bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic origins of individual differences in sound localization behavior
Authors: Wenzel Elizabeth , Wightman Frederic , Kistler Doris , Foster Scott
Published: October 2005

Human listeners vary widely in their ability to localize unfamiliar sounds in an environment devoid of visual cues. Our research, in which blindfolded listeners give numerical estimates of apparent source azimuth and elevation, suggests that individual differences are greatest in judgments of source elevation; listeners are uniformly accurate when judging source azimuth. The pattern of individual differences is the same for free-field sources and for simulated free-field sources presented over head-phones. Simulated free-field sources are produced by digital filtering techniques which incorporate the listener-specific, direction-dependent acoustic effects of the outer ears. Two features of this data bear on the question of the origin of individual differences in elevation accuracy: (1) a listener's accuracy in judging source elevation can be predicted from an analysis of the acoustic characteristics of the listener's outer ears; (2) the pattern of elevation errors made by one listener (A) can be transferred to another listener (B) by presenting to listener B the simulated free-field sources derived from the outer-ear acoustics of listener A. Thus it is believed that many of the individual differences in localization behavior are traceable to individual differences in outer-ear acoustics. The data have important implications for the study of localization in both basic and applied contexts. [Work supported by NASA, NSF, and USAF-AAMRL-AFSC.]
Prefiltering method for a head-related stereophonic system
Authors: Mizuuchi Takayuki , Okabe Kaoru , Hamada Hareo , Miura Tanetoshi
Published: October 2005

The prefiltering scheme of the usual head-related stereophonic system using two loudspeakers for reproduction [M. R. Schroeder et al., J. Acoust. Soc. Am. 56, 1195 (1974)] was modified. In addition to the usual filtering scheme, an additional filtering stage is introduced that converted the frontal incident characteristics of the dummy head into those for individual listeners. Using this filtering scheme, the exact reproduction of the frontal sound image becomes possible, which is difficult when the sound recorded through a dummy head is played back. The ability of this modified system to reproduce the original sound localization by a listening test in an anechoic chamber is evaluated. In the test, both the conventional scheme and the new one were evaluated. As a result, the localization of the frontal sound image was reproduced exactly using the new system, and the conventional system failed in this reproduction. It was also confirmed that sound from other directions in the three-dimensional space was almost perfectly reproduced using the new system.
Nonlinearity in sound beams, with application to the scattering of sound by sound
Authors: Tjøtta Jacqueline Naze , Tjøtta Sigve
Published: October 2005

This paper addresses the fundamental theory of nonlinear acoustics in a thermoviscous fluid. Emphasis is given to the combined effects of nonlinearity, absorption, and diffraction in sound beams. An overview is presented of the various mathematical models used for the propagation of a high-intensity sound beam, with a discussion of their range of validity. Some examples of nonlinear effects in a sound beam are shown. Nonlinear interaction between two real sound beams is also considered. The sources may possess arbitrary phase and amplitude shading, and different sizes and orientations. The obtained results are related to earlier works on the scattering of sound by sound, which are discussed. [Work supported by the IR&D program of ARL:UT, and VISTA/STATOIL, Norway.]
New measurement techniques developed on the basis of nonlinear acoustics
Authors: Sato Takuso
Published: October 2005

When nonlinear interactions between a medium and acoustic waves are used in addition to linear interactions, two main directions can be expected in the development of new measurement techniques: (i) the extraction of new characteristics of the medium, and (ii) the construction of completely new or more compact measuring systems. In this paper, a few applications are shown of nonlinear acoustics, picked up from a method based on the use of impulsive and high-pressure pumping waves to generate the required nonlinear effects and high-frequency, small amplitude continuous probing waves to detect the results. The applications include (i) measurements of gas flow velocity and temperature distributions, (ii) nondestructive measurement of the stress distribution in metals, and (iii) imaging of dynamic characteristics, including the nonlinear parameter of soft tissues as a new means of medical diagnosis. The exact construction of each system and the corresponding experimental results are shown in detail.
Theoretical approach to the virtual source based on the distortion in finite-amplitude waves
Authors: Watanabe Yoshiaki , Tsuchiya Takao , Urabe Yasumasa
Published: October 2005

An analytical approach is presented to derive the intensity of a virtual source from the viewpoint of the distortion in the finite-amplitude wave. The distortion in the arbitrary waveform over a small distance is discussed in connection with the local sound velocity which depends on the local particle velocity. From the variation in the particle velocity due to the waveform distortion, the intensity of the virtual source is derived. It is dearly shown that the virtual source can be derived using only distortion in the time domain. The present analytical approach will be useful in understanding phenomena of nonlinear acoustics.
Utilization of spatially correlated auditory information in localization of visual targets
Authors: Saberi Kourosh , Perrott David R. , Pacheco Sandra M.
Published: October 2005

Facilitation of a visual search task through presentation of spatially correlated and uncorrelated binaural and monaural cues was determined for five subjects using a two-alternative, forced-choice paradigm. Trains of 10-ms clicks were spatially correlated with a visual target (0.496° visual angle) randomly located in a ±120° azimuth ±46° vertical spherical visual field and presented to subjects in two conditions (0°, ±46° vertical). Visual search time was also determined for monaural conditions in the ±46° vertical ±120° azimuth paradigm. Results indicate a dramatic reduction in search time for spatially correlated cues from approximately 15% at 0° to 40% at ±120° azimuth in the 0° elevated condition, and from 35% at 0° to 50% at ±120° azimuth in the ±46° elevated condition. The search time function for the monaural condition is surprisingly more similar to that of the spatially correlated binaural one, particularly in the center regions. Data indicate that loss of search time at the periphery in the uncorrelated condition is mostly due to the search strategy employed and not head movement delays. Practical implications will be discussed. [Work supported by NSF and NIH.]
Minimum audible movement angle thresholds for broadband noise: Effects of the initial location of the source
Authors: Perrott David R. , Manligas Carol L. , Pacheco Sandra
Published: October 2005

Minimum audible movement angle (MAMA) thresholds were determined for a source producing a broadband noise (500–8000 Hz) moving at a constant angular velocity (20°/s). Nine regions of the field were sampled: 0°, 10°, 20°, 40°, and 80° to the subject's right and left. In agreement with earlier research that employed either static sources or “simulated motion,” acuity was best when the source was at 0° azimuth (1.1°) and poorest at the most lateral position (3.1°–3.5°). The ability to detect motion of a source emitting a broadband noise is clearly superior to performance obtained with tonal signals whether the latter paradigms include “actual” or “simulated” motion. In the more extreme lateral regions of the field, performance was actually better than that previously reported under static localization conditions. Vertical azimuths, ranging from 0°–87.5°, were also examined. Detection of motion was relatively insensitive to this latter parameter. [Work supported by NSF and NIH.]
Rotating tones and minimum audible movement angle
Authors: Perrott David R. , Meier B.
Published: October 2005

Minimum audible movement angle (MAMA) thresholds were determined for four subjects using a two-alternative, forced-choice adaptive paradigm. The motion was simulated by presenting a 200 to 1500-Hz tone (f0) to one ear and a second tone (f0) of a different frequency to the other ear. With interaural frequency differences (IFD) of 0.5 Hz, and f0 at or below 600 Hz, MAMA thresholds ranged between 10°–15°. Additional tests conducted in this frequency region indicate that the continuous shifts in phase generated by small IFDs produce performance in excellent agreement with those obtained in free-field localization tasks in which real and simulated motion has been considered. However, thresholds increase very rapidly at higher frequencies (e.g., MAMA exceeds 80° with an f0 of 850 Hz). There appears to be little agreement between the current “dichotic” rotating tone paradigm and other motion discrimination functions at these higher frequencies. The implications of these results will be discussed. [Work supported by NSF and NIH.]
Click lateralization by multiple sclerosis patients
Authors: Furst Miriam , Eyal Sara , Korczyn Amos D.
Published: October 2005

Lateralization of dichotic clicks can be tested with gradually increasing interaural level differences (ILD) and interaural time differences (ITD). However, the lateralization of dichotic clicks with ITD is limited to small ITDS only (< 1 ms). The ability to lateralize dichotic clicks was tested in multiple sclerosis (MS) patients with normal audiograms. Two kinds of psychoacoustical experiments were employed: (1) a matching experiment in which the subject was asked to match the perceived positions of two click trains, where one included dichotic clicks with ILD and the other included dichotic clicks with ITD; (2) a positional jnd experiment in which the subject was asked to determine the difference in position of two successive click trains. Two reference positions were tested, the head center (ITD = 0 and ILD = 0) and midway between the center and the ear (ITD = 0.8 ms and ILD = 0 or ILD = 20 dB and ITD = 0). For each reference the experiment was performed first with control on ITD and then with control on ILD. From a group of 15 MS patients, seven performed poorly in the positional jnd experiment when the control was on ITD, and normally when the control was on ILD. Those subjects also reported that the position of each dichotic click with ITD < 1 ms was perceived at the head center, and, therefore, they had difficulties in performing the matching experiment. Brainstem auditory potentials (BAP) evoked by dichotic clicks with different ILDs and ITDs were measured in all the above MS patients. Principal component analysis of the measured waveforms indicates an abnormal behavior as a function of ITD in patients who performed abnormally in the psychoacoustical experiments. The anaylsis of the waveforms of all patients as a function of ILD resembles the normal behavior.
Various laryngeal mechanisms in controlling the voice fundamental frequency
Authors: Honda Kiyoshi
Published: October 2005

It is generally believed that the muscular control for the voice fundamental frequency (F0) is performed mainly by the cricothyroid. However, it has been noted in several studies that the whole F0 range produced by humans cannot be obtained by cricothyroid activity alone. This study reports variations in the EMG activity of some laryngeal muscles associated with F0 variations in word utterances and the speculated mechanisms of FO control by these muscles. First, the cricopharyngeus (CP) exhibits an inverse correlation with F0, suggesting that this muscle can rotate the cricoid cartilage inversely. Second, the lateral cricoarytenoid (LCA) shows the highest correlation with F0, indicating its function in adjusting the effective length of the vocal fold vibration. Third, the oblique part of the cricothyroid (CT) has a higher correlation with F0 than the rectal part, and it is speculated that the rectal part produces the fast F0 change associated with laryngeal articulation and that the oblique part functions to expand the F0 range independently of articulatory gestures. These speculated mechanisms explain the observed nonlinear relation between vocal fold length and F0. [A part of this work was done at Haskins Laboratories, New Haven, CT.]
Gestural aggregation in speech
Authors: Munhall Kevin , Löfqvist Anders
Published: October 2005

It is well known that the units of speech are not produced strictly sequentially but overlap with each other; this phenomenon has been referred to as coarticulation, coproduction, or blending. Thus the vocal tract shape at any one time during speech represents an aggregate of gestures associated with different production units. The present experiment examines one intra-articulator example of temporal overlap, namely, the combination of successive opening and closing gestures in the larynx. Two subjects produced the utterance “Kiss Ted” at several different speaking rates and with stress on the first or second word. Laryngeal abduction-adduction was monitored using transillumination and fiberoptic video recording. At slow rates, two separate opening gestures occur associated with the fricative and the stop, respectively. At fast rates, a single smooth gesture is seen. At intermediate rates, partially overlapping gestures are found. These findings suggest that the two underlying gestures are being blended into a single aggregate and that the aggregation operation may be some type of summation. It is hypothesized that blending of overlapping gestures is a general phenomenon in speech production that accounts for commonly observed types of coarticulation. [Work supported by NINCDS Grants NS-13617 and NS-13870 to Haskins Laboratories.]
A model for neurologic sources of vocal instability
Authors: Titze Ingo R.
Published: October 2005

The activation and relaxation characteristis of thyroarytenoid and cricothyroid muscle twitches are used as basic building blocks to simulate a tetanic contraction in the laryngeal muscles. Approximately 100 motor units are used with random phase relationships and randomized firing rates. The fundamental frequency of the voice is calculated from the simulated tensions, and it is shown that jitter and shimmer vary inversely with mean motor unit firing rate and with the number of motor units within a given muscle. Jitter and shimmer vary directly with the coefficient of variation of motor unit size. Some low-frequency variations in F0 (tremor-like variation) are correlated with the mean firing rate of large single motor units. [Work supported by NINCDS Grant No. NS24409–02.]
Prosodic changes in speech following brain damage: Acoustic and neuroradiographic measures
Authors: Lancker D. Van , Hanson W. , Jackson C. , Lanto A. , Metter E. J. , Cummings J.
Published: October 2005

Two prosodic parameters, fundamental frequency (F0) and intensity, along with a measure of vowel duration, were studied in 11 Broca, 7 Wernicke, 15 Parkinson, and 15 normal-control subjects performing four speech tasks: reading, counting, conversation, and vowel prolongation. Tape-recorded speech samples were played into a microprocessor controlled speech analyzer (PM 301 Voice Identification, Inc.), where F0 in Hertz and intensity in relative decibels were calculated. Measures of mean F0 and F0 variability, mean intensity and intensity variability, and duration of the prolonged vowel were analyzed. Values differed across speech tasks: Overall, F0 and intensity values were higher in reading than in the other three tasks. Further, a significant group by task interaction was found for mean F0. Broca and Parkinson patient groups had abnormally high F0 mean values, but differed from each other in F0 variability (Broca having high and Parkinson having low F0 variability) and mean intensity; surprisingly, the Broca group had intensity values significantly lower than the other groups. All three clinical groups differed significantly from normals on the duration measure. Examination of PET and CT-scan data in individual patients indicated an association between prosodic impairments and specific frontosubcortical dysfunction, areas subserving motor abilities in speech production.
Perturbation functions and measures: A theoretical study
Authors: Pinto Neal B. , Titze Ingo R.
Published: October 2005

Acoustic analyses of the human voice have been developed to assist in clinical screening of laryngeal pathology. It is hypothesized that perturbation functions derived from parameters measured from the acoustic signal might reflect phonational irregularities due to randomness in the action potentials governing muscle tension, asymmetry in vocal fold geometry, randomness in the air stream from the glottis, interactions between source and tract, and other, as yet unknown, factors. A set of measures computed from these perturbation functions could provide a quantitative description of vocal fold pathology. Unfortunately, many perturbation measures in use today were defined in an ad hoc fashion, with little attention paid to comparatively assessing proposed measures against existing measures. This paper represents an attempt to put the study of voice perturbations on a sounder theoretical footing. Utilizing theories of finite differences and subsampling, algorithms have been developed to aid in discriminating between perturbations based on duration of ocurrence as well as the type of perturbation, i.e., random or periodic. The measures obtained are independent, one reflecting short-term periodic perturbations, another short-term noiselike perturbations, etc. By theoretical and experimental work, we hope eventually to tie these measures in to conditions at the glottis. [Work supported by NIH.]
Discriminant analysis of voices with and without hoarseness
Authors: Kikuchi Yoshinobu , Kasuya Hideki
Published: October 2005

In order to realize an objective method for evaluating hoarse voice, the relationships between various acoustic parameters and hoarseness grade as judged perceptually by a laryngologist were analyzed. The acoustic parameters included perturbations in pitch period and peak amplitude, the intensity of the turbulent noise produced at the glottis, and the intensity level difference between the high- and low-frequency regions. These parameters were measured from vowel samples uttered by more than 2000 speakers and were subjected to the correlation and discriminant analyses. It has been found that the relative level of vocal noise in a selected frequency band agrees best with perceptual judgments. Furthermore, an error rate of 16% was obtained in discriminating between normal and hoarse voices using all of the above parameters. With carefully recorded vowel samples, however, the error rate was reduced to only 8%.
Oral and glottal gestures and acoustics of underlying /t/ in English
Authors: Manuel Sharon Y. , Vatikiotis-Bateson Eric
Published: October 2005

In English, an underlying /t/ can be produced in various ways. The glottal gestures may involve glottal attack (glottal stop), spreading, or voicing. The oral gestures may include complete or incomplete alveolar closure; or, in the case of place assimilation (e.g., “notebook” surfacing as [nowpbUk]), they may entail another oral gesture. Thus some surface variation is due to the particular gestures used. However, since the relative timing of glottal and oral gestures may effectively preclude acoustic realization of some of them, the acoustic record alone may not reveal just which gestures have actually been produced, and in what order. Therefore, some perceived variation may be due to differences in timing and relative strength of articulatory gestures, rather than changes in the set of gestures. This investigation of alveolar stops of two talkers focuses in particular on the occurrence of glottalized /t/ and shows differences in articulatory patterning depending on talker, speaking style, and phonetic context. Data are based on electropalatography, transglottal illumination, fiberoptic video of the larynx, oral air pressure, and acoustic measures. [Work supported by NINCDS grants to MIT and to Haskins Laboratories.]
Cycle to cycle spectral perturbations in the voices of male and female speakers
Authors: Yonovitz A. , Yonovitz L.
Published: October 2005

The glottal function was obtained through the use of a reflectionless tube. This tube acted as a pseudoinfinite termination of the vocal tract. Male and female speakers phonated a neutral vowel while target matching to a 125- and a 210-Hz tone, respectively. The glottal waveform was digitized at 40k samples/s and each cycle was partitioned at zero crossings. This procedure provided an accurate determination of the period of each glottal pulse. Discrete Fourier analysis on each individual cycle indicated changes in the spectral content. The amplitude and phase of the first ten harmonics were utilized to obtain separate perturbation values as well as an overall amplitude measure. The data showed a systematic change in the spectral character of the sustained vowel source signal. Spectral perturbation analaysis may be a more inclusive measure of waveshape changes than jitter or shimmer.
Voice source variations during consonant-vowel transitions
Authors: Löfqvist Anders , McGowan Richard S.
Published: October 2005

Studies of the voice source during speech have been concerned mostly with variations in fundamental frequency and amplitude. However, the source variations also comprise the spectral characteristics and the harmonics-to-noise ratio. The present study reports detailed measurements of voice source properties during transitions between consonants and vowels. Oral air flow, oral air pressure, and transillumination were recorded from two subjects producing reiterant speech with the vowel /æ/ and different voiced and voiceless consonants; the flow signal was inverse-filtered to obtain an estimate of the glottal pulse. Results indicate a breathy phonation at the release of voiceless consonants as indicated by an open quotient close to 1. Peak flow during each glottal pulse is thus high at voicing onset following a voiceless consonant and decreases, with an undershoot, during the first 20 pitch periods. The source pulse is also skewed to the left during the first pitch periods following voiceless consonants. Source variations following voiced consonants are less pronounced. [Work supported by NINCDS Grants NS-13617 to Haskins Laboratories.]
Prospects for studying and interpreting wave processes induced by inhomogeneities in shells using wave-vector filtering
Authors: Pierce Allan D.
Published: October 2005

Wave-vector filtering allows one to isolate particular wave processes in situ when a complex structure is in a random and intricate state of vibration. The probability of success and the scientific and engineering values of such an achievement strongly depend, however, on a prior knowledge of what processes are likely and of the underlying physical principles. The present paper discusses processes observable on inhomogeneous structures that, for the most part, resemble thin-walled cylindrical elastic shells. In the absence of inhomogeneities, the basic shell equations are wave-field equations for a two-dimensional anisotropic and dispersive medium. At the frequencies of interest, longitudinal, shear (transverse), and flexural wave-types are all slightly modified by the finite radius of curvature of the shell. Inhomogeneities are characterized by finite regions where the shell's physical properties differ significantly from the “ambient,” or by lumped parameter quantities (such as added mass) at discrete points or along lines. In general, an incoming wave of any one type at an inhomogeneity will excite outgoing waves of all three types. At line inhomogeneities, the outgoing waves will correspond to a version of the trace velocity matching principle. Wave-vector filtering measurements in conjunction with a knowledge of the physics underlying the wave processes should allow one to indirectly infer gross properties of inhomogeneities. Energy accountancy principles, for example, enable one to determine the energy dissipation rate at an inhomogeneity. [Work supported by ONR.]
Time varying wavenumber-frequency spectra
Authors: Clark Joseph A. , Feit David
Published: October 2005

Under conditions of transient excitation, displays of time varying spectra can reveal significant space-time features of structural response as well as stationary wavenumber-frequency features. An example obtained from an investigation of wave propagation on a ribbed, cylindrical steel structure will be presented in this talk. The structure was immersed in water, and a hydrophone array was employed to measure responses to impulsive loading at 4096 points on a surface around the structure. A series of wavenumber-frequency plots were generated by transform processing selected temporal portions of the time-space data. The transformed data can be viewed either as veritcal layers of 2-D surfaces or as a motion picture of a single wavenumber/frequency surface. The displays of time varying spectra have been found useful as tools for analyzing the growth and decay of modes propagating along the structure as well as the coupling between modes.
Statistical reliability of wavenumber spectrum estimates with crossed-line multiplicative arrays
Authors: Berkman Frank , Martin Nathan , Korff Dale
Published: October 2005

In a previous paper [J. Acoust. Soc. Am. Suppl. 164, S124, (1978)], it was shown that in a spatially homogeneous noise field the mean response of a multiplicatively processed pair of crossed-line arrays with apertures 2L1 and 2L2 and appropriate shading is identical to the mean-squared response of a rectangular, separably shaded planar array with aperture L1 × L2. Thus the number of elements required for wavenumber spectrum measurement may be considerably reduced (from N2 to 4N for a square array) or the wavenumber resolution may be significantly increased for the same number of elements by the use of multiplicative crossed-line arrays. However, there is an additional trade-off of statistical reliability of the measurement for finite averaging time. This paper compares the variance of the wavenumber spectrum estimate obtained with rectangular planar arrays and with crossed-line multiplicative arrays.
Role of spectral derivatives of structure reactance in vibration problems
Authors: Chandiramani K. L.
Published: October 2005

Energy density and energy flux of resonant vibration of fluid-loaded structures are expressed in terms of spectral derivatives (i.e., derivatives with respect to frequency ω and wavenumber k) of structure surface wave reactance X. Two methods of derivation are presented: (1) Whitham's variational method is used after time-averaged Lagrangian density is expressed in terms of the structure teacrance X; (2) Pole contributions to structure transfer line admittance are evaluated. For small dissipation, both methods yield identical formulas for spatial and temporal decay rates of resonant vibration. Both methods are also capable of extensions that enable consideration of instabilities resulting from the presence of a uniformly moving fluid adjacent to the structure. [Work supported by the Office of Naval Research.]
Computational results using FOR3D and an analytic eddy model
Authors: Scully-Power P. D. , Lee D. , Botseas G. , Siegmann W. L.
Published: October 2005

A three-dimensional parabolic approximation model FOR3D has been developed. Its validity has been verified by means of test examples and comparisons. The present implementation of the model has some desirable capabilities, and additional useful ones are under development. A primary advantage of the model is the availability of treating azimuthal coupling. The FOR3D has been used to process environmental data obtained from ocean prediction models. In this report, an FOR3D is used to examine acoustic propagation through a parametric eddy model. Computational results will be presented, and issues relating to three-dimensional effects will be discussed. [Work supported jointly by NUSC and ONR.]
A marching-frame, finite-element, range-dependent, ocean acoustic propagation and scattering model for long-range acoustic propagation simulation
Authors: Murphy Joseph E. , Chin-Bing Stanley A.
Published: October 2005

The ocean acoustic propagation and scattering simulation model based on the finite-element method [J. E. Murphy and S. A. Chin-Bing, Math. Comput. Modeling 11, 70–74 (1988)] has been extended to long ranges using a marching-frame approach. This F_inite-element, F_ull-wave R_ange-dependent, A_coustic M_arching E_lement (FFRAME) model has the advantage of a forward marching model (similar to the marching algorithms of parabolic equation models) while allowing that within each elemental frame the computed pressure field is full wave and range dependent. Successive flames are coupled by imposing the pressures from the right-hand side of the Nth frame onto the corresponding nodes on the left-hand side of the (N + 1)th frame. The size of each elemental frame can be adjusted to include all of the significant effects due to full-wave propagation and scattering within that frame. Thus the forward propagating field between elemental frames correctly includes the losses due to backscatter. Numerical examples are presented that illustrate the advantage of the FFRAME model over conventional one-way ocean acoustic propagation models. [Work supported by ONR and NORDA.]
Measurement of the nonlinearity parameter B/A using the pulse-echo technique
Authors: Akiyama Iwaki , Nakajima Masato , Yuta Shin'ichi
Published: October 2005

A method for the measurement of the nonlinearity parameter B/A in biological tissues using the pulse-echo technique was studied. Since a finite-amplitude method is valid for the measurement of B/A in biological tissues, the values of B/A have been experimentally measured in vitro for several biological tissues. For medical applications it is necessary to have in vivo measurements, and thus it is desirable to use the pulse-echo technique. In this study, the second harmonic component of the echo signal was analyzed, and then it is shown that the rate of increase of the second-harmonic components with respect to time provides the value of B/A. This rate is, however, influenced by the attenuation coefficient and the reflection coefficient in biological tissues. In order to eliminate these effects, another pulse was used whose center frequency was twice as high as that of the former pulse. Also, the ratio of the second harmonic component of the echo signal of the former pulse and the fundamental component of the echo signal of the latter pulse is calculated. The value of B/A was determined by the rate of increase of the resulting quantity. The experiments were conducted to verify the feasibility of this technique, and the resulting values were in agreement with values from the literature.
Complex ray methods for flat and sloping waveguides
Authors: Westwood Evan K.
Published: October 2005

The problem of the interaction of a spherical wave at a plane, penetrable interface is solved in terms of ray quantities by using the saddle point method. When the plane-wave reflection and transmission coefficients are allowed to influence the saddle point criterion, the saddle points become complex, in general. As a results, the reflected lateral wave field and the transmitted evanescent field are included in this formulation. This method for solving the single interface problem is extended in a straightforward manner to the flat waveguide (the Pekeris model) and the penetrable wedge. In both cases, the total field is expressed as a sum of ray fields. For the flat waveguide, comparisons show nearly perfect agreement between the ray model and the SAFARI model at all ranges. In contrast, the discrete normal mode solution is incorrect (1) at short ranges in all cases, and (2) at all ranges when a mode is near cutoff. For the wedge problem, comparisons between the ray model and a two-way coupled mode model show close agreement. The interesting phenomenon of multiple lateral waves in a wedge will be discussed. [Work supported by Office of Naval Research Contract N00014-87-K-0346.]
Chaotic wave propagation in random media
Authors: Pidwerbetsky Alexander
Published: October 2005

Under certain conditions, wave propagation in a random medium can become chaotic, i.e., display extreme sensitivity to initial conditions and complex behavior. This problem has been treated by both ray and wave theory as well as simulations. Chaos is shown by the presence of a positive Lyapunov exponent. For some random media (irregularity spectra), the Lyapunov exponent can be theoretically calculated and agrees with the simulation results. In a ray model, a positive Lyapunov exponent results in the exponential divergence of nearby rays. In the wave case, narrow beams diverge exponentially with range, provided other effects (e.g., diffraction and scattering by small-scale irregularities) do not dominate. In both ray and wave cases, the local exponential divergence results in tangling of the global portraits of the wave fields in phase space. In regimes where it dominates, chaotic wave propagation has wide ranging implications for underwater acoustics, including the proliferation of caustics and uncertainties in predicting long-range propagation. Environments that produce multiple scattering (volume, surface, or bottom) by fluctuations with a large length scale are most likely to show chaotic wave propagation.
A coupled-mode method for sound interaction with an elastic oceanic bottom
Authors: Arvelo Juan I. , Talmant Maryline , Überall Herbert
Published: October 2005

The theory of coupled modes with elastic waves from the bottom sediments of a shallow oceanic environment is developed for a source at the water column. The shear and compressional attenuation coefficients have been included as a first- and second-order perturbation to the solution of the purely real eigenequation. Results of these calculations display the importance of the second-order perturbation calculation when radiating modes are included in the transmission loss calculations or when shear waves are included. The perturbed eigenvalues and eigenfunctions were used by an already developed coupled normal-mode computer code to provide the transmission loss in a range-dependent, shallow-ocean environment [Miller et al., J. Acoust. Soc. Am. 79, 562–565 (1986)]. The results obtained are compared to the ones by Miller et al. for upslope and downslope environments. [Work supported in part by the Individual Research Board at the Naval Surface Warfare Cener and by NORDA.]
A long-range acoustic experiment with sampling in the internal wave fluctuation band
Authors: Duda Timothy F. , Flatté Stanley M. , DeFerrari Harry A. , Nguyen Hien B.
Published: October 2005

Transmission at 460 Hz between two moorings centered about 600 km east of Miami is scheduled for August 1988. The 10-day, 260-km experiment has been designed to measure fluctuations induced by ocean internal waves (IW). The use of a 64-element, 150-m vertical receiver array, 6/h pulse rate, and high bandwidth allows measurement of pulse travel time (phase) to a fraction of a carrier period, and allows estimation of phase and intensity coherence times and the vertically lagged correlation function of the acoustic field, including the rms vertical wave front tilt. Path-integral solutions of the parabolic wave equation yield predictions of these statistical properties. For the Garrett-Munk IW model, rms travel-time predictions are 2–6 ms, and rms vertical angle predictions are 0.2–0.7 deg, with the lowest values for shallow turning rays and the largest for near axial rays. Expected phase coherence time scale is 5 min., with intensity time scale varying between 1 and 30 min., indicating the presence of both partially and fully saturated rays. These quantities yield a depth-dependent measure of rms vertical IW displacement, and some information about the IW spectrum.
Modeled time variability of acoustic propagation through a Gulf Stream cold core eddy
Authors: Mellberg Leonard E. , Robinson Allan R. , Botseas George
Published: October 2005

In a previous paper, A. R. Robinson [J. Acoust. Soc. Am. Suppl. 1 82, S2 (1987)] presented an overview and results from an ongoing forecast scheme for Gulf Stream oceanic mesoscale fields (temperature, sound speed, etc.) (gulfcasting). The coupling of the dynamical ocean model with an acoustic model and preliminary results were also presented. In the present paper, the coupled models are utilized to investigate the time variability of 25-Hz acoustic propagation through a GulfStream cold core eddy. Time variations of 2 days, 4 days, and 1 week are presented for ranges out to the second convergence zone. Shifts in propagation loss patterns of more than 5 km and variations in propagation loss of 5 dB are observed for a time change of 2 days. The relationships between the oceanographic and acoustic fields for the various time periods are discussed.
Three-dimensional, bottom-interacting propagation in the ocean
Authors: Collins Michael D.
Published: October 2005

A three-dimensional parabolic equation (3DPE) that handles wide angles in both the vertical and the azimuth is difficult to solve numerically. This motivated the development of a 3DPE that accounts for wide angles only in the vertical [Lee et al., Yale University, Department of Computer Science, Res. Rep. 463 (1986)]. An asymptotic derivation of a 3DPE that handles wide angles in the vertical will be presented as well as an efficient numerical solution based on the alternating direction implicit (ADI) method. A wide-angle starting field for initializing the 3DPE has been validated both asymptotically and numerically. Resutls will be presented for point source, multipole, and scattered fields including a benchmark calculation that demonstrates the validity of the ADI solution and the ability of the model to handle variations in azimuth. Shallow-water environments involving variable ocean depth will be considered including wedges and mounds. Two-dimensional and three-dimensional calculations will be compared.
Spectral ratios of acoustic log in marine sediments
Authors: Meredith Jeffrey A. , Cheng C. H. , Wilkens Roy H.
Published: October 2005

Diagnostic patterns have been noticed in spectral ratios of full waveform acoustic log data taken in slow marine sediments. The spectral ratio is computed with the full 2.56-ms time series after taking the Fourier transform and dividing the 3.05-m (10-ft) source-receiver offset transform by the 2.44-m (8 ft) one. The patterns show less attenuation at certain discrete frequencies in the spectra. The strongest observed peak in the spectral ratio was at slightly less than 7 kHz. Many of these patterns were duplicated by forward modeling consisting of calculating the branch cut integral of the compressional head wave at different source-receiver offsets and computing the spectral ratio. Preliminary analyses show that the presence and location of the peaks in the spectral ratio are controlled by the compressional wave velocity and the Poisson's ratio of the sediments, but the magnitudes of the peaks are controlled by their attenuation. The results were used to invert the full waveform log for shear wave velocity and compressional wave attenuation.
Transmission and reflection of acoustic waves through a composite slab using the finite element-eigenmode analysis
Authors: Jeng J.-H. , Varadan Vasundara V. , Varadan Vijay K. , Bao X.-Q.
Published: October 2005

A numerical approach is presented for solving the interaction of acoustic waves with a composite slab that has periodically distributed substructures and is immersed in an infinite fluid medium. Reflection and transmission characteristics are studied for the case of normal plane-wave incidence. The mathematical model proposed combined the finite element method and eigenmode analysis, and can reduce the boundary value problem to a typical force vibration problem. Thus the damping of the composite slab can easily be introduced in the formulation. The results have been plotted as reflection and transmission coefficients versus frequency for different substructures and have been verified according to exact layer theory and two simple vibration models. Good agreement is observed. The presented analysis may be easily extended to the cases of oblique incidence and should be useful for future applications. [Work supported by the Research Center for the Engineering of Electronic and Acoustic Materials.]
Acoustical design of a multichannel broadcasting sound studio
Authors: Fukunishi Tohru , Wakatsuki Toshio , Yamamoto Teruji
Published: October 2005

NHK has constructed a multichannel sound studio for the purpose of efficient production of music programs. In order to provide musicians with well-defined sounds and to pick up well-separated sounds individually, the studio has a main area, three booths, and three alcoves suited for each use. The largest booth, with a floor area of nearly 92 m2 and a height of 9.5 m, is for strings. It is acoustically separated from the main area by four sliding glass doors. Variable reverberation units installed on its walls can vary the reverberation time from 0.64 to 0.81 s at 500 Hz. The alcoves are designed so as to be usable as small separate booths, when necessary, by setting up two of the sliding glass doors, which can be housed in the inner walls. The floors of the electric instrument alcove and the drum booth are independently floated off the main floated floor. Furthermore, in this report, the details of the acoustical design, the inner sound insulation of each booth and alcove, the vibration proofing and noise control of the air-conditioning equipment, and the measurements of the acoustical characteristics are also mentioned.
A basic study of acoustical design for a four-channel sound control room
Authors: Wakatsuki Toshio , Fukunishi Tohru , Yamamoto Teruji
Published: October 2005

A number of experiments have been carried out in order to research how to design the interior of a four-channel sound control room for “high vision.” In this four-channel sound reproduction form, the three main channels are reproduced from the three front loudspeakers, and the surrounding sound of the fourth channel is reproduced from the two rear ones. In these experiments, interiors of the test rooms were varied in accordance with five measuring conditions. However, room shapes were not varied. The experimental items were: (1) static transfer frequency response, (2) mean frequency spectrum of music sound, (3) questionnaire, and (4) subjective estimation. The results from the following three view-points were analyzed: (1) less coloration, (2) the width of the listening area, and (3) the amenities of the sound production room. It was found that when treating the front walls, ceiling, and floor with absorbent materials and providing the rear with a diffusive and reflective surface, the results were superior for all experimental items. It was also confirmed that this concept is applicable to ordinary two-channel sound control rooms. Experimental results in actual two-channel sound control rooms are also mentioned.
Spatial Fourier transform method of measuring acoustic reflection coefficients at oblique incidence
Authors: Tamura Masayuki
Published: October 2005

A new method using the spatial Fourier transforms has been developed to measure acoustic reflection coefficients at oblique incidence. The method involves the measurement of complex pressure fields in two parallel planes lying close to the surface of an absorbing material, and the decomposition of each of the complex pressure fields into plane-wave components by using two-dimensional spatial Fourier transforms. The incident and reflected plane-wave components on the surface of the absorbing material can be mathematically separated by using the plane-wave propagation theory. This separation leads to a determination of the acoustic reflection coefficients at arbitrary angles of incidence. Polyurethane foam was used as a sample material to check the validity of the method. A comparison between the results obtained by the present method and results from an existing free-field method showed good agreement except at very oblique angles of incidence.
Measuring acoustic impedance: The results of a worldwide round robin
Authors: Haines James C. , Peppin Richard J.
Published: October 2005

ASTM Committee E-33 on Environmental Acoustics has published two different test methods for determining the normal incidence acoustic impedance and sound absorption coefficients of materials using an impedance tube. Method C-384 involves the use of the traditional standing-wave apparatus using pure tones. Method E-1050 involves the use of a two-microphone technique that provides improved measurement speed and increased detail in the performance versus frequency spectrum. Committee E-33 organized a round robin test program in order to generate ASTM required precision and bias statements for both test methods. Although not required by ASTM, the program also provided an excellent opportunity to compare the results obtained by the two measurement methods. Twenty-two laboratories expressed initial interest and fourteen laboratories from five countries throughout the world eventually participated in the program utilizing either one or both of the test methods. This paper discusses the organization of the program, the test results that were reported, and the conclusions that were drawn from a statistical analysis of the reported test results.
The three-microphone impedance tube
Authors: Bolton J. S. , Kompella M.
Published: October 2005

The two-microphone impedance tube technique introduced by Seybert and Ross, and Chung and Blaser, is now widely used and has recently been standardized by the ASTM. This standard does not account for the effects of wall attenuation on measurement accuracy. Chu has recently indicated how two-microphone measurements may be adjusted to account for wall attenuation if the latter is known either from theory or independent measurement. In the work reported here, the effects of wall attenuation on the accuracy of the two-microphone technique are illustrated by use of computer simulations. The results show that the largest errors occur when the impedance of the test material is large; this is often the case at low frequencies for layers of porous materials, for example. It will be shown that measurements with three equally spaced microphones may be used simultaneously to determine both the complex amplitudes of the forward- and backward-going wave components and the complex wavenumber in the tube. From this information, the impedance of the test material may be determined accurately even in the presence of significant wall attenuation. In this way, the general approach of the two-microphone technique may be extended to allow measurement of higher impedance materials than has formerly been the case.
A reexamination of the compensation effect in the mora hypothesis
Authors: Otake Takashi
Published: October 2005

The objective of this paper is to reexamine the compensation effect of the mora hypothesis in mora timing. An early investigation of the mora hypothesis presented the compensation effect in Japanese as evidence in support of the mora hypothesis [Port et al., Phonetica 37, 235–252 (1980)] and another presented contrary evidence against it [M. Beckman, Phonetica 39, 113–135 (1982)]. However, since Port et al.'s evidence was obtained in comparison with different test words produced by Japanese and Arabic speakers, their results need to be reexamined. In this paper, an experiment was conducted as to whether the compensation effect observed in Port et al.apos;s experiment will be relevant only to a mora-timed language by using the identical test words produced by Japanese and Arabic speakers. Contrary to Port et al.'s results, the results of this experiment indicated that the compensation effect was observed not only in Japanese but also in Arabic. These data indicate that the compensation effect may not be evidence for the mora hypothesis.