bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification and similarity judgments of environmental sounds
Authors: Gygi Brian , Kidd Gary R. , Watson Charles S.
Published: July 2002

As part of an ongoing study of environmental sounds, identification thresholds were obtained for a collection of 100 naturally occurring familiar sounds embedded in noise. Threshold event-to-noise ratios covered a range of over 23 dB. Differences in total energy or in the spectral–temporal distribution of energy accounted for, at best, only 45% of the variance in identification thresholds. To determine the association between stimulus similarity and differences in identification thresholds, a series of three similarity rating studies was conducted. Separate groups of subjects judged the similarity of the sounds based on actual acoustic properties (sounds heard), imagined acoustic properties (sounds imagined), and semantic properties (i.e., properties attributed to the source object or event). The MDS solutions for all three studies were quite similar and contained clusters suggesting that similarity judgments with these familiar sounds are based on a few very general acoustic properties including rhythmicity, continuity and spectral–temporal complexity. [Work supported by NIH.]
Unexpected benefits of training frequency discrimination on the learning and generalization of interval discrimination
Authors: Wright Beverly A. , Ortiz Jeanette A.
Published: July 2002

It is generally accepted that training on one perceptual task does not yield learning on untrained tasks. If so, interleaved training on two tasks should not affect learning or stimulus generalization on either task. Contrary to this prediction, six listeners trained 2730 trials each on interval- and frequency-discrimination tasks using the same stimulus (100 ms at 1 kHz) learned on the interval task 30% more with the trained stimulus, and 134% more with an untrained stimulus (100 ms at 4 kHz), than ten listeners trained 2934 trials on the interval task alone. Furthermore, listeners trained on both tasks with the same stimulus learned on the trained and untrained stimuli, respectively, (1) 105% and 136% more than 6 listeners trained 2160 trials each on both tasks but with a different stimulus (200 ms at 4 kHz) for the frequency task, (2) 19% and 42% more than 20 listeners trained 9675 trials on the interval task alone, and (3) 71% and 579% more than 6 listeners trained 9000 trials on the frequency task alone. Thus practicing a second task with the same trained stimulus unexpectedly enhanced learning and particularly stimulus generalization on the first task, more so than performing additional trials on either task alone. These results may guide the development of theoretical models and clinical applications of learning. [Work supported by NIDCD.]
Feedback criteria for edge tones and the multiple sources of choked jet screech
Authors: Powell Alan
Published: July 2002

Screech sound is generated by the interaction of jet instability waves with the spatially periodic cell structure of a choked supersonic jet, the sound initiating new instability waves at the nozzle. Its frequency is important because of possible structural damage to high-performance aircraft. It was hypothesized that the interaction resulted in a phased array of point sources, with an effective source at distance h′ from the nozzle. This reduced the phase feedback criterion to that of edge tones with frequency f=(U/h′)(N+p)/(1+M), where U, M are, respectively, the velocity and Mach number of the instabilty waves, N is an integer, and p an ideally fixed constant, 0≤p≤1. It was hypothesized that N takes the value yielding maximum feedback for maximum jet instability for edge tones, and that closest to perfect reinforcement, f→fPR=(U/s)/(1+M), s=cell length, for screech. Multiple-source feedback is now considered, allowing for a different (effective) first cell length. The preceding concepts are fully confirmed for screech, but N is not limited to integer values. As illustrated by experimental results, and though f→fPR, absolutely perfect reinforcement is unlikely to occur.
Active control of turbulent-boundary-layer-induced sound radiation from aircraft style panels
Authors: Gibbs Gary P. , Eure Kenneth W. , Loyd J. W.
Published: July 2002

The results of active control of TBL-induced sound radiation will be presented. In this test, a panel was constructed similar to the sidewall of an aircraft; however, the panel was flat to allow a simple incorporation into the wind tunnel wall. The static in plane stress normally associated with aircraft cabin pressurization (at 40000 ft) was provided via a tensioning fixture. Thus the smooth ‘‘exterior’’ side was subjected to TBL flow inside the tunnel, and the other (interior) side radiated sound into the model preparation room. Accelerometers were mounted on the interior side of the panel, and microphones were positioned in the model preparation room to monitor sound radiation. Experiments were conducted at both Mach 0.8 and Mach 2.5 flow conditions, and active control was performed on a single bay, and two bays. The results demonstrate reductions in total radiated sound power on the order of 10–15 dB at resonances, and 5–10 dB integrated over the band width of 150–800 Hz. This work represents the first known demonstration of ASAC of aircraft-style panels subjected to both subsonic and supersonic flows.
Controlling nonlinearity and chaos
Authors: Maestrello Lucio
Published: July 2002

Several unrelated experiments were conducted in which nonlinear and chaotic behaviors of structural vibration and shock waves from free shear flow were observed. Since each experiment is sensitive to the initial condition, this makes them highly receptive to active control. Control of the vibration of the structure and free shock shear layer was achieved by redistribution of energy, such that the energy in the system is nearly preserved. Experiments are conducted to illustrate the role of the initial conditions in the active control strategy.
The analysis of signals containing multiple chirps
Authors: Linnett Laurie , Rzhanov Yuri , Calder Brian , Capus Chris
Published: July 2002

The analysis of signals containing multiple chirps occurs in many situations in acoustics, for example, in the bioacoustics field in analyzing the sounds of bats and dolphins. In sonar and seismic, chirp signals are used because of their pulse compression properties. Recently, the fractional Fourier transform has shown that linear chirp signals may be recognized and this has greatly facilitated the use of these signals. This paper shows a method similar to that of the fractional transform and shows how other types of chirp signals, polynomial, and other functional forms may also be analyzed. It also looks at the resolution that can be achieved when separating chirps both in rate and in time. This is of particular relevance when dealing with dispersion in the propagation of signals through different media. Examples will be presented, for the analysis of some bat signals and for some seismic signals. The analysis of signals in the time frequency domain using piecewise linear chirps will also be demonstrated, and some further examples from synthetic seismic signals will be demonstrated.
Application of time-frequency analysis to landmine detection using a laser Doppler vibrometer
Authors: Valeau Vincent , Sabatier James , Xiang Ning
Published: July 2002

The feasibility of detecting landmines acoustically was recently demonstrated by measuring insonified ground surface velocity using a laser Doppler vibrometer (LDV), since the presence of a mine enhances ground matrix velocity [J. M. Sabatier and N. Xiang, J. Acoust. Soc. Am. 106, No. 4, Pt. 2 (1999)]. Although mines were initially detected using discrete LDV measurements, they were detected for this work by spatially continuous measurement, obtained by sweeping the beam onto the ground surface with a constant velocity in order to hasten the detection process. The ground was excited by single-tone acoustic waves. After LDV signal demodulation, a sine wave was obtained which was amplitude-modulated due to mine presence and corrupted by speckle noise ‘‘bursts’’ whose energy grew with the sweeping beam velocity. The signal was time-frequency analyzed by means of the smoothed Wigner distribution that provides straightforward physical interpretation since time is proportional to beam position. The mine was detected when the signal energy was enhanced at the excitation frequency. The wideband nature of speckle ‘‘bursts’’ allowed corrupted signal sections to be discarded. Results are provided for different mine depths, types of ground, and sweeping velocities. The limits of the analysis are investigated.
Designing and building for quiet in a school for deaf children
Authors: Guenther John , Adrian Marcus , Weissenburger J. T. , Clark William
Published: July 2002

Central Institute for the Deaf (CID) recently completed construction of a new 42000-sq. ft. school for deaf children. High priority was placed upon designing and building a facility that would provide ideal acoustic environments that fostered learning and auditory/oral communication for students wearing powerful hearing aids or cochlear implants and teachers. A team composed of scientists, architects, and acoustical engineers was assigned the task of designing and building a school that would provide classroom environmental levels at or below the NC 20 contour, interclassroom attenuation exceeding 50 dB, reverberation times on the order of 0.4 s, and sound reinforcement for teachers’ voices when facing the blackboard. In group spaces and in the hallways, higher noise levels and longer reverberation times were sought to provide students with experiences more like those faced in the real world. Challenges included a site bounded by a busy interstate highway and a medical center heliport. The team developed and implemented numerous unique acoustic treatments for the facility which are reviewed in the presentation. Although designed as a school for the deaf, the approaches are useful for designing any educational classroom environment. The school opened on 10 January 2000 and met all acoustic criteria.
Acoustical modeling and auralization as a design tool for a university concert hall renovation
Authors: Brooks Bennett M.
Published: July 2002

A 400-seat university concert hall was notorious for its bad acoustics. Music faculty identified the worst problem with this educational facility as poor stage communication, or the difficulty that performers had hearing one another. The hall was modeled using the CATT-Acoustic software system. Good agreement was found between objective measurements and model predictions for the original hall. Also, the subjective quality of the auralized model was judged to be an accurate representation of the original hall by the faculty. These results provided confidence in the model as a design tool for hall renovations. Design decisions were made based on objective parameters, such as early reflection density, and also on the subjective quality of the sound, for a series of model configurations. The final design was largely realized and the renovated hall has been well received by students, faculty, and community. Sound samples illustrating auralized design options will be presented.
Seeking improved speech intelligibility in a university classroom
Authors: Heerwagen Dean R. , Sampson Paul D.
Published: July 2002

Speech intelligibility has been studied while systematically modifying an existing classroom. The ‘‘original’’ classroom had acceptable background noise levels, but excessive reverberation. Room modifications included installing a lowered ceiling and successive additions of absorption to the classroom walls. The unoccupied rhyme tests (RTs) at 1 kHz progressed from an ‘‘original’’ 1.10 s to a ‘‘final’’ 0.53 s. Modified rhyme tests (MRTs) were also conducted with a volunteer group of faculty and staff. For each room condition, MRTs were administered across a range of signal-to-noise ratio (SNR) conditions. The principal parameters of this study were the physical conditions of the room (as indicated by RT and U50 measures), the test scores, the SNRs for the tests, distances between a loudspeaker and each volunteer, whether the volunteer was a native English speaker, and whether the volunteer was normal hearing or hearing impaired. Statistical analyses of the data indicate that the most important determinant of test performance was the SNRs. The correlation between test scores and RTs is also significant, but less so. Additionally, correlations between test scores and native and non-native speakers and between test scores and those with and without hearing impairment were also significant.
Further acoustical analysis of infant/toddler rooms in daycare centers
Authors: Golden Matthew V. , Frank Tom
Published: July 2002

At the last ASA meeting, preliminary data was shared on the background noise in daycare centers. At this meeting, further research in the acoustical analysis of infant/toddler rooms in seven daycare centers will be discussed in relation to speech communication. Information concerning the collection and analysis of ambient noise, signal-to-noise ratios (SNRs), reverberation times (RT), and early decay time (EDT) will be shared. Comparisons will be made between the measurements and data collection techniques of ambient noise from dosimeters, sound level meters, and other long-term data acquisition techniques. Comparisons of the overall and octave band RTs and EDTs from each of the rooms in the study will be shown. Finally, the calculation of SNRs will be shown for both steady-state and dynamic signals. The steady-state SNR uses several different speech spectra compared to the occupied 1/3-octave band noise levels. The dynamic SNRs are calculated using microphones placed at both the caregiver and the infant or toddler. [Work supported by PHS/NIH (1-R01-HD31540-01A2) Otitis Media, Behavior and Attention in Daycare.]
Discrimination of temporal features in complex sounds by the bullfrog, Rana catesbeiana
Authors: Simmons Andrea M.
Published: July 2002

The advertisement calls of the sympatric species the bullfrog (Rana catesbeiana) and the green frog (Rana clamitans) differ in duration and first harmonic periodicity. Sensitivity of male bullfrogs to complex sounds differing in these acoustic attributes was examined in the field using the evoked-calling technique. In experiment 1 (duration series), males were presented with a series of synthetic signals, all with the spectral structure of the bullfrog’s advertisement call, but varying in duration along a continuum from bullfrog-like to green-frog-like. In experiment 2 (pitch series), signals were of bullfrog-like duration, but varied in first harmonic periodicity in steps from bullfrog-like to green-frog-like. The number and latencies of the males’ evoked vocal responses differed significantly to the exemplars within both series. The forms of the discrimination functions suggest that males perceived these acoustic features as distinct categories. Discrimination was invariant with sound-pressure level over a 30-dB range. These data show that bullfrogs use temporal features to distinguish between conspecific and heterospecific vocalizations, and may achieve this by a process similar to categorical perception as defined in other animals.
Tomographic maps of the New England Shelfbreak Front
Authors: Chiu Ching-Sang , Lynch James F. , Gawarkiewicz Glen
Published: July 2002

In July 1996, an integrated acoustic-oceanographic experiment was carried out in the Mid Atlantic Bight south of New England to study the oceanographic structure of the shelfbreak front and its effects on sound propagation. The experiment employed a suite of acoustic and oceanographic sensors including sound sources on the slope, vertical hydrophone arrays on the shelf, and a SeaSoar (towed CTD) that provided several volumetric surveys of the frontal zone. In order to obtain accurate tomographic maps for this complex shelf-slope environment, an inverse scheme that can properly handle strong mode coupling was developed. In the formulation, a variation in the modal travel time is expressed as a function of the evolution history and coupling history of the modes associated with the ‘‘background’’ ocean and changes in these histories due to sound speed changes. The inversion of the observed modal travel times is accomplished using nonlinear least-squares estimations. In this presentation, the quality of these tomographic maps is discussed using results from a resolution-variance analysis. Additionally, the data and resolution kernels of the tomographic measurements are compared to those of the SeaSoar measurements to illustrate that the two independent data sets are highly complementary to each other.
Acoustic monitoring of oceanographic features and processes in the Arctic Ocean
Authors: Sabinin Konstantin , Lynch James
Published: July 2002

Acoustic transmissions can be used to monitor two of the most important features of the Arctic Ocean, namely, the heat content of the Atlantic water and the upper ocean salinity. In this presentation, we will first discuss the optimal configuration of an array that might be used for heat content studies. We will then look at the newer concept of monitoring the upper ocean salinity in the Arctic Ocean using acoustics, which we have dubbed ‘‘acoustic halinometry.’’ Both the basic concepts of halinometry and the configuration of a possible experimental array will be discussed. In particular, we will show the results of numerically simulating an acoustic halinometry experiment using data from large-scale Arctic oceanographic surveys conducted during 1973–1979. We will also look at the integration of the acoustics with conventional measurements in a ‘‘combined monitoring’’ array concept. This combined monitoring concept will be applied via simulation to one of the primary connections to the Arctic Ocean, the Bering Strait.
SWL stone fragmentation in vitro is improved by slowing the SW delivery rate
Authors: Lifshitz David A. , Williams James C. , Evan Andrew P. , Rietjens Drew L. , McAteer James A. , Bailey Michael R. , Crum Lawrence A. , Sapozhnikov Oleg A.
Published: July 2002

Fast shock wave (SW) rates in lithotripsy (SWL) generate enhanced cavitation that could promote stone fragmentation. We tested the idea that SWL at the high end of clinical SW rate (2 Hz) acts to improve stone comminution. Model stones (Ultracal-30 cement) were exposed to SWs (20 kV, 400 SWs) at 0.2, 0.5, 1, and 2 Hz in a research electrohydraulic lithotripter. Fragmentation was assessed by measuring number, size, and projected surface area of the fragments. Stones treated at 0.2 Hz exhibited significantly greater fragmentation (p<0.01) than stones at 1 or 2 Hz, while fragmentation between 0.2 and 0.5 Hz was similar. Mean ± SEM for fragment area increase was 370±53% at 0.2 Hz (n=10 stones), 280±34 at 0.5 Hz (8), 130±31 at 1 Hz (5), and 101±16 at 2 Hz (20). This pronounced enhancement of fragmentation at very slow SW rate was unexpected. High-speed camera images of cavitation at solid objects show an increased bubble cloud at faster SW rates. The bubble cloud may interfere with transmission of acoustic energy to the stone surface. These in vitro data suggest the possibility that patient treatment at fast SW delivery rates may decrease the efficiency of stone comminution. [Work supported by NIH P01-DK43881.]
Bubble translation due to radiation force in SWL
Authors: Sokolov Dahlia L. , Bailey Michael R. , Crum Lawrence A. , Sapozhnikov Oleg A.
Published: July 2002

The clustering of cavitation bubbles may lead to enhanced stone comminution and influence the extent of tissue damage during shock wave lithotripsy (SWL) treatment. Recent research has focused on changing the SWL pulse, or timing between pulses, to intensify or mitigate collapse or localize these clusters. Such research has targeted radial, not translational motion. We investigate whether bubble translation due to radiation force is sufficiently large to influence cluster formation. The translational dynamics of a single spherical bubble were modeled according to the formulation proposed by Watanabe and Kukita [Phys. Fluids 5(11) (1993)]. After radius-time data were obtained using the Gilmore equation, translational motion was calculated by numerical integration of the Watanabe equation. Calculations were performed for a range of bubble sizes (R0=2–20 μm) and pressure rise times (10−9–10−7 s). The results show that, during bubble growth and collapse induced by a single pulse or two pulses with microsecond delays, bubble translations are ∼0.1 mm. Although bubble translation from a single pulse may not have a noticeable effect on bubble distribution, the effect may be cumulative for the 1000+ shots fired during clinical SWL treatment. [Work supported by NIH DK43881, NSF, CRDF, and FIRCA.]
Directivity patterns of rectangular pistons on prolate spheroids
Authors: Boisvert J. E. , Van Buren A. L.
Published: July 2002

A general expression for the directivity of a rectangular piston arbitrarily located upon a rigid prolate spheroidal baffle is formulated. The piston is assumed to vibrate with uniform normal velocity, and Neumann boundary conditions are imposed in the solution of the problem. The formal solution is expressed in terms of a modal series representation in spheroidal wave functions, valid at any distance from the spheroid. The prolate spheroidal wave functions are obtained using computer programs that have been recently modified and extended to provide accurate values of the wave functions at high frequencies. Substitution of the limiting form of the radial wave functions (as r approaches infinity) into the solution yields the piston far-field single element pattern (SEP). The SEPs for several different piston sizes, orientations, and locations on the spheroidal baffle are presented at various frequencies. [Work supported by ONR Code 321 and Naval Undersea Warfare Center In-house Laboratory Independent Research (ILIR) program.]
Structure-borne noise reduction for an infinite cylindrical shell (theory of elasticity)
Authors: Ko Sunghwan , Seong Woojae , Pyo Sangwoo
Published: July 2002

A theoretical model was developed to evaluate the reduction of structure-borne noise generated by an axially symmetric ring force which is applied on the interior of the cylindrical shell. The vibrating cylindrical shell is coated with a microvoided elastomer that is acousically soft material designed for the reduction of the generated noise. The analytical model is a two-layer shell structure comprised of an outer layer of coating that is perfectly bonded to a cylindrical shell. The outer surface of the coating and the inner surface of the shell are in contact with water and air, respectively. The analysis for this problem is based on the theory of elasticity and pertinent boundary conditions. Effects of various parameters such as coating thickness and material properties on the noise reductions are presented.
An optimization process for estimating two-port parameters
Authors: Serbyn M. R. , Kumar A. P.
Published: July 2002

One process of parameter identification for a linear time-invariant two port consists of solving the inverse problem, given a set of values of the external variables. Such parameter estimates are subject to two sources of error: the measurement uncertainty and the propagation of error. The latter, in the worst case, can greatly exceed the former [M. R. Serbyn, J. Acoust. Soc. Am. 106, 2232 (1999)], but can be reduced by a judicious choice of the external variables, as implied by previously reported results, for example, [Li-Feng Ge, J. Acoust. Soc. Am. 97, 324–330 (1995)]. For this investigation a simple electrical circuit, characterized by a Moebius transformation, w=(a11z+a12)/(a21z+a22), with known parameter values, was chosen. It provided a baseline for comparing the parameter values estimated from measurements of z and w made at the output and input ports, respectively. Each estimate was based on a set of three (z,w) values and the reciprocity condition. By varying the nature and magnitude of the load impedance, z, and the corresponding input impedance, w, it was possible to minimize the errors in the computed values of the transformation matrix. Both simulated and experimental results were compared with the theoretical standard.
Review of ultrasonic transducer calibration techniques at Penn State University Applied Research Laboratory
Authors: Foulk Aaron M. , Hughes W. Jack , Van Tol David
Published: July 2002

Recent emphasis on development of higher-frequency transducers for use in medical ultrasound and sonar applications has necessitated the creation of a reliable means of evaluation of these transducers. This work provides an overview of recent progress in the development of a facility for this purpose at the Pennsylvania State University Applied Research Laboratory. [Research funded by ONR.]
The importance of critical book reviews
Authors: Marston Philip L.
Published: July 2002

According to C. S. Lewis, ‘‘Literature exists to teach what is useful, to honor what deserves honor, to appreciate what is delightful’’ [C. S. Lewis, The Discarded Image (Cambridge U.P., Cambridge, 1967), p. 214]. While Lewis’s context was remote from scientific and technical literature, these considerations are relevant to publication of timely book reviews in the Journal of the Acoustical Society of America. In addition to promoting a general awareness of books and the subject matter considered therein, book reviews can recognize and promote quality and the archiving of appropriate materials in libraries. The recognition of the real or apparent faults of a book is a valuable service along with the recognition of a book’s positive attributes; however, it is appropriate to remember that aspects of the publication process may not be controlled by a book’s author or authors.
The coupling of airborne sound into air-filled poro-elastic soils
Authors: Sabatier James M.
Published: July 2002

The coupling of airborne sound into near-surface soils will be reviewed. Particular emphasis will be given to research conducted at the National Center for Physical Acoustics over the past 10 years, including the works of Arnott, Frederickson, and Hickey. For the purpose of acoustically describing pore properties, the ground is modeled as an air-filled, porous, rigid-framed material. Measurements using both transmission and reflection of sound have been used in conjunction with rigid framed acoustic propagation models to determine air flow resistivity, porosity, and tortuosity. In other research, the ground is modeled as a layered poro-elastic medium following the work of Biot. Measurements of the motion of the elastic frame are made using geophones, buried microphones, and laser Doppler vibrometers. Responses of these sensors to airborne or acoustically induced seismic waves will be described. A recent application of this understanding of the ground is the detection of buried land mines. Some brief comments will be made with regard to this application.
Methods for measurement of the attenuation coefficient and phase velocity of Optison and their relevance to in vivo efficacy
Authors: Hughes Michael S. , Klibanov Alexander L. , Wible John H. , Brandenburger Gary H.
Published: July 2002

We report methods and results of measurements of contrast media attenuation coefficient and phase velocity for concentrations ranging from 1.7×105 to 21×106 particles/ml. These concentrations cover the range likely to occur during in vivo application of ultrasound contrast media such as Optison. For the concentrations cited in this study, the attenuation coefficient exhibits a single peak between 1 to 2 MHz, while the phase velocity rises sharply and then levels off, typically near the same frequency at which the attenuation peak occurs. Previous studies from our laboratory have shown that these acoustic properties of ultrasound contrast media can change significantly with changing experimental conditions. For instance, the frequency at which the peak attenuation of Albunex occurs can shift by as much as 1 to 1.5 MHz as the measurement temperature is increased from 22° to 37 °C. Similarly, the attenuation peak width (full width at half maximum) can narrow by more than a factor of 2 (the exact amount depends on concentration). The peak attenuation values can shift by as much as 50% with increasing acoustic pressure. The primary aim of this study is to measure acoustic properties which are as close as possible to those occurring in clinical practice.
Just a box of rain: Making rain with sound
Authors: Snoeyenbos Gretchen , De Santi Giovanni , Holt R. Glynn
Published: July 2002

Clouds don’t always produce rain. One of the reasons is that microdroplet coalescence does not occur fast enough to produce drops large enough to fall. A brief review of the literature on particle and aerosol agglomeration will be presented. The results of an experiment in which ultrasonic standing waves are employed to enhance microdroplet coalescence in a laboratory cloud will be reported. A force analysis will be presented to allow prediction of the efficiency of the coalescence process for arbitrary acoustic field frequency and droplet radius. If possible, a comparison will be made between experimental results and model predictions.
Amplitude variation of resonant frequencies and Q-factor in impulse acoustic resonant spectroscopy
Authors: Sutin Alexander M. , Guyer Robert A. , Johnson Paul A.
Published: July 2002

One of the oldest and simplest nondestructive tests of the quality of an object is to tap it and listen to the radiated sound. The translation of this test into a modern instrumentation system leads to impulse acoustic resonance spectroscopy, IARS. The processing of the acoustic time train after impulse excitation (tap) allows one to follow Q and resonance frequencies as a function of time. Examination of the time train can reveal important properties of this elastic state and of the state of the object. IARS will be illustrated with data on a suite of automobile brake drums made of powdered aluminum. The time evolution of Q and a resonance frequency will be described. Typically Q is of order one-half of its late time (equilibrium) value at short times whereas a resonance frequency shifts by of order 0.2% from early (0.2 s) to late (5 s) time. These qualitative properties have two possible explanations: (1) amplitude-dependent internal friction or (2) the ‘‘slow dynamics’’ that is characteristic of elastic systems inhabited by hysteretic elastic elements. [Work supported by Stevens and by the Department of Energy: Office of Basic Energy Sciences.]
Backscattering enhancements of ultrasound by tilted solid plastic cylinders in water due to the caustic merging transition: High angular resolution scans
Authors: Blonigen Florian J. , Marston Philip L.
Published: July 2002

Bulk shear and longitudinal waves can make important contributions to the scattering of ultrasound by tilted finite plastic and rubber cylinders in water when the phase velocity of the wave is less than the speed of sound of the surrounding fluid. At a certain critical tilt angle, a backscattering enhancement is observed as a result of merging rainbow caustics associated with bulk transmitted rays internally reflected off the cylinder truncation [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. 107 (2000)]. The backscattering away from this angle is otherwise weak. The critical angle is calculated using the Bravais effective refractive index for the projections of rays on the base plane of the cylinder. New ultrasonic observations are reported for a polystyrene cylinder over a wide range of tilt angles at high angular resolution. The backscattering amplitude angle scan takes on the shape of a Pearcey function with the peak amplitude offset from the critical angle. Backscattering amplitudes at the critical angle are also compared with a ray theory prediction as a function of frequency for both the polystyrene and a silicone rubber cylinder. [Work supported by ONR.]
Dispersion of axially symmetric waves in fluid-filled cylindrical shells
Authors: Bao X. L. , Überall H. , Raju P. K. , Ahyi A. C. , Bjo/rno/ I. K. , Bjo/rno/ L.
Published: July 2002

Acoustic waves normally incident on an elastic cylindrical shell can cause the excitation of circumferential elastic waves on the shell. These shells may be empty and fluid immersed, or fluid filled in an ambient medium of air, or doubly fluid loaded inside and out. Circumferential waves on such shells have been investigated for the case of aluminum shells, and their phase-velocity dispersion curves have been obtained for double fluid loading [Bao, Raju, and Überall, J. Acoust. Soc. Am. 105, 2704 (1999)]. Similar results were obtained for empty or fluid-filled brass shells [Kumar, Acustica 27, 317 (1972)]. We have extended the work of Kumar to the case of fluid-filled aluminum shells and steel shells imbedded in air. These cases demonstrate the existence of circumferential waves traveling in the filler fluid, exhibiting a certain simplicity of the dispersion curves of these waves. This is in striking contrast to the results for double (outside and inside) loading by two fluids of comparable density, where circumferential waves in both external and internal fluids were found, their interaction causing segmentation and repulsion phenomena of their dispersion curves. The condition of standing circumferential waves determines the eigenfrequency spectrum of the shell.
Damage detection in thin composites using guided waves
Authors: Valle Christine
Published: July 2002

Lightweight, high-temperature composite materials have the potential to provide significant economic and performance benefits to aerospace structures. However, one problem inherent in using composites within complex structures in harsh environments is the variety of damage mechanisms experienced by the composite itself. Therefore, conventional NDE techniques that are sensitive to only one kind of damage can give an overly optimistic assessment of the health of the composite. A global measure that takes into consideration all of the different damage mechanisms better addresses the nondestructive evaluation needs of composites used in critical applications. This study investigates the relationship between the composite’s dispersion relationship—generated with a 2D fast Fourier transform representation of transient ultrasonic signals, created with a finite-element (FE) model—and the energy content of the structure, as a function of damage amount. The total amount of energy contained in the structure is measured, and when normalized with respect to a virgin state, illustrates the loss due to a given amount of damage. This method provides a quantitative assessment of the amount of damage in the material, and establishes the numerical and analytical foundations for the application of FE models to damage monitoring in composites.
Auditory search asymmetry with pure tone, narrow-band noise, amplitude-modulated tone, and frequency-modulated tone
Authors: Asemi Noriaki , Sugita Yoichi , Suzuki Yôiti
Published: July 2002

To examine basic features of sounds used in the perception of sound environment, auditory search tasks seem promising to us. Thus the response time to detect a target sound among distracting sound(s) was measured by three experiments. In the first experiment, pure tones and narrow-band noises (1/12 oct) were used. Either of them was used as a target and the other was used as distractor(s). The number of the distractor was varied from 1 to 6. Each sound was presented from one of seven loudspeakers located on the horizontal plane. In the second and third experiments, pure tones and amplitude-modulated tones, pure tones and frequency-modulated tones, respectively, were used as either a target or distractor(s). Results show that the response time to detect a narrow-band noise, an amplitude-modulated tone, or a frequency-modulated tone among distracting pure tones was hardly affected by the number of the distractors. However, the time required to detect a pure tone increased with the number of distractors. These results indicated that our auditory system utilizes temporal changes in amplitude and frequency of sound as a basic feature for the detection of a sound in a sound environment. Precise experimental results as well as further consideration will be given in the presentation.
Perception of a secondary auditory image with three sound sources
Authors: Tan Bernard T. G. , Tang Sing Hai , Yu Gongqiang
Published: July 2002

The precedence effect with three sound sources, using loudspeakers placed in a horizontal plane at equal distances facing the subject, was investigated. In this three-source sound system, one of which is undelayed and the other two delayed, a listener facing these sources perceives an unexpected secondary auditory image in addition to the expected primary auditory image. The two delayed sources have time delays relative to the undelayed source within the range in which the precedence effect operates. The secondary auditory image is believed to be due to summing localization taking place between the two sound sources, which have been delayed, when the relative time delay between them is within the range for summing localization to occur.
Perception of acoustic occlusion using body-scaled judgments
Authors: Gordon Michael S. , Rosenblum Lawrence D.
Published: July 2002

Occlusion has been found to compel visual perception of object position and scene analysis [G. A. Kaplan, Percept. Psychophys. 6, 193–198 (1969); W. H. Warren and S. Wang, J. Exp. Psychol. 13, 371–383 (1987)]. Auditory occlusion may also provide salient information about the locations of both sound sources and surfaces in an acoustic scene. In the current experiment, blindfolded participants were asked to listen to sound occluded by an aperture and judge whether unobstructed passage was afforded for various aperture sizes (e.g., W. H. Warren and S. Wang, 1987). Judgments were found to be highly accurate, suggesting the salience of occlusion information for auditory perception. Information from the relative loudness between aperture sizes may have contributed to this ability.
Structural intensity in a line-excited infinite elastic plate in the high-frequency range
Authors: Hayek Sabih I. , Won Jungyun
Published: July 2002

An infinite elastic plate is excited by a mechanical line force, which generates an active structural intensity field in the plate. In an earlier paper [Hayek et al., J. Acoust. Soc. Am. 105, 1299 (1999)], the structural intensity was evaluated analytically for a plate using the Bernoulli–Euler theory, which is valid in the low-frequency range. The paper then employed the same theory for the active control of total structural intensity by use of colocated point forces and moments. In this paper, the evaluation of the structural intensity field due to line forces and moments is modeled by use of the more exact Mindlin plate theory, which is valid in a much higher frequency range. The main objective is to achieve active control of the total structural intensity in infinite elastic plates using the Mindlin plate theory through a colocated line force and a line moment actuators at an arbitrary location on the plate.
A new active structure acoustic control system
Authors: Zou Dingguo , Crocker Malcolm J.
Published: July 2002

The acoustic power radiated from any vibrating structure can be written as a quadratic form of the structural modal velocities. The quadratic matrix is real, symmetric, and positive definite. All of the terms with even–odd and odd–even indices are zero. The congruent transformation instead of orthonormal transformation was used to diagonalize the matrix. This method takes advantage of the good properties of the quadratic matrix more efficiently than the orthonormal transformation does. Also, the method greatly simplifies the design of the PVDF sensors, which filter the combination of appropriately weighted vibration modes, providing a specific performance index in control strategy. Based on this method, an active control system was implemented. To minimize the radiated power from a vibrating structure, a procedure to optimize the distribution of the actuators was applied to the control system.
Speech perception by normal-hearing listeners under modulated noise masker
Authors: Kwon Bom Jun , Turner Christopher W.
Published: July 2002

Previous psychoacoustic investigations on modulation detection interference (MDI) show that sensitivity to detect modulation in a target is reduced when the masker is modulated. The amount of reduction is primarily dependent upon modulation frequencies, but not as much upon carrier frequencies, supporting the existence of a modulation filterbank in the auditory system. In the current study, consonant identification by normal-hearing subjects was tested with noise maskers, either steady-state or modulated. Modulation interference (MI) was assessed by comparing recognition under the two masker types. In experiment I, speech with limited envelope modulations was tested with different rates of masker modulation. In experiment II, narrow-band speech and masker were tested under various carrier frequency conditions. Higher MI was observed when the rate of masker modulation lies within the range of speech modulations. Carrier frequency separation did not make a strong effect on MI except when the separation is zero. In many cases MI was small or negative, implying that a masking release also occurred. In conclusion, both modulation masking and masking release should be taken into consideration when addressing speech perception under modulated maskers. Psycho- acoustic MDI results, therefore, only partially predict the effects of modulation interference on speech recognition. [Work supported by NIDCD.]
Imitation of phrases in conversational speech
Authors: Pardo Jennifer S. , Fowler Carol A.
Published: July 2002

Linguistically significant gestures of the vocal tract play an important role in speech perception and production. Imitation of speech across conversational partners is a natural consequence of the close connection between perception and production. Following research that finds imitation in single-word shadowing, this study paired unacquainted same-sex talkers in a conversational task designed to induce repetition of key phrases across partners. Immediately repeated items were assessed for imitative fidelity by asking a separate set of listeners to choose the more similar item in an AXB task that compared the sample item from one talker (X) with a read and a repeated item from the other talker (A/B). In general, listeners chose the repeated over the read item as more similar to X. Additionally, read items that were sampled immediately after the conversation hindered a listener’s ability to choose the repeated item more so than items read long before the conversation. Other effects related to the timing of items in the conversation and the role of the participants in the conversation were also observed.
The role of prosody in scope relations
Authors: Baltazani Mary
Published: July 2002

It is well known that sentences with two quantifiers or operators can be ambiguous depending on their scope relation. For example, ‘‘She didn’t kick him because he screamed’’ can mean ‘‘His screaming prevented her kicking him’’ (because > not) or ‘‘His screaming was not the reason for her kicking him’’ (not > because). This paper reports on a production and a comprehension experiment on the role of prosody in disambiguating scope relations in Greek sentences. In the production experiment, five participants read aloud seven sentences each, containing negation and another operator (‘‘because’’ or a quantifier like ‘‘two’’), embedded in disambiguating contexts. Prosodic analysis of the utterances showed that speakers produced different prosodic structures for the two interpretations: a big prosodic boundary after negation to deliver the quantifier > negation interpretation, and no boundary for the reverse interpretation. In the comprehension study, 40 participants listened to the 35 sentences out of context and performed a forced-choice paraphrase selection task. The results show a significant correlation between prosodic cues and scope disambiguation in Greek. This suggests that both speakers and listeners unconsciously make use of these prosodic cues to interpret sentences.
Phoneme restoration in infants
Authors: Newman Rochelle S.
Published: July 2002

In a classic study, Warren (1971) replaced the medial /s/ in legislatures with a cough, and found that adult listeners heard the word as being complete. This auditory illusion demonstrates effects of both bottom-up and top-down information: it occurs only when there is a possible masking noise (it does not occur if the /s/ is replaced with silence), and it occurs at least in part because of the listener’s knowledge that legislatures is a real word. Thus, it involves an interaction between multiple sources of information. The present study investigates whether infants will also show such an effect, and thus whether this interaction between levels of language processing is itself something which develops over time. Infants are shown videos of a cat and a dog in a preferential-looking paradigm, and hear the words kitty and doggie both in the clear, and with the medial stop consonant replaced by either noise or silence. Results examine whether infants will treat the words as whole (that is, match them to the appropriate referent) when the middle sound is replaced with noise as compared to when it is replaced with silence. [Work supported by NIH Grant R03 HD37822-01 to the University of Iowa.]
Theoretical first-order bias and second-order variance for localization estimates from matched-field processing methods: Randomized signal
Authors: Thode Aaron , Naftali Eran , Makris Nicholas C.
Published: July 2002

The bias and variance of range and depth estimates obtained from matched-field processing (MFP) methods are difficult to obtain analytically. Instead, the Cramer–Rao (CR) bound is typically computed to estimate the minimum theoretical variance of a localization estimate. Recently, it has been shown [Makris and Naftali, J. Acoust. Soc. Am. 106, 2 (1999)] that the first-order bias and second-order variance of a general maximum-likelihood estimator can be computed analytically, using higher-order asymptotics in a Taylor series expansion. When applied to the specific case of a matched-field processor with a deterministic signal buried in correlated waveguide noise, it was found that the CR bound underestimates the true theoretical variance for low signal-to-noise ratio (SNR) signals and small sample sizes. Here, the case of a randomized signal in correlated ocean noise is addressed, which represents another facet of the generalized maximum-likelihood estimator problem. Similar to the deterministic case, it is found that the second-order variance term is significant even at 20 dB SNR, and that the localization bias becomes significant as the SNR approaches zero.
Quantifying data information content in matched-field inversion
Authors: Dosso Stan E. , Chapin Edward , Wimut Michael J.
Published: July 2002

In matched-field inversion, geoacoustic properties and/or source position are determined by minimizing an objective function that represents the mismatch between measured and modeled acoustic fields. As this is a strongly nonlinear problem, linearized inversion and appraisal algorithms do not apply. A problem of practical importance is to quantify how the inversion results are influenced by data factors such as (i) signal-to-noise level, (ii) number of frequencies included in the objective function, (iii) whether multiple frequencies are summed coherently or incoherently, and (iv) sensor array configuration. This problem is examined here by applying a fully nonlinear analysis based on Gibbs sampling to construct posteriori probability distributions (PPDs) for the unknown model parameters. Constructing PPDs for different realizations of the above factors allows their effect on the solution of the matched-field inverse problem to be quantified and exploited.