bluuebunny/crossref_metadata_2025 huggingface dataset:
Standards for human and human surrogate impact testing
Authors: Weiss Marc S.
Published: October 2005

Human and/or human analog response to shock and acceleration forces is a complex function of the interaction of the driving forces with the seating and restraint systems and the orientation and initial position of the subject with respect to the experimental environment. This response, correlated to specific anatomical segments and readily identifiable landmarks, requires considerable sophistication in instrumentation and data analysis techniques for an adequate analytical description. In addition, human volunteer impact acceleration experiments must be conducted at levels of acceleration that may produce discomfort yet have a negligible probability of producing any permanent or nonreversible injury. Impact levels that produce human injury and their correlation with dynamic response parameters must be inferred from experiments with human surrogates or from accident epidemiology data. The candidate human surrogates or analogs are human cadavers, animals with morphology similar to humans, and mathematical models. Each of these surrogates may provide valuable and complementary information concerning injury mechanisms and their correlation with human dynamic response data. These considerations form the basis of suggested standards and guidelines for formulating experimental protocols and reporting experimental results.
Fiber-optic push-pull hydrophones
Authors: Garrett S. L. , Brown D. A.
Published: October 2005

Optical fibers are neither intrinsically sensitive nor selective; hence, it can be difficult to design a fiber-optic hydrophone that is sensitive to acoustic pressure signals while rejecting variations in other quantities such as temperature, static pressure, or platform vibrations. One way to overcome this problem is to design fiber-optic interferometric hydrophones in which both legs of the interferometer are active and respond to pressure with strains of opposite sign. This talk will demonstrate the application of this “push-pull” design philosophy to bidirectional and omnidirectional hydrophones by describing several hydrophones that were developed at the Naval Postgraduate School. One bidirectional hydrophone measures the fluid-induced motion of a neutrally buoyant seismic sensor. The omnidirectional hydrophones create a push-pull strain using a flexural disk or a flextensional method. The dual-plate, four-coil, flexural disk hydrophone detects sound by measuring the surface strain on the two circular end caps of an air-backed cylinder. The use of two disks doubles the sensitivity to pressure while canceling any acceleration induced response. The flextensional hydrophone measures the difference between the strains in the equatorial and meridional circumferences induced when an oblate spheroidal shell is subject to a change in pressure. [Work supported by the Naval Sea Systems Command.]
Hot topics in architectural acoustics
Authors: Bradley J. S.
Published: October 2005

New developments in architectural acoustics are evident in both areas related to room acoustics and noise control in rooms. Six particular topics of activity will be mentioned that are from both of these two overall areas. (1) Perhaps the “hottest” topic of all is the development of increasingly improved computer modeling techniques. Models have been developed for both auditoria and industrial spaces and there is continuing evidence of gradually increasing sophistication in these models. (2) Subjective studies have continued to develop the results of the major studies of the 70s with a particular new emphasis on the acoustical conditions required by performers. (3) Studies involving the measurement of various newer auditorium acoustics parameters have been reported in several countries. (4) The renewed interest in solving low-frequency noise problems in rooms is indicated by the recent development of subjective rating schemes that extend to lower frequencies. (5) The increased interest in low-frequency problems is also seen in the physical measurements area where there is ongoing work to extend sound power measurement and transmission loss measurements in rooms to lower frequencies. (6) There is also evidence of considerable activity concerning the measurement and prediction of the properties of various types of acoustical materials.
Hot topics in psychological and physiological acoustics
Authors: Tangney John F.
Published: October 2005

Topical issues in the structure and the function of biological auditory systems are briefly reviewed. Techniques newly applied to structural issues of peripheral and central nervous systems are described. Novel approaches to the functional issues of fusion, localization, and recognition of acoustic patterns are presented by example.
Hydrophone noise induced by turbulent boundary layer pressure fluctuations
Authors: Dubus B. , Montgomery R. E.
Published: October 2005

The noise induced by the turbulent boundary layer pressure fluctuations on hydrophones embedded in an elastomer layer is usually predicted by assuming that the layer is unbounded in the lateral direction and the hydrophone does not influence the stress field [S. H. Ko and H. Schloemer, J. Acoust. Soc. Am. 85, 1469–1477 (1989)]. These predictions neglect the flow-induced noise associated with the edges of the layer as well as the diffraction, reflection, or shadowing of the stress field by the hydrophones. To avoid these limitations, the finite element code ATILA [B. Hamonic et al., J. Acoust. Soc. Am. 86, 1245–1253 (1989)] is used to model hydrophones embedded in viscoelastic layers of finite extent. The transfer function of the layer and/or the noise sensed by the hydrophone are computed for a given excitation of the outer surface or of the edges of the layer for different sizes. More complex multilayered structures are also examined. [Work partially supported by the Direction des Recherches Etudes et Techniques.]
A method for rapid computation of flow noise excitations of very large area planar arrays
Authors: Thompson W. , Montgomery R. E.
Published: October 2005

The output (power) of an acoustic sensor, in response to the pressure fluctuations in a turbulent flow of fluid over its surface, is predicted by a certain integral over all possible wave numbers in both the flow direction and transverse to that direction. The integrand comprises four real and positive factors that describe (1) the pressure spectrum of the flow, (2) the filtering action of any material positioned between the sensors and the flow field, (3) the spatial averaging effect associated with the nonzero size of one of the sensors, and (4) the additional spatial averaging due to deploying not one, but an array of such sensors. Computation of the filtering action can be extremely time consuming for a multilayered medium. In addition, the rapid fluctuation of the array function with wave number gives rise to an integrand that cannot be efficiently integrated by standard numerical methods. This paper presents approximate techniques that allow for accurate and near real time evaluation of flow noise power spectral density. Some results are presented for a large array.
The relationship between tempo and delay and its effect on musical performance
Authors: Willey Bob
Published: October 2005

A study was made into the effects of delayed auditory feedback on musical performance. Subjects heard their performance with various lengths of delay while playing at various tempi. This allowed for an investigation into the possible disturbing effects of delayed auditory feedback caused by different combinations of tempo and delay. Delay was most disturbing when its length was in a ratio with metronome beat length between 1:2 and 1:1. “Consonant” ratios were the least disturbing, with 2:1 and 3:1 as easy, or easier than the “fundamental” ratio of 1:1. This is in contradistinction to findings in speech research where the greatest disruption occurred when there is approximate equality between delay and syllable length. Research in delayed auditory feedback with speech has been more concerned with an absolute worst case for delay independent of rate. The results of this study are consistent with previous research that showed the most disturbing delay for music performance to be between 200 and 300 ms. In addition they support the hypothesis that disturbance depends on the ratio between the lengths of delay and beat. The implications for music performance are discussed, including the effect of pitch transformation during computer-mediated improvisation.
Conducting the MIDI Orchestra: Integrating the synthetic performer with the Acoustic Ensemble
Authors: Boulanger Richard
Published: October 2005

The commercial adoption of the Musical Instrument Digital Interface (MIDI)—a protocol that provides the syntax and structure for meaningful communication between virtually any computer and any digital synthesizer—brought a powerful set of tools for music composition, notation, sound design, and real-time performance from the university research labs to the private studios of the individual artist in the form of an affordable, powerful, and portable MIDI-based music workstation. Since its inception 7 years ago, MIDI has had a far reaching impact on virtually every aspect of professional music making. From the recording studio to the college classroom, MIDI-based workstations are playing a major role. Most importantly, however, is that MIDI has brought real-time computer-controlled and computer-generated sound to the concert stage. This paper addresses the question of how a composer today might integrate this computerized virtual instrument with traditional acoustic instruments. From the innovative use of commercial software, to the specialized applications of new computer interfaces such as Max Mathews' Electronic Stradivarius, Daton MIDI conducting surface, and Robert Boie's Radio Drum, this live musical demonstration will draw from the author's compositions Three Chapters from the Book of Dreams (1985), Shadows (1987), from Temporal Silence (1988), and Solemn Song for Evening (1989) to present a variety of practical and personal solutions.
An interactive performance software (Interactor)
Authors: Subotnick Morton , Coniglio Mark
Published: October 2005

The software described has both tempo and score following. A. Tempo following: (1) This has been approached so that it will be possible to follow any events that move in time and that can be converted to MIDI information. (2) The time between events is measured, converted to a tempo, and passed on to the next relevant “beat.” In order to achieve this, two things are needed: (i) accurate and musically relevant measurements and (ii) awareness of the metric organization of the score. Discussion, diagrams, and demonstrations will explain how these are achieved. B. Score following: (1) The most usual way to “score follow” is to compare what is supposed to be played with what is actually being played…and the awareness is usually heavily oriented toward the pitch information of the music. (2) In Interactor, (a) the computer need only know what is important to know so that it can rest and wait (much like musicians counting measures rest) until it is called into action; (b) the temporal organization is considered to be the most important, with pitch awareness used as needed; (c) discussion, diagrams, and demonstrations will explain how this is achieved. The result is an efficient processing of information that allows for real-time score following on small computers (a mac +, for instance), making it relatively easy to transport and use in performance even when the composer, programmer, etc. are not present. C. Demonstration: By using the first part of a Clementi Sonatina, the following will be demonstrated: (i) playing the right hand while the computer follows and plays the left hand; (ii) playing the left hand while the computer follows and plays the right hand; (iii) conducting (using a MIDI baton designed by Pat Downs). A summary will project the use of this kind of interaction in all performance environments.
The distortions of the sound field due to the presence of an operator
Authors: Kuhn George F.
Published: October 2005

Theoretical predictions of the distorted sound field, extending as far as 1 m from the center of the person, are presented. The effects of the operator, as measured on the surface of the body or head of the operator, have been presented before [G. F. Kuhn, J. Acoust. Soc. Am. Suppl. 1 79, S2 (1986)]. Here, a circular cylinder and a sphere, whose surface impedances can be specified, are used to approximate the torso or head. The predicted results of the distorted sound field are in general agreement with the experimental results of Brinkman and Obermayr [Noise Control Eng. 11, 32–39 (1978)], for example. Exact corrections for these distortions are difficult to specify categorically because of the many variables that affect the field measurements. However, noise surveys, in predominantly plane, progressive sound fields, appear “best” made with the microphone along a radius through the shadow boundary of the operator, or else directly at the head surface at the shadowed pole of the head, but not in the ear. Measurements off the body surface but at a close distance to the body facing the source as well as measurements in the geometrical shadow of the body are prone to the largest errors. Measurement errors elsewhere can be reduced substantially by frequency and/or spatial averaging.
Sound levels daring operation of magnetic resonance imaging systems
Authors: Lane Sam R. , Hurwitz S. Robert
Published: October 2005

The sound or noise levels at the patient position in the bore of several different magnetic resonance imaging (MRI) systems were measured. The measurements were conducted with the microphone/preamplifier component connected to the sound-level meter (SLM) with an extension cable so that the SLM was remote from the MRI scan room. Preliminary tests and analyses were conducted to ascertain that the microphone/preamp functioned normally in the strong magnetic field and rf environment. Subsequently, A-weighted, flat-weighted, and octave band noise levels were measured in the MRI system bore areas during a variety of image scanning sequences. The noise levels were in the range 75–95 dB A-wt., and 85–105 dB flat-wt. Greater noise levels tended to be correlated with greater magnetic field strengths and with more rapid and detailed image scanning sequences.
Work by virtual sources against in-phase and quadrature amplitudes of finite-amplitude harmonics: Impact on nonlinear attenuation
Authors: Woodsum Harvey C. , Hogan William
Published: October 2005

Prior results by Woodsum [J. Sound Vib. 69, 27–33 (1980)] on the propagation of sinusoidal harmonic components of a finite-amplitude plane wave are corrected to account for missing terms that are sometimes not ignorable, and to account for the phases of the harmonic amplitudes, as well as cases of cylindrically and spherically spreading waves. The result, as before, is based on the application of Westervelt's energy conservation equation, and recognition of the fact that work is performed independently by the virtual sources on the in-phase and quadrature components of each harmonic. The very general result obtained is compared to prior results obtained with Burgers equation, and applied to the calculation of a taper function for the parametric array.
Nonlinear model equations for waves in a stratified fluid
Authors: Tjøtta Jacqueline Naze , Tjøtta Sigve
Published: October 2005

The present work is a theoretical study of the combined propagation of acoustic and internal waves of finite amplitude in a stratified fluid. The motion is described within the framework of a thermoviscous fluid, although relaxation effects can be readily accounted for. Model equations are derived under the assumption of weak nonlinearity. The nonlinear terms combine to form source terms in two coupled, governing equations in the pressure and vertical particle velocity or displacement. Examples are given that show effects of nonlinear coupling between acoustic and internal waves. Generation of vorticity and steady flow (acoustic streaming), and their interaction with the sound field, is also discussed briefly. [Work supported by The Norwegian Research Council for Science and Humanities (NAVF) and VISTA/STATOIL, Norway.]
Experiments on linear and nonlinear wave propagation in periodic media
Authors: Meegan G. Douglas , McKenna Mark J. , Maynard J. D.
Published: October 2005

Recently, there has been interest in linear and nonlinear wave propagation in periodic and random potential fields. Studies of such effects using surface waves in adsorbed superfluid helium, which should show strong local nonlinear behavior, have begun. While there has been considerable theoretical attention given to nonlinear effects for these waves, there have been no systematic experimental studies. Research with a variety of experiments, including studies of linear and nonlinear propagation of these waves in uniform as well as periodic one-dimensional media, has begun. Measurements have been made with drive levels varying over five orders of magnitude. The results have been found to exhibit nonlinear effects including a velocity of propagation dependent on drive level. [Work supported by NSF DMR 9000549 and the Office of Naval Research.]
Physical interpretation of the general Poynting's theorem for shell vibrations
Authors: Pierce Allan D.
Published: October 2005

An improved derivation involving tensor analysis and covarient differentiation, as well as Hamilton's principle and a realization of Noether's theorem, is given for the energy corollary of the basic shell dynamic equations for a thin shell of arbitrary shape, and with position-dependent elastic modulus E, Poisson's ratio v, and shell thickness h. This corollary states that the sum of (i) the time derivative of an energy density and (ii) the divergence (within the shell middle surface) of a structural intensity vector is identically zero in the absence of external sound radiation and internal damping. The requirement that the intensity transform as a two-dimensional tensor removes the intrinsic ambiguity (with which intensity component does one associate a double derivative term?) that the author had previously reported in an analysis of shells of revolution. The compact tensorial form of this “Poynting's theorem” is seemingly simple, although its explicit unraveling for specific cases can lead to cumbersome expressions. The two tensorial groupings in the structural intensity reduce in the flat plate case to (i) energy flux associated with in-plane (e.g., stretching) motions and (ii) energy flux associated with bending (flexural) motions. Further clarifications of the derived expressions are found in the limiting cases of cylindrical and spherical shells, and in appropriate “high-” and “low-frequency” limits. The latter part of the paper discusses how the corollary may be extended (although with some approximations) to incorporate fluid loading and sound radiation. [Work supported by ONR.]
Scattering of a plane wave from a cylinder partially coated by a layer modeled as a dissipative fluid
Authors: Ginsberg Jerry H. , McDaniel James G. , Ferri Aldo A.
Published: October 2005

A previous investigation of scattering from a partially coated infinite circular cylinder employed a local impedance boundary condition to represent the interface between the coating and the exterior domain. Such a model led to a singularity in the surface response at the discontinuity. In addition, such a model is inadequate to describe dissipative effects of the layer. In the present paper, the partial coating is treated as a fluid layer bounded at its inner radius and azimuthal ends by a rigid cylinder, while continuity of pressure and particle velocity with the exterior fluid is imposed at the outer radius. Dissipative effects are included by allowing the wave number of the layer to be complex. The scattered pressure field in the exterior domain and the pressure within the layer are represented by azimuthal spectral series whose basis functions are solutions of the Helmholtz equation for the respective regions. The series coefficients for those series are obtained by using a collocation technique to enforce the continuity conditions at the outer radius in a point-wise manner. Results for a range of system parameters are used to investigate the effects of the surface discontinuity associated with the partial coating. [Work supported by ONR.]
Axisymmetric vibrations of spheroidal shells: Eigenvalue loci veering and parameter sensitivity of eigenfunctions
Authors: Chen Pei-Tai , Ginsberg Jerry H.
Published: October 2005

In a previous presentation [P. T. Chen and J. H. Ginsberg, J. Acoust. Soc. Am. Suppl. 1 86, S83 (1989)], the eigenvalue loci depicting the dependence of natural frequency of spheroidal shells on aspect ratio was discussed. Some anomalies regarding the alteration of mode shapes with changes in aspect ratio were observed. This problem is closely related to the properties of an eigenvalue system having two or more close eigenvalues. In the present work, a perturbation series expansion whose small parameter represents the deviation of the system from its reference state is applied to a general eigenvalue problem. It is shown that the eigenvalues of the associated loci veer away from each other, rather than intersecting, and that the eigenfunction associated with each locus consists of a linear combination of the reference state eigenfunctions for both loci. The insight gained from the general solution is used to study spheroidal shells. Of special interest is the change in energy distribution between bending and stretching in the vicinity of veering zones. [Work supported by the Office of Naval Research, Code 1132-SM.]
Acoustic scattering from submerged finite-length cylinders with end caps and internal ribs: A comparison of methods
Authors: Brill D. , Gaunaurd G. C.
Published: October 2005

The various methods that could be used to model the monostatic scattering of sound waves from cylindrical bodies of finite length with end caps and a coaxial set of reinforcing ribs, immersed in fluids, are compared. The various approaches include the Kirchhoff method, the Keller theory of geometrical diffraction (GTD), or combinations of these methods applied to soft cylinders having alternating bands of rigid and soft composition spaced at selected intervals on the cylindrical surface. The resulting four cases are tackled by the physical optics method and by the GTD. Parts of the work are compared to earlier findings [D. Brill and G. C. Gaunaurd, Proceedings, First French Congress on Acoustics, Lyon, Vol. 1, pp. 320–324 (1990)]. Numerical evaluations are produced in the various instances, analyzed, and they are contrasted to one another. In all cases the predictions reveal a lobe structure that resembles that of a diffraction grating. Ways to enhance or destroy this peculiar pattern, and other (more complex) ways to model this problem by accounting for the structure's elasticity, while retaining the simplicity of the above findings, are discussed. [Work supported by NSWC.]
An experimental and analytical investigation into foundation and hull strong coupling
Authors: Bowen David L.
Published: October 2005

The possibility of high levels of vibration being transmitted through a machine foundation to the hull of a ship is of concern to designers. It is possible that strong peaks in waterborne sound radiation are associated with strong coupling between foundation and hull modes, creating paired sets of “global” modes. Previous experimental work on a plate and cantilevered beam structure indicated that, if the moment impedances of these substructures were close in magnitude, then the addition of mass to the foundation would not affect hull modes, while masses added near the foundation/hull junction would not affect foundation modes. With this procedure, global modes could be detected using vibration response measurements made on the foundation only. The purpose of this study was to apply these ideas to a more complex structure, supplemented by its finite-element model. It was found that the above findings did not always hold, but that the mass addition procedure could be used to narrow down the number of global mode candidates. It was also found that, while global modes involve a superposition of the mode shapes seen when the foundation is “tuned away” from hull modes, the increase in energy transmitted to the hull was not as great as expected.
Acoustic power radiated by the hull partition of a ship measured with spatial intensity vector
Authors: Højbjerg Klaus
Published: October 2005

Generally, acoustic intensity fields in small enclosures are more or less rotational and acoustic energy flows along curved and closed streamlines. This kind of phenomena is also found in measurements of the spatial intensity vector in ship accommodations. Rotational character of the complex intensity field is stronger in the near field close to the vibrating partitions, but strong rotations can also be observed in the far field. These are caused by reflections from the walls or because of interference between the direct rotational field from the cabin partitions being coherent sources. Describing the structureborne noise field in small enclosures like ship accommodations with spatial intensity vector can be of great help in solving engineering problems in noise abatement work on ships. One of the main advantages of using sound intensity is that it is possible to identify the structureborne energy transmitted through different parts of the cabin partitions.
Steered conical beams using an annular ring array
Authors: Hughes W. Jack
Published: October 2005

It is shown that by appropriately processing the output signals from the ring elements of an annular ring array, a steered conical beam can be produced. The theory is based on the ability to produce a double-lobed steered beam using a particular weighted phase-symmetric line array, and is extended for use with an annular ring array. Chebyshev shading coefficients are generated and used to calculate the coefficients for the steered double-lobed beams of the line array, then appropriately modified for use with the annular ring array. Conical beams are formed and steered to a desired angle using a minimum number of sensor channels. In addition, steered null patterns can be formed. A low-frequency and a high-frequency annular ring array have been built and tested. Experimental patterns were measured and compare closely to the calculated values.
Acoustic properties for place of articulation in nasal consonants: A cross-linguistic study
Authors: Kurowski Kathleen Mary
Published: October 2005

Previous critical band analyses have shown distinctive energy patterns for place of articulation in nasal consonants in English [K. M. Kurowski and S. E. Blumstein, J. Acoust. Soc. Am. 81, 1917–1927 (1987)]. This study explored the extent to which these properties emerged across various languages (English, Polish, and French) by refining and evaluating a metric measuring rapid spectral changes in the vicinity of the nasal release. Utterances spoken by male and female speakers included nasals in five vowel contexts and two syllable positions. The results for syllable-initial nasals showed that the metric correctly classifies labial and coronal consonants in English (83%), Polish (87%), and French (78%). Nasals in syllable-initial clusters yielded similar results. Although some gender differences and vowel context effects were noted, the integrity of the boundaries of the broadly defined target areas of Bark 5–11 for labials and Bark 11–16 for coronals was generally maintained. The metric's overall success is viewed as support for a theory of acoustic invariance. [Work supported by NIH.]
Phonetic and phonological stages in stops
Authors: Henton Caroline , Ladefoged Peter , Maddieson Ian
Published: October 2005

Traditional phonetic analyses of stops have recognized three phases: onset, closure, and release. Using data from an expanded version of UPSID [I. Maddieson and K. Precoda, J. Acoust. Soc. Am. Suppl. 1 86, S19 (1989)] and from an ongoing project on the sounds of the world's languages [P. Ladefoged and J. Choi, J. Acoust. Soc. Am. Suppl. 1 86, S75 (1989)], it will be shown that phonologically only two phases—closure and release—are exploited. For example, independent distinctions of phonation type cannot be found in the onset phase. Similarly, only the release stage may be distinctively lateral. The phonological restriction applies to stops made with pulmonic and glottalic airstreams (velaric stops are not discussed here). Language-specific examples of contrasts in the closure and release phases are presented and some universal implications for consonant inventories are explored.
Use of spectral cues for initial-stop voicing perception by French-English bilinguals
Authors: Boulakia Georges , Hazan Valerie L.
Published: October 2005

The use of F1 onset information, which constitutes a cue to the voicing contrast in English, but not in French, was investigated in French-English bilinguals using a /pen/-/ben/ minimal pair, meaningful in both languages. Two stimulus continua were constructed by digitally editing natural speech tokens. In both, VOT varied from −40 to 40 ms but the [en] portion of the stimuli was taken from a [ben] token in the Ben/VOT condition and a [phen] token in the Pen/VOT condition. Stimuli were presented in identification tests in two language modes, with either an English or French precursor word before each token. Bilinguals resident in France or Great Britain were classified in terms of their degree of bilingualism and language bias. Results show a significant effect of vowel onset characteristics on phoneme boundary for all subject groups. Irrespective of language mode, listeners exposed to English early (monolinguals, “strong” bilinguals, and English-biased “mid” billinguals) were, on average, unable to consistently label stimuli in the Pen/VOT condition as voiced, even in the presence of prevoicing.
The recognition of quasiarticulatory tactile syllables after training with visual feedback
Authors: Piroth Hans Georg , Sladek Reiner
Published: October 2005

An experiment has been executed to test the recognition of consonantal patterns in an identification test after training with visual feedback. A German sentence ['ɪç'za:gəCi:] with six plosives and six fricatives varied in the place of C was recorded on videotape and manipulated in such a way that the only segment that varied was the CV syllable. The test itself is performed under three conditions: a tactile group, a lipreading group, and a mixed-condition group (tactile and visual stimuli presented at the same time). The electrotactile stimuli were taken from the SEHR-2 system. The encoding principles of SEHR follow articulation: As the place of articulation changes from front to back, so does the tactile stimulation along the left arm. This test was generated to show how subjects perform under the lipreading-alone, the tactile-alone, and the mixed condition. The results can be interpreted in terms of different strategies used by the Ss that can lead to integrative of additive percepts.
Two types of audiovisual integration for the identification of speech segments
Authors: Braida Louis D.
Published: October 2005

This paper contrasts two types of audiovisual integration that can be used to identify speech segments. In “prelabeling” integration, relatively continuous sensory data are combined across modalities before a response label is assigned. In “post-labeling” integration, a joint response is derived from the pair of responses that would be made under unimodal conditions. In many cases, post-labeling integration is inadequate to account for consonant identification accuracy. To characterize prelabeling integration, confusion matrices are described in terms of the locations of stimulus and response centers in a multidimension Thurstonian decision space [L. D. Braida, J. Acoust. Soc. Am. Suppl. 1 84, S142 (1988)]. The distance between a pair of stimulus centers determines how well two stimuli can be distinguished in a given experiment. In the multimodal case, the decision space is assumed to be the product space of the decision spaces corresponding to the stimulation modes. The predictions of this model of prelabeling integration are fairly consistent with published data on mutimodal identification accuracy.
Measurement of consonant confusions by human listeners in whispered speech
Authors: Martin Doug
Published: October 2005

The acoustic differences between whispered and normally phonated speech are large; yet whispered speech is still very discriminable. Since replacing a periodic voicing source with an aperiodic excitation does not significantly affect perception, there exists the possibility of a central processing stage to augment the normal peripheral processing. In our experiments, the 16 CV syllables used by Miller and Nicely (1955) are whispered by three male and three female talkers. The data are used to collect confusion matrices from listeners who discriminate among 64 sample syllables from each talker. Data are also collected with stimuli involving normal and loud speech, in an attempt to determine what, if any, acoustic cues might discriminate between the consonants across stimulus conditions. The consonant confusions are obtained using a multitalker babble as a masker. Babble is used instead of white noise because it should equally mask all speech stimuli, whereas white noise may mask some stimuli, such as fricatives, more than others. Probabilities of consonant confusions across the voicing dimension for whispered speech will be presented.
Acoustic evidence of overlap in consonant sequences
Authors: Zsiga Elizabeth C. , Byrd Dani
Published: October 2005

Acoustic evidence for temporal overlap of the two closure gestures in the environment VC♯CV was investigated. It was hypothesized that evidence of C2 would be found in the VC formant transitions and would increasingly dominate the transitions as rate (and by hypothesis, overlap) increased. Twenty repetitions (ten at a normal rate and ten at a rapid rate) of word pairs where the first word ended in /d/ and the second began with /p/, /t/, or /k/ were elicited in a sentence context from four subjects. Here, F2 and F3 transitions from the midpoint of V1 to just before closure were then measured. In all environments, C2 had a clear influence on the VC formant transitions. In the d♯k environment, the velar transitions were more prominent at the rapid than at the slow rate; however, the rate effects for d♯p were less clear. The acoustic influence of C2 on V1 suggests considerable temporal overlap of the two closure gestures, and at least for the d♯k case, increasing overlap as a function of rate. [Work supported by NIH Grant HD-01994.]
Measurements of low-frequency backscatter from the sea surface during SWAPP
Authors: Hill Steven , Farmer David
Published: October 2005

During the SWAPP (surface wave processes program) cruise off San Diego in February of this year, measurements of low-frequency acoustic backscatter from the sea surface were made. A surface-tethered instrument, suspended at a nominal depth of 55 m, carried acoustic instrumentation including a low-frequency (400–1000 Hz) projector, and an array of broadband omnidirectional receivers. Measurements to be presented include: nondirectional backscattering strength as a function of grazing angle and sea state; and backscattering strength as a function of azimuth, grazing angle, and sea state. Measurements of near-surface ambient noise will also be presented: These will include estimates of azimuthal variability.
Simulations of surface reverberation measurements using a tripod array
Authors: Baggeroer Arthur B. , Hodgkiss William S.
Published: October 2005

The scientific plan for the surface reverberation component of the ONR acoustic reverberation special research program (SRP) has placed special emphasis on low grazing angle backscatter and high wind speed conditions in the 15- to 30-kn region. One proposed array configuration for receiving the surface backscatter at 400 Hz is a submerged tripod with apex at approximately 100-m depth. This paper presents simulations of the expected reverberation level versus time at the output of the array beamformer. Two aspects of the array performance are considered: (i) the resolution and sidelobe rejection for isolating individual surface reverberation events in space and time and (ii) the estimation of the spectrum of the backscattered signal as a function of surface location. The first aspect emphasizes the array's ability to isolate specific physics while the second concerns the spatial distribution of scattered energy. [Work supported by ONR.]
A comparison of two hybrid modeling approaches to the problem of scattering from a rough sea surface
Authors: Keiffer Richard S. , Norton Guy V. , Chin-Bing Stanley A.
Published: October 2005

A technique used to couple 2-D propagation as calculated by PE with the 3-D scattering from a rough surface as calculated by the wedge assemblage method has been previously presented [J. Acoust. Soc. Am. Suppl. 1 86, S66 (1989)]. In this paper, the forward and backscattered fields resulting from interaction with a rough sea surface are predicted by this hybrid model and compared with predictions made by a hybrid PE-finite-element model (PE-FFRAME). [Work supported by the Office of Naval Technology.]
Theoretical predictions for the SASS experiment
Authors: Willemsen J. F. , DeFerrari H. A. , Pourkaviani M. , Roginsky J.
Published: October 2005

The geometry of experiments described by DeFerrari et al. at this meeting is considered. The aim of this paper is to supply a baseline of theoretical predictions for the backscattering strength and for the Doppler spectrum making use of Rayleigh-Rice perturbation theory to fourth order in the cross section. These calculations are performed over the ranges of incidence angles and frequencies relevant to the experiment, taking into account refraction in a model ocean without fluctuations. The calculations are performed using both Pierson-Moskowitz and Toba angle-averaged ocean surface spectra in a fully two-dimensional form, at wind speeds expected in the course of the experiments. These baseline predictions will enable us to quickly identify anomalous experimental results.
Reflections on the acoustical design of halls for music performance
Authors: Johnson Russell
Published: October 2005

The experiences of some 40 years of research and consulting in the design of concert halls, opera houses, and theaters are reviewed, beginning with the author's first professional projects under the leadership of the late Professor Edward C. Cole at Yale University through the recently completed Morton H. Meyerson symphony center in Dallas, TX. Included are the author's reflections on countless projects throughout North America and abroad during and following his “BBN years” during which he pioneered collaborative efforts integrating theater engineering and planning with the vitally interdependent discipline of acoustics. Some fundamental requirements for realizing satisfactory listening environments in halls for music performance are reviewed.
The active management of hydrodynamic sources of sound
Authors: Ffowcs-Williams John E.
Published: October 2005

The subject of hydroacoustics developed from the need to understand the causes and origin of flow-induced noise, a topic important to understanding the background noise of the natural ocean and to the construction of quiet underwater vehicles. There is much similarity between the hydroacoustic problem and the field of aeroacoustics, which grew from the need to control the noise of aircraft. In both, the major path to knowledge has been the study of sound generated by particular flow processes, processes chosen either for their engineering significance or for their analytical tractability. The source of sound, rather than the sound itself, became the center of attention, and new real problems of identifying the source had their origin in the fact that the source is essentially ambiguous. The source determines the sound but the sound cannot prescribe the source. Most views of what is and what is not a source of sound accommodate the notion that sound is a consequence of the source, the source comes first and the creation of sound leaves no mark on the source itself. But hydrodynamic sources are always associated with unsteady flow, most noisy flows being unsteady because the steady condition is unstable. Small perturbations about the steady state grow into turbulent sources of sound. Sound is also a small perturbation of the steady condition; in the hydroacoustic problem the distinction between instability waves and sound is not always clear and neither is it always real. Sound generated by turbulence can be the triggering disturbance of instabilities that grow into turbulence. Cause and effect are no longer distinct; the question of what came first is no simpler in hydroacoustics than with the chicken and egg. Though that view brings much confusion to the task of identifying natural source processes, it opens up a marvelous prospect of control, a prospect that rests on the introduction of secondary sound fields to interfere with the natural instability process on which the existence of turbulence depends. Antisound, a subject exploiting the destructive interference between sound and its artificially created inverse carries over to flow instabilities where its effect is changing the character of some very energetic and noisy flows previously thought, because of their high energy level, to be immune to the backreaction of their feeble acoustic emission. The active management of hydrodynamic sources of sound is the title I give to the subject of artificially stimulating unstable flows with the stimulation techniques coming from the same family as those used in antisound. The lecture will describe some demonstrations of the technique that certainly changes the noise, but that change is minor in comparison with the general character change on the much more energetic flow. Examples will be given where sound becomes the oil that calms otherwise troubled waters.
Gap flow noise
Authors: Gershfeld Jonathan L.
Published: October 2005

Experimental results are presented on the generation of aerodynamic sound by a lifting surface in the vicinity of and perpendicular to a plane. Interaction of the tip flow and the boundary layer flow of the planar surface creates an aeroacoustic flow source that is baffled by the surface. Acoustic pressure spectra are presented for variations in loading of the lifting surface and proximity of the lifting surface to the plane. Source strength estimates are made from wall pressure spectral measurements in the airfoil tip region. [Work supported by O.N.R.]
A simulation study of cross-basin sound transmission from Heard Island to California
Authors: Chiu Ching-Sang , Semtner Albert J.
Published: October 2005

An underwater acoustic technique was proposed by Munk and Forbes (1989) for monitoring greenhouse warming. It involves making decadal measurements of cross-basin acoustic travel-time variability. A 2-week global acoustic transmission experiment, led by Munk et al., will be carried out in January 1991 to evaluate the feasibility of this acoustic method. In support of the experimental effort, this modeling work simulates the influence of ocean fronts and eddies on the three-dimensional acoustic ray paths crossing the Indian and Pacific Oceans to the California coast from Heard Island, the location for the sound source. For the computation of the cross-basin acoustic paths, a three-dimensional Hamiltonian acoustic ray-tracing code developed originally by Jones et al. (1986) is used. The input sound-speed fields to the acoustic ray model are interpolated from gridded temperature and salinity ouput data from the Semtner-Chervin eddy-resolving global general circulation model (1988). Results from tracing rays to the California coast through sound-speed fields containing mesoscale variability are presented. In particular, the variabilities of the cross-basin ray paths, travel times, illuminated locations, and azimuthal arrival angles are examined.
Coupled-mode propagation through the transition zone between the Antarctic circumpolar current and the Pacific deep ocean
Authors: Ehret Laura L. , Chiu Ching-Sang
Published: October 2005

Using a 3-D Hamiltonian ray-tracing program with realistic topography and sound-speed distribution from the Semtner-Chervin eddyresolving global ocean model (1988), acoustic raypaths have been calculated from Heard Island near Antarctica to the central California coast in anticipation of the effort to monitor global warming using cross-basin acoustic transmissions (Munk and Forbes, 1989). These paths traverse two regimes, the relatively homogeneous circumpolar current (upward refracting) and the Pacific deep ocean (deep sound channel). The proposed Heard Island sources are low frequency, approximately 50 Hz, making an examination of mode-mode interactions critical to the understanding of acoustic propagation through the transition zone between the above regimes. The 3-D coupled-mode model of Chiu and Ehret (1989) is used to examine the behavior of the first ten modes in the transition zone.
Performance of a short parallel-plate thermoacoustic stack with arbitrary plate separation
Authors: Hofler Thomas J.
Published: October 2005

In 1983, Wheatley et al., using the analysis of N. Rott, showed that most of the heat transport in a thermoacoustic stack operating in the boundary layer regime (plate separations large compared to a thermal penetration depth) is due to standing wave phasing of the acoustic field (pressure and velocity in quadrature). With traveling wave phasing (pressure and velocity in phase), the heat transport is reduced by an order of magnitude. While the short stack approximation used in this calculation is reasonable (a longer stack can be considered to be a series of short stacks), the boundary layer approximation is more severe. Stirling cycle engines use regenerators with very small plate separations compared to a thermal penetration depth and a predominantly traveling wave phasing between pressure and velocity. The behavior of Stirling cycle engines as well as that of standing wave thermoacoustic engines should be contained in the complete thermoacoustic differential equations of N. Rott. Calculations of the performance of short thermoacoustic stacks with arbitrary plate separations and arbitrary acoustic phasing will be presented. [Work supported by ONR.]
Study of a parallel plate thermoacoustic prime mover
Authors: Bass Henry E. , Atchley Anthony A. , Hofler Thomas J.
Published: October 2005

The frequency response of a resonance tube including parallel plate heat exchangers and prime mover stack has been measured. The results are given in terms of the quality factor Q of the prime mover. As the temperature gradient across the prime mover stack is increased, the Q increases indicating a decrease in attenuation across the stack. When the temperature difference is sufficiently large (∼300 K), the resonator goes into self-sustained oscillation indicating negative attenuation. Observations of Q approaching the onset of self-oscillation are reported in helium gas at pressures from 170–500 kPa. The observed Q's and the resonance frequency are explained in terms of counterpropagating plane waves. [Work supported by ONR and the NPS Research Program.]