bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of F1 in the perception of voice offset time as a cue for preaspiration
Authors: Pind Jörgen
Published: July 2002

Preaspiration, an [h]-like sound inserted between a vowel and a following stop consonant, can be cued by voice offset time (VOffT), a speech cue which is a mirror image of voice onset time (VOT). Previous research has shown VOffT to be an effective cue for preaspiration and also that the perception of VOffT differs from the perception of VOT in that the former cue is much more sensitive to the duration of a preceding vowel than is VOT to the duration of a following vowel [J. Pind, Q. J. Exp. Psychol. 49A, 745–764 (1996)]. The hypothesis has been put forward that this is due to the fact that preaspiration in Icelandic follows a phonemically short vowel, whereas aspiration can precede either a long or a short vowel. Vowel quantity will therefore affect phoneme boundaries for VOffT, not for VOT. This hypothesis was confirmed in experiments where vowel spectra were used to manipulate quantity rather than vowel duration. The present paper reports experiments investigating whether this effect could possibly be mediated through the effect of F1 on perceived voicing. [Supported by Icelandic Science Foundation and University of Iceland.]
Acoustic analysis of American English vowels by native speakers of Russian
Authors: Romano Lisa Jayne , Bell-Berti Fredericka , Lorin Eugenia
Published: July 2002

The ability of individuals to learn a new language requires mastering the phonetic as well as lexical and syntactical aspects of the new language. As part of a larger study of second-language learning, the acoustical characteristics of American English vowel production by native speakers of Russian were explored and these characteristics were compared with the identification of these speakers’ English vowels by native speakers of American English. Four adult bilingual Russian/English speakers (two women and two men) participated in this study. Recordings were made of the subjects as they produced four repetitions each, in random order, of ten English words (heed, hid, head, had, hod, hawed, hood, who’d, hud, heard). The recordings were digitized using SoundDesigner II software with an audiomedia board; formant frequency analyses will be carried out using Signayze 2.0 software implemented on a Macintosh Quadra 800 computer. The acoustical analyses will be examined in light of the identification of the Russian speakers’ English vowels by native speakers of American English (reported in another paper at this meeting). [Work supported by St. John’s University.]
Implications of a bistatic treatment for the second echo from a normal incidence sonar
Authors: Heald Gary J. , Pace Nicholas G.
Published: July 2002

Echo sounders have traditionally been used for the measurement of water depth but recent developments have shown how the information contained in the acoustic backscatter, related to the sediment type, may be extracted. As echo sounders operate at normal incidence it is possible to use the first and second backscatter from the seabed for sediment discrimination. This study has investigated why additional information may be contained in the second backscatter. It is shown that the geometry for the second backscatter must be treated as an on-axis bistatic configuration in which the source is effectively 3 water depths above the seabed. The resulting scattering equations are used to show how the range dependence of the scattering places the receiver in the near field for the second echo. The importance of the sensor geometry and the processing of the received signals are also discussed. As a result, it is shown that the combination of information contained in the first and second backscatter may be used to descriminate between different sediments. The result from tank experiments using a 200-kHz transducer over different sediments has allowed comparison with the theory and shows the effect of different water surface roughness on the second backscatter.
A review of the SSA for rough surface scattering
Authors: Broschat Shira L. , Thorsos Eric I.
Published: July 2002

The small slope approximation (SSA) for scattering from rough surfaces was introduced by Voronovich in the mid-1980s [A. G. Voronovich, Sov. Phys. JETP 62, 65–70 (1985)]. Numerical studies have shown that the SSA gives excellent results over a broad range of scattering angles. However, in the high-frequency limit the second-order (in the field) SSA scattering amplitude reduces to the geometrical optics result and, thus, to a single scattering model limited to local interactions with the surface. In this paper, small slope theory will be reviewed briefly, expressions for the bistatic scattering cross section will be presented, and numerical results will be shown for a number of different problems and several different roughness spectra. In addition, in an effort to extend the nonlocal scattering effects, Voronovich modified the SSA. He applied the same approach underlying the SSA, but he began by iterating the integral equation of the second kind [A. G. Voronovich, Waves Random Media 6, 151–167 (1996)] which led to the nonlocal small slope approximation (NLSSA). While the main focus of this talk will be the SSA, the NLSSA will be compared with the SSA for selected results. [Work supported by ONR.]
Inversion of bistatic reverberation and scattering measurements for seabottom properties
Authors: Rogers Andrew , Muncill Greg , Neumann Peter
Published: July 2002

Considerations associated with the inversion of bistatic reverberation and scattering data from a three-dimensional space are discussed. The SCARAB (SCAttering and ReverberAtion from the Bottom) acoustic propagation and scattering model has been the kernel for the study. This model considers three-dimensional, non-plane-wave, range-independent acoustic signals in both mono- and bistatic source receiver configurations. Due to the computationally expensive problem of computing a reverberative field which includes many hybrid acoustic paths and the iterative nature of the inverse process, inversion for seabottom properties requires highly effective search parameter space reduction and algorithm optimization. The parameter space reduction methods and simulated annealing and genetic optimization algorithms utilized are discussed, and their effectiveness measured against several test cases. [Work supported by ONR.]
High-frequency sound propagation in shallow water with rough surface scattering
Authors: Tang X. , Badiey M. , Simmen J.
Published: July 2002

Sound propagation at mid to high frequencies (1–20 kHz) in shallow-water environments is extremely complicated, variable, and poorly understood due to multiple processes that cover a wide range of temporal and spatial scales. Numerical simulations using a full-wave PE model are carried out to interpret the acoustic data taken during very carefully designed experiments at a shallow-water site inside the Delaware Bay. Records of broadband acoustic wave time series (from hours to days) are numerically reproduced by using the collected environmental data as input to the PE model. The statistics of both measured and simulated multipath signals are calculated and compared in the presence of rough sea-surface scattering and surface bubble layer attenuation. The surface wind effects can be separated from the slowly varying volume fluctuations of sound speed, by comparing the temporal variations; while it can be separated from the bottom effects by examining different multipath arrivals. The dependence of coherence on the parameters of wind strength and acoustic frequency is examined.
The effect of F3 on the /ᴜ–ɪ/ boundary
Authors: Buehler Matthew R. , Nábělek Anna K.
Published: July 2002

Boundary locations (50% response points of identification) were tested for /ᴜ–ɪ/ continua for two different values of F3. All formants were steady-state. F1=250 Hz, F2 was varied in 20 steps from 1000 to 2000 Hz, and F3=2500 or 3000 Hz. All stimuli were 200-ms long. The boundaries for the two continua were determined with ten subjects. The boundary for F3=2500 Hz was 1652 Hz and for F3=3000 Hz was 1526 Hz. The difference between the boundaries was significant. These results indicate that F3 can affect the perception of F2. When F3 was increased the stimuli were identified as /ɪ/ at a significantly decreased value of F2.
Is allophonic variation in Japanese /ɾ/ a factor in Japanese listeners’ difficulty in perceiving English /ɹ-l/?
Authors: Ueno Mieko , Beddor Patrice S. , Akayane-Yamada Reiko
Published: July 2002

Japanese listeners’ difficulty in perceiving the English liquid (/ɹ-l/) contrast has been attributed to various phonological and phonetic factors. To explore allophonic variation in the Japansese flap as a contributing factor, American English listeners’ perception of Japanese /ɾ/ was investigated in a range of phonetic contexts. Stimuli were 152 Japanese words containing /ɾ/ in all phonotactically possible contexts produced by two native Japanese speakers. Three stimulus randomizations were presented to 12 American English listeners for identification as ‘‘l,’’ ‘‘r,’’ ‘‘D’’ (=flap), ‘‘d,’’ ‘‘t,’’ ‘‘no sound,’’ or ‘‘other sound.’’ Results showed strong effects of syllable structure: Japanese /ɾ/ sounded more stoplike (‘‘D,’’ ‘‘d,’’ ‘‘t’’ responses) in consonantal contexts and more liquidlike (‘‘r,’’ ‘‘l’’ responses) in vocalic contexts. However, liquid responses were more likely to be ‘‘r’’ intervocalically, compared with ‘‘l’’ in initial position. Vowel quality also had a strong effect: Japanese /ɾ/ elicited more stop responses in high vowel ([i u]) contexts and more liquid responses in lower vowel ([a o]) contexts. Acoustic measures of the stimuli were generally consistent with the perceptual patterns. The perceptual and acoustic findings are compared with the results of recent training studies [Akayane-Yamada, Proc. 3rd Joint Meeting of ASA-ASJ, 953–958 (1996)] with Japanese listeners on English /ɹ–l/.
Ultrasonic focusing through inhomogeneous media by application of the inverse scattering problem
Authors: Haddadin Osama S. , Ebbini Emad S.
Published: July 2002

A new approach is introduced for self-focusing phased arrays through inhomogeneous media for therapeutic and imaging applications. This algorithm utilizes solutions to the inverse scattering problem to estimate the impulse response (Green’s function) of the desired focal point(s) at the elements of the array. This approach is a two-stage procedure, where in the first stage the Green’s functions is estimated from measurements of the scattered field taken outside the region of interest. In the second stage, these estimates are used in the pseudoinverse method to compute excitation weights satisfying predefined set of constraints on the structure of the field at the focus points. These scalar, complex valued excitation weights are used to modulate the incident field for retransmission. The pseudoinverse pattern synthesis method requires knowing the Green’s function between the focus points and the array, which is difficult to attain for an unknown inhomogeneous medium. However, the solution to the inverse scattering problem, the scattering function, can be used directly to compute the required inhomogeneous Green’s function. This inverse scattering based self-focusing is noninvasive and does not require a strong point scatterer at or near the desired focus point. It simply requires measurements of the scattered field outside the region of interest. It can be used for high resolution imaging and enhanced therapeutic effects through inhomogeneous media without making any assumptions on the shape, size, or location of the inhomogeneity. This technique is outlined and numerical simulations are shown which validate this technique for single and multiple focusing using a circular array.
Performance of a diver-held sub-bottom sonar
Authors: Irza John W.
Published: July 2002

The system design of a hand-held parametric sonar for divers is presented. Operational and technology trades are discussed. Use of an embedded digital signal processing (DSP) device is presented in the context of nonlinear waveform generation and receive signal processing algorithms and data display. Field results from the commercially available diver sonar unit (Sygnus model PDS-120) are presented from various target and bottom experiments. Efficacy of various waveforms with respect to target detection and classification is discussed. Methods for exploiting target resonances excited by the (low-frequency) parametric source are presented.
Speech privacy in enclosed and open plan: A review and retrospective
Authors: Cavanaugh William J.
Published: July 2002

Research on speech privacy problems in buildings at Bolt Beranek and Newman in the early 1960s showed convincingly that a person’s sense of acoustical privacy was directly related to the intelligibility of the intruding speech signal over the continuous ambient sound present [Cavanaugh et al., ‘‘Speech privacy in buildings,’’ J. Acoust. Soc. Am. 34, 475–492 (1962)]. Both in laboratory and in real world settings people feel they have ‘‘confidential privacy’’ when the articulation index (AI) of the intruding speech is 0.05 or less. Higher values of AI are acceptable for less demanding tasks, i.e., ‘‘normal privacy.’’ The method quantifies each of the significant variables involved and compares a summation of these metrics with response data for prior case histories both to predict, and in the case of existing situations, to evaluate speech privacy conditions in particular cases. R. W. Young reviewed the analysis method and showed that sufficient accuracy was preserved if simple, commonly used A scale sound levels were used in place of more cumbersome frequency based metrics [Young, ‘‘Re-vision of the speech privacy calculation,’’ J. Acoust. Soc. Am. 38, 524–533 (1965)]. Later in the 1960s the method was successfully applied to open plan offices which were becoming more prevalent [Hirtle, Watters, and Cavanaugh, ‘‘Acoustics of open plane spaces...some case histories,’’ J. Acoust. Soc. Am. 46, 91A (1969)]. The lessons learned during the continued development and application of the ‘‘Speech privacy calculation’’ over the years is reviewed and discussed.
Transmission of sound through suspended ceilings from HVAC terminal units
Authors: Warnock Alf
Published: July 2002

An ASHRAE project to investigate factors determining the sound pressure levels in rooms below ceilings concealing air-terminal units has been completed. Four terminal units installed close to the six ceiling types used were the major noise sources. They were supplemented by two simulators powered by loudspeakers. Sound power was measured for each device in the 156 cubic meter test room in its reverberant condition. The levels in the room were measured for each combination of source and ceiling tile. Sound pressure level was measured as a function of distance from two sources in the room below. The main intent of the project was to validate ARI Standard 885 which provides a calculation method for such situations. Differences among ceiling types were less than expected; leakage around the edges of each panel is a dominant transmission path. Ceiling attenuations at low frequencies were found to depend on the area of the lower face of the units. Sound levels in the room were essentially uniform when the source was above the ceiling. The decay of sound with distance from the sources below the ceiling was found to depend on the inverse of the room reverberation time.
Nonlinear response and acoustic radiation from a curved panel structure
Authors: Maestrello Lucio
Published: July 2002

Periodic and chaotic responses on a fuselage type of structure are observed when forced by high intensity tonal sound at normal and oblique incidence angles. The experiment is conducted with an aluminum curved aircraft-type fuselage structure panel subdivided by a tear stopper mounted in a rigid baffle. A sound power level of 130 dB is used to produce periodic responses with two tori of two commensurable frequencies and 137 dB power is used to produce chaotic responses. The fundamental tone distributes energy to other components, and the response becomes temporally and spatially complex, an indication of nonlinear pattern formation in which temporal and then spatio-temporal chaos begins. At oblique incidence the panels response is bifurcated; as such, the waves lose their spatial homogeneity and chaotic patches form. Results for various input loads, structural response, and sound pressure transmission are discussed.
Calculations of acoustic scattering from an elastic ocean bottom
Authors: Wurmser Daniel , Gragg Robert F. , Gauss Roger
Published: July 2002

The problem of acoustic scattering from the rough interface between the ocean and an elastic bottom is examined. A recently developed reciprocal scattering formalism [D. Wurmser, J. Math. Phys. 37, 4434–4479 (1996)] allows existing numerical and operator expansion methods to be used to calculate scattering from rougher and/or higher-dimensional surfaces than would otherwise be possible. Here, the method is used to generate new physically intuitive versions of perturbation theory and the small slope approximation for the bottom scattering problem. The results are compared to those for the analogous two-fluid theory. The relative merits of the various approximations are discussed. Finally, the significance of the work to low-angle scattering is discussed. [Work supported by ONR.]
Coherent and incoherent shallow water matched field inversion
Authors: Michalopoulou Zoi-Heleni , Picarelli Michele
Published: July 2002

Matched field processing (MFP) for geoacoustic inversion has been applied largely in the frequency domain using an incoherent combination of correlations at several frequencies. In source detection and localization problems, similar incoherent broadband MFP techniques have been shown to be inferior to coherent MFP techniques. Coherent MFP exploits source spectrum information when this is available, yielding more robust detection and localization results. This experience suggests that there is potential to improve geoacoustic inversion by MFP using a coherent algorithm. This work assesses that potential through a comparison of inversion results from incoherent and coherent methods, evaluating performance and cost. Estimates are made of water column depth and sediment geoacoustic properties for both synthetic data and real data from the SWellEX 96 experiment. The SWellEX data processed in this work correspond to source transmissions of lfm and hfm pulses, the spectra of which are employed in the coherent processing. [Work supported by ONR, Ocean Acoustics.]
Efficiency of a monopole sound source in the vicinity of an elastically suspended, baffled disk
Authors: Kauffmann Christiaan
Published: July 2002

The acoustic power emitted by a point monopole sound source in the vicinity of an elastically suspended, baffled, circular piston is investigated. The sound source is located on the axis of symmetry at distance d above the piston. A closed-form analytic expression is derived for the power flow emitted by the source in terms of the radiation impedance of a baffled piston. The dependency of the result on the various parameters of interest is investigated numerically, while simple, analytical approximations are given in a parameter region that defines the near field. These parameters include: ka, kd, Ω=ω/ωr, μ′=μh/a, and γ, where k=ω/c is the acoustic wave number, ω is the circular frequency of the source, a is the piston radius, ωr is the natural frequency of the spring mounted piston, μ=ρp/ρ is the ratio of the volume densities of mass of the piston and the fluid, while h is the thickness of the piston disk and γ is the damping coefficient of the dashpot.
Response to “Representation of the displacement in terms of scalar functions for use in transversely isotropic materials” [J. Acoust. Soc. Am. 104, 3675 (1998)]
Authors: Honarvar F. , Sinclair A. N.
Published: July 2002

The authors comment on Rahman and Ahmad’s discussion on the representation of displacement fields by scalar potential functions.
Transient diffraction of a plane step pressure pulse by a hard sphere: Neoclassical solution
Authors: Huang H. , Gaunaurd G. C.
Published: July 2002

The transient diffraction of a plane step pressure pulse by a hard sphere is studied via the modal series solution in a neoclassical fashion. With the advent and availability of more powerful computers and increased sophistication of computational algorithms, it is now possible to (1) accurately compute the time histories of a sufficiently large number of terms of the modal series, and (2) use the Cesàro summation to completely eradicate the Gibbs’ phenomenon effects. This approach can be utilized to obtain the diffracted field in the entire space–time region. In particular, a complete treatment is developed for the diffracted field at the shadow boundary and in its neighborhood where heretofore no satisfactory analytical solution exists.
Effects of a background axisymmetric potential flow on vortex ring pairing sound
Authors: Tang S. K. , Ko N. W. M.
Published: July 2002

Sound generated by the pairing of two coaxial vortex rings in the presence of a background axisymmetric potential flow was studied numerically. Results show that the background flow substantially affects the sound generation process in the beginning of the vortex ring interaction. They also suggest that the axial jerk and radial acceleration/deceleration of vortex rings are the major mechanisms through which pairing sound is produced. The effect of background flow mean shear rate on sound generation is also discussed and the results suggest that higher sound levels will be generated when the vortex rings are interacting within the region of high mean shear in a low speed laminar jet.
Effects of time domain response on sonic characteristics of microphones
Authors: Findlen Benjamin D. , Reuter Eric L. , Campbell Richard H. , Michalson William R.
Published: July 2002

Among practitioners of the recording arts, a correlation is popularly deemed to exist between aspects of a microphone’s time domain response and its subjective qualities. This eperiment sought to reveal such correlations using appropriate measurement and statistical procedures. Impulse response tests were performed on a set of 12 microphones using both electric spark and maximum length sequence methods. Cumulative spectral decay waterfall plots were then carefully examined for unusual behavior which led to objective feature extraction. Feature-specific quantitative data were then mathematically scaled from both the impulse response and cumulative spectral decay plots to form the objective parameter base. Three musical examples were recorded at each of two proximities with each microphone, and subjective listening tests were performed on these recordings in a controlled environment using expert listeners. The recorded examples included 8 of the 12 microphones and were evaluated for three subjective qualities, namely warmth, brightness, and depth, which provided the subjective parameter base. The data from the objective and subjective tests were statistically analyzed using N-dimensional replacement [M. H. Moulton, U. of Chicago (1996)]. Complete experimental procedure, results, and implications will be presented.
Frequency spectrum of linear internal waves in shallow water and a modified Garrett–Munk model
Authors: Yang T. C. , Yoo Kwang
Published: July 2002

The properties of linear internal waves are well studied in deep ocean and are surprisingly well modeled by the Garrett–Munk model. In the Garrett–Munk model, the internal wave spectrum is the product of the modal spectrum and the wave-number spectrum. The properties of linear internal waves in shallow water are not well studied. In this paper the mode amplitude and frequency spectrum are deduced using the mode decomposition method based on the theoretical mode depth functions. The mode decomposition method is applied to the sound speed variation data as a function of time and depth. Advantages of using sound speed variation data versus the particle displacement data are discussed. The mode amplitude measurements agree with the results using the empirical orthogonal decomposition approach. A modified Garrett–Munk model is proposed to explain the deviation of the spectrum slope from the original Garrett–Munk model. [This work is supported by the Office of Naval Research.]
Medium effects on high-frequency propagation: Results from a recent experiment
Authors: Henyey Frank S. , Williams Kevin L. , Reynolds Stephen A. , Rouseff Daniel , Ewart Terry E.
Published: July 2002

In August 1996, a shallow-water experiment on high-frequency propagation was performed [Williams et al., J. Acoust. Soc. Am. 101, 3159(A) (1997)]. The primary frequency of interest was 75 kHz and the range was 815 m in 70-m-deep water. The focus of the experiment was on the distortion over a 10-m horizontal aperture caused by internal waves and possibly turbulence. Results are presented for two time periods. During the first period, the internal wave energy level was relatively small; nonetheless, constant through cubic terms in a Taylor’s series expansion of the acoustic phase can be extracted. These compare well to stochastic modeling results. The other period was during a solibore event where a train of high-amplitude, narrow-band internal waves was present. For this situation, the data are compared using deterministic modeling. [Work supported by ONR.]
The effects of ambient acceleration on bubble levitation and SBSL
Authors: Wyatt Sean C. , Roy Ronald A. , Holt R. Glynn
Published: July 2002

In order to prepare for pending experiments in variable-g environments some of the multiple effects caused by the time-varying acceleration of acoustic resonators used in bubble levitation experiments are considered. The coupled effects of the induced changes in ambient pressure (due to a changing hydrostatic head) and bubble position (due to a change in the buoyant body force) are modeled. Changing the ambient pressure, while holding the acoustic pressure amplitude constant, causes changes in the radial bubble response and diffusive equilibrium requirements. Changing the bubble levitation position causes both the local acoustic pressure amplitude and gradient to change, which will again impact bubble response. If the bubble must remain in stable diffusive equilibrium, both of these effects will force the bubble equilibrium radius to change. Finally, by using an empirical relation for emitted SL intensity versus bubble response, the variation of emitted light intensity as a function of the changing ambient acceleration is obtained. [Work supported by NASA.]
A comparison between two models for bubble dynamics and their predictions for the theory of sonoluminescence of Lohse et al
Authors: Hao Y. , Prosperetti Andrea
Published: July 2002

Lohse and co-workers [Hilgenfeldt et al., Phys. Fluids 8, 2808 (1996)] have formulated a theory of bubble stability in relation to sonoluminescence emission. The theory is based on a simplified model describing the spherical oscillations of a gas bubble. This paper compares the results given by that model with those of a more detailed one in which liquid compressibility and thermal effects in the bubble are accounted for with greater precision. A comparison of the results given by the two models throws some interesting light on the subtle effects of energy dissipation. It is shown that, even though the bubble radius versus time as predicted by the two models does not differ very much, derived quantities—such as various stability thresholds—are nevertheless substantially affected. In particular, the parametric stability threshold calculated by the new model is in better agreement with experiment. The parameter range where sonoluminescence should be observable according to the new model is enlarged with respect with the original theory of Lohse and co-workers. A study of whether light emission is indeed observable in this extended range should help examine the validity of the theory. [Work supported by the Office of Naval Research and NASA.]
Sensitivity to quantized variations in the amplitude and interaural phase of a stimulus
Authors: Brungart Douglas S.
Published: July 2002

The sensitivities of listeners to quantized changes in the amplitude and interaural phase of a stimulus were measured in two-alternative forced-choice experiments. In the amplitude experiment, listeners heard two diotic stimuli (500 Hz tone burst, 5 kHz tone burst, white noise, speech, or musical chord) that varied in amplitude over a 30 dB range either continuously or in discrete (equal dB) steps and were asked to choose the noisier stimulus. In the phase experiment, listeners heard two 500 Hz tone bursts that varied in interaural time delay (ITD) from −750 μs to 750 μs either continuously or in discrete steps and were asked to choose the noisier stimulus. The amplitude results vary widely across subjects, but indicate that listeners were most sensitive to discrete steps in the amplitude of a sinusoidal signal (threshold step size <0.375 dB), and least sensitive to discrete steps in the amplitude of white noise (threshold step size ≊2 dB). The ITD results indicate that the listeners were sensitive to discrete steps in ITD smaller than 2.5 μs. The results have implications in systems which require instantaneous switching between filters, such as virtual audio displays.
Gap detection thresholds as a function of marker duration in young and old listeners
Authors: Hamstra Stanley J. , Schneider Bruce A.
Published: July 2002

Twenty younger (normal hearing, mean age: 22 years) and twenty older adults (audiometric thresholds <40 dB HL for frequencies between 0.2 and 4 kHz, mean age: 72 years) were asked to discriminate between the presence versus absence of a gap between two equal-duration tonal markers constructed by summing 2-kHz Gaussian-modulated tone pips (sigma=1/2 ms) spaced 1/2 ms apart. The total duration of the two markers was constant within a block of trials but varied between 1 and 1000 ms across blocks. Gap detection thresholds were determined using a two-interval forced-choice procedure. Notched-noise, centered at 2 kHz, was used to mask on- and off-transients. Gap detection thresholds of older adults were markedly higher than those of younger adults for marker durations less than 150 ms but converged on those of younger adults at 1000 ms. For both age groups, gap detection thresholds were independent of audiometric thresholds. These results indicate that older adults have more difficulty detecting a gap than younger adults when short marker durations (i.e., durations characteristic of speech sounds) are employed. This loss of temporal resolution with age appears to be independent of the ability to detect a tone of this frequency. [Work supported by NSERC.] a)Present affiliation: Dept. of Surgery, University of Toronto.
Global reduction of aircraft interior noise using constant volume velocity actuators
Authors: Lane Steven A. , Clark Robert L.
Published: July 2002

Active noise control of an aircraft interior presents a formidable challenge as a result of the high modal density that is characteristic of such three-dimensional enclosures. In this work, a multiple-input, multiple-output feedback control strategy using a distributed array of sensors (microphones) and actuators (loudspeakers) was used to achieve global control within the fuselage of a typical business jet aircraft. The transducers were spatially weighted to focus control effort to the dissipation of low frequency acoustic modes of the system. Previous work has shown that global attenuation is indeed possible, but transducer dynamics limited the achievable performance of the controller. In this work, the actuators were compensated using a technique similar to motional feedback in order to approximate a constant volume velocity source over the control bandwidth. This essentially moves the actuator dynamics out of the control bandwidth, enhancing the performance of the active noise controller.
Effects of pressure loading on the dynamics of a curved piezostructure
Authors: Henry James K. , Clark Robert L.
Published: July 2002

Previous research in active structural acoustic control (ASAC) has focused primarily on flat plates. In order to facilitate the realistic evaluation of the closed loop performance of ASAC systems for aircraft cabin noise reduction, efforts are being made to consider complicating effects in panel dynamics to more accurately reflect the service conditions of aircraft fuselage panels. As part of these efforts, a model of a curved piezo-structure was developed and used to determine the effects of curvature on panel dynamics and transducer integration. Curvature was shown to affect transducer coupling and control system bandwidth. The present work considers the effects of internal pressure loading created by aircraft cabin pressurization. Internal pressure loading is shown to affect panel dynamics significantly, raising further issues in control system design and transducer integration for structural acoustic control applications. [Research supported by NASA Langley Research Center under Grant No. NCC 1 250.]
Processing vowels and lexical tone in Mandarin Chinese
Authors: Ye Yun , Connine Cynthia
Published: July 2002

Vowel and tone detection tasks were used to investigate the role of tone information in processing Mandarin. In experiment 1, the task required detection of a tone-plus-vowel combination (tone2-/a/). Possible ‘‘yes’’ responses occurred for both word and nonword syllables and showed a lexical advantage. ‘‘No‘‘ response target stimuli mismatched on either the vowel or the tone and showed faster detections for vowel mismatch stimuli. These results indicate a perceptual advantage for vowel detections. In experiment 2, separate vowel and tone detection tasks were used for target syllables that occurred phrase-finally in a predictive or neutral semantic context. In the neutral context, vowel detections were faster than tone detections. The vowel advantage was neutralized in predictive contexts where tone detections were somewhat faster. The results are discussed in terms of the relationship between the lexical representation of vowels and tones and their temporal availability in running speech.
Music on Image: Compositional strategies for a new art form
Authors: Piche Jean
Published: July 2002

From the author’s perspective, the design of video moving pictures, in both narrative and non-narrative forms, share many syntactic traits with music composition, especially electroacoustic composition. Many video art works can be experienced as a raw choreography of emotion where kinetic camera movements, color, and editing build, not a story or even perhaps a theme, but mainly a cortical experience of modernity; this is what much electroacoustic music is about. This talk will expand on key concepts of synchronicity/asynchronicity between musical and pictural materials. Examples will be drawn from the author’s recent development of ‘‘paNi IntiyA’’ in which the video editing/processing was done with a particular musical paradigm in mind, be it granulation, micro-montage, spatialization, cross-fades/morphing or electronic processing. The ultimate goal is to try and imprint onto the image the same generality as the expanded sonic vocabulary of electroacoustic composition. The author calls this form video-music. While this moniker will help to distinguish its intent from the ubiquitous music-video commodity, it more importantly indicates that the gestures, musical and visual, spring forth from the same mind as a single entity, and thus may represent a new form of mediatic expression.
Multi-aspect target classification using directionally dependent hidden Markov models
Authors: Runkle Paul , Carin Lawrence
Published: July 2002

Acoustic signals scattered from underwater targets often exhibit characteristics that vary as a function of target-sensor orientation. In this paper, target identification is performed by utilizing physics-based feature extraction in conjunction with discrete hidden Markov model (HMM) classifiers. The signal features are extracted using a matching pursuits algorithm to identify structures that are naturally present in general scattered signals, such as wavefronts and resonances. Although HMMs are traditionally applied to model the temporal variations of features extracted from speech signals, for this research, target-specific HMMs are designed to model the spatial variations of the scattered signal features. In particular, states of the HMM are conceptualized as corresponding to target-sensor orientation intervals. This approach naturally leads to constraints on the model structure that accommodate observations from multiple aspects. Discrimination results are presented for five distinct targets, demonstrating the potential of this classification technique. [Work supported by NRL.]
A direct inverse scattering method for imaging obstacles with unknown surface conditions
Authors: Norris Andrew N.
Published: July 2002

A new technique is described for imaging obstacles using the acoustic far-field response for plane wave incidence. The method requires no a priori information about the surface, nor does it depend upon prior knowledge of the surface boundary conditions. The algorithm is straightforward to implement and is illustrated by imaging multiple targets simultaneously for various surface boundary conditions: soft, hard, and impedance. The input data is the full acoustic scattering matrix at a single frequency, from which the eigenvalues and eigenfunctions of the far-field operator are determined. Associated incident wave functions are then used to compute a spatial indicator function which takes on large values in the exterior of the target but is bounded inside the obstacle, or obstacles when there are multiple disconnected surfaces. [Work supported by ONR.]
Physics of 3-D scattering from rippled seabeds and buried targets in shallow water
Authors: Schmidt Henrik , Fox Warren , Maguer Alain , Bovio Edoardo
Published: July 2002

A new wave theory model (OASES-3D) providing consistent modeling of seabed insonification, three-dimensional target scattering, and rough seabed reverberation has been used to investigate the spatial and temporal characteristics of the multistatic scattering and reverberation from rippled, shallow-water seabeds with buried targets. It is shown that the highly polarized spectral characteristics of ripple fields is associated with a reverberation environment which is highly sensitive to both the frequency and insonification aspect relative to the ripples. The theoretical study has suggested that significant gains in subcritical detection performance for buried objects can be achieved by band-limiting the processing to frequencies below typically 3–5 kHz. The results of 3-D target scattering and reverberation measurements performed by SACLANTCEN in shallow-water environments with rippled, sandy bottoms have confirmed this hypothesis. However, the experiments have consistently shown higher low-frequency reverberation than predicted by the model. Here, OASES-3D has been used to demonstrate that a very small amount of low-wave-number roughness components superimposed on the sand ripples can account for the observed reverberation. This in turn suggests that the use of new low-frequency sonar concepts for buried target detection and classification must be accompanied by adequate environmental assessment incorporating the long-wavelength (λ>25 cm) seabed roughness components. [Work supported in part by SACLANTCEN and ONR, Ocean Acoustics.]
Audio signal noise reduction using multiresolution sinusoidal modeling
Authors: Anderson David V. , Clements Mark A.
Published: July 2002

The multiresolution sinusoidal transform (MRST) provides a sparse representation for speech signals by utilizing several psychoacoustic phenomena. It is well suited to applications in signal enhancement because the signal is represented in a parametric manner that is easy to manipulate. The MRST has the additional advantage that it is both particularly well suited to typical speech signals and well matched to the human auditory system. The currently reported work removes noise from a speech signal corrupted by additive noise by applying an adaptive Wiener filter to the MRST parameters and then conditioning the parameters to reduce ‘‘musical noise.’’ In informal tests, MRST based noise reduction was found to provide significant reduction in background noise for moderate SNRs while virtually eliminating the ‘‘musical noise’’ often associated with spectral subtraction or adaptive Wiener filtering.
Investigation of underwater acoustic noise for three different areas
Authors: Esmaeili Dariush , Javaherian Abdolrahim , Zadeh Kourosh Kalantar
Published: July 2002

The results of underwater acoustic noise measurements at different sites in the Persian Gulf, Karadj Dam lake and at a small lake west of Tehran are investigated on the basis of time series and relative power spectra. Several possible sources such as shipping, wind, surf, industrial activities on shore, thermal agitation etc. are distinguished to determine the most probable origins of the observed noise. The ambient noise of the Persian Gulf is found to be a composite of at least three overlapping components: turbulent-pressure fluctuations, noise due to shipping with a maximum relative power around 50–60 Hz, and that due to wind with a maximum around 800 Hz. Spectrum characteristics of each component and of the composite are shown. The radiated noise of some different classes of ships and boats measured in the Persian Gulf and Karadj Dam lake are also discussed. Additional sources, including those of intermittent and local effects, such as bubbles, rain, snow, flying aircraft, etc., are also investigated in the small lake. Finally the Gaussianity and stationarity of the recorded data are studied through appropriate tests.
Acoustical design for organs in educational facilities
Authors: Cooper Russell
Published: July 2002

The organ as an instructional as well as recital instrument poses many acoustical challenges for the design team. Among those are the surfaces near the organist by which he can hear him/herself, overall volume for proper loudness, and the size of the organ relative to the size of the space. The design team must usually plan the space for an instrument that arrives long after opening night. This involves careful planning, experience in organ requirements, and a good relationship and coordination with the organ builder and faculty. Projects cited are The University of South Carolina, The University of North Carolina, The University of Georgia, Cleveland State University, and the University of North Texas.
Quality reverberation fields for organ music
Authors: Kinzey Bertram , Siebein Gary , Gold Martin
Published: July 2002

Organists and organ builders commonly specify a long reverberation time for a room for an organ. This simple quantitative statement ignores consideration of a larger specification required to insure appropriate quality of the reverberant field to insure that music heard has acceptable clarity, intimacy, diffusion, and other attributes required for excellent completion of the musical sound. Measurements other than reverberation time are examined to establish the role they should play in an adequate specification for a reverberant field for organ music. The acoustics of several rooms with large organs will be compared to illustrate the importance of these newer measures of acoustic quality in a more complete description of the rooms.
Ultrasonic periodontal probe
Authors: Hinders Mark , Guan Alan , Companion John
Published: July 2002

This talk discusses proof of concept in vitro testing of an ultrasonic probe for imaging periodontal structures. This technique allows accurate measurements of disease activity for patient risk assessment and treatment outcome evaluation without the need for ionizing radiography or manual periodontal probing. This technique promises reduced variability and improved ease of use, in comparison to conventional manual periodontal probing. The work discussed here is the first step to establish the ultrasound periodontal probe as a clinically valuable tool for patient assessment and the first noninvasive measure of periodontal disease activity. Data from cadaver samples using a prototype intraoral ultrasound instrument is compared to conventional manual probing subsequently performed on the annotated cadaver samples. The results discussed here are being used to refine the technique, improve the analysis of scan signals, and develop the framework of the software that will be used during a subsequent in vitro testing program.
Development of a passive sonar system for localization of an underground sound origin
Authors: Jarng Soon Suck
Published: July 2002

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100 m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. A new hybrid method has been developed for estimating the origin of the underground acoustic source by coupling both methods. The Nelder-Meade simplex search algorithm is then used to numerically estimate the position of the source in those methods. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is in some cases less than 6 m for a search area of radius 250 m.
Development of transducers to measure the velocity reduction of materials at flexural wave numbers
Authors: Klippel Patrick J. , Trivett D. H. , Young A. Mark
Published: July 2002

A major noise source for velocity sensors in a hull array configuration is back plane (i.e., hull flexural vibration) noise. The level of back plane noise is a function of frequency and wave number, and depends upon the velocity reduction properties provided by a pressure release decoupling baffle. The Naval Undersea Warfare Center, Division Newport, has designed, constructed, and tested two Flexural Wavenumber Transducers capable of measuring the velocity reduction of materials. One is designed to characterize materials along the flexural branch, in vacuo, of a thin steel plate supporting quarter-scale experiments and the other along the flexural of a thick steel plate supporting full-scale evaluations. Both transducers operate within an environmentally controlled pressure vessel allowing velocity reduction measurements to be made over a wide range of temperatures and hydrostatic pressures. Both the design and experimental results will be presented. [Work supported by PEO(USW)/ASTO, Code D3 and ONR, Code 334.]