on the initial curvature of the detachment point the bubble may break up into two or oscillate as a single bubble in a rather violent manner. Volume oscillations that are responsible for the radiation of sound are found to be affected by the shape oscillations. It is found that a traveling capillary wave on the bubble surface can cause a pressure pulse upon reaching the axis. As a result, the pressure signal may deviate substantially from the simple damped sinusoid of a spherical bubble. [Work supported by ONR.]
Direct numerical simulation of bubble behavior in oscillatory flow
Authors: Zhang D. Z. , Prosperetti A. , Sangani A. S.
Published: October 2005

The motion of spheres (bubbles) in an incompressible liquid undergoing a small-amplitude oscillatory motion is calculated by a multipole expansion method. In the limit of small viscosity, the Stokes layer is confined to the vicinity of the surface of the bubbles, which therefore interact approximately only through the pressure field. The motion of the spheres is parametrized in terms of added mass, Basset, and drag forces; the coefficients of which are obtained from the simulation. To obtain results useful for the study of pressure wave propagation in bubbly liquids, several bubble configurations are studied for different (finite) volume fractions and the results then averaged. The effects of surface tension and bubble density are also considered. [Work supported by DOE.]
Using neoprene-faced, PVDF transducers to couple ultrasound into solids
Authors: Habeger C. C. , Wink W. A. , Van Zummeren M. L.
Published: October 2005

This is a study of the quality of the acoustic coupling achieved by pressing a neoprene-faced transducer to a solid surface without an intervening couplant. Techniques for measuring the reflection coefficient at the interface between the neoprene and a sample, which is much greater than or much less than a wavelength in thickness, are developed. Experimental results showing the influence of frequency, loading pressure, and surface roughness are presented. A dimensionless number, the coupling ratio (CR), is introduced as a measure of the relative effect of poor coupling on acoustic transmission. In light of the experimental results, the benefits and limitations of dry neoprene coupling are discussed. In addition, the construction of the neoprene-faced, polyvinylidene fluoride (PVDF) transducers used in the study is described. Efficient acoustic coupling is realized with these transducers, when they are operated within the ranges established in the study.
Higher frequency ambient noise in the Arctic Ocean
Authors: Lewis James K. , Denner Warren W.
Published: October 2005

Higher frequency (1000 Hz) arctic ambient noise episodes during nonsummer months were used to study generating mechanisms. In most cases in which noise amplitudes were relatively high (>103 μPa), thermal fracturing of sea ice was responsible. Numerical simulations with a daily heating cycle and no snow cover implied that maximum noise occurred at 1900 h local. Radiational heat balances were more important than sensible heat flux in producing fracturing of sea ice. With snow cover, a daily heating cycle produces maximum fracturing at 0300–0800 h local, a common feature seen in noise data. Fracturing estimated from numerical simulations using observed arctic heat flux parameters was in good agreement with the observed 1000-Hz noise signal. However, results indicate that blowing snow and ice fog may be additional factors in the heat flux balance of sea ice and the generation of arctic ambient noise. The short space scales of higher frequency noise are likely a result of spatial variations in snow cover. The short time scales of such noise are not only a result of multiple noise-generating processes but also changes in cloud and snow cover.
Nonlinear effects in focused sound beams
Authors: Hart Timothy S. , Hamilton Mark F.
Published: October 2005

Nonlinear effects in focused sound beams are investigated with numerical solutions of the Khokhlov–Zabolotskaya–Kuznetsov (KZK) parabolic wave equation. The KZK equation accounts consistently for the combined effects of nonlinearity, diffraction, and absorption. To improve the efficiency of the calculations, a coordinate transformation is introduced that follows the convergent geometry of the focused beam. The transformation is similar to one introduced earlier to accommodate the divergent geometry of unfocused beams [Hamilton et al., J. Acoust. Soc. Am. 78, 202–216 (1985)]. A Fourier series expansion of the acoustic pressure is used to reduce the transformed KZK equation to a set of coupled parabolic equations that are solved using a finite difference method. Attention is devoted to radiation from circular sources with uniform amplitude distributions and linear focusing gains of order 50. The combined effects of nonlinearity, diffraction, and absorption in the focal region are clearly revealed in both the time and frequency domains. For the range of parameters considered, beam patterns in the focal region are found to be less dependent on source amplitude and absorption than are beam patterns in the farfield of unfocused sources.
Interactions of a spherical wave with a bilaminar plate composed of homogeneous and isotropic solid layers
Authors: Piquette Jean C.
Published: October 2005

The interaction of a spherical wave with a bilaminar plate of infinite lateral extent is considered theoretically. Each of the plate layers is assumed to be composed of a homogeneous and isotropic solid. Losses in the plate materials are modeled by using complex material properties. Both the source and the plate are immersed in an infinite, inviscid fluid. The solution is obtained by imposing appropriate boundary conditions on the full three-dimensional elasticity equations. Several cases involving a rubber-coated metal plate and a rubber-coated plastic plate are investigated numerically for a 1-kHz incident wave and for a 2-kHz incident wave. For the numerical study, the inviscid fluid is taken to be water. For vanishingly thin rubber coatings, the bilaminar plate results are found to approach the single-layer plate results [J. C. Piquette, ‘‘Spherical-wave scattering by a finite-thickness solid plate of infinite lateral extent, with some implications for panel measurements,’’ J. Acoust. Soc. Am. 83, 1284–1294 (1988)]. In the case of a single-layer plate, it was found that ‘‘overpressures’’ could be created.

That is, the amplitudes of the reflected and/or transmitted waves on the acoustic axis, evaluated on either surface of the plate, can exceed that of the incident wave. In the present work, it is found that for the case of rubber-coated plastic there is a transition thickness of rubber through which the reflected and transmitted waves on the acoustic axis are enhanced. That is, the amplitudes of the reflected and the transmitted waves can be greater than those obtained from an uncoated plate. However, if the rubber thickness is increased still further, it is found that the amplitudes of the reflected and transmitted waves rapidly collapse, the overpressures associated with the uncoated plate disappear, and the coated-plate results evaluated on the acoustic axis approach normal-incidence plane-wave results. This wave-field collapse does not occur in the case of a rubber-coated metal. An important conclusion of this research is that the spherical-wave effects that may be introduced into panel measurements in which a metallic support plate has been used may be reduced, or even eliminated, by replacing the metallic support plate with a plastic support plate.
Stripping one-dimensional acoustic pressure response into propagating- and standing-wave components
Authors: Spiekermann Charles E. , Radcliffe Clark J.
Published: October 2005

Most realistic boundary conditions are partially absorptive, with the rest of the incident acoustic power being reflected. This results in a response that can be viewed as a summation of propagating- and standing-wave effects. A one-dimensional, measurement-based, two-microphone spectral analysis technique is developed which s_eparates the t_otal acoustic r_esponse i_nto p_ropagating and s_tanding (STRIPS) wave components. STRIPS uses measurements that contain implicit information about the boundary condition to extract the propagating- and standing-wave components. These sum to be the total system response without requiring explicit knowledge of the particular boundary condition. An exact decomposition example for a one-dimensional acoustic pressure model with a known mixed boundary condition is used to validate the STRIPS method. The utility of the STRIPS method is demonstrated using experimental measurements from a tube as input to STRIPS to obtain the propagating- and standing-wave pressure components. Changes in experimental boundary absorptivity are seen in the STRIPS results when a flared end is attached to the tube.
Vocal tract shapes of a flautist in performance
Authors: Thomas Lyndal , Troup G. J. , Ferris N.
Published: October 2005

Lateral view x rays of a flautist in performance show that there is no variation in vocal tract shape with pitch, and that the larynx is lowered from the rest position when notes are played.
Ultrasonic backscatter from flowing whole blood. II: Dependence on frequency and fibrinogen concentration
Authors: Yuan Y. W. , Shung K. K.
Published: October 2005

Earlier studies showed that ultrasonic backscatter from erythrocytes suspended in saline is a function of hematocrit and frequency and that it can be affected by flow disturbance. The experimental data agree well with the theories. Recently, studies have been extended to flowing whole blood. The results indicated that ultrasonic backscatter from flowing whole blood differs from that from saline suspensions of erythrocytes in that it is shear-rate dependent and species dependent. In the present article, data on the dependence of ultrasonic backscatter from flowing whole blood on frequency and on fibrinogen concentration are reported. It was found that ultrasonic backscatter from flowing whole blood also depends on fibrinogen concentration when red blood cell (RBC) aggregation exists. Moreover, when the blood is under conditions that favor RBC aggregation such as low shear rates, high fibrinogen concentration, or high hematocrits, Rayleigh scattering apparently is no longer sufficient to describe its scattering behavior.
The acoustics of the vocal tract in the horseshoe bat, R
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Authors: Hartley David J. , Suthers Roderick A.
Published: October 2005

The transfer function of the supraglottal vocal tract of the horseshoe bat, Rhinolophus hildebrandti, was obtained by a noninvasive technique, based on incremental variations in the helium content of inspired gas, which also allowed the source spectrum to be determined. The acoustic role of the vocal tract chambers was examined by obtaining the transfer function before and after filling the chambers. Simultaneous recording of sound pressures in the trachea during these experiments allowed some analysis of subglottal acoustics. With the vocal tract intact, the transfer function was found to show sharp transmission minima at the fundamental and third harmonic and a broad transmission maximum at the emitted second harmonic. This transfer function shape, along with the source spectrum obtained, demonstrates that the second harmonic dominance in the emitted pulse is achieved by vocal tract filtering, although the source spectrum is different from that typical of man in that it does not show an f−2 harmonic decay. Changes in the transfer function caused by filling the nasal chambers suggest that these structures may play an impedance matching role at the second harmonic. Filling of the tracheal chambers did not affect the transfer function but changed the tracheal acoustics in a manner which suggests that these chambers may return backward-propagated sound to the larynx with a phase shift. The possible interactive role of the nasal and tracheal chambers in increasing vocal efficiency at the second harmonic is discussed.
Illusory continuity of tonal and infratonal periodic sounds
Authors: Warren Richard M. , Wrightson John M. , Puretz Julian
Published: October 2005

Temporal induction can restore masked or obliterated portions of signals so that tones may seem continuous when alternated with sounds having appropriate spectral composition and intensity. The upper intensity limits for the induction of tones (pulsation thresholds) are related to masking functions and have been used to define the characteristics of frequency domain (place) analysis of tones. The present study has found that induction also occurs for infratonal periodic sounds that require a time domain analysis for perception of acoustic repetition. Limits for temporal induction were determined for iterated frozen noise segments from 10–2000 Hz alternated with a louder on-line noise. Masked thresholds were also obtained for the pulsed signals presented along with continuous noise, and it was found that the relation between induction limits and masking changed with frequency. The results obtained for induction and masking are discussed in terms of general principles governing restoration of obliterated sounds.
Particle gathering and microstreaming near ultrasonically activated gas-filled micropores
Authors: Miller Douglas L.
Published: October 2005

Nonthermal bioeffects of ultrasound can be induced by the physical mechanisms of radiation force and acoustic microstreaming. In this study, microscopical observations of the influence of these mechanisms on small particles near ultrasonically activated gas-filled micropores in thin plastic sheets were compared to approximate theoretical treatments of the particle behavior. The microstreaming flow was localized within a toroidal eddy around an active micropore, as indicated by isopycnic 1-μm polystyrene spheres. The size of the flow pattern seemed to decrease slowly with increasing frequency in the range 0.7–3.5 MHz. Flow was radially inward along the surface, rather than outward as expected from the theory. All the particles tested, which included particles with density less than, equal to, or more than the medium, seemed to accumulate at the micropores. From the theory for the radiation force, the particles less dense than the medium were expected to be repulsed from the micropores. Therefore, the theories for these phenomena, at least to the level of approximation available, may not be completely adequate for the detailed analysis of these phenomena.
A new diagnostic method for separating airborne and structureborne noise radiated by plates with applications for propeller driven aircraft
Authors: McGary Michael C.
Published: October 2005

The anticipated application of advanced turboprop propulsion systems is expected to increase the interior noise of future aircraft to unacceptably high levels. The absence of technically and economically feasible noise source-path diagnostic tools has been a prime obstacle in the development of efficient noise control treatments for propeller-driven aircraft. A new diagnostic method that permits the separation and prediction of the fully coherent airborne and structureborne components of the sound radiated by plates or thin shells has been developed. Analytical and experimental studies of the proposed method were performed on an aluminum plate. The results of the study indicate that the proposed method could be used in flight, and has fewer encumbrances than the other diagnostic tools currently available.
Synchronous sounds produced by V
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Authors: Barenholz-Paniry Vered , Ishay Jacob S.
Published: October 2005

Sound production by larvae of the Oriental hornet Vespa orientalis (Vespinae; Hymenoptera) was studied and recorded. Larvae of instars 4 and 5 produce rhythmic sounds under certain conditions. If there is a mechanical disturbance near the comb, the larval sounds synchronize for brief periods of up to 1 min and are probably intended as warning signals. In experiments designed to quantify this phenomenon, the following findings were obtained. (1) After a single strike in the vicinity of the comb, most of the larvae in the comb cells respond with emission of synchronized sounds. (2) Under the influence of repetitive solid-borne sounds such as those produced by a metronome, there is emission of a sound analogous to what has previously been described as a hunger signal. This happens at 40–80 metronome beats per minute but not at higher rates. (3) Within the range of 40–120 beats per minute, when the metronome is stopped, there is synchronous sound production by numerous larvae, while the slower the metronome rate (within this range) at the moment of stopping, the larger the proportion of larvae participating in the synchronous ‘‘chorus.’’
Cues for intervocalic /t/ and /d/ in children and adults
Authors: Allen George D. , Norwood John A.
Published: October 2005

One naturally spoken token of each of the words petal and pedal was computer edited to produce stimuli varying in voice onset time (VOT), silent closure duration, and initial /q/ vowel duration. These stimuli were then played, in the sentence frame ‘‘Push the button for the ——,’’ to four adult and four 6-year-old listeners, who responded by pressing a button associated with a flower (petal) or a bicycle (pedal). Among the findings of interest were the following: (a) VOT was statistically the strongest cue for both listener groups, followed by closure duration and initial vowel duration; (b) VOT was relatively stronger for children than for adults, whereas closure and initial vowel durations were relatively stronger for adults than for children; (c) except for a probable ceiling/floor effect, there were no statistically significant interactions among the three acoustic cues, although there were interactions between those cues and both listener group (adults versus children) and the token from which the stimulus had been derived (petal versus pedal).
Synthetic vowel studies on cochlear implant patients
Authors: Tong Y. C. , Lim H. H. , Clark G. M.
Published: October 2005

Speech perception studies were conducted on three cochlear implant patients to investigate the relative merits of six speech processing schemes for presenting speech information to these patients. Electrical stimuli, described in this article as synthetic vowels, were constructed using tabulated data of formant frequencies of natural vowels. The six schemes differed in the number of formant frequencies encoded on the electrical signal dimension of electrode position, and/or in the range of electrode position used for encoding each formant frequency. Eleven synthetic vowels (i, I, q, 1, a, c, u, u, v, Q, A) were used and were presented in a single-interval procedure for absolute identification. Single-formant vowels were used in two of the six schemes, two-formant vowels in three schemes, and three-formant vowels in the remaining scheme. The confusion matrices were subjected to conditional information transmission analysis on the basis of previous psychophysical findings. Comparisons among the schemes in terms of the analyzed results showed that training, experience, and adaptability to new speech processing schemes were major factors influencing the identification of synthetic vowels. For vowels containing more than one formant, the information about each formant affected the perception of the other formants. In addition, there appeared to be differences between the perceptual processes for vowels containing more than one formant and the processes for single-formant vowels. Taking into consideration the effects of training, experience, and adaptability, the three-formant speech processing scheme appeared, on the basis of perceptual performance comparisons among the six schemes, to be the logical choice for implementation in speech processors for cochlear implant patients.
Effects of speaking rate on tongue position and velocity of movement in vowel production
Authors: Flege James Emil
Published: October 2005

This study used glossometry to examine the position of the tongue and the velocity of its movements in vowels spoken normally and at a self-selected fast rate. The subject in experiment 1 showed lingual undershoot for stressed vowels in ‘‘a bib again’’ and ‘‘a bob again.’’ The tongue was lower for /i/ and higher for /a/ at the fast rate than at the normal rate. The stressed vowels exerted an effect on unstressed vowels: The tongue was lower in the schwas that preceded and followed /a/ than /i/. Only one of the three subjects in experiment 2 showed no lingual undershoot for fast-rate /i/. The tongue was higher at the fast rate than at the normal rate in the schwas flanking /i/ so that the displacement was less at the fast rate than at the normal rate. Another talker increased the peak velocity of tongue movements at the fast rate and showed no undershoot for /a/. Multiple regression analyses showed that the timing of movements for successive phonetic segments accounted well undershoot in only one of the three subjects. The results suggest that in order to model the effects of speaking rate on the tongue movements used in forming stressed vowels, it will be necessary to take into account: (1) how much vowels are shortened at a fast rate; (2) how much the peak velocity of tongue movements is increased, if at all; and (3) the position of the tongue before and after the stressed vowels. All three factors are likely to be influenced by how clearly the talker wishes to speak.
Effects of noise on speech production: Acoustic and perceptual analyses
Authors: Summers W. Van , Pisoni David B. , Bernacki Robert H. , Pedlow Robert I. , Stokes Michael A.
Published: October 2005

Acoustical analyses were carried out on a set of utterances produced by two male speakers talking in quiet and in 80, 90, and 100 dB SPL of masking noise. In addition to replicating previous studies demonstrating increases in amplitude, duration, and vocal pitch while talking in noise, these analyses also found reliable differences in the formant frequencies and short-term spectra of vowels. Perceptual experiments were also conducted to assess the intelligibility of utterances produced in quiet and in noise when they were presented at equal S/N ratios for identification. In each experiment, utterances originally produced in noise were found to be more intelligible than utterances produced in the quiet. The results of the acoustic analyses showed clear and consistent differences in the acoustic–phonetic characteristics of speech produced in quiet versus noisy environments. Moreover, these acoustic differences produced reliable effects on intelligibility. The findings are discussed in terms of: (1) the nature of the acoustic changes that take place when speakers produce speech under adverse conditions such as noise, psychological stress, or high cognitive load; (2) the role of training and feedback in controlling and modifying a talker’s speech to improve performance of current speech recognizers; and (3) the development of robust algorithms for recognition of speech in noise.
Recognition of low-level alcohol intoxication from speech signal
Authors: Klingholz F. , Penning R. , Liebhardt E.
Published: October 2005

Eleven male subjects were required to read a text in both sober and alcohol intoxicated conditions. By means of statistical signal analysis, frequency distributions of fundamental frequency (F0), signal-to-noise ratio (SNR), ratio of first- to second-formant frequencies (F1/F2), variation speed of the frequencies F0, F1, F2, and the long-term average spectrum (LTAS) were determined. The distributions were examined for their suitability in discriminating between sober and intoxicated conditions. The SNR and F0 distributions as well as the LTAS discriminated with an error rate less than 5%. Combination of SNR and F0 profiles enabled correct discrimination in all cases. The parameter F1/F2 describing the articulation varied strongly among individuals. It was modified only with high levels of blood alcohol. Frequency variation speeds were not altered by intoxication. Speaker recognition by means of LTAS was more difficult in the intoxicated condition. The principal effect of intoxication on speech was interpreted as a perturbation of laryngeal movement control, where long-term voice effort was found to produce similar effects to alcohol intoxication. On the basis of the present results and various other factors (ambiguity of the sources of the acoustic effects, expense of the procedure), application of acoustic analysis in forensic medicine for recognition of low-level alcohol intoxication is considered inexpedient.
Underwater audiogram of a false killer whale (P
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Authors: Thomas Jeanette , Chun Norman , Au Whitlow , Pugh Kiana
Published: October 2005

Underwater audiograms are available for only a few odontocete species. A false killer whale (Pseudorca crassidens) was trained at Sea Life Park in Oahu, Hawaii for an underwater hearing test using a go/no-go response paradigm. Over a 6-month period, auditory thresholds from 2–115 kHz were measured using an up/down staircase psychometric technique. The resulting audiogram showed hearing sensitivities below 64 kHz similar to those of belugas (Delphinapterus leucas) and Atlantic bottlenosed dolphins (Tursiops truncatus). Above 64 kHz, this Pseudorca had a rapid decrease in sensitivity of about 150 dB per octave. A similar decrease in sensitivity occurs at 32 kHz in the killer whale, at 50 kHz in the Amazon River dolphin, at 120 kHz in the beluga, at 140 kHz in the bottlenosed dolphin, and at 140 kHz in the harbor porpoise. The most sensitive range of hearing was from 16–64 kHz (a range 10 dB from the maximum sensitivity). This range corresponds with the peak frequency of echolocation pulses recorded from captive Pseudorca.
Diffraction of sound above a curved surface having an impedance discontinuity
Authors: Bérengier M. , Daigle G. A.
Published: October 2005

This article describes theory and experiments in the case of propagation of sound in the presence of an impedance discontinuity and a curved surface (or sound-speed gradients). The theory is based on a residue series, or creeping wave, solution developed for the propagation of sound in a stratified medium under conditions favorable to the formation of a shadow zone. The creeping wave solutions on each side of the impedance discontinuity are coupled heuristically by assuming a virtual source above discontinuity. The theory is compared to controlled measurements made indoors above a curved surface having an impedance jump (hard to soft). The measurements were made using a point source driven by frequencies in the range between 0.3 and 10 kHz. The theory is also compared to measurements made outdoors above a flat ground having a mixed path (asphalt to grass) in the presence of realistic gradients. Pure tones in the frequency range between 0.5 and 5 kHz were generated from a point source and the resulting sound-pressure levels measured on a sound level meter after suitable filtering. In all cases, there is good agreement between measurements and theory.
Measurement of sound emitted by flying projectiles with aeroacoustic sources
Authors: Cho Y. I. , Shakkottai P. , Harstad K. G. , Back L. H.
Published: October 2005

Training projectiles with axisymmetric ring cavities that produce intense tones in an airstream were shot in a straight-line trajectory. A ground-based microphone was used to obtain the angular distribution of sound intensity produced from the flying projectile. Data reduction required calculation of Doppler and attenuation factors. Also, the directional sensitivity of the ground-mounted microphone was measured and used in the data reduction. A rapid angular variation of sound intensity produced from the projectile was found that can be used to plot an intensity contour map on the ground. A full-scale field test confirmed the validity of the aeroacoustic concept of producing a relatively intense whistle from the projectile, and the usefulness of short-range flight tests that yield acoustic data free of uncertainties associated with diffraction, reflection, and refraction at jet boundaries in free-jet tests.
Remote ultrasonic measurement of the thickness of thin films
Authors: Lefebvre J. E. , Bruneel C. , Delebarre C. , Lutgen P. , Ecker T.
Published: October 2005

The current techniques for the measurement of the thickness of films are time consuming or not very reliable when the thickness is in the micron range. In this article, a new noncontacting method for the measurement of the thickness of thin films of various materials is presented. This method relies on the variations of the transmission coefficient of ultrasonic waves through the film. The sensitivity and the relative precision of this measurement can be optimized by an appropriate choice of the ultrasonic frequency according to the range of thicknesses to be measured. The method presented in this article can be set up ‘‘on line’’ for regulating the thickness of the films produced.
Some remarks on Klatt’s ‘‘Review of text-to-speech conversion for English’’ [J. Acoust. Soc. Am. 8
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Authors: Hertz Susan R.
Published: October 2005

Dennis Klatt’s article ‘‘Review of text-to-speech conversion for English’’ [J. Acoust. Soc. Am. 82, 737–793 (1987)] provides an excellent review of many developments in the area of English text-to-speech conversion, an area in which Klatt has been an undisputed leader. However, as Klatt himself points out (p. 738), he is ‘‘an active participant in the field who has many biases that ... no doubt color the review.’’ Understandably then, Klatt emphasizes his own contributions in certain areas, focusing, for example, more heavily on phoneme-to-speech conversion than text-to-phoneme conversion, and on his own rules rather than those of others. This letter expands on the article by considering selected results of the work by myself and my associates in text-to-speech synthesis over the last 14 years. These results are presented primarily to broaden the reader’s perspective, but also to clarify some misrepresentations in Klatt’s article.
Swimbladder size variability in mesopelagic fish and bioacoustic modeling
Authors: Saenger R. Alfred
Published: October 2005

Bioacoustic predictions of volume scattering strength Sv(z, f ) below 20 kHz due to mesopelagic swimbladdered fish contain errors arising from biological sampling limitations and uncertainties in swimbladder target strength. These predictions all utilize allometric equations relating, say, swimbladder equivalent spherical radius R to fish standard length l. Since the equations take no account of swimbladder size variability that is acoustically significant, the predictions contain ‘‘swimbladder variability error’’ (SVE) as well. New modeling procedures are presented to reduce SVE in Sv predictions for arbitrary size-depth distributions of swimbladdered fish with gas-filled swimbladders. It is assumed that the swimbladder size allometry properties of these fish, either as individual species or as a species class, can be described by appropriate bivariate normal density distributions p(x,y), where x=ln l and y=ln R, as suggested by recent results of Saenger (submitted to Can. J. Fish. Aquat. Sci.). SVE in predictions using allometric equations is estimated by comparing theoretical predictions made, respectively, with a bivariate normal model and its associated simple allometric law regression equation. Results suggest that SVE is generally appreciable for naturally occurring fish size distributions and, in particular, is partly responsible for discrepancies commonly observed between predicted and measured values of Sv at low-kHz frequencies for nighttime near-surface scattering layers.
Annoyance factors for common neighborhood (stationary) noise
Authors: Alvord Lynn S.
Published: October 2005

Most existing information on annoyance to environmental noise comes from aircraft or traffic noise studies [Kryter, The Effects of Noise on Man (Academic, New York, 1970)]. Annoyance factors for nontraffic neighborhood sounds were analyzed by survey of 63 adults in Salt Lake City. Situational factors such as time of occurrence, frequency of occurrence, and meaning were found to occupy positions of greater importance for this category of noise. The most commonly mentioned annoying noise source, dogs barking, typifies the sporadic aspects of neighborhood noise as well as the difficulties encountered in enforcement. These aspects, as well as the importance of situational factors, raise the possibility of development of source-specific criteria.
Declination ‘‘reset’’ and the hierarchical organization of utterances
Authors: Ladd D. Robert
Published: October 2005

Sequences of accented fundamental frequency (F0) peaks (‘‘toplines’’) were measured for sentences of the form A and B but C and A but B and C, where A, B, and C are separate main clauses with three (four in a replication experiment) accented words each. It was hypothesized that the differences in boundary strength (but-boundary stronger than and ) would be reflected in the way declination was reset following the boundaries. There were significant differences between the toplines of the two sentence types, the most consistent being that the accent peaks immediately following the two boundaries were higher if they followed but than if they followed and . In other respects the toplines were similar, exhibiting declination within each clause and across the three clauses; corresponding clause toplines that began at different levels following different boundaries nevertheless tended to end at the same level. The fact that hierarchical organization is reflected intonationally in this way makes problems for models of F0 in which contours result from the interaction of a number of preplanned overall trends. Suggestions are made for the incorporation of hierarchical information into models that analyze F0 contours as strings of abstract targets.
Pitch perception of complex tones and human temporal-lobe function
Authors: Zatorre Robert J.
Published: October 2005

Sixty-four patients with unilateral temporal-lobe excisions as well as 18 normal control subjects were tested in a missing fundamental pitch perception task. Subjects were required to indicate if the pitch of a pair of tones rose or fell. The excisions encroached upon Heschl’s gyri in some cases, whereas, in others, this region was spared. All subjects included for study were able to perform well on a control task in which complex tones including a fundamental were presented. Stimuli for the experimental task, which was procedurally identical with the control task, consisted of several harmonic components spanning the same spectral range, but without a fundamental. Only subjects with right temporal lobectomy in whom Heschl’s gyri were excised committed significantly more errors than the normal control group on this task. Patients with left temporal-lobe lesions or with anterior right temporal-lobe excisions were unimpaired. These results suggest that Heschl’s gyri and surrounding cortex in the right cerebral hemisphere play a crucial role in extracting the pitch corresponding to the fundamental from a complex tone.
Auditory filter shape derived from binaural masking experiments
Authors: Kohlrausch Armin
Published: October 2005

The shape of the auditory filter was calculated from binaural masking experiments. Two different types of maskers were used in the study, a masker that was interaurally in phase at all frequencies (No), and a masker with an interaural phase difference of 0 below 500 Hz and of π above 500 Hz. The test-signal frequency varied between 200 and 800 Hz, and the test signal was presented either monaurally (Sm) or binaurally in antiphase (Sπ). By comparing the masked thresholds from the two experimental conditions, the following conclusion can be drawn: The threshold of the test signal is only affected by the masker phase within a narrow frequency range around the test frequency. Thus, for test-signal frequencies well above or below 500 Hz, no influence of the phase transition on the BMLD is observed, and normal masked thresholds for No and Nπ maskers are obtained. For test frequencies around 500 Hz, the step in interaural phase difference leads to a decrease in the interaural correlation of the masker within the critical band around the test-signal frequency. This results in strong threshold changes for both monaural and binaural signals. A calculation of the auditory filter shape from the masked threshold values was performed under the assumption that the masked threshold is only dependent on the interaural cross correlation of the masker within the filter band. Using the formula of the EC theory for the relation between masker correlation and BMLD, the experimental data are well described by a trapezoidal filter with an equivalent rectangular bandwidth of 80 to 84 Hz.
Localization of coherent and incoherent sound sources via an optimization process
Authors: Sidki Mouncif , Nicolas Jean
Published: October 2005

The problem of the localization and characterization of sound sources is discussed, for the case of a set of monopole sources, starting with the analytic expressions describing the field in combination with a gradient method for the optimization process. To locate the sources, three measurement variables are used: the 3-D vectorial active intensity, the normal active intensity, and the mean-square pressure. Simulations for three emitting sources, aimed at predicting their positions and spectral densities, are made. The minimum number of measurement positions that lead to convergence of the algorithm is investigated. The agreement between prediction and reality is good even when the sources are coherent. In parallel, the impact of the choice of measurement variable on the precision of the results is studied. In the very near field of the source, it is found that identification via 3-D intensimetry requires a significantly lower number of measurement positions than does that via normal intensity or mean-square pressure.
Improving the noise reduction of picket barriers
Authors: Wassilieff C.
Published: October 2005

A barrier diffraction theory incorporating the effect of partial sound transmission through a barrier of finite size is developed in this article. The insertion loss of picket barriers predicted by this theory on the basis of an optical model is shown to be significantly better at low frequencies than the measured insertion loss of real picket barriers. This is shown to be due to the actual acoustical boundary conditions at the barrier surface differing substantially from the classical boundary conditions assumed by the theoretical model. This article demonstrates two methods by which the classical boundary conditions can be satisfied and the insertion loss improved as a consequence. This improvement is in the frequency region where the sound transmitted through the gaps interferes destructively with the sound diffracted across the barrier top, resulting in enhanced noise reduction over that of an equivalent solid barrier. The performance of the picket barrier can be improved further by the introduction of sound absorbent into the gaps, yielding high-frequency performance approaching that of a solid barrier while retaining the better low-frequency performance of a picket barrier.
Factors affecting degree of perceived foreign accent in English sentences
Authors: Flege James Emil
Published: October 2005

This study used interval scaling to assess degree of perceived foreign accent in English sentences spoken by native and non-native talkers. Native English listeners gave significantly higher (i.e., more authentic) pronunciation scores to native speakers of English than to Chinese adults who began learning English at an average age of 7.6 years. The results for the ‘‘child learners’’ suggest that a sensitive period for speech learning is reached long before the age of 12 years, as commonly supposed. Adults who had lived in the U.S. for 5 years did not receive higher scores than those who had lived there for only 1 year, suggesting that amount of unaided second-language (L2) experience does not affect adults’ L2 pronunciation beyond an initial rapid stage of learning. Native speakers of Chinese who rated the sentences for foreign accent showed the same pattern of between-group differences as the native English listeners. The more experienced of two groups of Chinese listeners differentiated native and non-native talkers to a significantly greater extent than a less experienced group, even though the subjects in both groups spoke English with equally strong foreign accents. This suggests that tacit knowledge of how L2 sentences ‘‘ought’’ to sound increases more rapidly than the ability to produce those sentences.
The contribution of the excitatory source to the perception of neutral vowels in stuttered speech
Authors: Howell Peter , Williams Mark
Published: October 2005

The vowel in part-word repetitions in stuttered speech often sounds neutralized. In the present article, measurements of the excitatory source made during such episodes of dysfluency are reported. These measurements show that, compared with fluent utterances, the glottal volume velocities are lower in amplitude and shorter in duration and that the energy occurs more towards the low-frequency end of the spectrum. In a first perceptual experiment, the effects of varying the amplitude and duration of the glottal source were assessed. The glottal volume velocity recordings of the /æ/ vowels used in the analyses were employed as driving sources for an articulatory synthesizer so that judgments about the vowel quality could be made. With dysfluent glottal sources (either as spoken or by editing a fluent source so that it was low in amplitude and brief), the vowels sounded more neutralized than with fluent glottal sources (as spoken or by editing a dysfluent source to increase its amplitude and lengthen it). In a second perceptual experiment, synthetic glottal volume velocities were used to verify these findings and to assess the influence of the low-frequency emphasis in the dysfluent speech. This experiment showed that spectral bias and duration both cause stuttered vowels to sound neutralized.
Thermal noise in a fiber optic sensor
Authors: Hofler Thomas J. , Garrett Steven L.
Published: October 2005

The mean intrinsic thermal noise in a fiber optic interferometric sensor is calculated from the equipartition theorem. The spectral density of the fluctuating force is the mechanical equivalent of the well-known thermally induced voltage noise (Johnson noise) in electrical resistors. The consequent phase noise generated by this fluctuating force in a high-sensitivity fiber optic interferometric seismic sensor is found to dominate the phase noise of present opto-electronic interferometric demodulators, thus setting the limit for minimum detectable vibration amplitudes. This effect is identical to that found to limit the sensitivity of ‘‘mirrored galvanometers’’ as the optical leverage of the transducer was increased. It is shown that this contribution to the sensor noise is reduced when the sensor is used above resonance as a seismometer rather than below resonance as an accelerometer. The further increase in noise-limited detection thresholds introduced by aliasing of the noise concentrated about the resonance frequency in time-sampled accelerometers is emphasized.
Forchheimer-type nonlinearities for high-intensity propagation of pure tones in air-saturated porous media
Authors: Wilson David K. , McIntosh Jason D. , Lambert Robert F.
Published: October 2005

A linear rigid frame, cylindrical capillary theory of sound propagation in porous media is extended to include nonlinear effects of the Forchheimer type, by making a particle velocity-dependent correction to the complex density. This type of nonlinearity becomes important at incident sound-pressure levels above approximately 120 dB re: 20 μPa for highly porous fibrous materials. Data from three experiments on air-saturated porous media and foams, at levels up to 170 dB, are compared to the rigid frame theory with Forchheimer-type extension. One of the experiments measured a low-frequency approximation for the complex density directly; the others measured internal attenuation and surface admittance (inverse impedance). The generally good agreement found between predictions based on the Forchheimer-type nonlinear theory and each of the experiments suggests that this type of nonlinearity is the dominant one for propagation in many types of air-saturated fibrous porous media. Some interesting surface absorption characteristics are predicted at incident sound-pressure levels above 140 dB, especially at lower frequencies.
Bulk elastic wave propagation in partially saturated porous solids
Authors: Berryman James G. , Thigpen Lewis , Chin Raymond C. Y.
Published: October 2005

The linear equations of motion that describe the behavior of small disturbances in a porous solid containing both liquid and gas are solved for bulk wave propagation. The equations have been simplified by neglecting effects due to changes in capillary pressure. With this simplifying assumption, the equations reduce to two coupled (vector) equations of the form found in Biot’s equations (for full saturation) but with more complicated coefficients. As in fully saturated solids, two shear waves with the same speed but different polarizations exist as do two compressional waves with distinct speeds. Attenuation effects can be enhanced in the partially saturated solid, depending on the distribution of gas in the pore space. Two models of the liquid/gas spatial distribution are considered: a segregated-fluids model and a mixed-fluids model. The two models predict comparable attentuation when the gas saturation is low, but the segregated-fluids model predicts a more rapid roll-off of attenuation as the gas saturation increases.