bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of roving level variation on monaural detection with a contralateral cue
Authors: Koehnke Janet , Besing Joan M.
Published: October 2005

Monaural detection with a contralateral cue (MDCC) was measured with and without a 20-dB overall roving level to determine the contribution of loudness to performance on this task. Psychometric functions were obtained for three normal-hearing subjects as a function of the signal-to-noise ratio for pure-tone and 1/3-oct noiseband signals at 500 and 4000 Hz with a wideband noise masker. At 4000 Hz, the roving level degrades performance for the narrow-band noise signal by about 5.3 dB. In addition, the presence of the contralateral cue degrades performance for both the pure-tone and narrow-band noise signals at 4000 Hz by 3 to 6 dB. At 500 Hz, however, performance is not affected by the roving level, and is improved by 3 to 6 dB by the contralateral cue. These results indicate that loudness is being used as a cue only for detection of the 4000-Hz narrow-band noise.
Low-frequency direct path surface/near-surface scattering measured using intermediate-length narrow-band and broadband waveforms
Authors: Gauss Roger C. , Soukup Raymond J. , Fialkowski Joseph M.
Published: October 2005

Direct-path measurement in the surface/near-surface and air/sea interaction experiment in the Gulf of Alaska (February/March 1992) were designed to assess the Doppler, spatial, and temporal characters of very low grazing-angle backscatter as functions of frequency and environmental conditions. Fifty-four 30-min modules of data using cw, LFM, and PRN waveforms of intermediate duration (0.6 to 2.4 s) were collected during a variety of sea conditions, at wind speeds ranging from 4 to 19 m/s. Moreover, these data were collected simultaneously at two frequencies (usually 250 and 1000 Hz). The results show the contrast in spectral character, scattering strength, and ping-to-pong consistency between lower sea states where reverberation from fish is significant and higher sea states where bubble phenomena (clouds/plumes) are dominant. The data also illustrate the effect of subsurface bubbles on the elevation of observed surface strengths over predictions based on air–sea interface scattering theory.
Effects of surface-wave forward scattering on near-surface acoustics fields
Authors: Henyey Frank S. , Ballard John , Ewart Terry E. , Thorsos Eric I. , Farmer David M. , Hill Steven
Published: October 2005

The backscattering return from bubble clouds is proportional to the fourth power of the ensonifying field. This field, as determined by the interference of the direct field and that reflected from the wavy surface, has been studied both by modeling and by experiment. The modeling uses accurate wave methods, but is restricted to one horizontal dimension. The forward surface scattering experiment (FOSS) was carried out during the 1992 Gulf of Alaska reverberation experimental program. Both cw transmissions and explosive charges (1 oz. of high explosive) were used as sources in order to determine the temporal and frequency dependencies, respectively. The modeling and experimental results are compared, involving the strength, the frequency dependence, and the frequency shift (‘‘Doppler’’) spectrum. [Work supported by ONR.]
Bubble density and void fraction measurements in the Gulf of Alaska
Authors: Su Ming-Yang , Cartmill John
Published: October 2005

During February–March 1992, several measurements were made of the size density of near-surface bubbles for a radius of 34 to 1200 μm from a depth of 0.25 m down to about 6 m in the Gulf of Alaska by means of a vertical acoustic resonator array. Void fraction measurements were also made at the same time by means of a horizontal array (15 m long) strung along the tether cable for the above acoustic resonator array about 150 m from the R/V. The void fraction was measured by conductivity probes with threshold about 0.2%. The spans between the conductivity probes all located 0.25 m below the water surface are 1, 2, 3, 4, 6, 7, 8, 9, 11, and 15 m, respectively. All the conductivity probes were located 0.25 m below the water surface. The measured bubble density data have been used to compute the corresponding low-frequency (less than 1 kHz) sound speeds. The measured void fraction data have been used to infer the presence and intensity of breaking waves. In this talk some statistical characteristics of these bubble densities, low-frequency sound speeds, and breaking wave statistics are presented. A comparison of these with some previous measurements using the same technique at different field locations shall also be made. [Work supported by ONR Acoustical Reverberation SRP.]
Ultrasonic attenuation estimation i
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Authors: Zhou Kangyuan , Zhang Daofa , Lin Chuan , Zhu Shihong
Published: October 2005

In recent years, B scanners have been widely used clinically. Obviously, it is of particular importance to use the commerical B scanners to characterize tissue by estimating its ultrasonic attenuation in vivo. However, there are a lot of difficulties in doing so because the output of a B scanner is affected by many unknown factors. In this paper, a time domain method named the difference ratio correction (DRC) method is proposed to estimate the ultrasonic attenuation of tissue in vivo. In this method, three tissue-mimicking phantoms with known acoustical properties were employed to eliminate the instrumentation errors of the B scanner and the measuring system and to correct beam diffraction for correct attenuation estimation. Other advantages of this method are that it is very convenient to apply this method clinically and there is no need to change the inner construction of the B scanner because this method only utilizes the video output. Experimental and clinical results have proved the validity of this method.
Computer modeling of acoustic beam formation in D
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Authors: Aroyan James L. , Cranford Ted W. , Kent Joel , Norris Kenneth S.
Published: October 2005

It has been established that some dolphins possess well-developed acoustic orientation (echolocation) and information gathering abilities, though substantially less is known about the system of sound generation and beam formation. Dolphins use a narrowly focused sound beam that emanates from the forehead and rostrum during echolocation. The primary objectives of this study were to simulate the effects of anatomical structure on beam formation, and to test the viability of various hypothetical sound source locations. Outlines from parasagittal x-ray CT scans were used to construct a 2-D model of the head of the common dolphin, Delphinus delphis. Finite difference techniques were used to simulate sound propagation through tissues modeled as inhomogeneous fluids. Preliminary simulations confirm that beam formation results primarily from reflection off of the skull and the skull-supported air sac surfaces. For the frequencies tested, beam angles best approximate those measured by experimental methods for a source located in a region of the model referred to as the monkey lip/dorsal bursae (MLDB) complex. The results suggest that: (1) the skull and air sacs play the central role in beam formation; (2) the geometry of reflective tissue is more important than the exact acoustical properties assigned; (3) a melon velocity profile of the magnitude tested is capable of mild focusing effects; and (4) experimentally observed beam patterns are best approximated at all frequencies simulated when the sound source is placed in the vicinity of the MLDB complex.
Recovering articulator trajectories using task dynamics and a genetic algorithm
Authors: McGowan Richard S.
Published: October 2005

A method for recovering the movement of articulators from speech acoustics is proposed. This method consists of optimizing a fit between acoustic data and the corresponding acoustic parameters produced by an articulatory synthesizer (model synthesizer) over a time interval corresponding to either a vowel with closure, or a release with a vowel. In the simulation experiments reported here, the data consists of the first three formant frequency trajectories produced by the Haskins articulatory synthesizer, ASY [Rubin etal., J. Acoust. Soc. Am. 70, 321–328 (1981)]. The articulatory synthesizer used to fit the data is identical, but the parameters that control the synthesizer and are varied to provide the best fit are task dynamic variables as specified in a gestural score [E. L. Saltzman and K. G. Munhall, Ecol. Psychol. 1, 333–382 (1989); C. P. Browman and L. Goldstein, J. Phonet. 18, 299–320 (1990)]. A genetic algorithm is used to optimize the fit between the formant data and the formants produced by the model synthesizer. This approach appears to be able to recover the basic tongue body tongue tip, and jaw movements of the ASY vocal tract, but with substantial computing effort. [Work supported by NIH Grant No. DC-02147 to Haskins Laboratories.]
Measurement of sound-pressure distribution in replicas of the oral cavity
Authors: Motoki Kunitoshi , Miki Nobuhiro , Nagai Nobuo
Published: October 2005

The spatial distributions of sound pressure in artificial oral cavities were measured to examine the characteristics of wave propagation in the vocal tract. The measurement was performed with plaster replicas of the oral cavity, and pure tones were used as the driving signals to obtain both amplitude and phase distributions at varied frequencies. Plane-wave propagation, which has been widely assumed for speech production models, was examined from the measured spatial distributions of sound pressure. Trajectories of media particles and vectorial maps of acoustic intensity, which can be computed from the measured pressure distributions, were also presented to visualize the acoustic field in the oral cavity. The results showed that at certain frequencies there existed points where sound pressure was absolutely zero, with the phase spatially circulating around them. Up to about 4 kHz, except at these certain frequencies, the wave front was almost one-dimensional, though an amplitude gradient was seen in the vertical direction.
Spectral shape discrimination of narrow-band sounds
Authors: Green David M. , Berg Bruce G. , Dai Huanping , Eddins David A. , Onsan Zekiye , Nguyen Quang
Published: October 2005

Measurements are reported on the detectability of signals added to narrow-band sounds. The narrow-band sounds had a bandwidth of 20 Hz and were either Gaussian noise with flat amplitude spectra or sets of equal-amplitude sinusoidal components whose phases were chosen at random. Four different kinds of sinusoidal signals were used. Two signals produced symmetric changes in the audio spectrum adding a component either at the center of the spectrum or at both ends. The other two signals produced asymmetric changes adding a component at either end of the spectrum. The overall level of the sound was randomly varied on each presentation, so that the presence of a signal was largely unrelated to the absolute level of the signal component(s). A model is proposed that assumes the detection of the symmetric signals is based on changes in the shape of the power spectrum of the envelope. Such changes in the envelope power spectrum are probably heard as changes in the ‘‘roughness’’ or ‘‘smoothness’’ of the narrow-band sound. The predictions of this model were obtained from computer simulations. For the asymmetric signals, the most probable detection cues were changes in the pitch of the narrow-band sound. Results from a variety of different experiments using three listeners support these conjectures.
Acoustic image analysis of acoustic scattering from rigid spheroids and cylinders
Authors: Gaumond Charles F. , Sarkissian Angie , Dragonette Louis R.
Published: October 2005

Acoustic imaging can be used to display the spatial, frequency, and temporal effects of acoustic scattering. The quantitative images can be coupled with simple scattering models to elucidate scattering mechanisms. Acoustic scattering results are presented from rigid spheroids and spheroidally endcapped cylinders with similar length-to-width ratio. The bistatic patterns produced from end-ensonification differ due to the reflectivity of the ends and the amount of reradiation along the length of the scatterer. The ends of prolate spheroids possess higher curvature than endcapped cylinders and therefore reflect less into the back direction. The cylinders possess a straight section along which the creeping wave does not radiate. These scattering phenomena are shown in acoustic images formed from the far-field scattering patterns.
Scattering by an obstacle embedded in a plane-stratified, saturated, poro-elastic medium: Application to an obstacle in ocean sediments
Authors: Lim Raymond
Published: October 2005

A transition matrix formalism for calculating the field scattered by a bounded, three-dimensional obstacle buried in a plane-stratified, saturated, poro-elastic environment is described. The formalism yields an exact solution of the vector Biot equations, obeying all boundary conditions prescribed on the layer and obstacle boundaries. This is obtained by combining the recently derived free-field transition matrix for an obstacle in a porous medium [Kargl and Lim, J. Acoust. Soc. Am. 90, 2371 (A) (1991)] with a generalization of existing acoustic waveguide formalisms [see, for example, Hackman and Sammelmann, J. Acoust. Soc. Am. 84, 1813–1825 (1988)]. The solution is numerically implemented for a spherical obstacle buried in a layered ocean sediment and insonified by an acoustic source in an overlying water half-space.
Original Liberty Jazz Band
Authors: White Michael
Published: October 2005

America’s only true contribution to the arts, jazz, has become a popular worldwide phenomenon since its birth just over 100 years ago. Though it has evolved into several different styles, each with their own geniuses and heroes, none has remained more functional and socially vibrant than its original form: New Orleans jazz. Though the music has often been commercialized and misunderstood, the unique cultural environment that gave birth to jazz still exists in some form today and the music is still part of New Orleans celebrations: parades, weddings, funerals, parties, etc. The program ‘‘New Orleans Jazz: A Musical, Cultural, and Social Tradition,’’ is a rare opportunity to learn about and be entertained by this unique musical form. In the opening segment, Dr. Michael White outlines the origins, social significance, spread, and musical characteristics of New Orleans jazz. The next segment uses Dr. White’s internationally known Original Liberty Jazz Band (which consists of all New Orleans-born descendants of the first generation of jazz pioneers), to demonstrate the role of each instrument, various song types, and the characteristic process of ‘‘polyphony’’ or collective improvisation. The band will perform numerous standards of New Orleans jazz, including the works of the tradition’s most outstanding practitioners such as Jelly Roll Morton, King Oliver, Louis Armstrong, and Sidney Bechet. The music is highly emotional, spiritual, and exciting. Audience participation through discussion is welcome.
Development of a three-dimensional marching technique for backscattering
Authors: Lee D. , Botseas G. , Schultz M. H. , Siegmann W. L.
Published: October 2005

A marching method for numerical computation of weak backscattering has been constructed recently. A two-dimensional implementation of this method has been tested for accuracy with exact and benchmark solutions. The procedure has now been extended for application to three-dimensional problems with weak backscattering and full azimuthal coupling. The new numerical implementation will be described. Computational experience with the algorithm will be reported, including indications of convergence and attainable accuracy. Since fully coupled three-dimensional propagation can be produced by density variations, these must be incorporated accurately into the method. The numerical modifications to accommodate density variations will be described, and experience with the extended algorithm will be illustrated. The current objective of our development is the capability to calculate three-dimensional propagation features in the presence of weak backscattering, with future extensions to strong backscattering. [Work supported by ONR and NUWC.]
Four-dimensional rough surface scattering realizations for multilayered fluid-elastic media
Authors: LePage Kevin , Schmidt Henrik
Published: October 2005

Broadband synthetic seismograms of scattering from two dimensionally rough surfaces in a three dimensional, but horizontally stratified media are presented. These results are obtained using the elastic perturbation theory of Kuperman and Schmidt [J. Acoust. Soc. Am. 86, 1511–1522 (1989)] under the Born approximation, for scattering scenarios where rough surfaces of finite extent, which are different on each interface, are insonified by an acoustic point source. These results, while constrained to the single scattering physics of perturbation theory, graphically illustrate the conversion of acoustic energy into trapped Scholte interface modes on elastic half-spaces, and Von Schmidt, antisymmetric, horizontally polarized shear (SH) and Love waves in elastic layers, as well as into a continuous scattered spectrum in the water column. Examples include a small compact scatterer attached to an elastic plate insonified by an acoustic point source, where forward scattering into the flexural mode, backscattering into the quasilongitudinal mode and out-of-plane scattering into the SH mode may be observed. Point source scattering from a larger scattering region is also illustrated, where the effects of wave front curvature become important. The scattering region, which is a stochastic realization of an isotropic power law surface, excites forward-scattered flexural waves in a broad beam, but it is continuously observed that the off axis response is dominated by shear waves. Other scattering scenarios are also presented where the three-dimensional aspects of scattering continue to be important, even for plane wave incidence. [Work supported by ONR.]
More experimental data collected by comparison between the Schroeder’s back integration method and a new method based on sound intensity for measuring reverberation time
Authors: Stanzial Domenico , Carletti E. , Fausti P. , Pedrielli F. , Pedrielli F. , Pompoli R.
Published: October 2005

The experimental comparison between the Schroeder’s and the intensity-based method for measuring reverberation time [D. Stanzial etal., J. Acoust. Soc. Am. 91, 2368(A) (1992)] has been improved both in the enumeration of cases and in its methodology. The sound field was generated inside various test rooms of different volume by means of a reference isotropic source driven by a maximum length sequence signal. The measured (pressure) impulse responses of the rooms as well as the active and reactive sound intensity for the same input–output configuration of the acoustic system was then used for the reverberation time evaluation. The collected data by comparison between the two methods are reported here.
Predicting the absorption of pew cushions
Authors: Bradley J. S.
Published: October 2005

Previous research has shown that the sound absorption of arrays of theater chairs is related to the ratio of perimeter-to-area of a sample of chairs [J. Acoust. Soc. Am. 91, 1514–1524 (1992)]. Measurements of various sized samples in a reverberation chamber can thus be used to predict the expected absorption of a large array of chairs in an auditorium. This paper examines the related problem of predicting the absorptive effect of adding cushions to wooden church pews. The absorptive effect of the pew cushions was measured both in a reverberation chamber and in a church. Tests in the reverberation chamber included various sized samples of pews both with and without the pew cushions. The absorption of the pew cushions was also measured on the floor of the reverberation chamber without the pews. The added absorption of pew cushions is influenced by the presence of the pews, is largely independent of the pew sample size, and is predictable from reverberation chamber measurements.
Time domain processing for experimental studies of mid-frequency wave propagation in shells
Authors: Bondaryk Joseph E. , Schmidt Henrik
Published: October 2005

Experimental bistatic scattering measurements were made on two fluid-loaded, cylindrical shells in the frequency range of 2<ka<10. Data were collected for an empty shell and a duplicate shell stiffened with unequally spaced ring stiffeners and resiliently mounted wave-bearing internal structural elements. The shells were ensonified by wideband pulses of spatially plane waves at various angles of incidence. The scattered field was measured by a synthetic array in the transition and far-field regimes. Time domain focusing techniques are used to determine the transient dynamic structural response of the shell surface. Radon transforms are then used to identify and isolate individual wave events on the shell surface, such as the reflected and transmitted waves at a single ring stiffener. The results of these computations show that the internal structures greatly affect the dynamic response of the shell at these frequencies where the wavelengths are comparable to the lengths of the discontinuities in the shell. This research focuses on the effects of the ring stiffeners on the shear and compressional membrane waves in the shell. [The authors acknowledge NRL for acquisition of scattering data. Research supported by ONR.]
Time, frequency, and aspect analysis of monostatic scattering from a hemispherically end-capped steel cylindrical shell immersed in water
Authors: Yoder Timothy J. , Gaumond Charles , Dragonette Louis R.
Published: October 2005

A finite element simulation of a hemispherically end-capped steel cylindrical shell, immersed in water, and ensonified by plane acoustic waves is shown for a frequency band from ka=2.0 to ka=6.0. The monostatic far-field acoustic scattering from this simulation is determined by the following physical processes: the quasilongitudinal wave, the shear wave, specular reflection, and wave-vector matching with the radiation medium. The time, frequency, and aspect dependence of the monostatic far-field acoustic scattering is graphically analyzed to determine the physical process or combination of processes responsible for the scattering. This analysis reveals the location on the structure that scatters energy into a particular far-field highlight, the time that the structure scatters the energy, and the frequency dependence of the scattered energy. The transport of energy down the shell and the reflection of energy from the ends of the shell are also demonstrated through this analysis.
Time, frequency, and aspect analysis of bistatic scattering from a hemispherically end-capped steel cylindrical shell immersed in water
Authors: Yoder Timothy J. , Gaumond Charles , Sarkissian Angie
Published: October 2005

A finite element simulation of a hemispherically end-capped steel cylindrical shell, immersed in water, and end-ensonified by plane acoustic waves is shown for a frequency band from ka=2.0 to ka=6.0. The bistatic far-field acoustic scattering from this simulation is determined by the following physical processes: the quasilongitudinal wave, the shear wave, specular reflection, and wave-vector matching with the radiation medium. The time, frequency, and aspect dependence of the bistatic far-field acoustic scattering is graphically analyzed to determine the physical process or combination of processes responsible for the scattering. This analysis reveals the location on the structure that scatters energy into a particular far-field highlight, the time that the structure scatters the energy, and the frequency dependence of the scattered energy. The transport of energy down the shell and the reflection of energy from the ends of the shell are also demonstrated through this analysis.
Spectral characteristics of stops in connected speech and citation form: Evaluation of a vowel reduction hypothesis
Authors: Weismer Gary , Molis Michelle , Milenkovic Paul , Forrest Karen
Published: October 2005

Several different schemes for extracting consistent spectral features of stop bursts have been proposed, with a fair amount of success in classifying place of articulation. Most of the material that has been used for classification tests has been of citation form, and in some cases carefully articulated citation form. The present experiment investigates the hypothesis that classification will be better in connected speech samples than in citation form. The hypothesis is motivated by the expectation of a diminished influence of vowel identify on stop bursts in the connected speech sample, where vowel reduction is likely to occur. The vowel reduction hypothesis has been confirmed by vowel duration and format frequency analyses; the classification analyses, based on discriminant function classification of spectral moments [Forrest etal., J. Acoust. Soc. Am. 84, 115–123 (1988)] are in progress and will be reported at the meeting.
Simulator sickness
Authors: Lackner James R.
Published: October 2005

Motion sickness is commonly elicited in situations involving unusual patterns of acceleration (e.g., sea sickness, space motion sickness) or sensory stimulation (e.g., optokinetic drums). Symptoms are also evoked in flight and car simulators where the experienced motion and the inertial motion of the body do not correspond. Motion sickness is now being reported in virtual environments, especially those involving dynamic patterns of apparent self-motion. Such environments embody sensory and inertial discordances that are for physical situations of stimulation most provocative. Motion sickness embodies a wide constellation of signs and symptoms, not just nausea and vomiting. In fact, drowsiness, eye strain, lack of initiative, and fatigue are symptoms of motion sickness commonly elicited in relatively unprovocative environments. Progress in understanding and predicting the occurrence of motion sickness has been hampered by the lack of an adequate theory. This talk will include discussion of situations that elicit motion sickness, how symptoms vary for different situations, how adaptation can be hastened, and how it is possible to have multiple adapted states for different environments.
Fluid-loaded elastic slab excited by line and point loads
Authors: Gur Yuksel , Leehey Patrick
Published: October 2005

The plate equations are not sufficient to predict the response for high wave-number excitations. In order to determine the difference between plate and elastic slab results, and the range of validity of the plate equations, the following problems were solved: an infinite slab excited by a line load and a point load. The space above the slab contains an acoustic medium and below the slab there is a vacuum. It was proven that the point-loading case was formally identical to the line-loading case. The only difference was in the use of Hankel transforms instead of Fourier transforms. Full elastic slab equations were solved for this acoustic medium/elastic slab coupling problem with analytical and numerical techniques. Far-field-radiated pressure and surface interface displacement results indicated that full elastic slab equations predict lower radiated pressure and higher interface trapped wave amplitude compared to thin plate results for high-frequency excitations. The upper nondimensional frequency limit for the validity of the thin plate equations was determined to be ωh/cl≊0.17. By introducing structural damping, one is able to determine the interface displacements in the vicinity of the excitation. [Work supported by Mechanics Division, ONR.]
Experimental evaluation of time domain features of the backscattered field of finite cylindrical shells
Authors: Corrado Charles N. , Dyer Ira , Guo Yue-Ping
Published: October 2005

The mid-frequency scattering properties of three different cylindrical shell models have been evaluated experimentally to study the influence of resiliently mounted internal structures and typical structural discontinuities such as endcaps and transverse stiffeners. The models consist of an empty shell, and unequally spaced ring-stiffened shell, and a ring-stiffened shell with resiliently mounted, wave-bearing internal structural elements. The measurements were conducted over a frequency range of 2.75<ka<10.5 corresponding to 3/4 to 3 times the ring frequency of the empty shell. The measurements were all conducted with the use of wide-band pulses yielding good time resolution of propagating wave effects. Various time domain representations of the scattered field are presented to illustrate the evolution of observed backscattering processes. The influence of induced helical membrane wave propagation on the shell, scattering at the ring stiffeners, and interaction of the shell and internal structures is readily observed in the time domain. Monostatic and bistatic measurements are compared to contrast the fields observed in the specular and back directions. Emphasis is placed on evaluation of the scattered field properties observed over a range of aspect angles within 30 deg of beam aspect where phase-matched excitation of membrane waves can be accommodated over the cylindrical portions of the shells. [Research sponsored by ONR.]
Collapse of a bubble in the cavitation zone near a rigid boundary
Authors: Kurbatskii Konstantin A. , Kedrinskii Valery K.
Published: October 2005

This paper discusses the cavitation erosion problem and one of its difficult aspects, i.e., cumulative flow development in vapor-gas bubbles and evaluation of parameters of high-speed microjets as main sources of impulse influence on a nearby rigid wall (boundary). The axisymmetric potential problem of cavity collapse in a nonviscous and incompressible liquid with variable ambient pressure is considered. The Laplace’s equation is solved numerically by use of boundary-integral methods. The influence of a rigid wall is modeled by the reflection method. Ambient pressure is calculated by use of a two-phase liquid model describing cavitation cluster dynamics. The dynamics of a bubble situated near a rigid boundary is investigated and the results are obtained for cumulative jet formation in the bubble.
Radial wave thermoacoustic engines
Authors: Arnott W. Patrick
Published: October 2005

Thermoacoustic heat engines are used to produce sound from heat and to transport heat using sound. Most previous work has concentrated on engines in plane-wave resonators. This paper is about the analysis of engines in radial mode cylindrical resonators. Impedance and pressure translation equations are shown for open sections of the resonator and for heat exchangers. Coupled first-order differential equations are given for pressure and impedance in the temperature-gradient-supporting engine sections. These quantities are used in the computation of energy transfer, and allow for complete analysis of engines with a variety of boundary conditions. Analysis is compared for engines in cylindrical and plane-wave resonators. Previous work in plane-wave resonators has shown that the quality factor Q increases to ∞ as the temperature gradient across the engine becomes sufficiently large. An application of the derived theory is Q and dQ/(denvironment) control of a cylindrical resonator in the design of thermoacoustically enhanced photoacoustic spectrometers that are potentially useful for measuring light absorption by atmospheric aerosols.
Search for second sound in deep water gravity waves
Authors: Lawrence R. T. , Yarber R. K. , Keolian R. M.
Published: October 2005

Experimental investigation of a newly predicted propagating mode [Larraza etal., Phys. Rev. A 41, 3144 (1990)] on the surface of water, known as second sound, was performed in the laboratory. This collective mode propagates as an increase in energy density in the background spectrum of random waves. Individual waves of the background can be thought of as scattering ‘‘particles’’ forming a ‘‘gas,’’ and the second sound mode is a density wave in this gas of waves. In this experiment, a long tank was driven at one end by fans to provide different background spectra of random wind-driven waves and a paddle to provide variable wavelength coherent pulses. Wave height was measured with a four-wire probe at different locations along the tank. Thus far, energy transfer has been observed from shorter to longer wavelengths. Additionally, a rarefaction in the background spectral density atallfrequencies is observed to propagate at a single speed−the group velocity of the spectral peak of the wind-generated background spectrum. [Work supported by ONR and NPS.]
Acoustic phase velocity measurements in a bubbly liquid using a fiber optic laser Doppler velocimeter
Authors: Cheyne Stanley A. , Stebbings Carl T. , Roy Ronald A.
Published: October 2005

Acoustic phase velocity measurements of a bubbly liquid in a cylindrical tube have been made with a fiber optic laser Doppler velocimeter (FOLDV). Past experimental configurations of sound propagation studies in tubes filled with air–water mixtures consisted of hydrophones or piezoelectric pill transducers (PZPT) embedded periodically in the tube wall. Hydrophones placed in the sample impose a lower limit on the tube diameter. (The tube diameter must be large compared to hydrophone.) Embedded PZPTs are typically spaced periodically imposing a limit on the resolution of the measured profile of the standing wave due to the finite size of the transducers. The advantages of the FOLDV are the nonintrusive nature of the detection scheme, enhanced resolution, and continuous scanning capabilities over a wider range of frequencies limited by the frequency response of the receiving photodiode. The FOLDV consisted of a fiber optic beam splitter, a miniature lens, a photodiode, and a very thin reflective membrane which is flush against the interior tube wall. The membrane is suspended by a small torus-shaped magnet on the exterior of the tube wall allowing continuous maneuverability in the vertical position of the membrane. A more comprehensive description of the experimental configuration and experimental results will be presented. [Work supported by the ONR and ONT.]
Trajectories and interaction of two particulates in an acoustic field
Authors: Hoffmann Thomas L.
Published: October 2005

A numerical and experimental study is presented to visualize trajectories of a pair of particulates entrained in an acoustic field. A numerical scheme is developed for determinating the relative path of the particles under the influence of orthokinetic, scattering, and hydrodynamic forces. The importance of the different interaction mechanisms is evaluated for varying frequencies and sound-pressure levels. A bench-top experimental setup is used to visualize actual particle trajectories in a sound field with a high-speed video system. These trajectories are then mapped to determine the actual relative particle path of one particle against the other. The results of a comparison between the numerical simulations and the experimental visualizations are used to assess the validity of the existing theoretical models in respect to orthokinetic, scattering, and hydrodynamic interaction mechanisms.
Optimal focusing through plane interfaces using time-reversal methods
Authors: Cassereau Didier , Fink Mathias
Published: October 2005

For several years, time-reversal methods were developed in this laboratory, theoretically and experimentally, to optimize focusing of an ultrasonic pressure field on a target in homogeneous and heterogeneous media. In this work, the problem is analyzed in the case of focusing through a plane interface separating two media with different sound speeds and densities. The principle consists in considering the target as an active source of an acoustic field measured by a mirror. Then, the mirror time-reverses this field, and an acoustic wave back propagates and is focused on the initial target position. A theoretical approach and numerical simulations are presented using one or two plane infinite time-reversal mirrors working on the reflected and/or transmitted components of the field generated by the source. It is shown that it can be more efficient to time reverse the reflected or transmitted field, depending on the velocity contrast between the two media. The problem of mirrors of finite size is also discussed, resulting in a broader focusing peak. Finally, the time-reversal method is compared to the standard Fermat’s surface technique, that reduces to a time-delay computation according to Snell’s law. It will be shown how the time-reversal method, that takes into account the whole information coming from the medium, improves the focalization on the initial target position.
Estimating future noise levels from industrial noise sources
Authors: O’Neal Robert D.
Published: October 2005

The prediction of future sound levels at sensitive receptors around an industrial site is an important process when siting a new project or expanding an existing operation. Sound-level monitoring was conducted to establish existing broadband and octave band levels during a time period when operation of the new industrial source would have the most noticeable impact. Sound-level data for the proposed source was acquired either through manufacturer’s data or by a sound-level measurement program on a comparable existing facility. Future noise levels were calculated using the reduction with distance equation valid for point sources of noise. The predicted future noise level was compared to state and/or local regulations, or any appropriate client sound-level requirements. Where sound levels were predicted to be in violation of the relevant criteria, future sound levels were estimated with the addition of a barrier. This technique was applied to supermarket rooftop equipment and refrigeration trucks docked at a warehouse. Sound levels measured after the equipment commenced operation were within 2 dBA of the predicted levels.
Separation of depth and range localization by rank-reduction of the cross-spectral matrix
Authors: Dean E. A.
Published: October 2005

The least-squares expansion of a rank-N cross-spectral matrix obtained from a vertical array of N hydrophones in terms of M (M≤N) dyads of eigenvectors of its larger eigenvalues plus a diagonal uncorrelated noise matrix was investigated. For M propagating modes the expansion allows the stripping of uncorrelated noise from the matrix. When transformed to modal space, a rank-one reduction allows the stripping of modal uncorrelated noise. In addition to reducing the number of operations required for each point of the ambiguity surface, the rank-one reduced matrix simplifies the separation of depth and range localization of a source. The procedure was applied to data obtained off Panama City [Feuillade etal., J. Acoust. Soc. Am. 88, 423–433 (1990)]. [Work supported by Naval Research Laboratory through US Navy/ASEE Summer Faculty Research Program.]
Characterization of noise sources for predictions
Authors: Keith Reginald H.
Published: October 2005

With the advent and proliferation of computer technology, many design companies are creating and using computer modeling to determine noise control requirements for extensive installations such as petrochemical plants, cogeneration facilities, compressor stations, etc. However, in order to be effective these programs require correct input data on source characteristics such as source strength, frequency characteristics, directional characteristics, and temporal variations. This paper discusses the relative merits of the current methodologies used to obtain this data including manufactured supplied data, laboratory measurement methodologies, and field measurement methodologies. Current testing standard are also reviewed.
Rules for vowel durations in several metrical contexts
Authors: Rogers Catherine L. , Port Robert F.
Published: October 2005

This study sought to explore previous claims made about the interaction of several linguistic timing factors, and subsequently, to develop rules for the duration of vowels in several metrical environments. Two-word phrases that resembled personal names, like TuckTuckhouse, TackeryleTack and TickyTick, were constructed. The vowels [i, i, æ, Λ] were used as the stressed vowel in the word types Tuck, leTuck, deleTuck, Tucky, Tuckery, and Tuckhouse. For each vowel, the six word types were fully crossed, creating a list of 36 phrases. Three speakers produced three repetitions each. Measurements were made of the major segments in the stressed syllable of each word (t-voice-onset time, the vowel, and k closure), as well as of the word and phrase as a whole. The incompressibility property was observed for the interaction of word identity by position-in-phrase [cf. D. H. Klatt, J. Acoust. Soc. Am. 59, 1208–1221 (1976)], while the constant ratio hypothesis was found for the vowel by position-in-phrase interaction [partly replicating R. F. Port, J. Acoust. Soc. Am. 69, 262–274 (1981)]. A formal timing model, suitable for use in speech-synthesis-by-rule, is proposed to model these results.
Acoustic design for noise reduction (ADNR), a method and computer code based on the modelization of structural acoustic and vibration behavior for semicomplex structure
Authors: Nicolas J. , Atalla N. , Baubil Y.
Published: October 2005

Challenge of noise control in the nineties will be to introduce new tools in addition to classical ones (absorbing materials, enclosures, and mufflers) which have been used for several decades. For noise reduction at its source there are mainly two approaches: active noise control or passive noise control, based on a new mechanical design. This paper addresses the second possibility. To design and create a quieter product, an analytical model has been developed predicting the vibration and acoustic responses of a structure. The model is based on a variational method and the calculation of the Green’s function. Specific developments have been introduced to decrease the total computation time. The main design indicators are the quadratic velocity, the modal and global structural shape, the radiation factor, and the sound power. These indicators serve to illustrate how the various design specifications (geometry, thickness, added extended of local mass, added stiffness, stiffener, damping, excitation type, and location) can or cannot decrease the radiated noise. The implemented code appears to be a unique, powerful, and helpful tool for taking the right decision, as far as radiated noise is concerned, at the very beginning of the design stage.
Tailoring panel structural mode shapes for noise reduction across periodic panel frame structures
Authors: Srinivasan Ramakrishna , Bliss Donald B.
Published: October 2005

A solution to the low-frequency noise reduction problem associated with panel/frame structures is proposed by way of tailoring the structural mode shapes associated with individual panels. The panel is shown to be a poor acoustic radiator when the panel dynamics are altered by tailoring the structural mode shapes. This is achieved by choosing appropriate panel stiffness and mass distributions. Noise reduction is achieved in a frequency band between the resonances of the first and third panel modes, when their out-of-phase motions result in acoustic cut-off. Normally, in a homogeneous panel this effect is very small and is in a very narrow bandwidth; but, by suitably tailoring the third mode in such a way as to increase its volumetric flow this effect is shown to increase in magnitude and bandwidth. The present work investigates this effect in a two-dimensional panel model, and the results obtained compare favorably to results from similar techniques such as alternate resonance tuning.
A transfer function approach to panel/frame structural acoustics
Authors: Srinivasan Ramakrishna , Bliss Donald B.
Published: October 2005

A new homogenization approach to periodic panel/frame acoustics permits faster analysis and design of panel/frame structures. The approach involves incorporating periodic local transfer functions in a homogenized global problem. The transfer functions model the local-global interactions at various orders. The present work develops the idea of these transfer functions and the idea of tailoring these functions for noise control. The transfer functions are computed for idealized spring-mass-damper panel subsystems and for real flexible panel subsystems. Results are shown with problems incorporating different orders of transfer functions, and the frequency of applicability is shown to increase with higher-order corrections. Results are also shown where noise reduction is obtained across panel/frame structures incorporating tailored transfer functions.
Force displays for walkthrough simulator
Authors: Iwata Hiroo
Published: October 2005

This paper presents a virtual reality technology for walking through large scale virtual space such as buildings or urban space. Walkthrough simulation is effective for design and presentation of architecture and urban planning. Current systems for virtual reality use gesture input to move around virtual buildings. In terms of natural interaction, however, haptic feedback for walking motion is essential to exploration of virtual space. In this system, a walker wears omnidirectional sliding devices on the feet, which generate feel of walking while position of the walker is fixed in the physical world. The system provides a feeling of uneven surface of a virtual space, such as a staircase. While the walker goes up or down stairs, the feet are pulled by strings in order to apply reaction force from the surface. The motion of the feet and the head are measured by ultrasonic sensors. Scene of a virtual space is displayed on a head-mounted display corresponding with the motion of the walker. A 6 degree-of-freedom master manipulator is developed to apply reaction force to the hand of the walker. The manipulator enables the walker to feel weight or rigidity of virtual objects.
Implementation of surface impedance boundary conditions in the split-step parabolic equation
Authors: Ryan F. J.
Published: October 2005

The parabolic wave equation (PE) is a powerful numerical method for computing the full-wave complex acoustic pressure field in range-dependent environments. The split-step Fourier PE algorithm (SSFPE) of Hardin and Tappert provides a very efficient computational implementation of PE when the surface boundary condition is of the Dirichlet or Neumann form. This allows use of fast Fourier transform (FFT) methods to implement the SSFPE algorithm. In many cases, however, the surface boundary condition is of the mixed or impedance type which precludes use of simple FFTs. In this talk, generalizations of the SSFPE algorithm will be discussed that use a novel fast radiation transform (FRT). The FRT allows explicit incorporation of complex surface impedance boundary conditions into the SSFPE algorithm, while still retaining computational efficiency. Illustrative examples that use this new method will be shown.
Postnatal cochlear function development in normal dogs and deaf Dalmatians
Authors: Strain George M. , Tedford Bruce L.
Published: October 2005

Pigmentation-associated congenital deafness occurs in humans and other species, including dogs (especially Dalmatians). The deafness generally results from degeneration of the stria vascularis after an otherwise normal period of development; time of occurrence is unknown in humans but is early postnatal in several animal species. Noninvasive perinatal studies of audition in dogs are not possible until 2–3 weeks of age, when the ear canals open. Methods developed to follow the postnatal development of peripheral auditory function in dogs and preliminary findings in normal pups and deaf Dalmatians are reported here. Surgery was performed 24–48 h after birth to implant recording electrodes and tubing for auditory stimulation in the sealed ear canal near the tympanum. Pups stayed with mothers except for recordings. Daily recordings (150–3000 Hz, 10 ms) were collected between the implanted electrode and vertex in response to click stimuli (100 μs, 11.4/s, 135 dB SPL [machine setting]) applied through the implanted tubing. The normal postnatal pattern of response development is presented. Deafness in Dalmatians developed by 3 weeks following normal initial development. [Work supported by NIH/NIDCD.]