bluuebunny/crossref_metadata_2025 huggingface dataset:
Speech reception in deaf adults using vibrotactile aids or coehlear implants
Authors: Milner Paul , Flevaris-Phlllips Carole
Published: October 2005

Many post-lingually deafened adults rely heavily upon speechreading as the primary source of speech information. Vibrotactile aids or cochlear implants may help augment the limited visual cues of speeehreading, especially the ones which permit voiced/voiceless and nasality distinctions. Measures of the apprehension of voicing and nasality, as well as other attributes of speech reception, were obtained using the Diagnostic Rhyme Test [W. D. Voiers, in Benchmark Papers in Acoustics, Vol. 11, edited by M. Hawley, pp. 374–387 (1977)] with candidates for possible cochlear implantation. Results using vibrotactile aids or cochlear implants either individually or in combination with speechreading indicated that both vibrotactile aids and cochlear implants provided improvements in the perception of nasality, but voiced/voiceless distinctions were not as clearly recognized. [Work supported by Veterans Administration Rehabilitation Research and Development Service.]
Effects of aging on vibrotactile temporal resolution
Authors: Van Doren Clayton L. , Lanni Grace L. , Verghese Preeti , Verrillo Ronald T. , Gescheider George A.
Published: October 2005

Psychophysical thresholds for detecting a temporal gap centered in a background stimulus were measured by two-interval forced-choice tracking. The 16- to 256-ms gaps were flanked by 350-ms bursts of either 250-Hz sinusoidal vibration or bandpass noise. In each trial the threshold intensity was measured for detecting a gap of a fixed duration. This threshold decreased as gap duration increased and could be approximated by a power function of the form I = A(G/G0)−B + C. In this expression, I is the gap-detection threshold in dB SL, G is the gap duration in ms, Go equals 1 ms, A and C are constants in dB SL, and B is a dimensionless constant. A, B, and C increased with subject age. The primary effect of increasing age was a reduced temporal resolution for gaps smaller than 64 ms. This reduced sensitivity may effect tactile perception of some speech features such as voiced and unvoiced stop consonants in older subjects. [Work supported by NIH Grant NS-09940.]
Field tests of a wearable 16-channel electrotactile sensory aid in a classroom for the deaf
Authors: Saunders Frank A. , Franklin Barbara
Published: October 2005

Field testing of a wearable electrotactile sensory aid began in February 1985 at the Jackson Hearing Center, an oral program for deaf children in Palo Alto, CA. Six children, 3 to 8 years of age, participated in the study. Each had a profound congenital binaural sensorineural hearing loss in excess of 105 dB. The wearable sensory aid, the Tacticon model 1600, presents 16 channels of frequency information via a tactile belt worn around the abdomen. Wearing time for each child was gradually increased from half-hour daily lessons to 4 h of use per day. Environments included the classroom, outside recess with physical education activities, and field trips. Receptive training was directed at recognition of both suprasegmental and segmental features of speech. Suprasegmental features included duration, number of syllables, rhythm, and stress. Segmental features included the recognition of specific speech sounds in isolation, beginning with the Ling 5 sound test of /a/, /e/, /u/, /s/, and /sh/. The assessment procedure was conducted in three modes: (a) aided residual hearing alone, (b) aided hearing plus lipreading cues, and (c) aided hearing plus lipreading plus tactile cues from the sensory aid. The addition of tactile cues results in a significant increase in the discriminability of both suprasegmental and segmental features. The children also received experience with the sensory aid during speech training, attending to the tactile patterns resulting from different speech features such ns nasaiity, voicing, frication, and plosion, comparing their utterances with those of the teacher. Their performance indicated that the tactile feedback supported an improvement in speech production, as well as reception. [Work supported by SBIR/NIH: 2 R44 AG/NS04817.]
Psychoacoustic results supporting the assumption of binaural inhibition mechanisms
Authors: Lindemann Werner
Published: October 2005

This paper describes localization and lateralization experiments with stationary and nonstationary signals, the results of which can be explained by inhibitory mechanisms in binaural signal processing. Multiple auditory events are discussed which can be perceived with pure-tone stimuli at various combinations of interaural time and level differences. For noise signals, multiple auditory events are reported which occur as a function of the degree of interaural coherence. Inhibitory mechanisms as related to the law of the first wave front are investigated with pairs of impulses presented dichotically via headphones. The psychoacoustic results can be predicted by simulations based on a binaural cross-correlation model—extended by inhibitory mechanisms [W. Lindemann, J. Acoust. Soc. Am. Suppl. 1 74, S85 (1983)]. [Work supported by the Deutsche Forschungsgemeinschaft.]
The relationship between the cross-correlation function of two-channel acoustic signals reproduced through the headphones and spatial impressions of sound image
Authors: Kurozumi Kohichi , Ohgushi Kengo
Published: October 2005

White noises with various cross-correlation functions are reproduced through headphones. Subjects are asked to make similarity judgments and some subjective evaluations of pairs of noises. The experimental data are analyzed by Kruskal's multidimensional scaling (MDS) programs. The analysis of the experimental data shows the following: (1) spatial impressions of sound image depend mostly on the width, the elevation, and the lateral displacement of the sound image; (2) the width of the sound image increases as the maximum absolute value of the cross-correlation function decreases, and as its peak position goes away from τ = 0; (3) the elevation of the sound image tends to increase as the maximum value of the cross correlation function increases, as long as the maximum value is positive, (4) the lateral displacement depends on the asymmetry of the shape of the cross-correlation function and mostly on the positive peak position of it.
Masking level difference in infants
Authors: Nozza Robert J.
Published: October 2005

The binaural masking level difference (MLD) for a 500-Hz pure tone was estimated for infants between 6 and 8 months of age. A masker with bandwidth of 600 Hz (No = 35 dB SPL), geometrically centered at the test frequency, was presented in phase to a pair of TDH-49 earphones. Each subject was tested in each condition (NoSo and NoSπ) in a single session, the sequence counterbalanced among the subjects. A computer-controlled visual reinforcement head-turn procedure was used. Masked threshold was estimated using a simple up-down staircase procedure with a 5-dB stepsize. Infant MLD estimates compare favorably with those of an adult control group. However, the infants' masked-threshold estimates, used in computing the MLD, were evaluated relative to the adult group for each condition. [Work supported by Deafness Research Foundation.]
Stress groups and rhythm in American Spanish
Authors: Toledo Guillermo A.
Published: October 2005

This paper reports a description of rhythm in several discourses both in spontaneous speech and in the oral reading of narrative prose, essay, poetry in free verse, and sonnets in American Spanish. These speech materials were digitized and an acoustic study of the duration of stress groups—a word with primary stress plus unstressed words in proclitic and enclitic positions—was undertaken. A variance analysis of percentage deviations of these stress groups showed values in an ample range: a lower degree of variability in poetry reading and a higher degree in prose reading and spontaneous speech. Also, there was a certain tendency to temporal equalization in stress groups of different sizes and, inversely, a tendency to proportionality between the increment in size and the increased duration. This would appear to suggest that each discourse would be rhythmically supported by a twofold tendency, syllable- and stress-timing, combined in a free scheme. This claim agrees with previous research providing evidence on interstress interval patterns of similar oral discourses in American Spanish [G. Toledo, J. Acoust. Soc. Am. Suppl. 1 77, S53 (1985)].
Review of source spectrum level density of wind-generated noise
Authors: Wilson James H.
Published: October 2005

The source spectrum level density of wind-generated noise has been deduced from ocean measurements, laboratory experiments, and theoretical studies in the past 25 years. Selected contributions are reviewed and the results are compared. Since the source level results compare favorably, at least in deep water, an average source spectrum level density as a function of frequency and surface wind speed is proposed for use in noise models. The differences between the dipole and “rocking” dipole source directivity patterns is discussed and wind-generated noise modeling issues are addressed. There seems to be little agreement on the underlying physical mechanisms of wind-generated noise. The question of what information would be added to the source spectrum level densities if a theory for the underlying physical mechanisms were known is also addressed.
Low-frequency ocean surface noise sources
Authors: Carey W. M. , Bradley M. P.
Published: October 2005

The interaction of the wind with the ocean surface has long been recognized as the major source of ocean ambient noise. High-frequency noise data 1200 to 2 kHz) has consistently been found to have strong wind-dependent characteristics associated with spray, splashes, bubbles, and rain. Recently, wave-wave interaction has been shown to be a source of infrasonic (0.2 to 2 Hz) noise and ocean bottom microseisms. Generally, the low-frequency noise (2 to 20 Hz) is associated with noise from distant ships. However, narrow-hand (as opposed to 1/3-octave) measurements show in addition to the noise from ships a wind-dependent characteristic. Furthermore, mid-ocean basin vertical directionality measurements show noise intensity near the horizontal with a broad frequency characteristic in diverse geographic locations. These results suggest a wind-generated noise due to a mechanism such as wave-wave interaction, wind turbulence, or the interaction of surface waves with turbulence is coupled into the mid-basin sound channel by either a shallowing sound channel such as found at high latitudes or a down-slope conversion process due to the basin boundaries and sea mounts. Theoretical expressions are derived from first principles following the approaches of Yen and Pertone [Naval Underwater Systems Center TR5833 (1979)] and Huon Li [Naval Ocean R&D Activity, TN89 (1981)] yielding the frequency-dependent radiation characteristics for wave-wave interaction, wind turbulence, and wave-turbulence interaction. These results show that wave-turbulence interaction is a possible source of wind-driven noise in the 10- to 200-Hz regions. Other possible mechanisms such as nonlinear capillary wave interactions are discussed and compared to this wave-turbulence mechanism.
The role of duration in the perception of consonants within reduced syllables
Authors: Archambault Daniéle
Published: October 2005

The role of duration as a perceptual cue to the presence of two underlying consonants versus one is examined in Montreal French. Due to deletion of the intervening phonetic segments, two identical syllable-initial consonants may be joined in one articulation such that, for example, two plosives show a single burst. A series of utterances in which these double consonants and the corresponding single ones appear in identical segmental contexts was recorded and then presented to listeners in perceptual tests [e.g., la plupart (most of it)→/laplypar/→[lap:ar] as opposed to la part (the part)→/lapar/→[lapar]). To insure that listeners base their judgment on duration to distinguish between the utterances, they were also presented with the same utterances in which, by use of signal processing, the durations of the consonants were inverted, i.e., the double consonant was given the relative duration of the single consonant and vice versa. Results show that while a long duration consistently leads listeners to recognize a double consonant, a short duration does not automatically prompt them to identify a single consonant. Results also indicate that consonant duration must be considered in a larger context than that of the syllable. [Research done at the Université de Montréal and supported by the National Research Council of Canada and Québec Government.]
Perceived pitch (tonality) of nonsense syllables with phonemes homogeneously or heterogeneously grouped phonemes according to a pitch model
Authors: Asp Carl W. , Johnson Carole E.
Published: October 2005

Research involving the perceived pitch (tonality) [M. M. Peterson and C. W. Asp, J. Acoust. Soc. Am. Suppl. 1 52, S146 (1972) and C. W. Asp, J. S. Berry, and C. S. Bessell, J. Acoust. Soc. Am. Suppl. 1 64, S20 (1978)] and optimal octaves in phoneme perception [E. E. McKenney and C. W. Asp, J. Acoust. Soc. Am. Suppl. 1 51, S122 (1972) and R. M. Miner and J. L. Danhauer, J. Am. Audiol. Soc. 2, 163–168 (1977)] has supported the notion that phonemes may be “frequency specific.” For these studies, homogeneously grouped phonemes were selected according to a pitch model [C. W. Asp, J. S. Berry, and C. S. Bessell, J. Acoust. Soc. Am. Suppl. 1 64, S20 (1978)]. The purpose of this study was to determine the effects of homogeneously and heterogeneously grouping phonemes according to the pitch model. This included pairing a low /m/, a middle /l/, and a high /s/ consonant each with a low /u/, a middle /a/, and a high /i/ vowel. This resulted in three homogeneous (i.e., /mu, la, and si/) and seven heterogeneous (i.e., /ma, mi, lu, li, su, and sa/) nonsense syllables. Ten normal-hearing young adult listeners selected the syllable with the highest pitch in each pair within a paired-comparison paradigm. Results indicated that (1) the nonsense syllables could be ranked from high to low perceived pitch (i.e., /si, li, sa, mi, la, su, ma, lu, and mu/); (2) both consonants and vowels affected the listeners' judgments, although vowels appeared to have a greater effect; and (3) the rank order of the perceived pitch of the nonsense syllables was in agreement with past research. Tonality is discussed in terms of acoustic data as well as a mathematical perceptual model for predicting the pitch perception of phonemes in syllables and in words.
Limits of temporal discrimination for sequences of speech sounds
Authors: Gardner Daniel A. , Brubaker Brad S. , Warren Richard M.
Published: October 2005

Earlier studies from a number of laboratories found that the order of vowels in iterated sequences of three or four items could not be identified below durations of about 100 ms/item. The present study required untrained subjects to distinguish between iterated sequences of three vowels (/i/, /a/, /u/) presented in the same or in permuted order. As would be anticipated, distinguishing between permuted orders could be accomplished through naming of individual items at durations greater than 100 ms, but contrary to some theories, metathesis resulting in perceptual equivalency of different orders did not occur at item durations below 100 ms. Rather, permuted orders were readily distinguishable down to durations corresponding to single glottal pulses, although component vowels could not be recognized. These results are consistent with theories considering that comprehension of speech does not require the ability to detect component speech sounds and their orders, but is based instead on recognition of unresolved temporal patterns. [Work supported by NIH and NSF.]
The effect of sentence timing on the perception of word-initial stop consonants
Authors: Kidd Gary R.
Published: October 2005

The influence of temporal context on the perception of voice onset time (VOT) as information for the identity of a word-initial stop consonant was examined in three experiments. Different versions of a ten-word precursor phrase were constructed by recording the phrase at a fast and a slow rate and then combining words from the two original phrases to produce composite phrases with various patterns of rate changes. A final (target) syllable from a seven member /gi/-/ki/ VOT continuum constructed from natural speech was added to the end of the phrase after a variable pause duration. Subjects listened to each phrase version and judged the identity of the target syllable. In general, the VOT boundary was found to shift to shorter values with precursors that contained more fast words and shorter pause durations. Furthermore, while the rate of the words immediately preceding the target appeared to have the greatest effect, there were also significant rate effects due to the rate of stressed words early in the precursor and the pattern of rate changes throughout the precursor. [Work supported by NIMH.]
Use of timing to discriminate words
Authors: Reilly William , Port Robert
Published: October 2005

We sought to use timing measures alone to discriminate words with similar sequences of basic acoustic segments. Previous work by Waibel [J. Acoust. Soc. Am. Suppl. 1 72, S32 (1982)] and others showed that a crude segmental classification scheme could reduce the search space of the English lexicon to cohorts of fairly small size. We took two sets of six similar words, differing primarily in stress, voicing, and vowel length, including bacon, begin, Begin, pecan and zipper, supper, suburb. Thus they might fall in similar cohorts with a gross segmental classification. The words were spoken twice in a carrier sentence at two tempos by 12 speakers. Durations of segmental intervals (vowel and obstruent durations, VOT, etc.) were measured from sound spectrograms. Discriminant analysis was run on the set of first tokens and the derived classificatory equations were used to predict word identity for both the first and second set of tokens. Prediction accuracy for both sets was about 86% where chance performance is about 8%. That is, timing information about the whole word permitted very good identification from among cohorts of segmentally similar words. These results suggest that appropriate timing measures could be effective discriminators in whole-word speech recognition.
How cryptic is distorted speech?
Authors: Wingstedt Maria , Schulman Richard
Published: October 2005

A series of tests was conducted examining the ability of native Swedish speakers to learn to comprehend phonologically distorted speech. Two versions of the same text were produced: one with a heavy Chinese accent and one with an artificially produced accent (Cryptic) which was very different in character from the Chinese one. Two groups of 22 subjects listened to either one of the versions. A list of isolated words produced only with the Cryptic accent followed both of the text versions. A third group, acting as a control, listened only to the isolated Cryptic word list. It was shown that the group exposed to the Cryptic text version had almost double the comprehension of the word list as those exposed to either the Chinese accent or to no text prior to the list—both performing equally poorly. We conclude that learning to compensate for a particular accent is specific to that accent and its comprehension will not be augmented by prior exposure to a very different accent, and that this result should hold true for distortions in general. [Work supported by HSFR.]
Perception of stress pattern and word recognition
Authors: van Heuven Vincent J.
Published: October 2005

Theories of spoken word recognition do not explicitly take account of nonsegmental properties of the stimulus. The present research investigates how, and to what extent, acoustic information on the stress pattern of a (Dutch) word contributes to word recognition, both in hifi degraded natural speech and in synthetic speech (concatenated diphones). In a series of experiments, words with correct or incorrect stress position in the first, second, or third syllable were presented in isolation or preceded by a short carrier phrase. Words were made audible in fragments of increasing size (“gating”) so as to trace the respective contribution of stressed and unstressed syllables to the word isolation process as the stimulus develops in time. Whole word recognition was included in some of the experiments as a control task. Selected results will be presented and some of the consequences for word recognition models will be discussed.
A simple wave-based model for unsaturated fluctuations
Authors: Gabrielson Thomas B. , McDaniel Suzanne T.
Published: October 2005

Prediction of signal fluctuations, induced by sound-speed perturbations in a realistic, inhomogeneous environment in which diffraction is significant, requires the use of wave techniques. Ray-based models fail in regions of strong focusing and in regions where diffractive leakage is important. Consequently, a model has been developed based on the mode groups associated with the saddle points of the field integral for the unperturbed field and the eigenvalue shifts introduced by the perturbations. The results are directly applicable to acoustic propagation in either the atmosphere or the ocean.
Helmholtz integral formulation of the sonar equations
Authors: Schenck Harry A.
Published: October 2005

The sonar equations provide a convenient way to calculate the detection range of actual and proposed sonar systems. They are simple, but approximate, relationships between parameters which describe the effects of source, target, and acoustic medium independently. The purpose of this paper is to derive an exact form of the active sonar equation by using the Helmholtz integral formulation to solve the boundary-value problem with source and target both present in the medium. The resulting equation involves combinations of linear integral operators; however, it is suitable for solution by numerical techniques already developed for radiation from objects of arbitrary shape. Furthermore, it is shown that these integral operators reduce to multiplicative factors which represent general definitions of the source level, transmission loss, and target strength when the source-to-target distance is large. Thus this work establishes a basis for the sonar equations as the limiting form of an exact boundary-value problem and presents formulas for calculating the sonar parameters. [Work performed under a Naval Scientist Training and Exchange Program (NSTEP) assignment from the Naval Ocean Systems Center (NOSC).]
Calculation of underwater acoustic fields by Gaussian beam tracing
Authors: Porter Michael B. , Bucker Homer P.
Published: October 2005

The method of Gaussian beam tracing has recently received a lot of attention in the seismological community. In comparison to standard ray tracing, the method has the advantage of being free of certain ray tracing artifacts such as perfect shadows and infinitely high energy at caustics. The technique is especially attractive for high-frequency problems or problems with complex bathymetry where normal mode, FFP, or parabolic models are not practical alternatives. The Gaussian beam method associates with each ray a beam with a Gaussian intensity profile normal to the ray. The beam curvature and width are governed by an additional pair of differential equations that are integrated along with the usual ray equations to compute the beam field along the ray. Analytic solutions to the beam equations are available for certain canonical problems, including the cases where the sound speed or square of the index of refraction is a linear function of the space variables. Thus ray tracing codes that employ patches of such domains are easily adapted to the beam tracing method. We present an overview of the method and results for certain ocean acoustic scenarios, which illustrate the performance of the method.
Modified integral transform for weakly range-dependent shallow ocean Green's functions
Authors: Arnold J. M. , Felsen L. B.
Published: October 2005

Acoustic Green's functions for a range-independent ocean and bottom environment can be expressed as integral transforms with respect to the range coordinate. This rigorous formulation contains all of the relevant source-excited wave phenomena (rays, normal modes with inclusion of continuous spectra, etc.) and is amenable, furthermore, to direct numerical treatment via the fast field program (FFP). Because of these features, it would be desirable to extend this formulation to range-dependent configurations. While the ability to do so in general is open to question, progress can be made for weak dependence on range. Refining our earlier plane wave spectral (intrinsic mode) study of the wedge-shaped ocean Green's function [J. M. Arnold and L. B. Felsen, J. Acoust. Soc. Am. 73, 1105–1119 (1983)], we have been able to express the result as a range-dependent spectral transform that inverts an adiabatically approximated functional dependence on depth. This modified integral transform representation, which accounts for source effects, radiation into the bottom, uniform adiabatic mode transition through cutoff, etc., systematizes and generalizes the more heuristically derived form of Kamel and Felsen [J. Acoust. Soc. Am. 73, 1120–1130 (1983)]. We present the new derivation and properties of this representation as well as its numerical implementation and its potential for extension to three-dimensional weakly range-dependent environments. [Work supported by ONR.]
A discussion on the angle of propagation in relation to the parabolic equation approximation
Authors: St. Mary Donald F. , Lee Ding
Published: October 2005

In approximating the reduced wave equation by parabolic-like partial differential equations, it is interesting to observe that in the direction of propagation, the size of the angle is related to the order of the parabolic-like equation. The order of the Padé rational function approximation used in the derivation of the parabolic equation (PE) determines the order of the parabolic equation. The “standard PE” and the “wide-angle PE” can be thought of as having been derived through approximations by a Padé (1,0) and a Padé (1,1), and can be considered to have orders 2 and 3, respectively. In this paper, we discuss parabolic-like approximations using higher-order Padé rational functions which result in higher-order pseudopartial differential equations. Their behavior in relation to the angle of propagation is examined.
Direct generation of starting fields for parabolic equation models by perturbation theory
Authors: Robinson E. Richard , Wood David H.
Published: October 2005

It is well known that the standard approaches to the computation of parabolic equation model starting fields (such as Gaussian and normal modes) have definite drawbacks, with regard to running time or accuracy. In this paper, we present a method for computing the starting field which directly generates the combination of modes needed for the parabolic equation model's starting field. To demonstrate the speed and accuracy of the perturbation approach, we compute the starting field for a variety of system and environmental parameters. These results are compared to the more customary Gaussian and normal mode models.
Acoustical effects of ocean current shear in the parabolic approximation
Authors: Robertson J. S. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

In a previous study [J. S. Robertson, W. L. Siegmann, and M. J. Jacobson, J. Acoust. Soc. Am. 77, 1768–1780 (1985)], the authors developed a family of parabolic equations which include effects due to the presence of a steady, depth-dependent current. Three of these equations contained a new term which explicitly depended on current gradient. In this work, we study the effects of this new term. By appropriately transforming and simplifying, the equations are transformed into parabolic equations which can be integrated numerically with existing implementations. Presence of ocean current fine structure is one mechanism which can require new terms. Propagation is examined in a shallow isospeed channel with a lossy bottom and a variety of shear flows, some of which model actual ocean flows. Current fine structure can induce variations in intensity which are substantial and which depend on shear structure, source and receiver locations, and frequency. Finally, intensity differences are examined in reciprocal sound transmissions. [Work supported by ONR.]
Use of the complex intensity vector for sound radiation and sound field studies
Authors: Tichy Jiri , Mann Adin
Published: October 2005

The traditional intensity technique to determine the sound power radiated by sources or propagating through a sound field uses the real part of the complex intensity only. More information on the sound field and sound radiation can be obtained if both real and imaginary components of the intensity vector are considered. This paper presents the results of studies of the fundamental relationships between sound pressure, particle velocity, complex intensity, and both potential and kinetic energy. As shown before, the real part of the intensity vector is rotational (curl Ir ≠ 0, div Ir ≠ 0), while the imaginary (reactive) component of the complex intensity vector is irrotational (curl Ii = 0, div Ii ≠ 0). The conditions of the vortex formation were studied as a function of the source distribution. The relation between the extremes of the intensity curl and the energy in the sound field have been formulated. The applications of the sound intensity field structure on the sound radiation from complex radiators is shown using specific examples. New graphical methods of presenting the intensity field are shown. The paper also presents experimental results obtained by an automatic computer controlled system for intensity measurements.
Some problems associated with making sound intensity measurements in the presence of reverberant fields and/or background sources
Authors: Seybert A. F. , Holt J. A.
Published: October 2005

This paper is concerned with potential problems that one may encounter when attempting to use the two-microphone method to determine the sound intensity and sound power of a source when background and reverberant fields are present. Under such conditions, the primary variables controlling the accuracy of the sound intensity estimate are shown to be the ratio of the unknown intensity to the mean-square pressure of the background/reverberant field and the accuracy of the estimate of the phase angle between the two microphones. Proceeding from a few simple concepts we illustrate the abovementioned measurement problem with results obtained from a controlled experiment. [Work supported by International Business Machines Corporation.]
Acoustic intensity of scattered field from a rib-reinforced plate
Authors: Seren Cetin , Hayek Sabih
Published: October 2005

An infinite elastic plate which is reinforced by one rib is insonified by a plane incident wave. The diffracted acoustic pressure generated by the rib welded to the plate is computed by an asymptotic series and by using a new integral representation which converges very rapidly. The acoustic intensity in the nearfield and farfield of the plate are computed and exhibited as an intensity map. The intensity map shows the propagation of the diffracted acoustic energy from the rib and the local energy interchange with the elastic plate in its vicinity. [Work supported by NAVSEA.]
Power flow and traveling waves in structures
Authors: Tucker Albert J. , Clark Joseph A.
Published: October 2005

Recent experiments [J. A. Clark and A. J. Tucker, “Optical Measurements of Structural Intensity Distributions,” 2nd Int. Congress on Acoustic Intensity (Sept. 1985)] have revealed that the traveling waves associated with power flow in structures can be separated from the standing waves (mode shapes) associated with vibrational energy stored in structures. The separation is achieved by an optical measurement method which employs phase-resolved holographic interferometry to determine the instantaneous deformed shape of a structure when it is in quadrature phase relationship to the force driving the structure. In this talk, a theoretical analysis of the correspondence between power flow and the coincident and quadrature shapes of vibrating structures will be presented and the theoretical results will be compared with features of traveling and standing waves visualized in an actual vibrating structure. [Research supported by DTNSRDC and ONR.]
Jet noise source location via acoustic intensity
Authors: Richarz Werner G.
Published: October 2005

It is well known that sources of jet noise are described by a variety of models; thus there is no unique source distribution. If no assumptions are made about the nature of the sources, then one can infer virtual source distributions from certain farfield measurements. Here, however, the source locations are deduced directly from acoustic intensity measurements near an axisymmetric jet flow. The magnitude and direction of the acoustic intensity vector are found to be functions of position and source frequency. Acoustic intensity is measured along three directions in a plane of the jet axis; data are analyzed in 1/3 octave bands. The measurements are performed sufficiently far from the jet flow to avoid air flow over the probe. Clearly, the resolution of the source location scheme suffers with increasing probe-source separation: Thus a compromise is struck. The measured data permit the reconstruction of certain properties of the acoustic farfield and appear to demonstrate closure. [Work funded by Natural Sciences and Engineering Research Council of Canada.]
Underwater sound generation by a high-intensity laser pulse
Authors: Chotiros Nicholas P.
Published: October 2005

In the generic optoacoustic sound source, a laser beam is directed at the water surface to produce a controlled local reaction which, in turn, generates sound waves. The energy is delivered without physical contact. At low optical intensities, the reaction is a linear thermal expansion of the medium, but at high intensities, the reaction is nonlinear and more complicated. A simple blast model is used to predict the acoustic output of the high intensity reaction. The blast model is based on that of A. N. Pirri who successfully used it to model the momentum transfer between a high power laser blast on the surface of a solid. The Pirri model is general enough to be adapted for laser-induced blasts over water, The model predictions are compared with experimental results, The differences are discussed. [Work supported by ONR.]
Experiments with sound induced by a laser pulse moving at Mach 1 over a water surface
Authors: Berthelot Yves H. , Busch-Vishniac Ilene J.
Published: October 2005

Sound generated in water by a laser via thermal expansion, is usually of very low amplitude. However, experimental results show that, when the laser beam is moving on the surface of the water at velocities close to the speed of sound in water, a much stronger acoustic pulse is generated and propagates underwater. The linear theory describing the radiation of sound by thermal expansion underestimates significantly the acoustic levels observed experimentally in such a Mach wave. Experimental data also include pressure waveforms, directivity patterns, sound level dependence on source velocity, and distance of observation. The lasing wavelength dictating the penetration depth of light in water, could be either 1.06 μm (Neodymium:Glass) or 0.6943 μm (ruby).
Asymptotic analysis of diffraction effects in the radiation of underwater sound by interesting configurations of laser-generated heat deposition
Authors: Hsieh Hsiao-an , Pierce Allan D.
Published: October 2005

A previously proposed ideal configuration [J. Acoust. Soc. Am. Suppl. 1 77, S104 (1985)] for optimal laser-generated heating of water to achieve strong farfield acoustic signals with desirable properties suggests a number of pertinent boundary value problems in thermoacoustics. These progress in complexity and are analyzable with varying degrees of simplicity and thoroughness using mathematical physics techniques such as Fourier transforms, contour deformation, and the saddle point method. A simple class of such models assumes that the source term (associated with heat addition) of the wave equation is independent of the horizontal coordinate y, is a sinusoidal progressing wave in the horizontal coordinate x, and dies out exponentially with depth coordinate z. The source extent in the x direction is either taken as unlimited in the simplest idealization or non-zero only over a fixed length L. The pressure disturbance is described as a Fourier integral over wavenumber kx and angular frequency ω. The ordinary differential equation for the integrand is readily solved, and the resulting integrals are evaluated for positions and times of interest using complex variable techniques. [Work supported by ONR, Code 425-UA.]
A sound source near a velocity discontinuity in the presence of a rigid boundary
Authors: Pierucci Mauro , Nosseir Nagy
Published: October 2005

The problem of the interaction between an acoustic source and a velocity discontinuity is a problem of interest to researchers in different areas. Gottlieb [J. Acoust. Soc. Am. 32, 1117–1122 (1960)] has solved for the farfield acoustic radiation transmitted through a discontinuity. In this paper, the velocity discontinuity is assumed to impinge on a rigid surface so that the acoustic interaction is now between the source, the velocity discontinuity, and the rigid wall. Displacement of the interface has been evaluated numerically by the use of a fast Fourier transform subroutine on a CYBER 750 computer. Variation of the displacement as a function of the acoustic source location and of the mean flow velocities of the two media is presented. The results indicate that the interface displacement is very sensitive to the location of the sound source. For given flow conditions two optimum sound sources exist which will maximize the interaction between the sound source and the fluid discontinuity. For all cases run, the spatial variation of the displacement of the fluid interface is seen to be composed of the superposition of two wavelengths; the long wavelength is related to the acoustic wavelength while the shorter wavelength is a function of the local flow field conditions.
Transient acoustic radiation and scattering from one-dimensional fluid-loaded vibrators via impulse response methods
Authors: Ebenezer Duraisingh D. , Stepanishen Peter R.
Published: October 2005

A general time domain approach is presented to evaluate the transient velocity and pressure field of fluid-loaded one-dimensional vibrators, which are excited by broadband excitations. The approach is based on the use of time-dependent modal expansion for the velocity of the vibrator. As a result of the fluid coupling, the time-dependent coefficients of the modes are described by a set of coupled convolution integral equations which are solved for a specific excitation by marching forward in time. A time-dependent Green's function method is used to obtain a convolution integral representation for the pressure field. Numerical results will be presented for different types of one-dimensional vibrators which include both plate and beam configurations. Differences in the nature of the fluid coupling for the two configurations of vibration will be highlighted in the time domain. Numerical results will illustrate the importance of the modal coupling for both configurations. [Work supported by ONR.]
Alternative variational principles for sound radiation by vibrating structures
Authors: Pierce Allan D. , Wu X.-F.
Published: October 2005

Desirable features of variational principles are discussed and arguments are presented against indiscriminate uses of Galerkin's method that proceed from non-self-adjoint formulations. An ideal principle appears as a stationary functional for a quantity of direct physical interest, such that a mediocre estimate of trial functions results in a good estimate of that quantity. The authors' previously derived variational formulation, based on the Kirchhoff-Helmholtz surface integral corollary, is shown to yield a variational expression for a weighted average radiation impedance. Variational expressions for other quantities of physical interest are derived using the general technique of Gerjuoy et al. [Rev. Mod. Phys. 55, 725–774 (1983)]. Such includes the product of farfield pressure and radial distance in any specified direction, because this is expressible as a constant plus a weighted surface integral over pressure. The derived variational functional involves not only a trial function for the surface pressure for the originally posed problem, but also one for a secondary problem which usually has a clear physical interpretation. Analogies with scattering theories ensuing from the 1940s work of Schwinger and Levine are discussed and it is argued that advances in computer technologies make it desirable to reexamine such theories' acoustical applications. [Work supported by ONR.]
Finite element implementation of a variational formulation for acoustic radiation and scattering exemplified by the circular disk
Authors: DiMarco J. S. , Ginsberg J. H.
Published: October 2005

A previously derived variational principle [A. D. Pierce and X. -F. Wu, J. Acoust. Soc. Am. Suppl. 1 74, S107 (1983)] for the acoustic perturbation on the surface of a body, either vibrating or acting as a rigid-body scatterer, is a possible starting point for finite element formulations. The present paper studies the particular example of a circular disk that is presumed rigid and axisymmetrically excited; surface pressure is assumed to vary linearly between mesh points. An integrated Green's function that represents the signal at a field annulus due to a source annulus is pretabulated and interpolated in the computation scheme. The formulation yields a system of simultaneous equations for the pressures at the mesh points. Computation of coefficient matrix elements requires a twofold integration, with the axisymmetric annular Green's function in the integrand, and with the integration limits corresponding to the inner and outer edges of two annular regions. Numerical techniques for the integrations are discussed and the effects of mesh spacing and of numerical interpolation of the annular Green's function are explored. Results are compared with computations involving spheroidal wavefunctions and with computations using a Rayleigh-Ritz scheme based on the same variational formulation. [Work supported by ONR.]
Influence of baffle size and shape on farfield radiation patterns
Authors: Tanaka Shokichi
Published: October 2005

In underwater acoustics, transducers are often placed in some kind of a baffle. Then the farfield radiation patterns of the transducers vary with the property of the baffle and its size and shape. This paper describes the basic characteristics of the influence of a baffle due to its size and shape. Two shapes of baffles are treated to investigate the influence: (1) a three-sided semi-infinite baffle with a piston flush mounted in its middle side and (2) a semi-infinite circular cylinder baffle with a piston in its end side, both having either rigid or soft property. The geometrical theory of diffraction is used to calculate the farfield radiation patterns of the piston in the case of the middle side and the method of equivalent edge acoustic sources in that of the end side. Numerical results obtained with the methods in various baffle sizes and piston locations are presented. Measured patterns, which agree well with calculated ones in soft condition, are also presented.
Gaussian-Laguerre formulation of Lommel diffraction problem
Authors: Cook Bill D.
Published: October 2005

Solutions of Fresnel diffraction problems based on Gaussian-Laguerre functions are easily interpretable and can be calculated quickly because of recursive relations between the functions. I have applied them to solving the diffraction problem of a circular, receiving piston transducer in the field of a similar sending transducer. The pistons are coaxial but not restricted to being the same size. For equal size transducers, I find excellent agreement with earlier results [P. H. Rogers and A. L. Van Buren, J. Acoust. Soc. Am. 55, 724–728 (1974)]. When the receiving transducer becomes very small, the answer on axis agrees with the analytic point value. When the receiver has a radius twice as large as the sender, the Lommel diffraction correction is nearly a constant over a large range. [Work performed under the auspices of the U. S. Department of Energy and Lawrence Livermore National Laboratory, Contract No. W-7045-ENG-48.]
Experimental performance of single-and multiple-channel high-resolution spectral estimators
Authors: Marple S. L.
Published: October 2005

This presentation will examine the preformance characteristics of a wide variety of spectral estimators, including the techniques of MEM, Prony, AR (auto regressive), minimum variance or MLM, and eigenanalysis (singular value decomposition and multiple signal classification), to which high-resolution behavior has been attributed. A brief tutorial will review the basis for each technique. The performance of each will be depicted through a series of test cases of different signal classes, e.g., broadband, tonals, sunspots. The purpose of this is to demonstrate the strong and weak attributes of each method discussed.
Array processing and underwater acoustics
Authors: Cox H.
Published: October 2005

Many array processing algorithms for underwater acoustics now have been developed. Particular emphasis has been on obtaining both high resolution with small apertures and number of sensors and adaption to environmental noise fields. With the availability of high-speed and small digital signal processors many of these algorithms can now be implemented, often in real time. This presentation will review these algorithms and their effectiveness in underwater acoustics.
Locating underwater sources of sound, using sensors on a 3-D line of unknown shape
Authors: Bucker Homer P.
Published: October 2005

If sensors are located on a line of known shape, underwater sound sources can be located by matched-field processing [H. Bucker, J. Acoust. Soc. Am. 59, 368–373 (1976)]. That is, the sources are associated with relative maxima of a correlation function c(r,z,φ) which matches the received acoustic signals with calculated fields for source locations at different ranges (r), depth (z), and bearings (φ). If the line shape is not known, the methods of linear programming [H. Bucker, J. Acoust. Soc. Am. 63, 1451–1454 (1970)] can be used to find an “effective shape” that corresponds to maximum sharpness (s) of the “field of vision.” Here, s is the sum of c2 taken over all values of r, z, and φ. Examples will be presented showing sensitivity of the method to errors in the propagation model and to the effect of sources lying outside the matched-field points. [Work supported by NAVOCEANSYSCEN IR Program.]
Vertical directionality of ambient noise—A review
Authors: von Winkle W. , Browning D.
Published: October 2005

The vertical directionality of ambient noise in the sea falls into three frequency regimes: 0–200 Hz, dominated by long range sources; 200–10 000 Hz, relatively small directionality; 10 kHz and above, downward rays and heavily attenuated. A review is made of data mechanisms and our present prediction capability.