bluuebunny/crossref_metadata_2025 huggingface dataset:
Power flow for sound incident on a solid aluminum sphere in water
Authors: Hickling Robert , Burrows R. Kirk , Ball James F. , Petrovic Mirjana
Published: October 2005

Power flow is computed for sound incident on a solid aluminum sphere in water. First, power flow together with kinetic and potential energy distributions are investigated for the standing modes of free vibration of the sphere. The instantaneous power flow excited in the sphere by a continuous train of plane waves is examined next. Finally, time-averaged power flow is investigated. Little has been done so far to compute sound-power flow in structures immersed in a fluid. Computations of this kind provide a new insight into the relation between the elastic waves in the structure and the sound radiated into the fluid.
Numerical implementation of an adaptive fast-field program for sound propagation in layered media using the chirp z transform
Authors: Li Y. L. , Franke S. J. , Liu C. H.
Published: October 2005

Using the chirp z transform, a numerically efficient adaptive integration algorithm for fast-field programs has been developed. The fast-field program (FFP) is a numerically efficient algorithm for computation of the sound pressure due to a time harmonic point source above a general boundary in a layered medium. The new algorithm allows the user to specify the precise location of the range sample points, or “detectors,” independent of the horizontal wave-number sampling grid. This feature makes the algorithm particularly attractive for use in applications where sampling on a predetermined spatial is required. An example of such an application is the computation of the acoustic frequency response as a function of range. In this case the complex sound pressure must be computed at many frequencies while maintaining a constant range sampling interval. In addition, the algorithm can be used to recompute the sound pressure field with different range resolutions without recomputing the horizontal wave-number spectrum samples. It is also shown that the algorithm can be used to adaptively increase the number of integration points required to evaluate the Sommerfeld integral that results from the FFP type of formulation.
Equation of state of the system of magnetoacoustic waves
Authors: Nasir M. Y.
Published: October 2005

Magnetoacoustic waves are considered as a system. Bose–Einstein statistics are applied to find the equation of state and thermodynamic quantities of the system. It is found that energy and pressure of the system are directly proportional to the cube of absolute temperature. Adiabatic changes of the system are also discussed.
Diffraction of a cylindrical acoustic wave by an absorbing half-plane in a moving fluid
Authors: Asghar S. , Ayub M. , Ahmad Bashir , Qadir Asghar
Published: October 2005

Acoustic diffraction from a line impulse by an absorbing half plane in the presence of a moving fluid is considered. The field is calculated using spatial and temporal Fourier transforms. The results for a finite pulse are also presented. The physical interpretation of the results is then discussed.
Coupled perturbation series for disparate mixtures
Authors: Gillette Gregory
Published: October 2005

A technique is presented which has been developed for calculating fields in two-phase mixtures when the material properties of the two phases are very dissimilar. A pair of coupled integral equations are derived and then solved together using an alternating recursion. This gives rise to a pair of coupled perturbation series (corresponding to the field point being in one or the other of the two phases). Truncations of the series then lead to descriptions of the solution fields which are valid in the regime of very small (but not necessarily zero) material property ratios. The specific problem of acoustic-wave fields due to a point source in a two-fluid mixture is treated in full and serves to illustrate the procedure. The results are applied to the case of plane-wave interaction with a flat plane interface, where it is shown that the perturbation series do indeed produce expansions of the exact solutions.
Acoustical tweezers
Authors: Wu Junru
Published: October 2005

A stable force potential well was generated by two collimated focused ultrasonic (3.5 MHz) beams propagating along opposite directions. Latex particles (270-μm diameter) and clusters of frog eggs were trapped in the potential well. The trapped object can be moved axially or laterally by moving one of the PZT focusing transducers that generate the ultrasonic focused beams. The axial position of the trapped object can also be maneuvered by tuning the frequency of the electrical voltage applied on the transducers.
Low-resolution acoustic scattering models: Fluid-filled cylinders and fish with swim bladders
Authors: Clay C. S.
Published: October 2005

Low spatial resolution acoustic scattering models were developed to model the scattering by objects that are less ideal than perfect cylinders, i.e., fish. The models used the first few modes of solutions for finite and bent fluid cylinders [T. K. Stanton, J. Acoust. Soc. Am. 83, 55–63 (1988) and 86, 691–703 (1989)]. Empirical mode attenuation factors and bent cylinders were used to control the spatial resolution. All computations were for backscatter in the far field. First, numerical evaluations were made for frequency domain scattering amplitudes. The scattering amplitudes were inverse Fourier transformed to time domain for identification of the reflection and diffraction components. Gas-filled cylinders represented fish swim bladders. Fish bodies were represented by a liquid-filled cylinder where the liquid had a density and a sound velocity a little greater than water. Gas-filled cylinder: The sum of the zeroth and first mode gave a reflection from the front face and a diffraction from the boundary of the insonified and shadow zone. Summations over 23 modes gave a single reflection and no boundary diffracted wave for ka<20, where k is wave number and a is cylinder radius. Liquid-filled cylinder: The sum of the zeroth and first mode gave reflections from the front and back faces and shadow boundary wave. The shadow boundary wave was larger than the reflected components. The sum of 23 modes gave reflections from the front and back face and no shadow boundary wave for ka<20. Fish model: The theoretical models were compared to measurements of sound scattered by anchovy ([R. H. Love, J. Acoust. Soc. Am. 49, 816–823 (1971) and D. V. Holliday, J. Acoust. Soc. Am. 51, 1322–1332 (1972)]. The matches of data and theory were excellent. Comparison of the bent cylinder theory and measurements to the traditional spherical bubble model showed that the spherical bubble was a poor approximation to the swimbladders of these fish. The research shows that acoustic modeling needs fish length, fish mass, fish and swimbladder morphology, etc.
Bistatic reverberation calculations using a three-dimensional scattering function
Authors: Ellis Dale D. , Crowe D. Vance
Published: October 2005

The ocean bottom scattering function depends, in general, on the grazing angles and the azimuthal angles of the incident and scattered energy. However, most measurements are for backscatter only. The few general measurements that are available indicate strong forward scattering near the angle of the specularly reflected ray and weaker, azimuthally isotropic, diffuse scattering away from the specular angle. By combining Lambert’s law scattering with a surface scattering function based on the Kirchhoff approximation, Ellis and Haller [J. Acoust. Soc. Am. Suppl. 1 82, S124 (1987)] proposed a function that incorporated these features. The function is quite simple, and depends on three parameters that can be fitted to backscatter measurements. The functional form thus allows a reasonable extension from backscatter to the general three-dimensional scattering function, which can then be used in bistatic reverberation calculations. It is an improvement over two commonly used methods (which do not include azimuthal dependence) for extrapolating backscattering to general scattering: the separable approximation, and the half-angle approximation. This paper discusses the three-dimensional function in more detail, and presents some comparisons between model predictions and measured bistatic reverberation.
Environmental mismatching effects on source localization processing in mode space
Authors: Shang E. C. , Wang Y. Y.
Published: October 2005

In this paper the source localization performance degradation of the matched field processing (MFP) caused by environmental mismatch has been discussed for HRMM processor [E. C. Shang, J. Acoust. Soc. Am. 86, 1960–1964 (1989)] in mode space analytically. By using the approximate modal eigenvalue solution, the analytic expressions for describing the impacts of water-depth mismatch in a Pekeris waveguide and sediment-type mismatch have been derived. By using the modal perturbation theory an indicator for assessing the range performance degradation caused by sound-speed profile (SSP) mismatch has been proposed. Analytic results have been verified by numerical simulations.
Wave-number frequency response of beams to an array of point drives
Authors: Hutto F. M. , Burroughs C. B. , Hughes W. J.
Published: October 2005

An analytical model using Timoshenko beam theory is formulated for the free response of a thick free–free beam and the forced response of the same beam to an array of point drives. To validate this model, comparisons are made between predictions and measurements of the free response of the beam and of the forced response of the beam using one, two, and three point drives. Measured and predicted results of the magnitude and phase of the beam admittance and the wave-number-frequency response of the beam are compared. Excellent agreement between theory and experiment is noted, especially when the measured forcing functions were input to the model. The analytical model is then used to investigate the wave-number response of the beam to an array of point drives. The forced wave-number response is achieved by an array of point drives that are amplitude weighted to form a standing wave pattern. Analytical model calculations of the wave-number-frequency response of the beam show that the unwanted free wave-number response of the beam at resonance frequencies can be reduced by: (1) applying Hanning shading to the point drives, and (2) increasing the damping in the beam so that admittance measurements of the beam can be made at nonresonance frequencies and forced wave numbers.
A hierarchy of performance analysis techniques for adaptive active control of sound and vibration
Authors: Morgan Dennis R.
Published: October 2005

Active control for silencing sound and vibration has recently become the subject of much investigation and is now being enhanced by the advent of adaptive filtering techniques. In this paper, an approach to adaptive active control performance analysis is developed that involves a hierarchy of techniques, starting with an ideal simplified problem and progressively adding practical constraints and other complexities. Four levels of performance analysis are defined: Level I derives fundamental performance limits given continuous measurements over the entire performance surface; level II brings in the practical constraint of a fixed number of sensors at discrete locations; level III incorporates knowledge of the transfer function structure; and, level IV adds in all of the other practical effects and design constraints required for detailed performance calculations. At each step, a degree of confidence is gained and a benchmark is established for comparison and cross-checking with the next level of complexity. Following this methodical process leads to a baseline architecture, which can then be subjected to detailed performance analysis in order to arrive at a final design. The four levels of performance analysis are discussed in detail and are illustrated by numerical example for a vibrating cantilever beam using a graphics display that was developed for real-time interactive design.
An investigation of the acoustic emissions from a bubble plume
Authors: Kolaini Ali , Roy Ronald A. , Crum Lawrence A.
Published: October 2005

This letter presents some preliminary results of an experimental study of the underwater sound field emitted by a bubble plume. The densely populated bubble plumes were generated by dropping a fixed volume of water, held in a cylindrical container, onto a still water surface. The characteristics of plumes were varied by changing the container volume and height above the surface. Acoustic emissions from these plumes appear to depend on the volume of the injected water, with the emitted frequency band decreasing with increasing plume volume. In addition, large-amplitude, low-frequency emissions correlate well with the observed detachment of “substructures” with the plume. The frequencies of the acoustic signals associated with the formation of these structures range as low as a few tens of Hertz.
Are spontaneous otoacoustic emissions generated by self-sustained cochlear oscillators?
Authors: Talmadge Carrick L. , Tubis Arnold , Wit Hero P. , Long Glenis R.
Published: October 2005

Theoretical analyses supporting the assumption that spontaneous otoacoustic emissions (SOAEs) can be described as self-sustained oscillations (requiring a power source) are reviewed and extended. Spectral and statistical properties of spontaneous otoacoustic emissions are examined and shown to be consistent with this assumption. Several alternative models of spontaneous emissions (noise-driven saturating memoryless nonlinearity, noise-driven nonlinear-stiffness oscillator) are examined. Although some of these models are able to produce the types of statistical distributions of amplitude and displacement similar to those observed in the experimental data, this similarity is destroyed upon narrow-band filtering.
Comments on “Theory of laminated piezoelectric plates for the design of distributed sensors/actuators. Part I: Governing equations and reciprocal relationships” [J. Acoust. Soc. Am. 87, 1144–1158 (1990)]
Authors: Laura Patricio A. A.
Published: October 2005

This Letter comments on, and analyzes the boundary conditions that had been previously studied and discussed by C. K. Lee [J. Acoust. Soc. Am. 87, 1144–1158 (1990)]. Some additional pertinent references are indicated.
The theoretical description of wave–wave interactions as a noise source in the ocean
Authors: Kibblewhite A. C. , Wu C. Y.
Published: October 2005

The historical development of the theory governing the generation of ULF ocean noise by random surface fluctuations is reviewed. Emphasis is directed at the intrinsic relation between the two main theories currently in vogue, the perturbation procedure and that using an integral procedure based on Lighthill’s equation. The relative contributions to the underwater pressure field from the direct radiation of turbulent air motion and the interaction of surface waves is examined. It is shown that even though the direct radiation can approach or even exceed the contribution from wave interactions in the early stages of sea development, overall it is much smaller than the latter. The use of the perturbation expansion in the theoretical analysis of wave interactions at low frequencies is justified. An estimate of the contributions from wave interactions of different order shows that the spectral levels decrease rapidly with increasing order, an increase in the order from m to m+1(m⩾2), resulting in a decrease in the spectral peak level by about 25 dB. At the same time the peak frequency shifts from mσp to (m+1)σp, where σp is the peak frequency of the ocean wave spectrum. With the basic importance of the second-order wave–wave interactions in the generation of the noise field confirmed, the formulas currently used to describe this interaction are reexamined and extended to include other wave effects including the contributions of the inhomogeneous component. This leads finally to a more comprehensive expression for the wave-generated ULF noise spectrum.
Airborne sound insulation of thin walls
Authors: Ljunggren Sten
Published: October 2005

Approximate analytical solutions are presented for the transmission of airborne sound through a plate between two rooms. The rooms are placed above each other and are of different size. The area of the plate is larger than the area of either room. Simple formulas are derived from the Euler–Bernoulli plate theory for the transmission due to the forced as well as the resonant field of the plate. The most interesting result concerns the forced response at coincidence, which is shown to be heavily dependent on the size of the excited area. A “rise length” on the analogy of the rise time in a single-degree-of-freedom system is introduced. Within the rise length, which is often very large, the displacement is proportional to the trace length on the plate of the exciting sound ray. The mean transmission factor due to the forced response at frequencies above the critical frequency is for this reason dependent on the source room area, but not on the loss factor. The coupling between a diffuse sound field and the free waves is, on the other hand, loss factor dependent, but the dependence of the coupling on the angle of incidence is shown to be quite different from that in the corresponding case of an infinite plate.
Airborne sound insulation of thick walls
Authors: Ljunggren Sten
Published: October 2005

The airborne sound insulation with respect to a diffuse sound field is discussed for the case of thick walls of typical building materials. It is shown, with the help of an analytical expression valid for arbitrarily thick plates, that the classic thin-plate expression for the transmission loss can be used approximately two octaves above the limit usually imposed on thin-plate solutions. Thus, the new frequency limit can be calculated from the condition that the wavelength of the free bending wave equals three times the plate thickness or, alternatively, that the corresponding Helmholtz number equals 2. From this new limit and a couple of octaves higher, the transmission-loss curve forms a plateau with pronounced dips due to the thickness resonances of the P wave. The thickness resonances of the S wave do not, on the other hand, influence the transmission loss.
Use of the trans-spectral-coherence technique to separate signals from noise
Authors: Vaidya P. G. , Anderson M. J.
Published: October 2005

A new technique to separate signals from noise is proposed. This technique is specifically meant for signals that are wholly or partly generated through some nonlinear process. A signal processing technique is described, which is specifically aimed at such signals. As long as the underlying process can be assumed to be nonlinear, this technique can be beneficially used, even if the details of the generating mechanism are unknown. To accomplish this goal, three new concepts have been introduced. The first is the concept of the transphase. This is a generalization of the concept of phase, except that it applies to two different frequencies. The second concept is that of the trans-spectral coherence (TSC). This is the generalization of the concept of ordinary coherence and is once again valid for two signals at different frequencies. The third concept is that of the auto-trans-spectral coherence (ATSC), which applies to two signals that are duplicate copies of the same signal. It has been shown that these concepts can be used to detect the presence of minute signals (of a nonlinear origin) even when they are mixed with a random noise that exceeds the signal in magnitude. It is shown with a simulated signal that the presence of a signal could be detected when the ratio of signal amplitude to the standard deviation of the noise was 0.1.
Transverse vibrations of a Timoshenko beam of nonuniform cross section elastically restrained at one end and carrying a concentrated mass at the other
Authors: Rossi R. E. , Gutierrez R. H. , Laura P. A. A.
Published: October 2005

The present study deals with the determination of the lower natural frequencies of vibration of the structural system described in the title, in the case where one end is elastically restrained against rotation and translation. The cross-sectional area varies in a discontinuous fashion (for the sake of generality two steps are assumed to take place along the beam length).
The general problem of elastic wave propagation in multilayered anisotropic media
Authors: Nayfeh Adnan H.
Published: October 2005

Exact analytical treatment of the interaction of harmonic elastic waves with n-layered anisotropic plates is presented. Each layer of the plate can possess up to as low as monoclinic symmetry and thus allowing results for higher symmetry materials such as orthotropic, transversely isotropic, cubic, and isotropic to be obtained as special cases. The wave is allowed to propagate along an arbitrary angle from the normal to the plate as well as along any azimuthal angle. Solutions are obtained by using the transfer matrix method. According to this method formal solutions for each layer are derived and expressed in terms of wave amplitudes. By eliminating these amplitudes the stresses and displacements on one side of the layer are related to those of the other side. By satisfying appropriate continuity conditions at interlayer interfaces a global transfer matrix can be constructed which relates the displacements and stresses on one side of the plate to those on the other. Invoking appropriate boundary conditions on the plates outer boundaries a large variety of important problems can be solved. Of these mention is made of the propagation of free waves on the plate and the propagation of waves in a periodic media consisting of a periodic repetition of the plate. Confidence is the approach and results are confirmed by comparisons with whatever is available from specialized solutions. A variety of numerical illustrations are included.
A half-space response to a finite surface source of an impulsive disturbance
Authors: Ziv M.
Published: October 2005

The response of an ideal elastic half-space to an impulsive load is obtained by a computational method based on the theory of characteristics. The impulsive load is distributede unevenly but radially over the entire boundary of a semicircular infinite canyon embedded in the surface of the half-space. For this configuration, a wave characteristics formulation is presented where its differential equations are extended to accommodate strong discontinuities which occur in the material motion of the half-space. A step-by-step numerical integration of these extended differential equations is then carried out in a two-dimensional curvilinear wavegrid, formed by the bicharacteristic curves of the wave characteristics formulation. The resultant transient deformation of the half-space is shown by plots which give the time history behavior of the dependent variables at a specific spatial location. In these plots, the various wave fronts traversing the half-space explicitly reveal themselves.
A new efficient algorithm to compute the exact reflection and transmission factors for plane waves in layered absorbing media (liquids and solids)
Authors: Cervenka Pierre , Challande Pascal
Published: October 2005

This paper describes a matrix method for computing the exact reflection and transmission coefficients for harmonic plane waves within a stratified medium of homogeneous, isotropic, and absorbing plane layers. The new feature is that each layer can be either liquid or solid, whatever their successive order. Furthermore, this algorithm takes into account evanescent waves, but also applies whatever the thickness of each layer. A numerical example is shown.
Diffraction tomography and the stochastic inverse scattering problem
Authors: Rouseff Daniel , Porter Robert P.
Published: October 2005

The Fourier diffraction theorem is the basis of diffraction tomography. The theorem states that the field scattered by a semitransparent object maps onto arcs in the Fourier space of the object. In this paper, the stochastic analog is derived to the theorem for a general anisotropic, statistically homogeneous random continuum. By acoustically probing the random medium from various angles, the second-order statistics of the medium can be recovered from the second-order statistics of the perturbed field. The robust nature of the result is confirmed by numerical experiments using finite arrays and autocorrelation estimation theory.
Decibel annoyance reduction of low-frequency blast attenuating windows
Authors: Schomer Paul D. , Buchta Edmond , Hirsch Karl-Welhelm
Published: October 2005

In this study, the acoustical benefits of improved, blast noise reducing retrofit windows are determined using the methods of paired-comparison testing with panels of subjects. The results show that the retrofit windows reduce the received indoor C-weighted SEL by about 7 dB. The retrofit windows result in about a 14-dB improvement in terms of community response. Further, a regression line is fit to the indoor measured blast CSEL and their correspondingly equivalent control noise ASEL. The slope of this line is 2.5, indicating that a 1-dB change in CSEL corresponds to about 2.5-dB change in control ASEL. This corresponds to the result one would get if one used loudness to describe both indoor signals instead of describing the control (indoors) using ASEL and the blast (outdoors) using a variety of descriptors such as peak, CSEL or FSEL, etc.
A new technique for designing a postbeamformer interference canceller
Authors: Er M. H.
Published: October 2005

This paper presents a new approach for designing a postbeamformer interference canceller (PIC). The technique basically explores the use of the eigenvectors of a certain Q matrix as the signal and interference beamforming weights in the PIC. Numerical results show that the new PIC performs better, on the average, than the conventional PIC. Furthermore, the optimized new PIC achieves almost the same performance as the optimum element space processor without precise knowledge of the interference direction.
A system for signal processing and data extraction from aerodynamic, acoustic, and electroglottographic signals in the study of voice production
Authors: Perkell Joseph S. , Holmberg Eva B. , Hillman Robert E.
Published: October 2005

A software system, implemented in the MITSYN languages, is described for signal processing and data extraction from oral airflow, intra-oral air pressure, vocal fold contact are (EGG) and sound pressure signals. Signal processing algorithms are specified in the form of block diagrams; examples are shown for demultiplexing signals into bandwidth-specific, time-aligned signal stream files and for inverse filtering the oral airflow waveform to obtain an approximation of the glottal airflow waveform. Interactive and algorithmic data extraction is performed with a menu-driven procedure that displays the stages of analysis, graphical indications of the results of algorithmically made decisions, and derived results. The system has proven to be useful for obtaining quantities of detailed data on voice production.
Fundamental frequency and perceived prominence of accented syllables
Authors: Terken Jacques
Published: October 2005

Perceived prominence differences between accented words have been accounted for in terms of fundamental frequency (F0) variations. In one theory prominence is related to the relative magnitude of F0 changes, and in another theory prominence is related to relative frequencies of F0 maxima. Two experiments with the same group of subjects contrasted the two theories. The experiments used reiterant speech consisting of “maMAmamamaMAma” utterances with synthesized F0 contours, with F0 maxima on the second and penultimate syllables (P1 and P2, respectively). In one experiment the utterances had no baseline declination, and in the other experiment the slope of the baseline was varied. In both experiments, subjects performed an adjustment task under two different instructions: They were instructed to adjust P2 so that it had the same pitch or prominence as P1. The results show that both variables (instruction and presence or absence of baseline declination) affect the adjustments of P2. It is concluded that neither theory gives a satisfactory account of the results, and that perceived prominence is related in a complex way to the range of F0 values employed.
Measurement of the sound produced by a tipping trough with fresh and salt water.
Authors: Carey W. , Monahan E. , Fitzgerald J. , Wang Q. , Parssinen E.
Published: October 2005

Experiments have been performed with a calibrated trough developed by the Univ. of Conn. The bubble size distributions created by this trough were measured and characterized. The size distributions for fresh and salt water were different; the salt water bubbles were characteristically of smaller sizes. The water entry from the tipping trough emitted sounds from the impact and subsequent bubble production. These sounds were observed by the pressure fluctuation versus time, averaged transient capture spectra, and sonargrams (intensity versus frequency and time). Similarities in the lower frequency time evolution were observed; however differences were observed in the character of the sounds produced in salt water and fresh water. The salt water was found to produce spectra with richer low- and high-frequency sounds. [Work supported by ONR and NUSC/IR.]
Analysis of marginal ice zone noise events.
Authors: Chen Chi-Fang
Published: October 2005

Acoustic transients observed in a noise time series, called noise events, are believed to be the major contributor to Arctic Ocean ambient noise. Underwater ambient noise data from the Marginal Ice Zone Experiment 1984 (MIZEX84), at frequencies between 20 and 2000 Hz, are studied. Results show that temporal and spatial distribution of events are characterized by clustering and seem to depend on environmental conditions such as swells and ice concentration. Event densities increase as f at frequencies below 200 Hz, decrease as f −1 at frequencies above 300 Hz, and reach a maximum at frequencies between 200 and 300 Hz. The change in trend may indicate a transition in the source mechanism for frequencies below 200 Hz and above 300 Hz. [Work supported by Office of Naval Research.]
Cardioid directivity pattern hydrophone using an acoustical phase shift.
Authors: Richard Monique
Published: October 2005

The characteristics of a directional electroacoustical transducer are presented. The directivity pattern of the transducer is cardioid-shaped. The transducer can be used as a hydrophone within a frequency band from 2 to 15 kHz. The sensitivity ratio for θ=0° and θ=180° is greater than 10 dB and the reception sensitivity is greater than −198 dB re: 1 V/μ Pa with a capacity equal to 2 nF. These acoustical characteristics are obtained with a trilaminar vibrator working in bending mode under the effect of a pressure gradient induced by the acoustical wave in front of the hydrophone and by the acoustical wave which passes round and enters it through an acoustical window and an acoustical cavity as well. This phase shift is adjusted in such a way that the directivity looks like a cardioid pattern at a given central frequency. The diameter of this hydrophone is 38 mm and its thickness 13 mm. Different applications can be imagined, such as a component of an array without reflector (sono-buoy towed array), or flank arrays (high sensitivity for external signal, low sensitivity for noise coming from the vibration of the hull). A further project is to design a smaller hydrophone (scale 3/4) for other applications.
Acoustical radiation of bubbles in water.
Authors: Naugol’nykh Konstantin A.
Published: October 2005

The radiation of sound by a single bubble and by a cloud of bubbles is considered. It is assumed that initially the pressure inside the single bubble exceeds the ambient pressure in the surrounding liquid. As a result the bubble expands, radiating an acoustical pulse. If the speed of expansion is moderate compared to the sound velocity, the process may be described by using the nonlinear acoustics approximation or by taking the Kirkwood–Bethe (KB) approach. The limitations of these methods are discussed and a modified KB approach is presented. Theoretical results are compared with our experiments made with a focused laser beam in liquids. In the case of a cloud of bubbles, interaction effects should be taken into account. Some approximate models to describe the interaction are discussed.
An investigation of cavitation activity produced in a standing wave field.
Authors: Gardner Edward A. , Apfel Robert E.
Published: October 2005

A 45-kHz continuous standing wave field was used to produce cavitation in water seeded with particles to act as nuclei. Light transmitted through the fluid was monitored with a photodiode. Cavitation bubbles in the fluid caused the photodiode signal to decrease and thus could be counted. The event rate produced by several different nuclei types was measured and compared to expectations based on porosity and hydrophobicity. The propensity of each nuclei type to produce cavitation which would disturb the surface of a levitated drop and possibly cause two levitated drops to coalesce [Gardner and Apfel, J. Acoust. Soc. Am. 89, 1862(A) (1991)] was also investigated. [Work supported by NASA through JPL, Contract No. 958722.]
Collective oscillations in fresh and salt water bubble clouds.
Authors: Roy Ronald A. , Nicholas Michael , Markiewicz Ken , Crum Lawrence A.
Published: October 2005

Several investigators have observed the presence of low-frequency resonance excitation due to collective oscillations of bubble columns in water. In the current set of experiments, a bubble column is produced by forcing a continuous flow of air through a fritted disk situated at the bottom of a small plexiglass tank filled with either fresh water or salt water. Acoustical noise from the resulting bubble column is detected using a submerged hydrophone and recorded on a digital oscilloscope. Bubble size distirbutions (measured photographically) and noise obtained for the fresh water and salt water cases are compared. Results indicate that although salt water bubble columns exhibit a marked reduction in the average bubble size distribution, the low-frequency peak in the noise spectrum corresponding to collective oscillations is virtually identical for the two cases, provided the void fraction is fixed. [Work supported by ONR, ONT, and AEAS.]
Low-frequency acoustic scattering from a submerged bubble cloud.
Authors: Roy Ronald A. , Crum Lawrence A. , Nicholas Michael , Schindall Jeffrey A. , Carey William M. , Conrad William A. , Marshall William J. , Monahan E. C. , Prosperetti Andrea
Published: October 2005

A group of us has undertaken a series of measurements of the low-frequency scattering from a bubble cloud produced by a submerged bubble maker in Seneca Lake. Acoustic scattering from this cloud for a range of frequencies, for a number of different acoustic sources, and for a variety of cloud compositions and geometries has been examined. The latest results of these experiments will be reported. [Work supported in part by ONR, ONT, and AEAS.]
Military applications of barriers.
Authors: Lewis Nelson D.
Published: October 2005

Many commanders of Army installations are concerned about the noise environment from their activities. Seeing that noise barriers reduce the noise from highways, they believe that these same barriers can reduce the noise from their sources. These noise sources typically include small arms ranges, tank firing ranges, field generators, and vehicle test tracks. The current studies have shown that properly designed and located highway-type barriers can be used to reduce the impact of generators, vehicle test tracks, and some small arms ranges. For larger caliber weapons, the dimensions of the barrier required for a noticeable reduction in the noise level make them impractical. For these noise sources, the impact can be reduced by locating the firing point so that neighboring hills can act as barriers.
A Monte-Carlo approach to the simulation of fluctuations in ray tube areas during propagation through atmospheric turbulence.
Authors: Sparrow Victor W. , Pierce Allan D.
Published: October 2005

A simple but approximate theory for the variation of ray tube areas along ray paths leads to the prediction that such areas are the product of the two similar factors, Ψ(x) and Φ(x), each satisfying the generic harmonic oscillator equation, d2Ψ/dx2+f (x)Ψ=0, where the function f (x) (which takes on both positive and negative values) is different for the two factors and depends on the second derivatives of the apparent sound speed with respect to coordinates transverse to the propagation path, and where x corresponds to distance along the path. The theory makes use of a coordinate system, possibly twisting, which follows a central ray and which yields (∂2c/∂y2)/c0 for f (x), where c is an effective sound speed which includes the effect of wind in the direction of ray propagation, c0 is the ambient sound speed. The present paper proceeds from applicable models of turbulence to simulate possible statistical realizations of the random process f (x) and gives the corresponding realizations for the area factor Ψ(x). [Research supported by NASA Langley.]
Atmospheric sound propagation using a three-dimensional parabolic equation.
Authors: Delrieux Yves
Published: October 2005

A numerical method for solving the three-dimensional parabolic wave equation (3-D PE) is presented to investigate long-range sound propagation in the atmosphere near the ground. An implicit finite-difference scheme based on the alternating directions method is formulated. The pressure field is calculated in cylindrical coordinates for all the azimuth ranges from 0° to 360°, so that only a periodicity condition is required. A hard reflecting ground is considered and a homogeneous boundary condition at the top of the mesh is applied. The validity of the 3-D PE is shown by comparison with measurements carried out in an anechoic chamber. The diffraction of sound behind a thin barrier of finite length is studied. A good agreement with calculations is obtained for the sound-pressure level behind the barrier. In particular, the term involving azimuth derivatives is taken into account in the 3-D PE and enables one to properly calculate the diffraction from both side edges of the screen. Moreover, calculations show that the presence of wind may modify the position of interferences created by the screen. [Work supported by Direction des Recherches Etudes et Techniques.]
Waves on fluid-loaded thin elastic plates near the coincidence frequency.
Authors: Manley Martin G.
Published: October 2005

An elastic, infinite plate of finite thickness with fluid loading on one side and vacuum on the other is considered. Thin plate models are generally adequate for this problem, but fail near the coincidence frequency. Predictions based on the full elastodynamic equations will be presented for waves near the coincidence frequency. [Work supported by the PSU Applied Research Laboratory Exploratory and Foundational Research Program. The author acknowledges the advice of A. D. Pierce.]
Relating formant variability to vowel constriction features extracted from pellet positions.
Authors: Jung Tzyy-Ping , Krishnamurthy Ashok , Ahalt Stanley , De Jong Kenneth , Lee Sook-hyang , Beckman Mary E.
Published: October 2005

Quantal theory claims that sounds which are common in phoneme inventories, such as [i] and [a], are articulated in vocal tract regions where acoustic patterns are relatively insensitive to variation in constriction location. Perkell and Nelson [J. Acoust. Soc. Am. 77, 1889–1895 (1985)] tested this claim using a principal components analysis of x-ray microbeam data. As predicted, tongue pellets showed most positional variation in an axis parallel to the hard palate in [i] and to the pharynx wall in [a]. An earlier replicative study using [i], [a], and three other vowels [Ahalt etal., J. Acoust. Soc. Am. 89, 1871 (1991)] showed that pellet data are more easily interpreted in terms of relative variation in constriction location and degree if they are transformed nonlinearly into a coordinate space where x and y values express location along and distance from the opposing wall of the vocal tract. The present study examined the relationship between formant values and pellet positions in this transformed space, and found some support for quantal theory. In particular, all good correlations involved positional variation in the y dimension for pellets near the constriction. [Work supported by the NSF.]
An abductive articulatory recognition system−A preliminary study.
Authors: Fox Richard , Josephson John , Erickson Donna
Published: October 2005

A system has been constructed for articulatory recognition in question–answer utterances such as ‘‘Is it five five nine pine street? No its five NINE nine pine street’’ [J. Westbury and O. Fujimura, J. Acoust. Soc. Am. Suppl. 1 85, S98 (1989)]. This system takes as input microbeam pellet movement data currently from five speakers. It uses an abductive problem solving strategy [J. Josephson, AAAI Spring Symposium Series: Automated Abduction, 140–144 (1990)], first hypothesizing gestures (e.g., labial and apical closure for consonantal identification, dorsal motion for syllable nuclei, mandible movement for emphasis) in examining the pellet data, and then explaining these gestures in terms of possible word and emphasis hypotheses. Uncertainties in gesture identification are handled by including noise hypotheses. Pellet position thresholds used for identifying gestures vary depending upon the syllable’s position within an utterance. Initial results indicate a very high accuracy in inferring the correct words and emphasis without using acoustic signals.
Anomalous PE results for propagation in leaky surface ducts.
Authors: Porter Michael B. , Jensen Finn B.
Published: October 2005

Surface ducts are formed by wind mixing at the ocean surface and are a common feature. These surface ducts have the effect of channeling acoustic energy for long ranges. In this paper, the focus is on the energy that leaks out of the surface duct; paths that are typically neglected by ray models. It is found that the leakage energy can be surprisingly strong so that a receiver in a ray-theory shadow zone is actually well illuminated. Furthermore, the leakage energy is refracted back into the duct where it may dominate the ducted paths. Inside the duct, these two arrivals add up constructively or destructively resulting in anomalously high or low acoustic levels in the surface duct relative to a prediction that neglects the leaky arrival. Thus a full-wave model is needed; however, certain types of PEs fail dramatically for these problems because they scramble the phases of the two dominant arrivals. Small changes in the environment−for instance, a change in the mean duct speed of 0.5 m/s−can produce analogous large changes in the acoustic levels.
The influence of the reference wave number.
Authors: Pierce Allan D. , Lee Ding , Botseas George
Published: October 2005

The application of the PE method for the prediction of wave propagation requires the selection of the reference sound speed, c0, which is related to the reference wave number k0. The influence on the acoustic field by the choice of the c0 is rarely visible. Even if it is noticeable, the difference is small and is usually negligible. In a realistic application to solve a scattering problem by a PE-type method, the choice of c0 was found to produce different acoustic results when compared with a known reference exact solution. These differences in acoustic fields are not small and may be considered non-negligible. A proper choice of the c0 was made using a range-dependent c0 formula introduced by Pierce; then, an accurate calculation of the acoustic field was achieved by the proper choice. In this paper, use is made of the numerical results to discuss the c0 influence. [Work supported jointly by ONR and NUSC.]
The curtain effect in a shallow water environment.
Authors: Browning David G. , Herstein Peter D. , Monti Joseph M. , Christian Raymond J.
Published: October 2005

The curtain effect, which controls sound propagation in a sound channel [Browning etal., J. Acoust. Soc. Am. Suppl. 1 88, S132 (1990)], is shown to exist in modified form for severely bottom-limited propagation conditions that can exist in shallow water during the summer. The initially dominant loss component, whose rate decreases with range, is now angular-dependent multiple bottom bounce propagation loss. The range-independent component is an effective attenuation which includes low-angle bottom loss. The transition between these components is equivalent to the crossover of the components in the sound channel case. An effective range can be obtained by extending the effective attenuation component back to the intersection with the rate of spreading loss component. Illustrations are given for several shallow water areas.
Ambient sound in the ocean produced by heavy precipitation and the subsequent predictability of rainfall rate.
Authors: Nystuen Jeffrey A.
Published: October 2005

Results from an experiment in the Gulf of Mexico to characterize the underwater sound generated by heavy convective precipitation are reported. For a given rainfall rate, the sound levels are higher at the beginning of the storm or when the rainfall rate is increasing than at the end of the storm or when rainfall rates are decreasing. This is likely to be due to changing storm characteristics during the lifetime of the storm. Very heavy rainfall (rate ≳150 mm/h) generates near surface bubble layers or bubble clouds which attenuate sound energy at higher frequencies (≳15 kHz). The distinctive 15-kHz peak in the sound spectrum for light rain is absent during heavy rain suggesting that the sound production mechanism previously identified for small drops (0.8- to 1.1- mm diameter) is suppressed by heavy rain even though small drops are undoubtedly present during heavy rainfall. These data show a very high correlation between underwater sound levels and rainfall rate. Algorithms for measuring rainfall rate from underwater sound will be presented and discussed.
Minimalization of travel time bias using the tomographic inverse method.
Authors: Nakano Iwao
Published: October 2005

The error involved in measured data of travel time of multipaths is difficult to remove even though the tomographic measurement of travel time is so precise and accurate. So the error of travel-time measurement and source–receiver displacement seems to cause a bias which affects the total data of travel time of multipaths and decreases the accuracy of the tomographic estimation. But this bias is correctable by means of the linear tomographic inversion, just like the focusing and defocusing process with a single lens reflex camera. The criterion is minimalizing a mean variance of the estimated sound-speed anomaly. The order of bias is roughly 20 ms, equivalent to 30 m. It is more likely with no acoustic transponder tracking system.
High-intensity acoustics for space.
Authors: Wang Taylor G.
Published: October 2005

With the advent of space shuttle flights by NASA, scientists traditionally not involved with the space program will have opportunities to participate in performing experiments in an environment unique to space-extended microgravity. One class of experiments that takes the fullest advantage of what space has to offer is containerless science and applications. For the first time, scientists can study and analyze physical, thermal, and chemical phenomena without the influences of both gravity and a container. However, in space, the residual drag of the space craft, crew motion, and space craft thrust firing all contribute to a background force (∼10−6g) that needs to be compensated for in order to allow scientists the necessary time for experimentation. Addressing that need, a three-axis acoustic levitation and manipulation system was invented (Wang, 1975), and has been flown on Spacelab III (1985) and will be flown again on the USML-1 mission (1992). In this talk, the principals and operations of the system will be presented. The science and the potential application will also be discussed.