bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation near a sea mount
Authors: Pitre Richard
Published: October 2005

Shadowing and reflection effects by a cylindrically symmetric sea-mount are computed for an off-axis source. The computation is an implementation of horizontal ray theory [Weinberg and Burridge, J. Acoust. Soc. Am. 55, 63 (1974)]. The waveguide model consists of an isovelocity water column with a perfectly reflecting bottom. These idealizations enhance the refraction effects of the seamount beyond what would be expected for a more realistic waveguide. Frequency limitations and methods for incorporating attenuation and subbottom structure will be discussed. For a particular choice of bathymetry, analytic expressions for ray paths, phases and amplitudes of modes are obtained in terms of elliptic integrals of the first, second, and third kind. Numerical results are presented for a seamount which has a height of 1 km, a depth at infinite range of 2 km and a maximum slope of 5 degrees. For a 20-Hz source there are 52 propagating modes. The first 26 modes propagate over the seamount with refraction effects which increase with mode number. The first ten modes are virtually unaffected. Mode numbers 27 and above are completely reflected by the seamount and a caustic forms separating the illuminated and shadow zones. There are generally two horizontal ray paths connecting source and receiver for these reflected modes and mode contributions to reflected energy increase with mode number. [Work supported by Naval Ocean Research and Development Activity.]
Spectral and hybrid ray-mode formulations for sound radiation in a weakly range-dependent ocean
Authors: Kamel A. , Felsen L. B.
Published: October 2005

By a recently developed theory [reported in J. Acoust. Soc. Am. Suppl. 1 70, S3 (1981)], the method of characteristic Green's functions (resolvents) for range-independent ocean environments has been generalized to accommodate weak range dependence of the bottom. The generalization has been made so as to generate the conventional adiabatic mode representation whenever that is applicable, but the new formulation for the radiated sound field is valid everywhere, including those regions where one of the adiabatic modes passes through cutoff. Numerical evaluation of the Green's function integral for a wedge-shaped ocean has shown close agreement with results computed independently by the parabolic equation algorithm. The analysis has now been carried further to explore alternative representations of the general solution in the water and the bottom. These include a plane wave spectral integral, hybrid ray-mode formulations, and asymptotic evaluations that yield transition functions valid through the cutoff region of one of the adiabatic mode fields. One thereby gains detailed insight into the various ray or mode propagation mechanisms that explain the numerical data. Comparisons are made with other procedures which have recently been presented for this class of propagation problems. Generalizations to depth and range dependent water sound speeds are under study. [Work supported by ONR Ocean Acoustics Branch.]
Influence of gravity and other stresses on vlf sound in almost fluid sediments
Authors: Tolstoy I.
Published: October 2005

Relatively unconsolidated sediments of low rigidity μ are common. Shear modes of low velocity (cs ≲ 102 ms−1) then exist, as well as slow boundary waves of phase velocity v < cs at the water-sediment interface (Stoneley modes). In such cases gravity and other stresses may introduce small corrections to the propagation velocities. The role of gravity is twofold. On the one hand, it introduces buoyancy forces and internal gravity waves (negligible for frequencies above 10−1 Hz) and, on the other, it introduces hydrostatic stresses which affect the velocity of shear modes in the sediment—leading to corrections of the order of ρgz/μ (for an overburden of height z in a sediment or sediment-water column of mean density ρ). While the latter measurably affects propagation speeds in sediments, it is an isotropic effect which will, in practice, find itself lumped with other mechanisms of velocity stratification. Interesting and perhaps more easily diagnosed in experiments are the effects of anisotropic stress fields—e.g., tensions or compressions associated with gravity slumping mechanisms on slopes and, for deeper and somewhat more consolidated sediments, with forces of local origin such as island loading or tectonic stresses. These may introduce measurable anisotropies into the propagation of low-frequency, bottom-associated modes. [This work was supported by ONR.]
Ray methods for scattering of elastic waves by convex obstacles
Authors: Brind R. J. , Steinberg R. D. , Achenbach J. D.
Published: October 2005

The application of ray theory to the three-dimensional problem of the reflection of curved wavefronts from curved surfaces (arbitrary curvature) is investigated. To assess the accuracy of the short wave approximations, the scattering of time-harmonic longitudinal plane waves by a circular cylindrical cavity and a spherical cavity are considered as special cases. Both the direct ray theory results and the Kirchhoff approximations are examined, but it is found that for reasonable wavelengths the diffracted waves must be taken into account. For the case of a circular cylindrical cavity the creeping waves are evaluated from exact expressions and from asymptotic formulae. A hybrid approach, in which the creeping rays are used to compute the field on the scatterer in the shadow zone, and in which this field is then used in the representation integral, is developed and shown to give good results. The generalizations necessary to deal with scatterers of variable radii of curvature are discussed. The results in the frequency domain are transformed numerically into the time domain, and an example of the application of these methods to the detection of indentations on the surface of a plate is presented.
Resonance theory of acoustic scattering from objects of arbitrary shape: Finite-cylindrical targets
Authors: Tanglis E. , Gaunaurd G. C. , Überall H.
Published: October 2005

Standard separation-of-variables methods permit calculations of scattering amplitudes from simple-shaped bodies such as spheres or infinite cylinders in the form of normal-mode series. For scatterers of more general shapes, Waterman's [J. Acoust. Soc. Am. 45, 1417 (1969)] T-matrix method generates a coupled-mode solution, which we adopt for present purposes. Incident acoustic waves generate a resonant excitation of the eigenvibrations of the target at its eigenfrequencies, and one may separate the resonant amplitudes from the background [Überall, Gaunaurd, and Tanglis, J. Acoust. Soc. Am. Suppl. 1 70, S7 (1981)]. Numerical studies have been carried out for the example of a finite-length fluid cylinder in air, for which the interior resonance frequencies were obtained earlier [Gaunaurd, Tanglis. and Überall, J. Acoust. Soc. Am. 67, 764 (1980)], interpreted as the manifestation of helical surface waves. We find resonances in the scattering amplitude appearing at the predicted eigenfrequencies, together with a smooth background. [H. Überall is also at Catholic University, Washington, DC, supported by the Offce of Naval Research.]
Comparison of the finite element method and the T-matrix approach for acoustic wave scattering by cylinders of arbitrary cross section
Authors: Varadan V. V. , Varadan V. K. , Su J. H.
Published: October 2005

Recently several numerical techniques have been developed to study acoustic wave scattering by obstacles of arbitrary shape. In this paper we wish to evaluate and compare two methods namely the T-matrix method (null field approach) and a global-local finite element method. The scattering of harmonic acoustic waves by infinitely long rigid cylinders is considered. The cross section of the cylinder is arbitrary and the examples chosen are elliptical, square and a circular cylinder with an off set origin. Both surface pressure and the far field are studied as a function of frequency. The two methods are compared for their ability to handle difficult geometry as well as increasing frequency of the incident wave.
T-matrix analysis of sound scattering from finite elastic cylindrical shells
Authors: Flax L. , Green L. H. , Werby M. , Varadan V. K. , Varadan V. V.
Published: October 2005

In this paper, the T-matrix approach is applied to the scattering of plane acoustic waves incident upon finite elastic cylindrical shells in water. The form function will be examined for various angles of incidence and thickness ratios. Shells with l/a ratio from 2 to 5 will be investigated for ka ⩽ 10, where k is the wavenumber of the incident sound wave, a is the radius of the cylinder, and l is the length of the cylinder.
Analysis of liquid-filled target sphere
Authors: Folds D. L.
Published: October 2005

The liquid-filled target sphere is a high target reflector which, since its first use in 1971, has proven to be of great utility in sonar research. The spherical metal shell filled with a low-velocity liquid is being used as a calibrated, passive, aspect-independent target. To date, the characteristics of this target have only been described in a narrow ka range by simple ray theory models [D. Folds, J. Acoust. Soc. Am. 49, 1596–1599 (1971)]. In this paper a comprehensive treatment from 0 < ka < 100 for various shell materials, thicknesses, and filling fluid refractive index is presented using results from wave theory analyses. Both form function versus ka plots and echo time history plots versus target strength are presented. Results show good agreement between computed and measured target strengths. These results permit an accurate prediction of target strength over a wide range of frequency and temperature and an in-depth understanding of the focusing mechanism yielding the high amplitude backscattered wave.
Experimental analysis of an acoustic scatterer in the presence of a reflective boundary
Authors: Numrich S. K. , Dragonette Louis R.
Published: October 2005

Solid spheres and spherical shells have been suspended in a water tank and insonified from below, thereby allowing the air-water interface to serve as a reflective boundary. Backscattered echoes are analyzed in the time domain where temporal separation of the returns shed light on the scattering mechanisms. As time separation is not always possible, additional analysis is performed in the frequency domain, using the known form functions in an effort to analyze the complex return and extract target information.
Review and funding of research grants pertaining to hearing at NIH and NSF
Authors: Naunton Ralph , Elkins Erleen , Dolan Terrence R.
Published: October 2005

Officials of the NINCDS (NIH) and NSF will describe the programs and grant mechanisms available for the support of research in hearing. Also, the procedures involved in the review and funding of grant proposals will be described. Finally, the fiscal outlook for research in these areas will be considered. These discussions are intended particularly for new scientists and individuals not familiar with these processes.
Adaptive computation of articulatory parameters from the speech signal
Authors: Levinson S. E. , Schmidt C. E.
Published: October 2005

An unconstrained optimization technique is used to find the values of parameters of a combination of an articulatory and a vocal tract model that minimize the difference between model spectra and natural speech spectra. The articulatory model is anatomically realistic and the vocal tract model is a “lossy” Webster equation for which a method of solution is given. For English vowels in the steady state, anatomically reasonable articulatory configurations whose corresponding spectra match those of human speech to within 2 dB have been computed in fewer than ten iterations. Results are also given which demonstrate a limited ability of the system to track the articulatory dynamics of voiced speech. This is a continuation of work reported earlier [S. E. Levinson and C. E. Schmidt, J. Acoust. Soc. Am. Suppl. 1 68, S19 (1980)].
Discriminability of unresolved two-component Complex tones: Effects of signal level and duration
Authors: Mott J. B. , Feth L. L.
Published: October 2005

In the study to be reported, the discriminability of unresolved two-component complex (UTCC) tones has been investigated as a function of signal level and duration. These signals were composed of two sinusoidal components separated in frequency by a small ΔF (5, 10, 20, 50, and 100 Hz), and in amplitude by a small ΔI (0, 1, or 3 dB). The complement of each two-component combination was a signal with the same component frequencies but opposite amplitude ratio. In experiment one, comparisons were made between pure-tone frequency DL's and the discriminability of members of complementary pairs. In experiment two, discriminability of each member of an UTCC pair from a third UTCC signal having equal component amplitudes was investigated. Changes in the DL were examined as signal level and duration were independently manipulated. Signal durations ranged from 500 to 20 ms. Signal levels ranged from 50 to 10 dB HL. Preliminary analysis of the results of experiment one shows that the DL for pure tones and the discriminability of complementary-UTCC tones co-vary with changes in presentation level and duration. For experiment two, the preliminary analysis shows that members of complementary pairs of UTCC tones are more discriminable from one another than from an equal amplitude-UTCC. Further analysis should show the asymmetries in discriminability evident in the pitch matching of the equal amplitude UTCC tone to each member of the complementary pair [Feth, O'Malley, and Ramsey, J. Acoust. Soc: Am. (in press)]. [Work supported by grants from NINCDS.]
Masking patterns for unresolved two-component complex tones
Authors: Kirby V. , Feth L. L.
Published: October 2005

Previous research in this laboratory on the pitch of unresolved, two-component complex tones (UTCC) indicated that these complexes may have an asymmetric representation in the auditory periphery. These signals are composed of two sinusoidal components separated in frequency by a small ΔF, and in amplitude by a small ΔI. While the long-term spectra of these signals do not vary with time, they have short-term periodic variations in both amplitude (envelope) and frequency. For one member of a UTCC pair at a given ΔF, the lower frequency component is more intense than the higher frequency one; for the complementary signal the amplitude relationship is reversed. When the lower component is more intense, the pitch of the complex is slightly lower than the pitch for the signal with a stronger higher component. Pitch matches to these complementary signals reveal asymmetries that are not evident in the calculation of the short-term frequency fluctuations of each signal. This study was designed to determine the masking patterns for complementary two-component complex tones using a simultaneous masking procedure similar to Ronken's [J. Acoust. Soc. Am. 54, 905–915 (1973)]. Each two-component signal was used as a masker, in turn. The brief (10-ms) probe was fixed in level and occurred at selected times throughout the course of the 300-ms masker. The adaptive procedure of Levitt [J. Acoust. Soc. Am. 49, 467–477 (1971)] was used to adjust the probe frequency. Masker complexes were centered at 1000 Hz, and ΔF ranged from 5 to 100 Hz. All subjects tested had normal hearing and were well practiced in the task. Results should help to determine whether asymmetric excitation patterns contribute to the asymmetric pitch matches to symmetrically spaced complex signals. [Research supported by grants from NINCDS.]
Transitivity of forward masking
Authors: Neff Donna L. , Weber Daniel L.
Published: October 2005

For three temporally distinct stimuli, A, B, and C, if A masks B, and B masks C, does A mask C? We measured forward-masked threshold for a 1O-ms, 1000-Hz sinusoid, C, as a function of the level of a 20-ms masker, B, for six different masker frequencies (700, 850, 950, 1000, 1100, and 1200 Hz). From these growth of masking functions, we identified levels of the B stimuli which produced a given amount of masking. We then measured the level of a 290-ms stimulus, A, required to mask a B stimulus of the same frequency. In addition, we tested A stimuli at the above five frequencies for B at 1000 Hz. This yielded levels of A and B such that A masked B and (independently) B masked C. When this procedure was followed for low levels of C (roughly 8 dB SL), the majority of the cases we tested essentially showed “transitivity” (i.e., A just masked C). The relative effectiveness of the A and B maskers remained constant regardless of the A frequency, for B at 1 kHz, as well as for A and B of the same frequency. We believe that transitivity can be interpreted by analogy to behavior of auditory-nerve fibers. [Research supported by NSF and NIH.]
Psychophysical measures of two-tone unmasking and distortion products f2 − f1 and 2f1 − f2
Authors: Humes Larry E.
Published: October 2005

Measures of two-tone unmasking and the levels of the f2 − f1 and 2f1 − f2 difference tones were obtained for identical stimulus conditions from four normal-hearing young adults using a forward-masking paradigm (where f1 and f2 represent the input frequencies with f2 > f1). Data were obtained for f1 values of 750, 1500, and 3000 Hz while f2/f1 values investigated were 1.1 1, 1.26, and 1.41. Values of L1 and L2 (the levels of the tones at f1 and f2, respectively) were selected such that L2 was fixed at either 40, 55, 70, or 85 dB SPL while L2 varied over a 30–40-dB range around L1 (e.g., L1 − 20 dB to L1 + 20 dB). These data provide a basis for examining the relationship between these three psychophysical measures of nonlinearity when using identical stimulus conditions and obtaining all data from the same ears. [Work supported by NSF.]
Performance of 146 normal adult listeners on a battery of auditory discrimination tests
Authors: Watson C. S. , Jensen J. K. , Foyle D. C. , Leek M. R. , Goldgar D. E.
Published: October 2005

Two groups of young adult listeners were tested on the Boys Town Auditory Discrimination Test Battery. Performance on each of the tests was used to estimate group threshold values for listeners ranked in deciles. Relying on a weak assumption about the form of the underlying psychometric functions, these averaged data allow the estimation of threshold values for individual listeners on each of the tests, despite the small number of trials and the irregular form of the observed data for individual listeners. This method of estimating thresholds compares favorably with other estimation methods. Intercorrelations between the various tests, and several factor-analytic efforts, suggest a moderately strong general auditory discrimination ability, with several weak subsidiary factors possibly contributing to discrimination performance. No strong relations were observed between test performance and self-reported listeners' characteristics, including sex, age, academic skills, reading, musicianship, or history of auditory disease. A few individuals were found to have patterns of weaknesses on some tests and strengths on others. [Work supported by NIH/NINCDS.]
The relations among critical bands, critical ratios, and intensity difference limens in man
Authors: Schlauch Robert S. , Wier Craig C. , Norton Susan J.
Published: October 2005

Band-narrowing estimates of the critical bandwidth (CB) are consistently larger than critical-ratio (CR) estimates for the same signal frequency. Bilger [in Hearing and Davis: Essays Honoring Hallowell Davis, edited by S. K. Hirsh et al. (Washington U. P., St. Louis, 1976), p. 191] hypothesized that this difference can be accounted for by reference to intensity-discrimination performance (CF[Hz]/CB[Hz] = ΔI/I). To test this hypothesis, band-narrowing, critical-ratio, and intensity-discrimination data were collected from four subjects. Signal frequency was 2000 Hz and two noise spectrum levels were used: 20 and 50 dB. The psychophysical procedure was an adaptive, two-interval, forced-choice, converging on 70.7% correct. Based on critical-bandwidth estimates obtained from the band-narrowing experiments using common two-line regression techniques, critical-ratio estimates for pure-tone detection in broadband noise, and intensity-discrimination for critical bands of noise, the results across experimental conditions for individual subjects are not well described by Bilger's equation. [Work supported by NIH and the Deafness Research Foundation.]
The influence of vocalic context on the /s/ − /∫/ distinction in initial and final position
Authors: Soli Sigfrid D. , Mann Virginia A.
Published: October 2005

Using natural FV and VF productions, where F = /s/, /∫/ and V = /a/, /u/, a series of hybrid stimuli were made by replacing the natural friction with synthesized noises from a nine-member /s/ − /∫/ continuum. Listeners were asked to label the fricatives in these stimuli as /s/ or /∫/. The identity of both the vowel and the (excised) original fricative influenced labeling of the synthesized noises. More /s/ responses were given in the /u/ context than in the /a/ context for both the FV and VF stimuli. However, the influence of the original fricative was greater for the FV than the VF stimuli. FV stimuli originally beginning with /s/ received more /s/ responses than VF stimuli originally ending with /s/. The acoustic consequences of articulatory timing in FV and VF production can account for these results. Equivalent anticipatory and perseveratory lip rounding in utterances with /u/ should produce symmetrical vowel context effects in perception, while the asymmetrical perceptual influence of original fricative identity can be attributed to differences in the timing of both assimilatory tongue movement and the alternation of periodic and friction noise sources in FV and VF productions. [Work supported by NICHD and BRS.]
Development of perceptual adjustment for the coarticulatory effects of rounded vowels on preceding fricatives
Authors: Mann V. A. , Dorman M. F. , Strawhun D. , Sharlin H. M.
Published: October 2005

When synthetic fricative noises from an [∫] − [s] continuum are followed by [a] and [u], listeners perceive more instances of [s] in the context of [u] [V. A. Mann and B. H. Repp, Perc. Psychophys. 28, 213–228 (1980)]. This perceptual context effect presumably reflects adjustment for the coarticulatory effects of rounded vowels on preceding fricatives. We have begun to examine the development of this effect, asking children to label stimuli from “save”-“shave” and “sue”-“shoe” continua, constructed by following noises from an [∫] and [s] continuum with periodic portions excerpted from natural tokens of “shave” and “shoe.” The subjects include normal adults, 5-, 7-, and 9-year-old children who correctly produce both [∫] and [s], and 7-year-olds who misarticulate these fricatives. Thus far we have found that the magnitude of the vocalic context effect is typically greater for adults, yet children at all ages show a significant effect whose magnitude is not a function of age. These findings, to be supplemented with those obtained from the misarticulating children, may clarify the developmental basis of listeners' tacit knowledge of coarticulation. [Work supported by NICHD and BRS.]
On the use of the sameness measure in scaling analysis of confusion matrices
Authors: Yuchtman Moshe , Bilger Robert C.
Published: October 2005

A measure of sameness, S, is often used as a metric in scaling procedures applied to confusion matrices [L. Goldstein, UCLA-WPP 39, 1–35 (1977)]. The sameness between any two sounds in a matrix is defined as the ratio between the frequency of incorrect responses (Fij + Fij) and the frequency of correct responses (Fii + Fjj). Assuming equal a-priori stimulus probabilities we can transform Fii and Fji to proportions of hits, P(H), and false alarms, P(FA), respectively. For a constant S, P(H) is related to P(FA) by a linear function with a slope of 1 in ROC space. This function implies that for a given signal discriminability, P(H) and P(FA) can vary only to the extent that a constant proportion of correct responses is maintained. Furthermore, it implies a decision axis in which the two sounds are each represented by a rectangular distribution. The literature of psychophysics suggests that perceptual processes are not well approximated by such distributions. In an attempt to further study this issue, confusion-matrix data reported by Miller and Nicely [J. Acoust. Soc. Am. 27, 338–352 (1955)] and by Wang and Bilger [J. Acoust. Soc. Am. 54, 1248–1266 (1973)] were reduced to individual 2 × 2 matrices. In addition to S, the index of sensitivity d′, amount of transmitted information Uxy, and phi-squared were calculated. The last three measures, which are not based on rectangular distributions, were linearily related to each other and were nonlinearily related to S. The results of scaling analyses employing these measures will be discussed in reference to the role of speech features in speech perception.
Context effects in Japanese perception of English /r/ and /I/
Authors: Dissosway-Huff Patricia , Port Robert
Published: October 2005

Perception of English /r/ and /l/ is a well-known difficulty for Japanese learning English. An identification test for minimal pairs read by two American speakers was administered to 32 Japanese students of English, first just after arrival in the United States, and then nine weeks later at the completion of an intensive English program emphasizing oral skills. Little improvement was observed after oral training. The perception of /r/ and /l/ as singletons and in consonant clusters exhibited quite opposite trends. In clusters, /l/ was perceived more accurately than /r/ (66% versus 52%), while for singletons, /l/ was somewhat worse than /r/ (64% versus 70%). Singleton consonants in word-final position were more accurately perceived than initial singletons (77% versus 57%) while for clusters, the finals were slightly worse than initials (56% versus 62%). Thus both the /r-l/ effect and word-position effect interact with the singleton-cluster factor but not with each other. These findings will be discussed in relation to the phonotactics of both Japanese and English and in terms of their acoustic correlates. [Supported by NIH, HD12511.]
A cross-language study of categorical perception for semi-vowel and liquid glide contrasts
Authors: Best Catherine T. , MacKain Kristine S. , Strange Winifred
Published: October 2005

Recently we replicated categorical perception of /r/ and /l/ in Americans and its absence in native Japanese, whose language lacks that contrast; Japanese with extensive conversational English experience (experienced), however, showed greater categoricity [MacKain, Best, and Strange, Applied Psycholinguistics (in press)]. We retested 18 of the same subjects (nine Americans, nine Japanese) on perception of a prevocalic /w/-/j/ continuum; these glides contrast phonemically in both languages. The phonetic and acoustic characteristics of /w/-/j/ place them between prototypical vowels and consonants, suggesting perception should be less categorical than for a clearer consonantal contrast such as /r/-/l/. Results upheld predictions derived from the language differences: Japanese and Americans showed equally categorical /w/-/j/ perception, but the Japanese were less categorical on /r/-/l/ than on /w/-/j/. Experienced Japanese showed this pattern also, but perceived /r/-/l/ more categorically than the less experienced subgroup. Although for Americans, /w/-/j/ identifications appeared somewhat more continuous than for /r/-/l/, the difference was nonsignificant. Prevocalic semi-vowels may thus be perceived as categorically as natively contrasting liquids. [Supported by NINCDS, NICHD, and NIH.]
Acoustic and perceptual correlates of nasal vowels
Authors: Stevens Kenneth N. , Hawkins Sarah
Published: October 2005

Various versions of different nasal vowels have been synthesized by systematically modifying the all-pole transfer function corresponding to nonnasal vowels. These modifications were achieved by manipulating the frequencies and bandwidths of the first ferment and of an added pole-zero pair over ranges that are consistent with acoustic theory and analysis of nasal vowels, including the effect of the sinuses. The stimuli were evaluated or identified by listeners (principally Gujarati speakers) whose language included a nasal-nonnasal opposition. Nasal judgments were obtained when the pole-zero pair was in the vicinity of 400 Hz, but for some vowels (especially high vowels) nasal responses were also obtained when the additional resonance was at a higher frequency. It is concluded tentatively that the nasal-nonnasal distinction in language is based on the fact that the auditory system responds distinctively when the spectrum in the vicinity of the first formant is flattened to yield a less prominent low-frequency spectral peak. This modification is achieved by the introduction of additional low-frequency resonances and by increased bandwidth for some of the low-frequency peaks. [Supported in part by a grant from NINCDS.]
Bimodal speech perception in early infancy
Authors: Kuhl Patricia K. , Meltzoff Andrew N.
Published: October 2005

We previously reported preliminary data on infants' abilities to detect the cross-modal correspondences between the visual and auditory concomittants of speech [Kuhl and Meltzoff, J. Acoust. Soc. Am. Suppl. 1 70, S96 (1981)]. We have now completed testing on 32 4.5- to 5-month-old infants. Each was shown a filmed display of two faces, one producing the articulatory movements corresponding to the vowel [a] and the other producing the articulatory movements corresponding to the vowel [i]. One of the sound tracks (either [a] or [i]) was played in synchrony with the faces. The infants' visual fixations to the faces were scored by an observer who could not hear the sound track presented to the infant nor see the faces. Results demonstrated that the infants looked longer at the face matching the sound being presented than at the nonmatching face (p < 0.01). We hypothesized that the recognition of these cross-modal equivalences was based on the structural correspondence between a particular articulatory movement and a particular vowel sound, rather than on any temporal correspondence between a particular face-sound pair. This hypothesis predicts that if the crucial spectral information is removed from the vowels while the temporal information is preserved, performance should drop to chance. Experiment II tested this hypothesis using pure-tone stimuli. Performance fell to chance. [Supported by NSF.]
Acoustic wave propagation in a two-dimensional flexural duct in the presence of a uniform flow
Authors: Ko Sung H.
Published: October 2005

An investigation was made of the phase velocity of acoustic waves propagating in a two-dimensional flexural duct with a uniform flow. The flexural duct considered herein is composed of two parallel, thin elastic plates. The outer surfaces of the duct are in contact with a stationary fluid medium and its inside contains a uniform fluid flow. An eigenvalue problem was formulated for a two-dimensional flexural duct by satisfying pertinent boundary conditions across the fluid-plate interfaces. The acoustic pressure inside the duct is a summation of partial wave pressures, each of which is associated with a wave mode having its own phase velocity. Some of these waves are propagating in the duct without attenuation, whereas others are decaying as they travel along the duct, or are not capable of being propagated in the duct. It is found that the wave modes of which phase velocities are larger than the sound velocity of the outer stationary medium radiate sound energy outward.
Incoherence in the propagation of sound close to the ground in summer
Authors: Daigle G. A. , Piercy J. E. , Embleton T. F. W.
Published: October 2005

We have measured the transverse coherence of pure tones with frequencies between 250 and 4000 Hz during propagation over ranges up to 250 m with generally upward refracting (summer daytime) conditions from a point source placed on flat ground. Microphone heights up to 7 m above the ground were utilized and there were simultaneous measurements of wind and temperature fluctuations (profiles were also measured). Some of the results were discussed previously [J. Acoust. Soc. Am. Suppl I 70, S54 (1981)]. Further analysis indicates that the intensity coherence length for the incoherent wave varies between about 0.1 and 2.0 m depending on both frequency and height above the ground. It is least for the highest frequencies and decreases with decreasing height below the refractive shadow boundary. The implications of these results for the propagation of the incoherent wave, in general, and community noise levels in shadow zones near the ground, in particular, will be discussed.
A new look at the effect of atmospheric turbulence on acoustic propagation
Authors: Roth S. David
Published: October 2005

It has been shown theoretically that turbulent scattering explains fluctuations of mean outdoor noise levels by only 2 to 4 dB. Our measurements of broadband noise propagating over a grassy field have shown fluctuations of levels by greater than 20 dB. Fluctuations of phase causing the smearing of interference minima cannot explain these fluctuations nor can they explain the apparent increase in acoustic levels. Some early literature in outdoor sound propagation has noted this phenomenon and suggested that the greater fluctuations were in some way associated with the wind. In more recent literature this idea has been dismissed without proper consideration. Our measurements clearly demonstrate that the time scales of motion in the atmosphere are of the same order as these fluctuations. A discussion of the atmospheric structure and processes which can cause this acoustic fading phenomenon is presented. [Work supported by the USDA Forest Service through the Consortium for Environmental Forestry Studies.]
Pressure transfer function of a JTI5D nozzle due to acoustic and convected entropy fluctuations
Authors: Miles J. H. , Krejsa E. A.
Published: October 2005

An acoustic transmission matrix analysis of sound propagation in a variable area duct with and without flow [J. H. Miles, J. Acoust. Soc. Am. 69, 1577–1586 (1981)] is extended to include convected entropy fluctuations. Relations between the entropy fluctuations and the pressure fluctuations are considered. The effects of changes in the nozzle impedance due to flow are also studied. The nozzle pressure transfer function calculated with this analysis is compared with JTI5D nozzle data. The agreement between the measured and calculated results is shown to be good. Predicted and measured auto-spectra are also compared.
Strategy for high quality speech elements formant synthesis
Authors: Badin P.
Published: October 2005

To obtain high quality replication of natural speech elements using a formant synthesizer and investigate distinctive features of phonemes, we must determine the evolution of the 19 control parameters of the synthesizer. But there is no algorithm capable of automatically tracking all these parameters. Therefore we have developed a method of computer-aided manual synthesis. The analysis-synthesis process consists of three steps. The first one is an automatic analysis of the natural signal: analysis by linear prediction (to get poles and bandwidths) and pitch detection by the SIFT algorithm. Then the acquisition of certain parameters (F0, formants, bandwidths, and voicing amplitude) is manually carried out using the previous results. The third step is iterative: the other parameters are determined by the trial and error method; to perform the comparison between the original and synthesized signal, we use the FFT, a visual inspection of temporal signal and the “substitution” method (hearing the original sound and a sound composed of the original signal in which one part is replaced by the synthesized signal). This method may be long, but leads to high quality synthesis. We are now experimenting with this method in the synthesis of the French voiced fricatives ([v], [z], [ȝ]) in the context CVCV.
Analysis and synthesis of fundamental frequency contours of English sentences
Authors: Fujisaki Hiroya , Hirose Keikichi
Published: October 2005

The voice fundamental frequency contour (henceforth the F0 contour) has been known to be an important acoustical correlate of sentence intonation in English. Quantitative relationships between the characteristics of an observed F0 contour and the underlying linguistic information, however, have not been fully clarified. In the present paper, we apply a method of analysis of F0 contours originally proposed for the analysis of sentence intonation in Japanese. The method is based on a quantitative model of the process of conversion from discrete linguistic units into an observed F0 contour, represented by the logarithm of voice fundamental frequency as a function of time. The validity of the model for English intonation has been demonstrated, firstly by analysis-by-synthesis, i.e., by showing that the model can produce close approximations to actual F0 contours of English sentences, and secondly by perceptual experiments in which the naturalness of intonation was verified for synthetic sentences with F0 contours generated by rule based on the proposed model. [Work supported by Ministry of Education Grant-in-Aid for Scientific Research No. 56580020 and No. 00551101.]
Noise reduction in speech using adaptive filtering I: Signal processing algorithms
Authors: Christiansen R. W. , Chabries D. M. , Lynn D.
Published: October 2005

Adaptive filtering is employed in configurations to filter narrow-band speech corrupted by noise. These configurations utilize either an independent sample of the input noise or rely on correlation properties of the speech to accomplish cancellation. Necessary constraints on the algorithms to retain and/or improve intelligibility for normal and hearing-impaired populations are presented. Previous work with the LMS algorithm is compared to the performance resulting from new methods which address the problem created by widespread eigenvalues in the speech plus noise correlation matrix. It is shown that failure to deal with this problem in the single reference application results in a muffling resonant distortion of the speech spectrum. Spectral averages of the original and processed versions of the speech segments are compared to determine improvement. Auditory tests are presented in the companion paper.
Applications of nonlinear acoustics to materials characterization
Authors: Cantrell John H.
Published: October 2005

Many nonlinear properties of materials result from the anharmonic nature of the interatomic potential. Among the nonlinear acoustic properties are the functional dependence of the sound velocity on stress, the variation of the elastic coefficients with temperature, harmonic generation, and ultrasonically induced dilatation. Recent theoretical and experimental developments in these areas of nonlinear acoustics are discussed. Present applications and potential future uses of nonlinear acoustics in the quantitative nondestructive characterization of materials are examined.
Ultrasonic scattering from weld structures
Authors: Lewis Kent , Fitting Dale , Adler Laszlo
Published: October 2005

Broadband ultrasonic experiments were carried out to study the integrity of multipass weldments. A digital spectrum analysis system was used to evaluate both the surface structure and the internal structure of the welds. Experimental results were analyzed based on existing theories.
Measurement of the acoustic Lloyd Mirror interference pattern at the midfrequency
Authors: Feuillet Jean-Pierre , Carey William M.
Published: October 2005

Calibrated measurements of the Lloyd Mirror interference pattern were performed with two arrays at midfrequencies; one in the Western Gulf of Mexico during the Spring of 1979 and the other in the Northwest Atlantic during the Spring of 1980. These tests used a Webb organ-pipe sound source driven at 175 Hz (170 dB re 1 μPa at 1 m) and 175 Hz (169 dB re 1 μPa at 1 m). These tests were designed to measure the sum of the surface reflected and direct sound path arrivals, which results in the reinforcements and cancellations of the sound field along a towed path. These tests performed with hydrophones of sensitivity −186 dB re IV/μPa showed a distinct interference pattern which previously had been clearly demonstrated only at the higher frequencies. Experimental results agreed extremely well with theoretical calculations and, assuming a reflection coefficient of (μ = 1), showed a mean difference of less than 0.9 dB at a sea state of 2. Theoretical results indicated that the Lloyd Mirror pattern becomes less distinct with increasing sea roughness (μ < 1) and increasing sea swell (μ = 1). Discrepancies on the order of ±3 dB were shown to be a result of a drift in position of the source relative to its anchor.
A new towed array shape estimation technique using directional sensor outputs
Authors: Sharma Rama K. , Bangs William J. , Breed Ben R.
Published: October 2005

Based on Kennedy's (NUSC 93231-TMU-8-79, July 1979) analysis of Paidoussis's [J. Fluid Mech. 26, 717–751 (1966)] equation for the dynamics of a towed cylinder, a computer model has been developed, which estimates array shape using a Kalman filter, with directional sensor information as inputs. Kennedy and Rispin [J. Underwater Acoust. 30, 111–123 (1980)] have validated the concept that the propagation down the array of disturbances at the forward end of an array is governed by a dissipative and dispersive wave equation whose coefficients are functions of the ratio of the longitudinal to the transverse drag coefficient, array length, and tow speed. We formulate the partial differential equation describing array motion as a linear, discrete, state-variable, matrix difference equation with the state vector elements being the transverse displacements of specified array grid points. Using directional sensor outputs as the observations, the system has been shown to be observable. The model has been used to predict array motions using real sea data. Comparison of predictions to measurements are encouraging.
Degradation of coherence and correlation when sound from a moving source is reflected from solid surfaces
Authors: Hutton James P. , Barss Walter M.
Published: October 2005

The propagation of sound in ice-covered waters, as in Canadian Arctic archipelago, is complicated by the sound's repeated encounters with the under surface of the ice. The essential elements of such a propagation environment were modeled, in air, in an anechoic chamber. The study concentrated on the effects of source motion, in the presence of various reflecting surfaces, on the coherence of sound received at a pair of sensors. The electrical signals from the sensors were processed in real time by a typical dual-channel spectrum analyzer. The study shows that when the sound reaches the sensors by reflection from an irregular solid surface, the degradation may be attributed to changes in the Doppler shifted components of the sounds at the sensors and to changes in acoustic interference patterns.
Design of a pneumatically isolated servo-controlled floor system for a dedicated computer wafer manufacturing facility
Authors: Baxa Donald E. , Dykstra Richard A.
Published: October 2005

The equipment used to fabricate microelectronic computer wafers have stringent environmental vibration limits; but pneumatic isolators, incorporated into a complete vibration isolation system, can meet those stringent demands. This paper first reviews basic vibration isolation theory and then describes a facility that uses pneumatic vibration isolation in its dedicated computer wafer manufacturing area.
Noise reduction in speech using adaptive filtering II: Speech intelligibility improvement with normal and hearing-impaired subjects
Authors: Brey R. H. , Robinette M. S.
Published: October 2005

An adaptive LMS filter is employed to filter speech in signal-to-noise ratios varying from −8 to +12 dB. The filter configuration used is that previously proposed by Widrow, Boll, and Pulsipher and commonly called noise cancellation. Intelligibility measures were obtained using speech selected from (CID) W-22 word lists. Fifteen lists of 50 words each were selected. Ten normal-hearing and six hearing-impaired individuals were subjects. Sound-field and free-field measurements, as well as processed and unprocessed data, were obtained and analyzed. Intelligibility was near zero for all SNR's less than 0 dB prior to processing. Following processing scores increased 30% to 40% for both normal and hearing-impaired groups. For SNR's of +4 to +12 dB, intelligibility scores prior to filtering ranged from 10% to 50%; after filtering the scores improved to within 10% of the noise-free sound-field measurement. The specific test configuration, SNR improvement estimates, as well as additional results and comparisons, will be presented.
Reynolds and Strouhal numbers in woodwind musical instruments
Authors: Keefe Douglas H.
Published: October 2005

It is convenient to use dimensional analysis in investigating nonlinear effects in woodwind instrument air columns. One dimensionless quantity characterizing the flow is the Reynolds number. There is both a time-varying particle velocity as well as a time-independent streaming velocity within the woodwind, and the Reynolds number R defined in terms of the streaming velocity may be written as R ≃ d2/δ2. The time-varying particle displacement is d and the viscous boundary layer thickness is δ. R ≪ 1 corresponds to the type of streaming first considered by Rayleigh, whereas the streaming at larger values of R is more complicated. The Strouhal number S associated with the oscillating flow and characteristic length L is S = L/d. The criterion that the nonlinear convective acceleration term (v∇v) in the Navier-Stokes equation be small relative to the linearized acceleration is that S ≫ 1. The particle displacement has been estimated at a fortissimo dynamic level on a flute, clarinet, and alto saxophone by means of pressure level measurements at the first open tone hole and the known radiation impedance of the hole. The streaming Reynolds number is approximately 0.2 for the flute and in the range 9–20 for the clarinet and sax for low register tones at the frequency of the repetition rate. Both R and d rapidly decrease for higher frequency components. The particle displacement ranges from 0.1 mm for the flute to 1 mm for the clarinet and saxophone. The Strouhal number of interest is defined for a characteristic length L on the order of the radius of curvature of the sharp corners within the woodwind bore; for definiteness, I take L = 0.5 mm. The resulting Strouhal number is of order 5 for the flute and 0.5 for the clarinet and saxophone. Since the Strouhal number is not large compared to unity, then the nonlinear effects are important near sharp corners within the bore and particularly so for the clarinet and sax.
Flexible fiberoptics for evaluation of singers' and speakers larynges: An audiovisual concert
Authors: Selkin Stuart G.
Published: October 2005

Viewing the larynx has been revolutionized by the advent of flexible fiberoptic scopes. A subject may inspire, expire, cough, swallow, phonate sounds, words, sentences, or passages, and even sing as examination provides. The stunningly clear images may be adapted for production of color transparencies, prints, and color and sound videotapes. Using techniques he has devised, the author presents color transparencies, and color and sound videotapes demonstrating normal and abnormal laryngeal physiology, with normal and abnormal voices. Highlighting the presentation are the larynges of young professional opera singers, performing arias in full voice with full orchestral accompaniment.