bluuebunny/crossref_metadata_2025 huggingface dataset:
Caustics and the spreading of adjacent acoustic rays
Authors: Kinney W. A.
Published: October 2005

In a letter to the editor, Barash [J. Acoust. Soc. Am. 43, 378–380 (1968)] presented experimental evidence of the fact that for a divergent wave in a refractive medium caustics and turning points are clearly separated and phase shifts occur at the caustics only. In a rebuttal, Tolstoy [J. Acoust. Soc. Am. 43, 380–381 (1968)] implied that while Barash's evidence was interesting, the accompanying conclusions lacked generality. In another letter, Silbiger [J. Acoust. Soc. Am. 44, 653–654 (1968)] illustrated that there was theoretical evidence for Barash's conclusions by deriving an asymptotic short-wave length solution to the wave equation appropriate to a point source in a vertically stratified medium by means of the WKBJ method. In this paper it is demonstrated that for a purely refracted ray emanating from a point source in a vertically stratified medium which possesses a single sound-speed minimum, (1) the ray first encounters a caustic after its first turning point and before its second, (2) the ray encounters only one caustic between turning points, and (3) for that ray, turning points and points of encounter with caustics approach one another with increasing range from the source. These conclusions are in agreement with those of Silbiger, but are arrived at through rigorous geometrical acoustic means. [Work supported by AFGL.]
A comparison of measured and predicted compressional wave attenuation in ocean sediments
Authors: Beebe J. H.
Published: October 2005

Propagation losses off the Jacksonville, Florida coast due to sedimentation volume attenuation are analyzed over a frequency range of 40 to 800 Hz and compared with the attenuation predicted by the sediment models of Biot [M. A. Biot, J. Acoust. Soc. Am. 34, 1254–1204 (1962)] and Hamilton [E. L. Hamilton, “Geoacoustic Models of the Sea Floor,” in Physics of Sound in Marine Sediments, edited by Lloyd Hampton (Plenum, New York, 1974), pp. 181–221]. A model of the bottom is first established through short range (35 to 100 m) seismic refraction measurements, and then confirmed by a low-frequency dispersion analysis of water-borne signals. Propagation losses over a range of 20 to 95 km are corrected for attenuation due to cylindrical spreading and conversion to shear waves at the water-sediment interface. Bottom attenuation coefficients due to compressional wave volume attenuation in the sediment are then calculated. Core and grab sample data are used in the sediment models of Biot and Hamilton to predict compressional wave bottom attenuation coefficients for comparison with the experimental results.
A different … view … of attenuation … Part II
Authors: Maples Louis C.
Published: October 2005

The paper, “A Different Point of View on the Role of Attenuation as a Component of Total Propagation Loss in Underwater Acoustics.” presented at the 96th Meeting of the Acoustical Society, advanced a new ray-theory expression for total propagation loss between source and receiver on the axis of a depressed sound channel. This expression, when used to evaluate attenuation coefficients from measured propagation losses, produces coefficient values generally lower than those obtained by Thorp, Browning et al. from the same data. In this sequel to that paper, the new approach is applied to raw propagation data not available earlier, and the data are fitted by statistical techniques without assumptions as to which propagation equation is valid—or more suitable. The best form of the expression is then determined by the analysis itself, in a more realistic assessment both of methods and results, producing a more meaningful form of the propagation loss equation, and a useful assessment of the accuracy of attenuation coefficient determinations. [Work supported by the Naval Underwater Systems Center.]
Error estimates for reflection coefficients calculated with the homogeneous-layer approximation
Authors: Gilbert Kenneth E.
Published: October 2005

The plane-wave reflection coefficient for a continuously stratified fluid sediment can be simply calculated by representing the sediment as a stack of thin homogeneous layers. The error in such an approximation is usually estimated by increasing the number of layers and comparing the result with the original calculation. This kind of iterative approach can be both time consuming and frustrating. In this paper, the distorted-wave Born approximation (DWBA) is used to derive a formula for the error associated with a single thin layer (local error) as well as for the total or global error. The local error formula can be used to devise a reasonable a priori layering scheme for any continuous fluid sediment. The global error formula then allows an accurate estimate of the total error to be calculated at the same time as the reflection coefficient. Numerical results are presented for the case where the square of the wave number varies linearly with depth. The DWBA formula is shown to give an excellent estimate of the actual global error. [Work supported by Naval Electronic Systems Command.]
Short-range sound transmission between moving receivers and sources in the deep ocean
Authors: Kays J. L. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Effects on a CW signal transmitted over short ranges in a deep ocean are examined when both the sound source and receiver exhibit linear motion on the ocean surface. For an observer on the moving receiver there is an apparent current which must be included in the study. Time-variable numerical results are presented for the amplitude and phase of the received multipath signal. Then, general analytical expressions, which closely approximate numerical results, are used to study the total acoustic field in terms of motion parameters and source-receiver range. Amplitude displays a rapidly oscillating pseudosinusoidal behavior whose oscillation rate increases with increasing relative speed and range. Phase exhibits an overall parabolic pattern over time, with a subtle oscillatory behavior. The time rate of change of phase increases with range and relative speed. Many results of this study differ markedly from those for longer ranges. [Work supported by ONR.]
Phase variations in short-range transmissions produced by cyclonic eddies
Authors: Henrick R. F. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Mesoscale cyclonic eddies are characterized by cores of low sound speed and counterclockwise rotational currents. These effects are approximated using a parametric eddy model [J. Acoust. Soc. Am. 62, 860–870 (1977)] derived by the authors. Their influence on acoustic phase variations in short-range propagation between a surfaced source and receiver is studied using ray theory. In contrast to previous acoustic investigations, eddies of arbitrary size and strength are considered, effects of both currents and horizontal and vertical sound-speed variations are incorporated and arbitrary position and orientation of the source and receiver within the eddy are permitted. Currents are shown to be responsible for up to 20% of the total phase variation, indicating their importance in eddy-acoustics problems. Significant differences in phase variations resulting from changes in source-receiver location and orientation, in an eddy of fixed size and strength, are demonstrated. Then, general results are presented to illustrate how phase variation depends on parameters characterizing eddy size and strength. [Work supported by ONR.]
The effect of the East Australian Current on sound propagation near New Zealand
Authors: Browning D. G. , Bannister R. W. , Denham R. N. , Guthrie K. M.
Published: October 2005

It has recently been determined that the East Australian Current swings away from the Australian coast at 32° south latitude flows east across the Tasman Sea past the northern tip of New Zealand. As a result this large current may have a significant effect on sound propagation conditions near the north island of New Zealand. Sound propagation predictions are obtained using a multi profile modelling program. First, comparison is made between sound crossing the current and sound propagation in a normal subtropical water mass. The relative importance of thermal structure, bottom slope and bottom absorption are then determined for current flow near the continental shelf and bathymetric features such as the Lord Howe Rise and Three Kings Islands. Finally, results are compared to data obtained during Project Span Three.
Preliminary results of underwater acoustic measurements at a mid-ocean site, 1977
Authors: Ewart T. E. , Reynolds S. A.
Published: October 2005

The Mid-ocean Acoustics Transmission Experiment 1977 (MATE), was conducted to measure the acoustic variability at four frequencies from 2 to 13 kHz over an 18 km path at Cobb Seamount. Preliminary results indicate time of arrival fluctuations for a single refracted path are well predicted by internal wave theories. The variation in acoustic intensity of the single path, however, is not well predicted. Simultaneous environmental measurements make possible a careful comparison between the observed acoustics and the physical fields. The environmental data sets suggest alternative mechanisms which must be considered in predicting the observed acoustic variability. [Work supported by ONR.]
An examination of multipath processes in a range dependent environment within the context of adiabatic mode theory
Authors: Rutherford Steven R.
Published: October 2005

An extension of the work of Tindle and Guthrie [C. T. Tindle and K. M. Guthrie, J. Sound Vibration 34, 291–295 (1974)] allowing one to extract ray path information within the context of adiabatic mode theory has been carried out. The purpose of this extension is to examine the adiabatic solution with respect to the process of multipath conversion due to a sloping bottom to determine whether this process is contained within the adiabatic solution or if it is entangled in the coupling coefficients which are neglected within the adiabatic approximation. Through the application of Tindle and Guthrie's method to the description of acoustic propagation over a sloping bottom, it has been possible to show that the multipath structure of the field is described quite well by the adiabatic solution for bottom slope angles up to 10°. [Work supported by the Naval Ocean Research and Development Activity and the Naval Electronic Systems Command.]
Measurement of the attenuation of acoustic normal modes
Authors: McDaniel S. T.
Published: October 2005

The attenuation of the first acoustic normal mode was measured for sound propagation in shallow water off the coast of Daytona Beach, Florida. The use of small explosive charges as a source permitted mode attenuation measurements over a frequency range extending from 40 to 800 Hz. Isolation of the first mode was accomplished by selecting source and receiver depths to minimize excitation and reception of the second and third acoustic normal modes. Higher order modes decayed rapidly with range and hence constituted a negligible contribution to the received pressure field. The results obtained from short range measurements are compared with long range propagation loss. [Work supported by the Naval Sea Systems Command.]
Waves in periodically layered media
Authors: Herrmann G.
Published: October 2005

Waves in linearly elastic media of infinite extent, composed of alternating layers of two different materials with perfectly bonded interfaces, exhibit some special features which are due to periodicity and impedance discontinuities at each interface. Floquet's theory permits an analysis of such waves which naturally separates into problems of anti-plane and plane strain. The recently developed dispersion relations for such waves will be discussed, placing emphasis on the special features, such as existence of stopping bands, transition points, conical points, and asymptotic behavior. More. recent work on the applicability of Floquet-type solutions in anti-plane strain to layered semi-infinite media with traction-free surfaces parallel to the layers and to layered plates will also be discussed. A new class of surface is shown to exist which are dispersive, are restricted to a limited frequency range in some cases, and which can be propagating or evanescent. Finally. attempts to mathematically, model waves in periodically layered media by means of approximate theories will be mentioned, in particular the class of “effective dispersion” theories, which contain both the dispersive and the filtering properties.
Wave propagation in single and multiple visoelastic layers
Authors: Madigosky Walter
Published: October 2005

This paper summarizes recent progress in wave propagation in fluid, elastic, and viscoelastic layers. This work finds application in underwater acoustics, NDT, geophysics, SAW devices, medical acoustics, etc. The role of absorption in viscoelastic layers can be accounted for by introducing complex propagation constants into elastic theories. This necessitates the need for four independent material constants, one of which (the shear loss) is difficult to obtain experimentally. This difficulty has been overcome by introducing a physical model relating the shear to longitudinal absorption. In the case of inhomogeneous layers (frequently encountered in practice) a theory which predicts effective material constants, including dynamic effects, is introduced. These constants can then be used in computer codes to calculate the transmission (T), reflection (R), and absorption coefficients for single and multiple layered configurations. The effect of finite thickness and fluid loading on the acoustic properties has recently been clarified by the application of the resonance theory which readily allows the interpretation of resonances in T and R. Resonance widths and amplitudes are modified by the presence of absorption loss, and the interaction between resonances accounts for an apparent violation of the coincidence rule in viscoelastic layers.
Attenuation of Stoneley waves on boundaries between thin bonded glass substrates
Authors: Claus R. O. , Renfro R. L.
Published: October 2005

Variations in the attenuation of Stoneley waves on the glued boundaries between several thin aluminized front surface mirrors and flat 7070 Pyrex glass samples are reported [R. Stoneley, Proc. R. Soc. London Ser. A 106, 416–428 (1924)]. The Pyrex samples were ground using successively finer grades of carborundum abrasive. Nine megahertz surface acoustic waves (SAW) generated on the mirror surface were converted to Stoneley waves on the 2.54 cm by 0.635 cm mirror glass/ground glass sample boundary and then back from Stoneley to SAW on the opposite side of the sample. Stoneley wave attenuation was determined for each pair by optically measuring incident and transmitted SAW amplitudes via fixed input beam differential interferometry [C. H. Palmer, J. Acoust. Soc. Am. 53, 948–949 (1973)]. Preliminary results indicate a correlation between measure Stoneley wave attenuation and adhesive bond and interface quality. [Work supported by NSF under Grants ENG-78-05773 and ENG-78-11040.]
Existence of Stoneley waves on boundaries between acoustically similar solids
Authors: Renfro R. L , Claus R. O.
Published: October 2005

Stoneley waves exist on the boundaries between a limited range of isotropic and anisotropic solids and have been directly and indirectly detected on several pairs at ultrasonic frequencies [D. A. Lee and D. M. Corbly, IEEE Trans. Sonics Ultrason. SU-24, 206 (1977); R. O. Claus and C. H. Palmer, Appl. Phys. Lett. 31, 547 (1977)]. Of particular importance to current optical measurements are those waves that exist between pairs of transparent glass substrates for which Weichert's condition, μ1/μ2 ≈ ρ1/ρ2 ≈ 1, is nearly satisfied. We study the range of possible existence for these pairs and indicate that the existence region in the (μ1/μ2), (ρ1/ρ2) plane defined by Scholte [Proc. Ned. Akad. Weten. 45, 20, 159, 380, 439, 516, (1942)] degenerates to a single point when the media obey Weichert's equality. Experimental implication of the theoretical results is discussed. [Work supported by NSF under Grants ENG-78-05773 and ENG-78-11040.]
Torsional waves in a bimetallic rod with laminated, periodic structure
Authors: Kaul R. K. , Muller W. , Shaw R. P.
Published: October 2005

Torsional waves are studied for an elastic traction free circular cylinder with an axial periodic structure and a cylindrical core and concentric casing (of differing materials) radially. Pochhammer type solutions are obtained first and the dispersion spectrum is found in terms of an interfacial coupling coefficient, Q. As Q approaches zero, or infinity, the problem reduces to a core and casing with traction free surfaces and a core with a displacement free outer boundary and casing with displacement free inner boundary and traction free outer boundary, respectively. The actual spectrum is bounded by these two cases; furthermore, invariant points exist in the spectrum which do not depend on the material properties. The frequency equation is solved explicitly for long wavelengths using McMahon type expansions and various features of the spectrum at long wavelengths and high frequencies, asymptotic results for slopes and curvatures, are discussed. Next, the propagation of Floquet waves is examined; at the end of each Brillouin zone, the frequency equation uncouples and the presence of passing and stopping bands and conical points is exhibited. [Work supported by ONR.]
Viscoelastic effects in resonant sound scattering from layered cylindrical shells
Authors: Gaunaurd G. C. , Überall H.
Published: October 2005

We consider a layered cylindrical structure consisting of an inner elastic shell supporting an outer viscoelastic layer. The structure is immersed in an outer fluid and it contains a dissimilar fluid in its interior. We study the scattering of sound waves normally incident on the structure utilizing the recently developed resonance theory of sound scattering. The role of the viscoelastic properties of the outer layer in the damping of the scattering resonances is investigated, as well as their effect on the partial wave scattering amplitudes, making up the monostatic cross section of the structure. For the purpose of this investigation, we have isolated the resonances from the composite partial-wave contributions, and we have quantitatively shown to what extent their strength can be effectively reduced, for all modes, by increasing the viscous level of the outer layer. [H. Überall is also at Catholic University, Washington, DC, and was additionally supported by Code 421 of ONR.]
On the formation of parametric acoustic arrays in layered media
Authors: Fenlon F. H. , Yeager D. L.
Published: October 2005

The interaction of directive finite-amplitude waves in a liquid layer embedded in two isotropic homogeneous “liquid-like” (i.e., low shear moduli) half-spaces of arbitrary impedance is reviewed in this paper via analytical solutions of the second-order acoustic wave equation. Necessary conditions for mode-locking in the layer are deduced in terms of the boundary-induced dispersion characteristics of the composite medium and the angle of intersection of the primary waves. On the basis of these results, the potential utility of parametric acoustic arrays for directive “low-frequency” penetration of typical geophysical strata is then briefly addressed.
Diffraction at a caustic—A correction to ray theory
Authors: Hudimac A. A.
Published: October 2005

It had been shown that the errors of a ray theoretic solution could be corrected by the radiation from a volume distribution of simple sources having the phase of the ray theoretic solution at that point, and a strength proportional to the Laplacian of the ray theoretic amplitude. On the boundary between an ensonified region and a shadow zone, the correcting distribution is a surface distribution of simple sources and/or dipoles. This correction remains valid even in the case of a caustic. Previous calculations have been extended for a particular example of a caustic, and the evanescent field has been calculated. The comparison between this approximate result and the known result obtained by a wave theoretic method is good.
An articulatory model of the tongue based on a statistical analysis
Authors: Maeda Shinji
Published: October 2005

An articulatory model of the tongue composed of linear components was determined by a statistical analysis of tongue shapes and jaw-opening measured on lateral x-ray motion pictures. The sum of the four components describes adequately the tongue shapes observed during utterances of 12 French vowels in sentences and of pV1CV2 disyllables, where V1 V2 = [i,a,u] and C = [b,d,g]. These components represent the effect of the jaw articulator, of the tongue-body articulator, of the dorsal articulator, and of the apical articulator upon the tongue shape, respectively. The vowels plotted on the articulatory space, where the x axis corresponds to the tongue-body component and the y axis to the jaw component, form the vowel triangle. The model seems to explain, at least in part, the origin of articulatory “front-back” and “high-low” dimensions. We speculate that such model should be suitable for the description of the dynamics of the tongue, since that of the individual articulators may be governed by a relatively simple law.
A speech microscope
Authors: Vemula N. R. , Engebretson A. M. , Monsen R. B. , Lauter J. L.
Published: October 2005

The speech microscope is a software system designed to conveniently record, store, display, playback, and analyse the waveform of speech signals. The system is highly interactive, allowing control of a variety of options through a keyboard and display oscilloscope. A display window enables the user to “walk through” a recorded sound and examine successive segments of the waveform. The window acts as a “temporal microscope,” showing a whole syllable at a time or only a few milliseconds. For any segment, the user may obtain a spectral or linear prediction analysis. An analysis window (rectangular, Kaiser, cosine) appropriate for the signal is selected and the program then calculates the discrete Fourier transform and linear-prediction coefficients. The linear prediction analysis provides center frequencies and bandwidths of formants and the vocal tract function. The user can then select any of a variety of printouts, such as copies of waveform segments, the waveform with phase spectrum, etc. The temporal flexibility and analysis features of the system allow for precise measurements of the duration of speech sounds, accurate spectral description of both periodic and aperiodic sounds, and ease in examining dynamic characteristics such as formant transitions. [Supported by NINCDS Grant NS03856 and NIH Grant RR 00396.]
On determining EMG onset time
Authors: Baer T. , Bell-Berti F. , Tuller B.
Published: October 2005

Each of two methods was used to determine the onset time of EMG activity associated with speech gestures in two data sets. Each data set contained between 10 and 20 tokens (repetitions) of several utterances. Onset times were specified in relation to a reference point in the speech signal. In one method, measurements were made from the digitized waveforms for the individual tokens. Average onset time for each utterance type was calculated by averaging measurements from its tokens. In the other method, the ensemble average of the EMG signals from tokens of each utterance type was calculated after carefully aligning them at the reference point. Onset time was then measured for each utterance type from the ensemble-average waveform. Onset-time measurements from ensemble averages were consistently earlier than corresponding averages of individual-token measurements. For some utterances, the ensemble-average onset time was earlier than any individual-token measurement. These results confirm the value of ensemble averaging for reducing the inherent noise in EMG signals associated with speech gestures. [Work supported by NINCDS and BRSG.]
An effect of phonetic environment on voicing control mechanisms during stop consonants
Authors: Westbury J. R. , Niimi S.
Published: October 2005

There are abundant data which show the vocal folds to be abducted during closure for intervocalic /p,t,k/ in American English. Vocal-fold abduction during such stops is reliably indicated by a rapid rise in intraoral pressure following oral occlusion. Recent recordings of intraoral pressure during an adult male English-speaker's productions of labial and alveolar stops in a variety of environments suggest, however, that vocal-fold abduction is characteristic only for voiceless stops which precede vowels. Synchronous recordings of intratracheal pressure showed during the closures of stops in all environments that the driving pressure for speech remained appreciably greater than atmosphere. But, during the closures for voiceless stops occurring initially in certain medial consonant clusters, and utterance finally, intraoral pressure generally did not rise above atmosphere. These facts together suggest that /p,t/ in these latter environments were voiceless by virtue of interruption of transglottal flow at the glottis. [Work supported by NSF grant BNS 77-07686.]
Laryngeal adjustments during American English consonant cluster production
Authors: Yoshioka H. , Löfqvist A. , Hirose H.
Published: October 2005

The glottal opening gesture and its timing control in clusters of voiceless obstruents was investigated by use of electromyography. Two distinct peaks in the abductor muscle (PCA) activity curve were found for /sk/ sequence when a word boundary intervened. but only one for the same sequence without the boundary. For the geminate combination /ss/ or /kk/, the abductor activity pattern was characterized by one single peak surrounded by gradual slopes, although a word boundary intervened within the cluster. In the case where word final /k/ was followed by word initial /s/ or /sk/, however, the abductor muscle showed one broad continuous but rather small peaked curve during the whole cluster. These results. together with transillumination and fiberoptic data, suggest that each voiceless obstruent characterized by aspiration or frication noise tends to require a single separate opening gesture, while an unaspirated stop in voiceless environment can be produced within the opening gesture attributed to the adjacent aspirated stop or fricative. [Work supported by NINCDS and BRSG.]
Articulatory and acoustic correlates of the [s-š] distinction
Authors: Perkell J. S. , Boyce S. E. , Stevens K. N.
Published: October 2005

Spectra for the consonants [s] and [š] show a distinct difference in the frequency of the lowest major spectral peak. Introspection suggests that the difference is due to the creation of a space between the tongue tip and the mandibular alveolar ridge for [š] but not for [s]. Acoustical calculations show that the abrupt decrease in the natural frequency of the cavity anterior to the tongue constriction as contact between tongue tip and lower teeth is broken has a magnitude consistent with acoustical observations. To test this hypothesis concerning the distinctive differences in tongue-tip contact associated with the [s-š] contrast, observations of contact of the tongue with the lower incisors and alveolar ridge were made by looking at the change in resistance caused by bridging across two electrodes fixed to the teeth. Although the transduction technique did not permit as detailed an examination as desired, data for three subjects indicate that there is a strong contact for /s/ and little or no contact for /š/. A side result is the finding of an apparent anatomically dependent contact for front vowels versus lack of contact for back vowels. [Supported by NINCDS.]
Frequency of occurrence of fricatives and their net perceived loudness
Authors: Javkin Hector
Published: October 2005

Over two-thirds of the fricatives in a sample of 225 languages (Stanford Phonology Archive) occur at places of articulation at or anterior to the palatal region. An even higher preponderance of front fricatives can be seen if /h/, which often functions like a voiceless vowel, is excluded. A partial explanation for the preponderance of front fricatives is the finding of K. Stevens [J. Acoust. Soc. Am. 50, 1180–92 (1971)] that there is a generally higher level of energy produced as the place of articulation moves forward in the vocal tract. The synthesis of a number of fricatives using a program that traces the volume velocity wave in the vocal tract and the application of equal loudness contours [based on S. Stevens, J. Acoust. Soc. Am. 51, 575–601 (1972)] suggests that net perceived loudness (the spectrum of fricative noised produced with the effect of that spectrum on the auditory system) strongly favors fricatives produced toward the front of the mouth. [Work supported by NIH.]
On the nasal-fricative sequences in English
Authors: Ali Latif H.
Published: October 2005

This paper is designed to assess the likelihood of the presence of the intruded silent gap in British English nasal-fricative sequences [Liberman et al., Lang. and Speech 4, 175–195 (1961); Ali et al. to appear in Phonetica (1979)]. It also attempts to examine the possibility of the existence of some consonant segments specified [+nasal], other than the traditional nasals in English [Fischer-Jørgensen. Trends in Phonological Theory (1975)]. Aerodynamic and spectrographic investigations were carried out to examine several points of interest for three subjects, in particular to measure and calculate certain characteristic behaviors of nasal air flow, oral air flow, duplex noise friction, and velopharyngeal voicing prints of [ns], [nθ], [nf], and [mf] in natural sequences of utterances. The results lead to the conclusion that since the homorganic intrusive stops were sporadically observed, then it is by no means a universal phenomenon, nor is it found in all dialects of English. Therefore, a stop of this kind is not really a physiological necessity and thus should not be represented in the phonological underlying representations of the English lexicon.
Mandible movement for /s/-defective and normal children
Authors: Wilcox K. , Daniloff R. , Stephens M. I.
Published: October 2005

Using a linear impedance-pneumograph taped to the mandible, the mandibular movements for normal and 3 differing types of /s/-misarticulating children were measured as they spoke sentences containing /s/ in a wide variety of cluster and vowel contexts, with varying stress and juncture, at two differing tempii of production. Simultaneous audio/jaw displacement recordings reveal that the /s/-defective children, if anything, are somewhat less context sensitive in their /s/-target positions than are normals, and their abnormal mandible targets for /s/ are as stable as those for normal speaking children. Results are discussed in terms of current speculations concerning defective articulation development.
Modeling children's vocal tracts
Authors: Goldstein Ursula G.
Published: October 2005

Several researchers have noted that a child's vocal tract is not simply a smaller version of an adult man's vocal tract, but that the ratio of pharynx-cavity length to oral-cavity length is substantially different. In order to study the acoustical implications of this difference, a static articulatory vocal-tract model is being developed with dimensions that can be varied for male and female speakers over all age ranges. The model has parameters specifying the position of an elliptical tongue body relative to the angle of the jaw, similar to the model developed by Mermelstein for adult men [P. Mermelstein, J. Acoust. Soc. Am. 53, 1070–1082 (1973)]. Other parameters specify positions of tongue tip, lips, and hyoid bone. The sizes of the various parts of the vocal tract are specified by growth curves which express anatomical distances as a function of age. The growth curves were obtained by performing least-squares fitting of two- through six-parameter curves to measurements reported in the medical literature. This research has implications for a better understanding of infant phonetic capabilities, articulatory configurations used by women and children, and vowel normalization. [Work supported in part by the National Institutes of Health.]
Five decades of research on cochlear mechanics
Authors: Zwislocki J. J.
Published: October 2005

The history of modern research on cochlear mechanics begins with Békésy's experiments, the first of which were published only one year before the inception of ASA. The cochlear traveling waves and the frequency-dependent maximum of basilar-membrane vibration Békésy discovered have been explained theoretically on the basis of the hydrodynamic theory of surface waves and confirmed experimentally, first indirectly, through recording of cochlear microphonics, later directly, with the help of the Mössbauer technique and capacitive probes. These measurements revealed the vibration maximum in the cochlea of a live mammal to be sharper than observed by Békésy in post-mortem preparations. However, the neural tuning found in cochlear nerve fibers appears to be still sharper, and the same is true for the receptor potentials of the inner hair cells. The mechanisms underlying the additional sharpening are currently under intensive investigation. They may be associated with cochlear nonlinearities, part of which appear to be generated mechanically. [Work supported by NIH.]
Cochlear anatomy related to cochlear mechanics
Authors: Lim D. J.
Published: October 2005

It is well known that the width of the basilar membrane is narrower in the basal turn than in the apical turn, and the width and thickness of the tectorial membrane follow the pattern of the basilar membrane. The size of the organ of Corti and angle of slope of the reticular membrane in relation to the basilar membrane are larger in the apex than in the basal turn. Ciliary height of the sensory cells also gradually varies from apex to base. Inner hair cell cilia are uniformly taller than the first row of outer hair cell cilia. In the apex and midturn the cilia of the third row of outer hair cells are tallest, but in the basal turn the inner hair cell cilia are tallest (twice as tall as the outer hair cell cilia), as shown in Table I. The possible implications of the mechanical coupling of sensory cilia to the tectorial membrane are discussed. [Work supported by U.S.A.F. and The Deafness Research Foundation.]
Cochlear partition vibration—Recent views
Authors: Rhode W. S.
Published: October 2005

Recent measurements obtained with a variety of techniques have extended von Békésy's observations of cochlear partition mechanics including the traveling wave pattern and the frequency-place relation. While the cochlear mechanical filter has been shown to be sharper than expected, on the basis of Békésy's results, it apparently is not sharp enough to account for the frequency selectivity observed in auditory nerve fibers. The principal disagreement in the area is whether the vibration of the basilar membrane is linear or nonlinear. Steady-state nonlinearities that disappear rapidly upon death, transient nonlinear response and two-tone suppression have been observed in only one species in the mid-frequency range. Whether this is due to a species difference or a frequency-place difference remains unresolved.
Cochlear mechanics: Physiologically vulnerable nonlinear behavior as reflected in ear-canal pressure and cochlear-nerve-fiber responses
Authors: Kim D. O. , Molnar C. E. , Matthews J. W.
Published: October 2005

For decades, many studies have confirmed Békésy's findings of the existence of traveling-wave motion and spatially based frequency selectivity in cochlear mechanical responses. Three currently unresolved issues in cochlear mechanics are nonlinearity, physiological vulnerability, and sharpness of tuning. A problem is posed by the fact that Rhode and his co-workers have directly observed physiologically vulnerable nonlinear behavior in basilar-membrane motion whereas others have shown conflicting results. Studies conducted in our laboratory of spatial distributions of responses of populations of single cochlear nerve fibers in normal cochleas and in cochleas exposed to intense sounds have led us to conclude that mechanical distortion signals (2f1−f2) and (f2−f1) are generated in the cochlear region where the primary-frequency responses are both large, and then propagate mechanically like single-tone responses over the region apical to the generation region [Kim et al., Scand. Audiol. (in press); Siegel et al., JASA, 1977]. Recent studies of acoustic signals in the ear canal show mechanically-present nonlinear behavior that has been attributed to the cochlea [Kemp, JASA, 1978]. Observations of effects of anoxia and temporary fatiguing on distortion products (2f1−f2) and (f2−f1 in acoustic signals near the eardrum clearly demonstrate physiological vulnerability of mechanically-present nonlinear behavior [Kim (in preparation)]. We shall attempt to reconcile these and other observations using models containing nonlinear dynamics of the cochlear partition [Matthews et al., this meeting]. We hypothesize that many of the observed auditory nonlinear phenomena are present in basilar-membrane motion and that the functional state of the organ of Corti significantly affects basilar-membrane motion. [Supported by NIH.]
Sound-induced resistance changes in the inner ear
Authors: Geisler C. D. , Mountain D. C. , Hubbard A. E.
Published: October 2005

Sound-induced resistance changes (CR) in scala media in response to pure-tone stimuli were measured by injecting alternating current into guinea-pig cochleas [C. D. Geisler et al., J. Acoust. Soc. Am. 61, 1557–1566 (1977)]. Computer analysis of simultaneously recorded CR voltage components and cochlear microphonic (CM) indicates that the CR harmonics, in both amplitude and phase, behaved differently with sound intensity and with asphyxia than did the CM harmonics (A. E. Hubbard, Ph.D. thesis, Univ. of Wisconsin-Madison, 1977). Direct current injection and stimulation of the crossed olivo-cochlear bundle (COCB) indicate further differences between CM and CR (D. C. Mountain, Ph.D. thesis, Univ. of Wisconsin-Madison, 1978). Positive dc caused an augmentation of CM that grew with sound intensity, and a reduction in CR magnitude that decreased with intensity. Negative dc caused effects of similar magnitude but opposite sign. COCB stimulation caused enhancement of both CM and CR. A model (D. C. Mountain, Ph.D. thesis, Univ. of Wisconsin-Madison, 1978) which can account qualitatively for these effects includes a nonlinear resistance dependent on hair-cell voltage as well as the usual time-varying acoustically modulated resistance.
Basilar membrane motion in the alligator lizard: Its relation to tonotopic organization and frequency selectivity
Authors: Peake W. T. , Ling A.
Published: October 2005

The configuration of the inner ear in the alligator lizard allows (from a single approach) electrical and mechanical probing of the entire sensory organ. Studies of nerve fiber responses [Weiss, Mulroy, Turner, and Pike, Brain Res. 115, 71–90 (1977)] and intracellular responses in the receptor organ [Weiss, Mulroy, and Altmann, J. Acoust. Soc. Am. 55, 606–619 (1974)] have demonstrated that responses can be placed in two categories based on their frequency selectivity [viz., a high characteristic frequency (CF) group associated with the basal end of the organ and a low CF group associated with the apical end]. These two regions of the cochlea differ in morphology of the cilia and tectorial membrane [Mulroy, Brain Behav. Evol. 10, 69–87 (1974)]. Measurements of velocity using the Mossbauer method indicate that the motion of the basilar membrane is virtually the same in both regions. Thus, tonotopic organization and frequency selectivity are not determined by the basilar membrane motion. This finding suggests that other mechanisms, perhaps involving the cilia and tectorial membrane, provide spatially varying frequency selectivity in this species. Similar mechanisms may play a role in mammalian cochleas, where the basilar membrane apparently provides tonotopic organization and at least some of the frequency selectivity. [Supported by NIH.]
Impulse noise of army weapons
Authors: Garinther Georges R.
Published: October 2005

Exposure to the impulse noise produced by certain weapons is known to cause hearing loss among Army personnel if they do not wear hearing protection. These high levels are produced by weapons as small as a 5.56 mm rifle up to as large as a 155 mm Howitzer. Typical sound pressure levels and B durations produced by weapons are:

22 cal rifle: 140 dB; 2 ms 155 mm Howitzer: 178 dB; 50 ms

5.56 mm rifle: 155 dB; 4 ms M72 Rocket Launcher: 179 dB; 12 ms

105 mm Howitzer: 171 dB; 30 ms Dragon Rocket Launcher: 185 dB; 5 ms.

The hazard to hearing presented by these weapons has been assessed by MIL-STD 1472 which is based upon the Impulse Noise Hearing Damage Risk Criterion of CHABA Working Group 57. This Standard considers peak pressure level, duration, number of pulses, interval, orientation of the ear, percent risk, and hearing protection. Attempts have been made to reduce the noise produced by these weapons with good success for small caliber weapons, but very limited success for large weapons. A different approach to the assessment of the hazard of impulse noise, which considers spectrum, is presently being studied at the US Army Human Engineering Laboratory.
Status of knowledge of sonic boom
Authors: Maglieri Domenic J. , Carlson Harry W. , Hubbard Harvey H.
Published: October 2005

Numerous sonic boom studies were accomplished in the last two decades as a result of increased operations of high performance military aircraft, the proposed US/SST, and the anticipated entry of the Concorde into commercial airline service. Much in the way of documentation of the phenomena and its effects was suitably summarized by the society in the first and second Sonic Boom Symposiums of 1965 and 1970, respectively. The present decade has seen a continuation of these efforts, both analytically and experimentally by laboratory and flight tests, in areas such as sonic boom minimization through vehicle design, sonic boom behavior at transonic and low supersonic Mach numbers, and the extension of the predictive schemes to very high altitudes and Mach numbers associated with space launch vehicles such as Space Shuttle. More recently, a renewed interest and concerted effort has been directed towards the long range “over-the-top” sonic boom phenomena in the thermosphere in connection with certain “mysterious” noises observed along the east coast. This paper will present an overview, together with a discussion of the latest developments of the sonic boom problem.
Temporal correlates to [voice] in Arabic-accented English
Authors: Flege James
Published: October 2005

This study explores the phonetic basis for the frequent failure of Arab speakers of English to produce a voicing contrast for stops, especially /p/ (which Arabic lacks). Stressed and unstressed English CVC's were produced in a carrier sentence by Americans and two groups of Saudis. The VOT, vowel duration, and closure duration correlates to [voice] in pre- and post-vocalic position were measured from spectrograms. Closely comparable data were gathered for Arabic, including durations of long and short vowels and consonants. Preliminary results show that the [voice] contrast presents difficulty for both experienced and inexperienced Arab speakers. Temporal specification of [voice] often resembles Arabic phonetic norms: voiceless stops are often produced in the short-lag range; vowel duration usually corresponds to that of short Arabic vowels; vowel duration fails to be exploited as a correlate to consonant [voice] (although closure duration sometimes is). The voicing contrast is usually weaker in unstressed than in stressed words, and for labial than alveolar and velar stops, suggesting that both phonological and phonetic patterns of Arabic influence phonetic specification of [voice] for many Arab speakers of English.
Spectral continuity of burst and formant transitions as cues to place of articulation in stop consonants
Authors: Kewley-Port D.
Published: October 2005

A recent approach to characterizing place cues in stop consonants dissociates the temporal properties of the burst spectrum at onset from the time-varying formant transitions which follow [K. N. Stevens and S. E. Blumstein, J. Acoust. Soc. Am. 64, 1358–68 (1978)]. Two experiments were carried out to examine this perspective on analyzing the acoustic correlates of place of articulation in stops. Spectral sections were calculated every 5 ms using linear prediction analysis for five repetitions of the stops /b, d, g/ before /i, ɪ, e1, ε, æ, a/ for one talker. In the first experiment formant transitions were measured and shown to differentiate place among these stops for only the vowel /æ/. This result indicates that formant transitions measured from real speech are not sufficient to cue place of articulation. A second experiment established a well-defined spectral continuity between burst and the early portions of the formant transitions. Subjects were required to classify visual displays of running spectra of these CVs according to a three-feature matrix. The results showed agreement on 95% of the feature assignments. Correct identification of the consonant from these features was 88%. These three features can be rationalized in terms of the theoretical output of the vocal tract and early sensory coding of speech by the auditory system. [Supported by NINCDS Grant NS-12179.]
Vocal loudness and effort in the speech of 3-year-old children
Authors: Garber S. R.
Published: October 2005

Siegel, Pick, Olsen, and Sawin [Developmental Psychology 12, 255–261 [1976)] found that young children decrease their vocal intensity less in response to sidetone amplification than adults. Perhaps when the child alters his vocal intensity, the acoustic cues accompanying the change differ from those available to the adult speaker. The present study was designed to determine whether the acoustic cues for vocal loudness and effort are the same in child and adult voices. The study is a replication of a study done with an adult speaker by Brandt, Ruder, and Shipp [J. Acoust. Soc. Am. 46, 1543–1548 (1969)]. Children and adults repeated a sentence at seven intensity levels from 65 to 95 dB SPL. Adult listeners heard the sentences in a normal condition (as originally produced], with effort constant and intensity varying and with effort varying and intensity constant. Listeners rated the loudness and effort of each sentence. Preliminary results indicate that cues for loudness and effort are present in the speech of children as well as adults.
Periodicity perception in bat sonar
Authors: Simmons J. A.
Published: October 2005

Echolocating bats (Eptesicus fuscus) can detect jitter in the arrival-time of sonar echoes as small as 500 ns. These bats could thus detect fluttering motions of prey resulting in displacements in range as small as 100–200 μm The range-axis acoustic image of a planar target corresponds to the half-wave-rectified crosscorrelation function between the bat's broadband FM sonar transmissions and echoes. Eptesicus can perceive echo phase information as would be encoded by phase-locked discharges to excitatory half-cycles of transmission and echo waveforms, which cover the frequency span from 25 to 100 kHz. Ambiguity in echo arrival-time perception occurs for time-separations corresponding to small integer multiples of average signal periods. The time-domain neural crosscorrelator required here for extracting periodicity in sonar sounds and echoes has the desirable properties of recovering harmonic-interval or “missing fundamental” periods in complex sounds and extraction and representation of periodicity information potentially for pitch perception. The data indicate that phase-coding occurs in the auditory systems of bats at very high stimulus frequencies.