bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflection of acoustic waves at a water-sediment interface
Authors: Stoll Robert D. , Kan T. K.
Published: October 2005

Reflection and refraction of plane acoustic waves are studied for the case where the sediment is modeled as a porous viscoelastic medium. The model is based on the classical work of Biot which predicts that three different kinds of attenuating body waves may propagate in the sediment. As a consequence when homogeneous plane waves in water are incident to a water-sediment interface, three nonhomogeneous waves are generated in the sediment. In these waves the direction of phase propagation and the direction of maximum attenuation are not the same and particle motion follows an elliptic path. Moreover, the velocity and attenuation of the refracted waves become dependent on the angle of incidence and no “critical” angle occurs. Numerical examples show that the reflectivity of a porous viscoelastic model differs significantly from the case where the sediment is modeled as a viscoelastic solid with constant complex modulus. Finally, because of the frequency dependence of reflectivity in the porous model, it is found to act as a filter with respect to broad band energy.
Binaural spatial resolution with an improved ultrasonic sensor for blind
Authors: Kay Leslie , Kay Nora
Published: October 2005

Angular spatial resolution using a new design of spatial sensor has been compared with those reported in the literature [L. Kay, Animal Sonar Systems, edited by R. G. Busnel and J. F. Fish (Plenum, New York, 1980), Chap. 6]. Subjects were required to count the number of vertical rods placed at constant radial distance in the field of view of the sensors. The number of rods and their angular spacing were varied randomly. Two binaural sensors A and B had field of view of 60° and 35°, respectively. A monaural sensor C had a field of view of 10° and the new sensor D had a binaural field of view of 47° upon which was superimposed a central monaural sensing field of 1O°. Special envelope shaping of the signals from sensor D emphasized the characteristic echo quality in the central field and the binaural section was especially sensitive to relative lateral motion. Correct counts (at the 75% level) were obtained for angular spacing of (sensor A) 46°, (sensor B) 20° (sensor C) 8°, and(sensor D) 11°. Increasing the field of view from 10° to 47° reduced resolution by only 30% in sensor D compared with 350% for simple binaural resolution.
Comparison of impact noise transmission using experimental impactors
Authors: Warnock A. C. C.
Published: October 2005

Preliminary experience with the modified tapping machine proposed by Schultz was described at the 96th meeting of the Acoustical Society of America. Since that time the impact sound transmission through more than twenty floor systems has been measured using the standard ISO tapping machine, the machine proposed by Schultz, an experimental system, and two live walkers. Although the system suggested by Schultz is an improvement over the ISO machine it appears to have an impact velocity that is too high. The experimental NRC hammer with a lower impact velocity and added mass and compliance gives data that correlate better with the live walker results. Some development work remains to be done but these initial results are promising.
Reflections on and of the syllable: Does a medial consonant in a VCV belong to the first or second syllable?
Authors: Tartter Vivien C. , Kat Donna , Samuel Arthur G.
Published: October 2005

Previous research has shown that adaptation effects in speech are position specific: consonant-vowel (CV) syllables do not affect labeling of vowel-consonant (VC} syllables, and vice versa. The present study uses this fact to test whether a medial stop consonant in a VCV utterance belongs to the first syllable, the second syllable, or both. Three test series were constructed: one in which the medial consonant was represented by transitions into the stop (/ɑb_ɑ/—/ɑd_ɑ/), one in which the transitions were out of the stop (/ɑ_bɑ/—/ɑ_dɑ/), and one with both incoming and outgoing transitions (ɑbbɑ/—/ɑddɑ/). Adaptation with /bɑ/, /ɑb/, /ɑ_bɑ/, /ɑb_ɑ/, and /ɑbbɑ/ was conducted on all three continua. The pattern of results is used to address the syllabification issue, and the acoustic-phonetic issue which has been discussed in the adaptation literature.
TOT: An acoustic CV syllable temporal onset analog?
Authors: Pastore R. E. , Harris L. B. , Kaplan J.
Published: October 2005

Temporal order identification threshold (TOT) exhibits some similarities to the labeling boundary for several types of CV syllables varying along temporal onset continua. These continuum involve very roughly a 30-ms onset asynchronies and exhibit selective adaptation. Like the speech continuum, TOT for tones is not fixed, but is a continuous function of the total stimulus duration [R. Pastore, L. Harris, and J. Kaplan. J. Acoust. Soc. Am. 67, S7 (1980)]. If TOT exhibits other characteristics similar to initial speech boundaries, then the various types of continua may have a common basis. However, if the continua exhibit different characteristics, then either only some of the underlying processes are common to the perception of the continua or the perception of the two continua only seem similar under certain conditions. This latter finding would have major implications for infant and nonhuman research which demonstrate behaviorally measured perceptual discontinuities with approximately 20-ms VOT onset asynchronies. We investigated TOT for tones either varying rise time or with trailing stimuli. Differences were found between TOT and the category boundary for CV and CVC syllables contrasted in initial onset characteristics. [Supported by NS 10995 from NINCDS and from NSF.]
Cochlear initiation sites of human auditory frequency following potentials
Authors: McDermott John C. , Glattke Theodore J.
Published: October 2005

Initiation sites of the frequency following potential (FFP) along the cochlear partition have been thought to be dependent upon stimulus SPL. However, information regarding initiation sites of the FFP have come from simultaneous masking studies, and results from these studies may be confounded by interference from bio-electric potentials generated by distortion products of the masking stimulus. This study used a series of forward masking tone bursts set at the subjects' pulsation threshold level (PTL) to establish physiologic tuning patterns for a 500-Hz tone burst at 80 and 100 dB SPL. Tuning patterns for these levels were determined during the presence or absence of continuous high-pass noise masking. Results from this study revealed selective FFP amplitude reduction by forward masking stimuli of 500 Hz as well as maskers up to 2000 Hz. Tuning patterns were consistently broader for the higher stimulus levels. These findings suggest multiple cochlear initiation sites for the FFP and do not support its use as an audiologic tool for low-frequency hearing assessment.
Some electrophysiological support for phonological distinctive features
Authors: Polen Samuel B. , Blakney Steven E. , Seilo Michael T. , McRandle Carol C.
Published: October 2005

Among researchers who agree on the existence of phonological distinctive features, there is no general consensus as to the articulatory, psychological, and/or acoustic characteristics comprising elemental phonemes. To date, little evidence has been presented describing the electrophysiological reality of these phonological distinctive features. The lack of agreement among distinctive feature theorists as to the acoustic, articulatory, or psychological reality of phonological distinctive features, in the absence of hard physical evidence to support distinctive feature theory, has led some researchers to question the basic constructs of these theories [LaRiviere et al. (1974); Walsh (1973)]. This study investigated the physiologic reality of phonological distinctive features by using an orienting response paradigm to obtain unique evoked potential responses for target phonemes that varied from a contextual phoneme by at least one distinctive feature. The results of the analyses supported the existence of phonemic distinctive feature representation at the cortical level and provides substantial evidence that there are unique corresponding electrophysiological representations of distinctive features that may be differentiated one from another.
Measurement of vehicle sensitivity to driveline excitation
Authors: Krenz Robert A. , Peithman Harlan W.
Published: October 2005

In order to control passenger car interior noise levels due to first order driveline excitation, a procedure was developed to measure the acoustical vehicle sensitivity to driveline excitation sources. Vehicle sensitivity is expressed as the ratio of sound pressure level (output) to excitation level (input) as measured at a particular first order driveline frequency. Rear axle drive vehicles potentially have several types of vibration excitation which add vectorially at any given frequency to comprise the total excitation. Although not necessary to calculate vehicle sensitivity, it is occasionally useful for purposes of problem analysis to identify the magnitude and phase of each type of excitation. Using a cross section of vehicle types and an array of excitation levels evaluated subjectively and measured with instrumented tests, vehicle sensitivity zones have been established as a reference for judging concepts, prototypes, and production vehicles. The vehicle sensitivity approach clearly separates the contribution of driveline excitation and vehicle system response. This type of information aids management in setting specific objectives for the Company's future products.
Prototype model of diesel engine vibration and noise generation
Authors: Pierce Allan D. , Dimitriadis Emillos
Published: October 2005

Insight into how combustion-pressure time variations generate external noise results from analysis of a simplified model of a single cylinder four-cycle engine. The crankcase is a long rectangular “thin-walled” box that vibrates as a cantilever beam. Oscillations are excited by forces exerted on the main bearings, these forces being transmitted from the combustion cavity through the piston and connecting rod. The oil pan is a thin plate whose oscillations are driven by displacements along its perimeter, these displacements resulting from the crankcase beam oscillation. The engine head is assumed rigid. Damping results from the sliding of the piston relative to the block. Analysis leads to a detailed description of the outer surface vibrations. Sound generation is bracketed by computations based on (1) the multipole matched-asymptotic-expansion model (low frequencies) and (2) the geometrical theory of diffraction (high frequencies). The result relates ratio of pressure spectral densities (external to internal) to engine structure dimensions, mass distribution, elastic modulus, piston-cylinder dashpot constant, and engine speed.
The vibration of rectangular plates treated using simply supported plate functions in the Rayleigh—Ritz method
Authors: Dickinson S. M. , Li E. K. H.
Published: October 2005

The problem of the flexural vibration of rectangular plates has been treated extensively, with good result, using appropriate beam vibration mode shapes as admissible functions in both the Rayleigh and Rayleigh—Ritz methods [D. Young, J. Appl. Mech. 17, 448–453 (1950); G. B. Warburton, Proc. I. Mech. E. 168, 371–384 (1954); A. W. Leissa, J. Sound Vib. 31(3), 257–293 (1973); S. M. Dickinson, J. Sound Vib. 61(1), 1–8 (1978)]. An alternative set of admissible functions, derived from the mode shapes of vibration of plates having two parallel edges simply supported and boundary conditions on the other two edges appropriate for the plate under consideration, was suggested by Dickinson [J. Sound Vib. 59(1), 143–146 (1978)] and their use in Rayleigh's method demonstrated. The present paper describes the use of these functions in the Rayleigh—Ritz method and illustrates the improvement (or otherwise) in the natural frequencies so calculated over those obtained using beam functions for several example plates. It is found that for plates supported in some manner on all four edges, the simply supported plate functions yield superior results.
Synthesis of piano tones from first principles
Authors: Weinreich Gabriel
Published: October 2005

A computer model of a piano has been constructed which includes the following features: A pair of strings with realistic intrinsic inharmonicity; a bridge admittance whose real and imaginary parts vary irregularly with frequency to simulate the resonant behavior of the soundboard; a hammer with finite mass, coupled to the string by nonrigid felt; a small mistuning between the unison strings; and a soundboard transfer function of a relatively primitive kind. All parameters can, of course, be varied. Problems involved in the model—both solved and unsolved ones—will be discussed, and an illustrative tape played.
Violin pitch detection
Authors: Kohut J. , Mathews M. V. , Miller Joan E. , Zukofsky P.
Published: October 2005

An instrumentation for measuring and recording the pitches produced by a violinist is described. The four strings are measured simultaneously and independently so chords, as well as single pitches, can be studied. Measurements are made with an accuracy of one part in 4096. A special bridge, which has a ceramic microphone under each string, is attached to the violin. Signals from the microphones go into four pitch period detectors, the design of which is facilitated by the sawtooth shape of string oscillations. The duration of each period is measured by counting the number of cycles of an 800-kHz clock in the period. These counts are then read into a computer at rates determined by a user-specified setting of an external oscillator. The pitches are thus available for real-time displays which are presented to the performer on a CRT and/or are stored for post-processing and analysis. This facility provides an effective means for detailed studies of performance practices such as vibrate, shifting, and matters of intonation.
Control of critical resonances in violin bodies
Authors: Pickering Norman C.
Published: October 2005

Spectral response of 25 violins was obtained by tapping the bridge under computer control synchronously with digital recording of data from a spectrum analyzer. Correlation with subjective judgment of competent players is closer than for any other excitation method used so far. This paper deals with the three strongest peaks of response, their amplitudes and frequencies in good and bad instruments, and how they can be controlled by the violin maker.
A uniformly accurate description of finite amplitude sound radiation from a harmonically vibrating planar boundary
Authors: Ginsberg Jerry H.
Published: October 2005

The velocity potential for the two-dimensional, finite amplitude acoustic waves induced by harmonic excitation on a region in an infinite baffle was obtained recently [J. H. Ginsberg, J. Acoust. Soc. Am. Suppl. 1 68, S47 (1980)]. The analysis, which represented the response in terms of a continuous spectrum of wavenumbers parallel to the boundary, was valid only for limited distances from the boundary. The current analysis employs the perturbation method of renormalization to derive expressions for the pressure and particle velocity that are uniformly accurate up to the location where a shock forms. The response consists of radiative and evanescent waves, with nonlinearity being significant only for the former. The solution is described as inversions of Fourier cosine transforms featuring a straining transformation of the space-time coordinates which is also dependent on the wavenumber. A quantitative example for the case of an intense high-frequency excitation is shown to lead to a sound beam in which the nonlinear distortion is asymmetrical between the compression and rarefraction phases. [Work partially supported by NSF grant No. ENG 7824602.]
Electromechanical equivalent circuit for cylindrical waves in thick walled hollow piezoceramic cylinders
Authors: Wilder W. D.
Published: October 2005

An exact distributed electromechanical equivalent circuit is derived for purely cylindrical waves in an axially polarized piezoceramic thick walled hollow cylinder. The analysis applies to either stress free or clamped in the axial direction, and the theory may be used to account for losses.
Farfield calibration of large aperture arrays
Authors: White Bryan F.
Published: October 2005

The calibration of large aperture sonar transducers in the farfield is difficult due to the problems of propagation and mechanical stability. An experiment is described in which several transducers with apertures up to 40λ were calibrated at 100 kHz, at ranges in excess of 30 m. The measurements were made in a commercial facility which consists of an instrumented barge in a flooded quarry near Cornwall, Ontario. The transducers calibrated are commercial side scan sonar tow fish. The farfield measurements were made with a hydrophone positioned from the ice surface, in late winter. A baffling arrangement arising from a composite tow vehicle configuration was demonstrated to be inappropriate. An alternative two vehicle configuration was subsequently evaluated by calibration at the same facility in summer with the reference hydrophone mounted on a guyed tower. This calibration arrangement proved less practical than the ice based scheme.
Acoustic radiation pressure produced by a beam of sound
Authors: Chu B.-T. , Apfel R. E.
Published: October 2005

The second-order force produced by a sound beam directed normally at a plane target is calculated. Previous theories on acoustic radiation pressures associated with plane acoustic waves are examined critically, and erroneous results, where they exist, are noted and rectified. A number of general relations are established using a new approach which avoids the necessity of dealing with detailed solutions of the governing nonlinear equations. Some of the concepts inferred from known solutions obtained by previous authors require drastic revision in the light of the present study. Specifically, the notion that Rayleigh radiation pressure depends on the nonlinearity of the medium (while Langevian radiation pressure does not) is not true in the case where the medium is bounded by a partially reflecting wall. Again, the concept that the Rayleigh radiation pressure depends on the acoustic field only through the energy density of the field is shown to be false. An example is given showing that it depends also on how the field is maintained. [Work supported by Physics Program, ONR.]
An analytical solution to the problem of noncollinear three-phonon interaction in an isotropic solid plate
Authors: Chao Tai—San , Ngoc Tran D. K.
Published: October 2005

Noncollinear three-phonon interaction of acoustic bulk waves has been treated analytically by solving the nonlinear equations of motion through the combination of the perturbative and the Green's function techniques. In particular, the Green's function was constructed by the imaging method. For the more complicated structure of a solid plate, noncollinear three-phonon interactions take place in the form of two Lamb waves interacting to produce a third Lamb wave. Experimental evidence has been obtained in the latter case for a nonpiezoelectric isotropic solid plate [N. G. Brower and W. G. Mayer, J. Appl. Phys. 49, 2666–2668 (1978)]. In the present paper, a theoretical investigation of the noncollinear three-phonon interaction of Lamb waves in a nonpiezoelectric isotropic solid plate is presented. The same approach as that used for bulk waves is employed except that under the new boundary conditions the Green's function is to be constructed by the eigenfunction expansion technique. The theoretical solution is compared to the experimental findings of Brower and Mayer.
A phonetic model for phrase structure perception in Swedish
Authors: Nordstrand L. , Engstrand O.
Published: October 2005

In a series of experiments recently developed algorithms and programs have been used to modify prosodic parameter values obtained from natural speech analysis data. Listening tests showed that certain conditions on fundamental frequency (F0) were necessary and sufficient to elicit unanimous judgements as to the phrase structure of the test utterances. Thus neither intensity nor duration, nor those parameters combined, were capable of superseding the effect of F0. Perceptual tolerances to deviations from F0 means were found to be temporally related to supraglottal events. Thus certain critical points in the time-frequency domain, rather than the complete shape of the F0 curvature, were crucial to the assessment of underlying phrase structure. A computer program for perceptually based synthesis of phrase structure prosody has been devised. Critical F0 values are given by rules in the program and transitions between values are specified in terms of simple sine functions. By means of these rules and procedures, a completely natural speech output is achieved.
Predicting lexical stress in English letter-to-sound conversion
Authors: Hertz Susan R.
Published: October 2005

A new set of English letter-to-sound rules has been developed within the recently revised rule framework provided by SRS, the interactive synthesis rule development system at Cornell University. Text-modification rules, conversion rules, and feature-modification rules apply in succession to convert a text string into a set of phonetic features. Text-modification rules augment the spelling with morphological and stress-related information. Conversion rules produce a string of phonemes and an associated feature matrix on the basis of the augmented spelling. Feature-modification rules modify the feature matrix produced by the conversion rules. These rules use the stress-related information originally provided by the text-modification rules to make final stress assignments and to reduce vowels. It is the addition of text-modification rules to SRS that makes possible the simple and efficient assignment of lexical stress.
A simple mathematical model for TTS
Authors: Maslen K. R.
Published: October 2005

Published data on TTS suggest that, in many cases, the rms pressure at threshold during and after exposure to noise varies in a simple exponential manner, and that the ultimate shift of threshold pressure for exposure to steady noise is dependent on the mean-square pressure of that noise. This response could occur if some part of the hearing mechanism were heated by exposure to noise and were at the same time subject to Newtonian cooling, and if the change in the pressure threshold were proportional to the change of temperature. This model can explain the shapes of many growth and recovery curves given in dB, why time constants found for recovery from TTS appear greater than those for growth and why threshold shifts measured on ears with elevated thresholds appear smaller than those for ears with low thresholds. Because of individual variation, averaged dB results mask the nature of the processes involved. Hence, for better understanding of TTS, individual ears should be studied separately, and, if possible, measurements should be made in rms Pa instead of dB.
Fundamental frequency characteristics of the speech of the hearing impaired
Authors: Osberger Mary Joe
Published: October 2005

The purpose of this study was to develop a quantitative description of the fundamental frequency (F0) characteristics of the speech of profoundly hearing impaired talkers. Measures of F0 were obtained on utterances spoken by 20 profoundly hearing-impaired subjects, 10 males and 10 females, 13–15 years of age, and a group of normal hearing males and females in the same age range. When compared with hearing subjects of the same sex, the hearing-impaired females tended to show greater deviancies in F0 than did the hearing-impaired males. Both hearing impaired males and females showed greater intra-group variability in F0 than was observed for the normal-hearing subjects. On the average, the F0 of stressed vowels was higher than that of unstressed vowels in the speech of both groups of hearing-impaired speakers. There were, however, large individual differences on this measure. For the majority of hearing-impaired males, the minimum F0 value within a sentence occurred on the last syllable. This pattern occurred infrequently in the speech of the hearing-impaired females. While the maximum F0 value in a sentence tended to occur on the first stressed syllable in sentences produced by the normal hearing speakers, no systematic pattern in the location of the maximum F0 value was evident in the speech of either group of deaf speakers. [Work supported by ASA F. V. Hunt Fellowship.]
Voice onset time: The development of Spanish/English distinction in normal and language disordered children
Authors: Konefal Joanne A. , Fokes Joann
Published: October 2005

Voice onset time (VET) values for the six English and Spanish stops in word initial position were measured from items spoken by Spanish speaking children who learned English as a second language. The two younger children aged four and seven had progressed normally in language development while the ten year old had a delayed onset. Spectrographs of ten tokens of each of six words in English and in Spanish were analyzed. VOT values in both languages for the younger children were significantly different. A developmental trend was noted in that the seven year old had acquired the Spanish prevoiced stops while the four year old employed the short lag range. Both had acquired the short lag range for voiceless Spanish stops. The ten year old language delayed child, however, employed the VOT values of English for the Spanish voicing categories. From the results of this study, two conclusions were made. First, there is support for a developmental pattern of VOT durations. Secondly, a child who has a language disorder may also manifest a delay in language specific acoustic parameters of speech.
Consonant clusters in children's spontaneous and imitative speech
Authors: Bond Z. S.
Published: October 2005

Although differences between a child's spontaneous speech and his imitative speech have been debated at least since the beginning of articulation testing, there is still no consensus on the issue. Some researchers suggest that the two modes of speech do not differ, since both are produced in terms of a child's own linguistic system; others argue that imitating a model calls on skills different from those employed in spontaneous speech. Furthermore, the effects of imitation may show themselves on the phonological or only on the acoustic-phonetic levels. In order to obtain further insight into the issue, consonant clusters, thought to be particularly susceptible to differences between the two speech modes [J. D. Kresheck and G. Socolofsky, “Imitative and Spontaneous Articulatory Assessment of Four-Year-Old Children,” J. Speech Hear. Res. 15, 729–733 (1972)], in young children's spontaneous and imitative speech were compared. Ten children, five two-year-olds and five three-year-olds, were recorded individually in a play situation; any spontaneously produced words beginning with an initial consonant cluster were also recorded imitatively at the end of the session. Transcription of the spontaneously and imitatively produced words showed no differences in the proportion of correct productions of clusters for either the younger or the older children; measurement of voice onset time from wideband spectrograms also gave no indication of a systematic acoustic-phonetic difference between the two modes of speech.
A finite-difference treatment of irregular interfaces for the parabolic wave equation
Authors: Lee Ding , McDaniel Suzanne T.
Published: October 2005

A finite-difference approach, introduced to handle the horizontal interface condition, is extended to treat the irregular interface condition for the parabolic wave equation. The irregular interface condition is developed to preserve the continuity of pressure as well as continuity of vertical particle velocity. The formulation of irregular interfaces is by means of a finite-difference scheme in conjunction with the Taylor series expansion while the handling of the irregular interfaces is by a line segmentation. The complete mathematical development will be outlined. The method is designed to be implicit and is conditionally stable. This treatment is extended further to handle the irregular boundary. The validity of this approach is clearly shown by the theory, however, a test example is presented as a supporting evidence. [Work supported by NAVSEA.]
A finite element method for the parabolic wave equation
Authors: Gilbert Kenneth E.
Published: October 2005

A semi-discrete elliptic wave equation is derived and used to develop a parabolic equation which allows propagation angles of up to 40° with respect to the horizontal. The derivation is based on the minimization of a Lagrangian in which the vertical dependence of the acoustic field is written explicitly in terms of finite elements and the nodal values of the pressure and vertical particle velocity. Since the resulting wave equation is in terms of continuous field variables, discontinuities in sound speed and density are easily handled. Numerical results for some simple cases are presented.
Some applications of nonlinear goal programming in acoustics
Authors: Buehler B. G.
Published: October 2005

Researchers are often required to solve problems involving multiple and conflicting nonlinear objectives. Nonlinear goal programming (NLGP) [J. P. Ignizio, J. Opl. Res. Soc. 29, 11 (1978)] is a reasonably straight forward optimization technique which the author has used to determine (post facto) the time varying geometry of a bistatic sonar experiment, to derive complex shading coefficients for acoustic arrays, to design space tapered acoustic arrays, and to design finite impulse response (FIR) filters. The purpose of this presentation is to describe some of the capabilities of NLGP and to present examples of its successful application. [Work supported by NAVSEA.]
A critical comparison of acoustic and radar sea surface backscattering
Authors: Gorman A. D. , McDaniel S. T.
Published: October 2005

Sea surface backscattering of underwater acoustical signals has long interested both acousticians and oceanographers. More recently, airborne radar measurements have been employed to study surface backscattering. We have normalized pertinent environmental and data reduction parameters to enable a meaningful comparison of acoustical and radar backscatter. Data is presented in the frequency ranges 2–5 kHz acoustical (428- and 1228-MHz radar), 15–30 kHz acoustical (4455-MHz radar), and 58–60 kHz (8910-MHz radar).
Contribution of near-surface bubbles to surface reverberation
Authors: McDaniel S. T. , Gorman A. D.
Published: October 2005

A simple model of reverberation due to near-surface bubbles is applied to compute the surface backscattering strength due to a bubble layer. Results obtained using measured bubble data are compared with experimentally measured surface reverberation for frequencies of 20–60 kHz. The computed bubble contribution is shown to provide excellent agreement with reverberation data and also to predict the saturation that occurs with increasing windspeed.
Spatial coherence computed from a plane-wave model
Authors: Field Robert L. , Morris Gerald B. , Bucker Homer P.
Published: October 2005

Spatial coherence of bottom-interacting sound is dependent on sediment properties of the bottom and the experimental geometry. The influence of two of these sediment properties, namely, compressional sound-speed gradient and attenuation on the coherence is investigated and compared with the influence of the experimental geometry. Complex plane-wave reflection coefficients, generated from a multilayered bottom model for various grazing angles, were used to synthesize frequency spectra from which spatial coherences were calculated. The coherences were computed both by ensemble averaging over a set of lossy fluid bottom and by frequency averaging over a single bottom with properties equal to the average of the ensemble. The two methods are in close agreement for those grazing angles where the cross-power spectra are sufficiently smooth. It is concluded that the general pattern of the coherence, as a function of frequency and receiver separation, is more sensitive to experimental geometry and attenuation, while the frequency band in which this pattern occurs depends on all three. [Work supported by NORDA-ONR.]
Some highlights of human and animal research on auditory fatigue
Authors: Mills J. H.
Published: October 2005

Prior to the 1960's most of the behavioral experiments on auditory fatigue (TTS, PTS) were done in the laboratory or field with human subjects. In 1963 a lengthy monograph appeared [J. D. Miller, C. S. Watson, and W. Covell, “Deafening Effects of Noise on the Cat,” Acta Oto-Laryngol. Suppl. (1963)] and indicated, among other things, that many of the scientific issues could only be resolved by research with animals and with cooperation among the field of psychology, anatomy, and physiology. Thus the stage was set in the mid 1960's for coordinated studies on the behavioral, anatomical, and physiological effects of exposure to noise. What are the most significant outcomes of these animal experiments and what have they revealed about the human animal? While the list of dividends is large and no doubt controversial, the focus here is restricted to striking similarities in regard to TTS and PTS; recovery in humans and animals, the correspondence between recovery and some anatomical and physiological data; and lastly, some examples of psychophysical and physiological data which question the utility of the audiogram in detecting alterations of the inner ear. [Work supported by NIEHS.]
Further evaluation of the effects of training, head movement, elevation, and azimuth on sound localization in monaural and binaural humans
Authors: Russell Paul J. , Gatehouse R. Wayne
Published: October 2005

The effects of (a) pretest training (two levels: Training, no-training), (b) stimulus elevation (0, ± 30°), (c) stimulus azimuthal angle (30, 60, 90 … 0°), and (d) head movement (head rotate, head fixed) on the accuracy of monaural versus binaural directional hearing were examined using 72 university students tested in a mixed design experiment having stimulus azimuthal angle and head movement as the within-block treatments. The blindfolded subject sitting at the center of a clock face marked out on the floor of a sound-proofed room was required to verbally indicate using the clock numbers the direction of a 2-s pulsed white noise stimulus. Analyses revealed three, three-factor interactions and one, four-factor interaction,with one of the main results being the following: On their occluded side, untrained and head fixed monaural listeners were clearly inferior to binaurals; whereas, on their nonoccluded side their performance often matched that of binaurals. The implications of these interactions for the manipulation of variables and for the design of localization studies will be discussed.
Factors influencing the temporal integration of threshold and suprathreshold signals
Authors: Ahaus W. H. , Million P. C.
Published: October 2005

A study was conducted to explore the effects of frequency, method, and level on temporal integration both at and above threshold. Listeners' thresholds were measured at three frequencies (250, 500, and 4000 Hz) using two methods (tracking and 2 IFC adaptive procedure), for duration of 20, 80, and 640 ms. Employing the same frequencies and signal durations, loudness-balance data were obtained from the same group of listeners at 40 and 70 dB SPL using two different loudness balance methods (a method of adjustment and an adaptive procedure). Major findings were (1) threshold integration varied inversely with frequency, particularly for the tracking procedure; (2) temporal loudness summation varied inversely with level for both methods with little difference in integration values as a function of frequency; and (3) no one method emerged superior with respect to variability at either threshold or suprathreshold. [Work supported by the Veterans Administration.]
Psychophysical tuning curves in normal-hearing and hearing-impaired listeners: Effects of masker duration
Authors: Mason C. R. , Kidd G. , Feth L. L. , Corban M. A. , Binnie C. A. , Carney A. E. , Cooper W. A.
Published: October 2005

Psychophysical tuning curves (PTCs) were obtained from listeners exhibiting moderate-to-severe sensori-neural hearing impairments. These PTCs were measured in a forward masking paradigm with a 300-ms masker followed by a 20-ms probe tone at 10 dB SL with a delay of 10 ms. As expected, for these hearing-impaired subjects the PTCs were broader than comparable measures (equal sensation levels) in normal-hearing listeners. For one subject the PTC was essentially flat and fell below the probe presentation level. Given the intensity levels necessary to attempt these measurements and the possibility that these listeners exhibited recruitment (abnormal growth of loudness), it was thought that reducing the masker duration to 35 ms would reduce the loudness sufficiently to permit the determination of frequency selectivity. PTCs for brief maskers were also obtained for a group of normal-hearing listeners. Comparisons will be made between normal and hearing-impaired listeners for both long and short duration maskers. In addition, estimates of temporal integration in these two groups will be presented. Discussion will center on the summation of energy in forward masking. [Supported by a contract and grants from NINCDS.]
Subaudible tones and the pulsation threshold procedure
Authors: Ayres Thomas J. , Papsin Blake C. , Clack T. Dean
Published: October 2005

A pulsing, audible maskee at a low sensation level appears to stay on continuously when the interruptions are filled by a pulsed masker at a different frequency. The perceptual continuity of the maskee changes to discontinuity when its intensity is raised above its “pulsation threshold.” In this study, an additional tone with the same frequency as the maskee (800 Hz) was presented with the masker (500 Hz). The added tone had the effect of raising the pulsation threshold only when this tone was presented above its masked threshold. Thus the pulsation threshold procedure cannot be used to detect the presence of a masked subaudible tone. An important implication is that contrary to recent applications the existence and characteristics of inaudible subjective tones cannot be studied with this method. [Work supported by NIH and the Department of Otorhinolaryngology, University of Michigan Medical School.]
Intrinsic tongue musculature: Apical retraction for vowels and velar stop consonants
Authors: Zerling J. P.
Published: October 2005

Cine-x-ray lateral views of the vocal-tract and corresponding acoustic data were analysed for symmetric [əCVC] utterances combining vowels [i, ε, a, ɔ, u] and stop consonants [b, d, g] for 2 French speakers. Previously published data was also searched for confirmation. Data reveal that vowels may be divided into 2 groups according to extrinsic muscular activity. Also, apical shape, which depends on intrinsic muscles, proves to be flat for vowels [i, ε, a] and retracted for [u] and [ɔ]. Apical shape categorization strongly affects the articulation of velar slops and their transitions. During [Vɡ] transitions, there is no motor activity for the tongue tip: its position is always pointing downwards. During [ɡV] transitions, motor control is observed: Apical shape of following vowel is anticipated. Consequently, [ɡV] transitions for vowels between [i] and [a] are the only ones using a flat apical shape. All other transitions use a low or retracted apical position. These articulatory phenomena may explain several acoustical peculiarities: In [ɡV] utterances, second formant transitions start from a locus placed before the vowel for vowels between [i] and [a], whereas they seem to converge towards a virtual locus located in the vowel for vowels [u] and [ɔ]. Also, third formant onset and offset frequencies are generally lower than vowel formant frequencies, but this is not true if velar stop is followed by vowels between [i] and [a].
Initial acoustic analysis of Exercise CAPER
Authors: Pedersen Melvin A. , Hosmer Rawson F.
Published: October 2005

The principal objective of Exercise CAPER was to measure the interference of cw sound signals caused by a well-surveyed isolated seamount (Stoddard Seamount). The planning phase of the exercise is addressed as well as three major areas of analysis. The first area is the convolution of ray diagrams with bathymetry to delineate the shadow zones behind the seamount. The major effect of the seamount is to intercept the leading portion of the convergence zones. The second area is a comparison of acoustic and satellite navigation ranges. Comparison of differences between 52 pairs of acoustic and satellite ranges showed a mean difference of 117 m with a standard deviation of 272 m. The third area is to asesss the effect of range-dependent sound-speed profiles. Propagation involved four distinct near-surface water masses. These range-dependent profiles produced a range difference of as much as 13.2 km in the eighth convergence zone when compared to a single range-independent profile.
Acoustic shadowing and reflections from Stoddard Seamount, Northeast Pacific
Authors: Morris Gerald B. , Fincke William B.
Published: October 2005

Acoustic propagation experiments at 104 Hz were made over Stoddard Seamount, about 800 km west of Los Angeles, to measure experimentally the interference of cw signals from a well-surveyed seamount. The receiver station was the Research Platform FLIP which was placed in a three-point moor about 220 km from the seamount peak. Four groups of hydrophones were deployed beneath FLIP at depths ranging from 94 m below the surface to within 140 m of the ocean bottom. The geometry of the experiment was such that for the source depth of 122 m, the convergence zones for the deeper hydrophones were shadowed by the seamount. However, the geometric shadowing had little effect on the level of signals in the bottom bounce range intervals between the convergence zones, Doppler-shifted bottom reflections were observed when the source was approximately 15 km in front of the seamount. The levels of this doppler shifted reflection reached maximum values which were from 5–10 dB below comparable convergence zone signals.
Extension of acoustic levitation to the measurement of the properties of micron-size particles
Authors: Weiser M. A. , Apfel R. E.
Published: October 2005

In the past, acoustic levitation has been used to measure the mechanical properties of millimeter diameter liquid samples in a less compressible host liquid [R. E. Apfel, J. Acoust. Soc. Am. 59, 339 (1976)]. The application of this technique has been extended to include levitation of samples consisting of a large number of micronsize particles (e.g., emulsions and red blood cells} in a more compressible host liquid. Modification of the previous technique to accommodate this new class of materials involved apparatus changes as well as greater attention to terms previously neglected in the theory describing the forces acting on a compressible sphere in a standing wave field. The adiabatic compressibility of a sample consisting of a large number of micron-size droplets of a pure liquid (hexane) was measured using this technique. The results were within 4%–5% of that obtained using a traditional technique. The technique was also used to measure red blood cell compressibility, and results were within 1% of that deduced from measurements of the sound velocity in a suspension of red cells. [Work supported by NIH.]
Nearfield acoustic radiation from spherical shells
Authors: Wong Edmond H. , Hayek Sabih I.
Published: October 2005

In this study, the acoustic nearfield of excited spherical shells is investigated. The interaction of the acoustic medium with the vibration response of an elastic spherical shell due to an excitation by a point force or an acoustic point source is investigated analytically and experimentally. Thus, only axisymmetric, nontorsional motion of the spherical shell is considered, with a thin shell theory that includes extensional and bending deformation. The elastic spherical shell resonances were computed when in vacuo and when submerged in light (air) and heavy (water) acoustic medium. These were verified experimentally by testing two duralumin shells, a = 8 in. in radius and wall thicknesses h = 0.0514 and 0.1069 in. The measured resonance frequencies were within 5% of those predicted in air and in water for identified mode numbers up to 34. The measured mean-line driving point admittance also agreed well with the predicted ones to within 3 dB. [Work supported by NAVSEA.]
Sound pressure in air from a source in water for the case of a directional spherical wave
Authors: Mikeska E. E. , Shooter I. A.
Published: October 2005

An upward looking 11-in. circular piston source in water was used to obtain a series of pressure measurements in air and water for the frequency range of 15–40 kHz. Transmission across the air-water interface showed the expected loss of 65.4 dB ± 0.5 dB for local conditions of temperature and barometric pressure. Horizontal scans across the acoustic axis showed that the beam pattern of the circular piston could be faithfully reproduced in air as well as in water. However, measurements along the acoustic axis in air departed significantly from the predictions of geometric acoustics. These results will be compared with a numerical solution of the Helmholtz equation for a distribution of sources along the surface of the water. [Work Supported by Office of Naval Research.]
Interaction between two gratings of compliant tubes
Authors: Radlinski R. P.
Published: October 2005

Multiple scattering effects for a normally incident plane wave on two gratings of high aspect ratio compliant tubes were studied both experimentally and analytically by varying the distance between the layers of tubes. The even-even modes of the tubes were modeled as two clamped beams and the end conditions chosen for the even-odd beam modes were zero slope and zero transversed force. Combinations of single gratings of various grating spacings and tube characteristics were considered. For relatively large separation distances between gratings, only the compliant even-even structural modes are strongly excited and broadband transmission loss can be achieved. As the separation distance is decreased, the pressure field in the nearfield of the tubes is less uniform and the noncompliant even-odd modes may be excited. The net result of the nearfield interaction tends to severely modify broadband performance. Optimal tube characteristics for maximum transmission with two gratings are discussed. Comparisons of theory and experiments are presented. [Work supported by NAVSEA.]
Spontaneous activity and signal processing in the cochlear nerve of kittens
Authors: Romand R. , Dauzat M.
Published: October 2005

The activity of the auditory nerve was studied in kittens during the first postnatal month. At two days, fibers possessed minimal or no spontaneous activity. At 10 days, most fibers demonstrated mean resting rates below 10 sp/s. Although the subsequent number of high resting rate fibers increased, average fiber activity had still not reached adult levels at one month. The majority of rate-intensity functions studied at characteristic frequency for the 6-day-old kitten has a triangular shape showed rapidly increasing then decreasing spike rates. Between 10–15 days, some fibers reached an adult-like stage while others continued to vary. The adult stage for most fibers was reached between the third and fourth week. The rate-intensity function was found to correlate with frequency selectivity. Prior to day 10 low and mid frequencies demonstrated a reduced dynamic range, and the rise and fall of the intensity curve reflected poor frequency selectivity of the tuning curves. In the days that followed, frequency selectivity was more adult-like with intensity values approaching normal.