bluuebunny/crossref_metadata_2025 huggingface dataset:
Objective and perceptual characterization of microphone arrays for virtual acoustics applications.
Authors: Warusfel Olivier , Nicol Rozenn , Mahieux Yannick
Published: October 2005

Microphone arrays represent an attractive sound pickup solution for virtual acoustics applications where a high rejection of the acoustic environment (ambient noise and reverberation) is needed for minimizing artifacts during the postprocessing of the sound (filtering, spatialization, artificial reverberation). This study intends to evaluate, on the basis of simulations and experiments, different prototypes of microphone arrays designed at CNET. The different steps of the array processing (i.e., band filtering of subarrays, sensors weighting, beamforming, and steering) are implemented on a signal processing prototyping environment. This program is used to synthesize the impulse response of the microphone array in a real acoustic field. The input signals are the impulse responses successively measured between a source and each sensor location of the array in real rooms. The objective characterization of the array is based on classical criteria used in room acoustics and on the analysis of the time–frequency envelope of the late reverberation. The perceptual analysis is performed by convolution of the array responses with anechoic signals. A parametrical study is undertaken in order to study the influence of the geometrical and signal processing characteristics of the array. Theoretical and experimental results are compared and discussed. [Work supported by CNET.]

All posters will be on display from 10:00 a.m. to 3:00 p.m. Contributors will be at their posters from 10:00 a.m. to 1:00 p.m. To allow for extended viewing time, posters will remain on display until 3:00 p.m.
Vehicle interior noise. II. Modeling.
Authors: DeJong Richard G. , Parrett Alan V.
Published: October 2005

An overview is presented of several methods available to determine the interior noise in a vehicle under given operating conditions. Issues covered include: how and when these methods can best be applied; the limitations imposed by the methods themselves; and some of the difficulties associated with modeling vehicle structures. Current modeling methods used in automotive noise problems include finite element, boundary element, statistical energy, and power flow methods. Each method has domains of applicability, but more specific to the automotive design process, they have different applicability at different stages in the design cycle. There are practical limitations, such as the lack of detail early in the design process which presents difficulties for deterministic methods at high frequencies. In contrast, later in the process when details are available, there may be the need for more specific answers to design trade-offs than statistical methods can give. Examples are given of some practical problems encountered in vehicle noise modeling, illustrating areas where improvements are still needed.
On the development and application of automotive sound package materials.
Authors: Saha Pranab , Chahine John
Published: October 2005

It is important to understand not only the noise problem, and the functional and aesthetic issues of an automobile, but also the environmental and competitive issues of the industry to develop appropriate sound packages that will meet the customer requirements. The vehicle manufacturers and their suppliers do so within the bounds of the material and process development technology that is available. The evolution of the basic automobile design and construction also has a significant impact on the sound package development. This may require an entirely new type of material application or an innovative process and product. The paper reviews different types of sound package and process developments that have evolved over the years in some specific applications. These developments not only provide balanced acoustics inside the automobile, but also meet various challenges of the industry.
Light vehicle exterior noise: Measurement, regulation, tires, and pavement.
Authors: Donavan Paul R. , Schumacher Richard F.
Published: October 2005

Exterior noise is the only acoustic attribute regulated for passenger cars and light trucks. The primary procedure used to quantify this noise is an outdoor passby test conducted under full-throttle acceleration. Unless specified noise levels are met under this procedure, a vehicle may not be sold in a given market jurisdiction. Recent reduction of European regulatory limits by 3 dB has re-enforced many of the technical challenges faced in designing and testing vehicles to meet these new requirements. These challenges include: better understanding and control of test and environmental variables, more accurate methods of noise prediction, and improved techniques for isolating and reducing individual source contribution. In recent investigations, sound intensity has been employed to isolate tire/pavement interaction noise for vehicles under passby conditions. This has led to the determination that tires can produce significantly higher noise levels under the torque of acceleration than under cruise conditions. As a result, tires are often the major noise source when the total vehicle noise approaches the new regulatory limits. This paper reviews the variables associated with the passby test procedure, the effects of vehicle acceleration on tire/pavement interaction noise, and the needs for improved predictive methods.
The effect of surface variability on the short-range propagation of tire/road interaction noise.
Authors: Yim Denny M. B. , Bolton J. Stuart
Published: October 2005

The object of this work was to identify the origin of differences between sound levels measured on two track types used for standardized motor vehicle passby noise tests: i.e., the ISO and SAE surfaces. The measured differences could result either from the effect of the road surface on tire/road interaction noise generation, or from surface sound absorption differences. Near-field intensity data measured at the tire/road interface on vehicles in motion were first examined to establish the correlation between surface type and source spectrum and level. Source levels were approximately 1 dB higher at SAE sites than at ISO sites. Two-microphone methods were then used to estimate the acoustic impedance of both the ISO and SAE surfaces. The surface impedances were used together with measured tire source spectra and sound propagation theories to calculate the passby level variability that could be attributed to variations in test site acoustic impedance. It was found that differences in propagation transfer functions for the ISO and SAE surfaces were on the order of only 0.3 dB. Thus it was concluded that the differences in passby levels measured at ISO and SAE sites resulted primarily from differences in tire/road interaction noise generation.
Two-microphone measurements of the acoustical properties of plane asphalt surfaces in the presence of wind and temperature gradients.
Authors: Hartwig Troy J. , Bolton J. Stuart , Yim Denny M. B.
Published: October 2005

When performing two-microphone measurements of surface properties, an algorithm is used to find the properties that give the best fit between measured and predicted transfer functions between the two microphones. Recently it was found necessary to adjust certain geometrical parameters, e.g., the separation between the source and microphones, to obtain an acceptable fit between measured and predicted data measured over asphalt surfaces. It was hypothesized that it was necessary to allow that variation to account for the effects of wind and temperature gradients. That hypothesis has been confirmed by using ray tracing techniques to simulate the effect of wind and temperature gradients on two-microphone measurements. It has been found that near-surface gradients have significant effects on both the angle of specular reflection and the path length difference between the direct and reflected arrivals. These effects are particularly important when estimating the properties of high impedance surfaces owing to the rapid change of the reflection coefficient at near-grazing angles in that case. Nevertheless, it will be shown that the impedance of asphalt can be estimated accurately if the effect of ray curvature is accounted for when fitting measured and theoretical transfer functions.
Modeling of noise spectra of axial flow fans in free field.
Authors: Su Shigong , Wu Sean F. , Shah Hemant S.
Published: October 2005

A semi-empirical formula for predicting the noise spectra of axial flow fans in a free field is developed. In deriving this formulation it is assumed that sound radiation from an axial flow fan is primarily due to fluctuating forces exerted on the fan blade surface. These fluctuating forces are correlated to the total lift force exerted on the fan blade, and is approximated by pressure pulses that decay both in space and time. The radiated acoustic pressure is then expressed in terms of superposition of contributions from these pressure pulses, and the corresponding line spectrum is obtained by taking a Fourier series expansion. To simulate the broadband sounds, a normal distribution-like shape function is designed which divides the frequency into consecutive bands centered at the blade passage frequency and its harmonics. The amplitude of this shape function at each center frequency is unity but decays exponentially. The decay rate decreases with an increase in the number of bands. Thus, at high frequencies, the narrow bands merge to form a broad band-like spectrum. The noise spectra thus obtained are compared with measured ones from four different types of axial flow fans running under various conditions.
Fetal hemorrhage from lithotripter fields.
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H. , Cox Christopher , Penney David P. , Carstensen Edwin L.
Published: October 2005

Fetal hemorrhages were observed when late term pregnant female mice were exposed to a lithotripter field with peak positive pressures as low as 1 MPa. On the 18th day of gestation, the abdomens of pregnant mice were exposed to 200 pulses from a piezoelectric lithotripter delivered at a rate of ∼ 1 Hz. Hemorrhages occurred in the exposed fetuses most often near bony and cartilagenous tissues—head, limbs, and ribs—while soft tissues such as the liver, intestine, and stomach were relatively free of hemorrhage. Thresholds for these effects were < 1 MPa.
Noninvasive spatially contained high-power ultrasonic system (NSHUS) for blood clot disintegration.
Authors: Grandia Willem , Siegel Robert J. , Bar-Cohen Yoseph
Published: October 2005

Ultrasonic waves can be focused from a point outside of the body to an internal blood clot without using invasive techniques. Noninvasive focused ultrasonic techniques for blood clot disintegration may allow for prompt treatment, and eliminate the need for costly and time-consuming invasive catheter-based interventions. Thus this noninvasive approach using therapeutic ultrasound could greatly reduce patient mortality, morbidity, duration of hospitalization, convalescence, and cost of care. An ultrasonic system was designed to operate from 25–200 kHz and provide a localized high power. The profiles of the field and localization effects were analyzed to optimize power containment to the area of the blood clot. To demonstrate system performance tests were initially made to dissolve sugar blocks mounted in an ice/water bath. At this water freezing point, conditions of 0 °C, the rate of sugar dissolution is very slow and it provided a baseline as a measure of ultrasound effect. Various ultrasonic frequencies and power levels were introduced to determine the ultrasonic dissolution/disintegration capability. Simulated blood clots were then exposed to the localized high power and the characteristics of the disintegration as a function of power and frequency were examined. The duration of exposure has been a key parameter in this investigation.
Robert Beyer—A profile.
Authors: Apfel Robert E.
Published: October 2005

From 1942, when he began his doctoral studies, to the present time, Bob Beyer has been a leading voice in the discovery and discernment of acoustical phenomena, the development of educational programs to support students in acoustics, and the dissemination of information regarding acoustics. This introductory presentation will summarize the ‘‘parameter space’’ over which Bob has modestly but impressively held sway. It will include the fields of acoustics to which he contributed, his career as teacher–scholar at Brown University, his activities with the Acoustical Society of America, the American Institute of Physics, and other professional societies and organizations, and his many activities to aid in the internationalization of science, in general, and acoustics, in particular.
Acoustics at Brown University: 1956–1958.
Authors: Maidanik G.
Published: October 2005

In earlier and in those years the physics department at Brown University was mostly acoustics: Profs. B. Lindsay, A. O. Williams, R. Beyer, P. Westervelt, W. Nyborg, R. Morse, and others were all major acousticians in those days, in fact, I converted from low-energy physics to acoustics under their guidance. The news of conversion was drowned, however, by the noise that Sputnik generated in 1957. While the physics and engineering departments were engaged in noise control activities in the populace at large, Prof. Beyer characteristically turned his energies to upgrading high schools’ proficiency in physics. In a few months, a ‘‘summer teaching for the teachers’’ was organized at Brown University and a dozen years later we did get to the moon.
Bob Beyer’s nontechnical contributions to acoustics.
Authors: Strasberg M.
Published: October 2005

A review of Bob’s contributions to the goals of our Society, including his services to the Acoustical Society of America, the American Institute of Physics, the International Commission on Acoustics, and translation journals, interspersed with anecdotes highlighting his remarkable erudition, talents, and humor.
Robert T. Beyer’s interaction with foreign acoustical scientists.
Authors: Naugolnykh Konstantin
Published: October 2005

The very essence of a scientific society is the promotion of cooperation and the exchange of information among scientists. Bob’s contribution to acoustics in this field is twofold. First, he is deeply involved in the publication of acoustics literature, particularly the Russian Acoustical Journal (previously Soviet Physics—Acoustics, now Acoustical Physics). Perfect knowledge of the languages, a deep interest in the creative work, a wide range of interests, and an extensive outlook help him in this activity. Second, being openhearted and having a friendly nature, with a live interest in his colleagues, he does a lot to develop scientific links and contacts. When he visited USSR in 1958, he immediately switched on acoustical community activity, participated in the Ph.D. thesis defense of Lev Zarembo, and started a long-lived cooperation with Russian colleagues. He has educated Ph.D. and postdoctoral students from China, Norway, Russia, etc. All of them are grateful to Bob and keep a lot of good recollections. Each meeting with him leaves you with a feeling of cordial warmth and friendly concern.
Robert T. Beyer’s impact on the development of nonlinear acoustics.
Authors: Westervelt Peter J.
Published: October 2005

If it had not been for R. T. Beyer there would not have been papers by me and my students for JASA to reject. Why is this? He (and A. O. Williams) wrote most of my contract proposals and the associated progress reports. He and his students Stanton, Bellin, and Korman performed definitive experiments supportive of my much criticized theories. In this tribute to Beyer I will discuss these experiments and touch upon my interaction with Gene Fubini.
Vintage Beyer—Teacher, advisor, and mentor—an era of experimentation on the nonlinear interactions of sound with noise and with turbulence.
Authors: Korman Murray S. , Stanton Timothy K.
Published: October 2005

When Professor Beyer taught us ultrasonics or nonlinear acoustics at Brown, he emphasized the historical genesis of scientific ideas and included insight into the works of greats like Rayleigh and connections to Lighthill. He personalized the science. His lectures on ‘‘Radiation Pressure — The History of a Mislabeled Tensor’’ [J. Acoust. Soc. Am. 63, 1025–1030 (1978)] are vintage Beyer. If our research topics were a canvas he would motivate the development of our creativity. If you asked him which color to use, you would get a philosophical story—but not which color. He provided guidance but the final brush strokes were yours. TKS and RTB’s ‘‘interaction of sound with noise’’ (1978) featured the growth of sum and difference frequency sidebands that agreed with Westervelt. MSK and RTB’s ‘‘scattering of crossed ultrasonic beams in the presence of turbulence’’ (1988) measured turbulent velocities. Some of Beyer’s daily comments still ring through our minds ‘‘Don’t just stand there — go write a thesis,’’ or ‘‘once a graduate student — always a graduate student.’’ However, at key talks, like our thesis defense his ‘‘When you are on the goal line shoot straight up the middle and do not attempt a long forward pass,’’ will always echo in our minds.
Beyer’s B/A parameter and the equation of state.
Authors: Hartmann Bruce , Lee Gilbert F. , Balizer Edward
Published: October 2005

Beyer’s B/A parameter for liquids can be calculated using an analytical PVT equation of state supplemented with specific heat data. Results for two equations will be investigated: the Tait equation and our own. The calculations of sound speed, sound speed derivatives, and the two components of B/A will be compared with experimental data for a series of normal alkane liquids. A comparison of these results with the prediction of Ballou’s rule (linear relation of B/A vs 1/c) will be presented. Tentative conclusions about the relative utility of the two equations will be presented as well as the outlook for the approach using any PVT equation of state. [Work supported by Naval Surface Warfare Center’s in-house Laboratory Independent Research Program sponsored by the Office of Naval Research.]
Lateral position of dichotic pitches can be substantially affected by interaural intensitive differences.
Authors: Grange Anthony N. , Trahiotis Constantine
Published: October 2005

Three listeners used an acoustic pointer to match the intracranial position of dichotic pitches presented with interaural intensitive differences (IIDs). Unlike data reported previously [Raatgever, ‘‘Binaural time processing and time-intensity trading,’’ in Psychophysics, Physiology, and Behavioural Studies in Hearing, edited by G. van den Brink and F. A. Bilsen (Delft U.P., Delft, The Netherlands, 1980), pp. 425–453], the intracranial position of the dichotic image was moved substantially by IIDs. Large effects of IIDs were found in a variety of stimulus conditions, including one investigated by Raatgever. When the dichotic stimuli were not pulsed, but were presented continuously and turned off only when the acoustic pointer was presented, one of the listeners produced data like those previously reported by Raatgever. It appears that intracranial images produced by stimuli which support dichotic pitches, like images produced by other binaural stimuli, can be affected substantially by IIDs. Consequently, in terms of lateralization, it does not appear necessary to maintain a theoretical cleavage between images produced by dichotic pitches (previously thought to be influenced only by ITDs) and images produced by other binaural stimuli. [Work supported by Grant No. 5 RO1 DC00234-13 from the National Institute on Deafness and other Communication Disorders, NIH.]
Perceptual fusion of multiple echoes.
Authors: Guzman Sandra J. , Yost William A.
Published: October 2005

In a natural environment, perceptual fusion of a sound may occur despite the fact that multiple echoes exist. If a train of repeating sources and echoes is established experimentally, the echoes are suppressed and perceptual fusion is established. In the present study, perceptual fusion was investigated by having listeners attend to the last sound presented in a train of sources and echoes. The effects of the number of sounds presented during a train, time delay between sources and echoes, relative amplitude between sources and echoes, and number of echoes presented were investigated. Results indicate that there is an interaction between time delay and number of echoes in perceptual fusion. Relative amplitude of the source and echoes also affected perceptual fusion. These findings will be discussed in terms of the conditions under which perceptual fusion seems to occur and its relation to a listener’s prior experience in an acoustic environment. [Work supported by NIDCD and AFOSR.]
Multimicrophone directional hearing aid using hybrid adaptive beamforming.
Authors: Gibian G. L. , Koroljow W. S.
Published: October 2005

Recent studies have demonstrated some success in improving speech intelligibility when either competing voices or reverberation are present, using an adaptive beamformer in the first case and a fixed-weight beamformer in the second. The present study evaluates the effectiveness of a hybrid beamformer incorporating the strengths of an adaptive beamformer with the advantages of an optimally chosen fixed-weight beamformer. Received signals at a short array of microphones in a room were simulated for a single talker and for a babble of voices at each of several interferer locations. Three rooms with different absorption coefficients were simulated. Conditions with more than one simultaneous interferer location and with starts and stops of an interferer are being tested. Success of the hybrid adaptive beamformer is being assessed by informal listening and by measuring the intelligibility-weighted improvement in SNR. Preliminary results appear promising.
Application of matched-field processing to structural vibration problems.
Authors: Turek Gabriella , Kuperman W. A.
Published: October 2005

The applicability of matched-field processing (MFP) [Baggeroer et al., IEEE J. Ocean. Eng. 18, 401–424 (1993)] techniques to localize sources of vibration in structures and to perform nondestructive testing is explored. MFP is a generalized procedure of array processing used in ocean acoustics to either localize sources or perform inversions. MFP involves correlations between the solutions (or ‘‘replicas’’) of the wave equation for a given acoustic model of the ocean and the data measured at an array of sensors. The correlations are made using an assortment of linear and nonlinear methods. These techniques were successfully tested using simulation for the relatively simple problem of localizing a harmonic point force on a simply supported laterally vibrating beam. Wave equation solutions for describing the vibration of more complicated structures (simulated by adding spring constraints to the beam) become, at some point of complexity, intractable. Often statistical techniques provide the only practical description of such structural vibration problems. Multiple constraint MFP methods, tolerant to solution mismatch, were used to deal with these more complicated structures. Finally, it was demonstrated that MFP methods might also be used as a means of nondestructive testing in order to locate defects.
Adaptive control of modular sound enclosure.
Authors: Martini Kyle , Stokes Ann
Published: October 2005

This paper presents an experimental demonstration of the active control of a novel, modular sound enclosure that is built of panels which are stiffness controlled throughout the frequency range of interest. In this range, traditional passive noise enclosures are difficult to successfully implement. The design of the lightweight, stiff panels permits active control with a manageable number of actuators and sensors. The control technique is the adaptive, feedforward, filtered-x approach. Adaptive control is needed because realistic changes in the enclosure temperature and structural resonances would degrade the performance of fixed feedforward filters. The design of the enclosures makes this adaptive approach computationally feasible. Two performance criteria are evaluated: the minimization of the sum of the squares of the accelerations of the panels, and the minimization of certain supersonic wave-number components of the surface vibration field. Both approaches are straightforward for this enclosure design, where each panel behaves like a piston. [Work supported by the National Science Foundation.]
A general dynamic theory of thermopiezoceramic shells.
Authors: Altay G. Aşkar , Dökmeci M. Cengiz
Published: October 2005

This study presents a general theory for the motions of a ceramic shell in which there is coupling among mechanical, electrical, and thermal fields. The coated ceramic shell is treated as a two-dimensional thermopiezoelectric medium and a separation of variables solution in terms of the thickness coordinates, the midsurface coordinates, and time is sought for its field variables. Then, a variational averaging procedure [M. C. Dökmeci, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 35, 775–787 (1988)] together with the solution is used so as to derive the system of approximate equations of ceramic shell. The invariant system of governing equations which are expressed in both differential and variational forms accounts for all the types of motions of ceramic shells. Certain cases involving special geometry, material properties, and motions are considered [e.g., M. C. Dökmeci, J. Math. Phys. 19, 109–126 (1978)]. Also, the sufficient boundary and initial conditions are given for the uniqueness in solutions of the fully linearized system of shell equations. The results are shown to generate a series of known shell theories [e.g., M. C. Dökmeci, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 37, 369–385 (1990) and references therein]. [Work supported by TÜBA-TÜBİTAK.]
Specific damping capacity for high-loss materials.
Authors: Lee Gilbert F. , Hartmann Bruce
Published: October 2005

The purpose of this presentation is to establish the relation between specific damping capacity and loss factor for high-loss materials. The motivation for this work is that the commonly used relationship between these variables is only valid for low-loss materials and leads to significant errors as the loss increases. The relationship cited in numerous references between specific damping capacity is ΔW/W=2π tanδ. This equation is only valid for very small values of δ. Another difficulty with the above relationship is that the specific damping capacity is generally assumed to represent the fraction of energy converted to heat. For large values of tan δ, ΔW/W can be greater than one, which seems to be a contradiction. In this presentation, a relationship between specific damping capacity and loss factor is derived, which is valid for all values of tan δ. In the limit as the loss factor approaches infinity, the specific damping capacity approaches unity. A comparison of our relationship with others found in the literature will be presented. [Work supported by Naval Surface Warfare Center’s In-house Laboratory Independent Research Program sponsored by the Office of Naval Research.]
Perceiving and encoding timbre.
Authors: Pitt Mark A.
Published: October 2005

Interactions with the auditory environment often require accurate recognition of sound objects and events (e.g., voices and instruments, and the utterances that emanate from them). Two lines of research in the lab have been exploring how listeners process the auditory dimension of timbre as one step toward understanding object recognition. In one, commonalties in processing different classes of timbres (human voices, musical instruments) using the selective adaptation paradigm are explored. In the second, the characteristics of timbre memory using the interpolated tone paradigm are examined [Deutsch, Science 168, 1604–1605]. Findings will be discussed in the context of similar results in the literature.
Perceptual anchors and magnets in infancy.
Authors: Trehub Sandra E.
Published: October 2005

Research on adults’ and children’s perception of tone sequences or melodies reveals that they more readily detect the same magnitude of change in the context of a ‘‘good’’ or well-formed sequence than in the context of a ‘‘poor’’ or less well-formed sequence. Because well-formedness is typically confounded with familiarity, the origin of such performance asymmetries often remains unclear. In recent studies, however, 6-month-olds exhibited adult-like patterns of performance, raising the possibility of processing predispositions for good auditory sequences. Such sequences could be considered ‘‘natural’’ prototypes, and would be expected to occur frequently across cultures. Natural prototypes might serve a perceptual anchoring function for novice and experienced listeners, facilitating the acquisition of certain kinds of information. Kuhl argues, however, that phonetic prototypes operate differently, being less discriminable from other sounds within the same category than are nonprototypes. In other words, the good instances function as magnets rather than anchors. On the one hand, it is useful for natural prototypes to function as anchors, being highly distinctive and memorable. On the other hand, sufficient flexibility is necessary for the acquisition of culture-specific or ‘‘magnetic’’ prototypes.
Recent shallow-water acoustic measurements of sound transmission, reverberation, and coherence.
Authors: Carey William M. , Cable Peter , Steele Mike
Published: October 2005

Recent experiments performed in the shallow waters (100 m deep) of the Gulf of Mexico, East Continental Shelf of America, and the Korean Straits under the condition of downward refraction with sandy–silty clays are discussed. These experiments were performed with both explosive, air gun, and continuous sources covering the 100-Hz to 1-kHz frequency range. The receivers were both horizontal arrays on the bottom and vertical arrays which spanned the water column. Precise navigation was employed to eliminate range uncertainties and all measurement systems were calibrated to a traceable standard. The results are presented in the categories of sound transmission, reverberation, and coherence. Sound transmission results were found to generally agree with wave-theoretic numerical codes and shear was not found to be important. The reverberation was found to have a frequency-dependent characteristic consistent with sediment layering. Coherence lengths are estimated from array signal gain measurements in the midfrequency range and compared to previous measurements in both deep and shallow water. Results were found to be influenced by a variety of factors such as water column variations. Estimates of the importance of these factors under downward refracting conditions will be made and extended to other sound velocity profiles.
Interference patterns of frequency-dependent transmission loss for shallow-water propagation.
Authors: Bongiovanni Kevin P. , Badiey Mohsen , Siegmann William L.
Published: October 2005

Transmission loss (TL) as a function of frequency, for fixed source and receiver positions, provides a means to investigate the influence of environmental mechanisms on broadband acoustic propagation. These curves exhibit an analogous behavior to cw loss curves as a function of range, with null-peak interference patterns observed in both experimental data and numerical simulation. An analytic approximation for the resulting patterns in a Pekeris type range-independent medium employing normal-mode theory is developed. Broadband signals are partitioned into bands for which accurate modeling can be achieved. Narrow-band approximations are then used to derive formulas for the null-spacings of the curves. These expressions connect the interference structure, through the modal group velocities and appropriate boundary conditions, to volume and seabed structure and composition. This work extends a previous development for a zeroth-order ocean [Badiey et al., J. Acoust. Soc. Am. 98, 2897(A) (1995)]. A qualitative assessment of the formulation is achieved by comparisons with both parabolic equation simulations and high-resolution geoacoustic/acoustic experimental data, for several different environments. The evolution of TL versus frequency patterns in range will be discussed in light of range-dependent environmental parameters.
Frequency dependence of forward propagation through a layered dipping sediment.
Authors: Oba Roger M.
Published: October 2005

Forward propagation is used to compute the acoustic field in a shallow-water environment with a layered dipping sediment. The sediment is assumed to be silty with several thin sandy layers with higher density and sound speed. The sandy layers slope within the entire sediment layer so that the depth of a sand layer varies linearly with range. The sediment is modeled as a fluid of uniform horizontal thickness over a range-independent hard sub-bottom. The water sound speed is range independent and depth dependent in a fixed depth environment. This range-dependent sediment geometry leads to transmission loss significantly different from those with fixed layer depths, even when the dip gradient is very slight. These differences and their mechanisms are explored for varying frequencies and interlayer distances.
Invariant imbedding analysis of seabed acoustics.
Authors: Khashanah Khaldoun , McKee Thomas G.
Published: October 2005

The linear acoustic equations for the bounded slab of fluid ocean and elastic seabed with cylinderical symmetry are reduced to a set of coupled boundary value problems using separation of variables. In order to have a computational technique capable of handling stratification effects in the seabed, invariant imbedding is used to replace the boundary value problem with an initial value problem. As an initial approximation, the case of an ocean with a reflective bottom is considered and the change in the solution, as the depth of the seabed increases, is calculated. The method of invariant imbedding is shown to be numerically stable and has the advantage of assessing the effects of including an interactive seabed on the solution to the underwater acoustics problem with a reflecting seabed.
Mode coupling analysis for a resonance effect due to an internal soliton.
Authors: Broadhead Michael K. , Field Robert L.
Published: October 2005

As pointed out by Zhou et al. [J. Acoust. Soc. Am. 90, 2042–2054 (1991)], nonlinear shallow-water solitary internal waves (SIW’s) can enhance the bottom interaction of underwater sound. For a lossy ocean bottom, this has the effect of a level change (in addition to fluctuations) in the transmission loss at preferred frequencies. The mechanism for this effect is acoustic mode coupling due to the depression of higher sound-speed water into lower speed water (at the pycnocline). It is also possible for this mechanism to induce a transfer of acoustic energy from below the thermocline into the mixed layer, as has been shown elsewhere, where a two-layer pycnocline/sound-speed environment was used, along with a KdV soliton. Over the frequency range studied (900–1030 Hz), the energy transfer spectrum exhibited a doublet resonant structure. It was also found that an increase in the SIW length scale was accompanied by a positive shift in the resonant frequencies. A simple model is offered that qualitatively accounts for these two features which is based on mode coupling theory. Also presented is the dependency of the resonance frequencies on the sound speeds and layer thicknesses of the acoustic environment.
Estimation of nonlinear effects in global scale ocean acoustic propagation.
Authors: McDonald B. Edward
Published: October 2005

The nonlinear progressive wave equation (NPE) [B. E. McDonald and W. A. Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] is used to derive quantitative estimates for the magnitudes and characteristic features of nonlinearities generated by finite amplitude acoustic signals during propagation across ocean paths of global scale. Nonlinear effects accumulate over long propagation paths, and are accentuated at convergence zone caustics. The goals are to estimate (1) levels of harmonic generation in ocean tomographic experiments and (2) waveform steepening in underwater explosions. Harmonic generation (1) is estimated from a linear baseline solution involving vertical eigenmode expansion. The result implies second harmonic magnification at odd numbered convergence zone ranges. Waveform steepening (2) is estimated by time-domain numerical integration and related to modal excitation differences in the far field [J. Ambrosiano, D. R. Plante, B. E. McDonald, and W. A. Kuperman, J. Acoust. Soc. Am. 87, 1473–1481 (1990)]. [Work supported by ONR.]
Hot topics in engineering acoustics.
Authors: Garrett Steven
Published: October 2005

Engineering acoustics attempts to utilize contemporary developments in many areas of science, technology, and analysis to produce acoustical systems and products which address existing needs or create new opportunities. Topics in engineering acoustics become ‘‘hot’’ when there is a convergence which facilitates a ‘‘quantum leap’’ in some particular application area. Fusion of new sensor technologies, microprocessors, signal processing, and electronic data communication has produced new options in condition-based monitoring of machinery and industrial processes. Advances in the speed and reduction of cost in A–D and D–A converters, coupled with high memory density, has permitted the development of acoustic time reversal mirrors which could have application to ultrasonic nondestructive evaluation of materials. Computing power, new inversion algorithms, and novel transducers have led to the commercialization of resonant ultrasound spectroscopy which can determine the complete set of elastic moduli for materials with sample sizes which can be less than 1 mg. The availability of fast, accurate one-dimensional computer-based acoustic modeling tools and new research results in studies of the transfer to heat from acoustically oscillating fluids to solid surfaces are providing a new foundation to design and optimize the next generation of thermoacoustic engines and refrigerators.
Shock wave lithotripsy: A demonstration of experimental methods for in vitro shock wave exposure and analysis of cell injury.
Authors: McAteer James A. , Andreoli Sharon P. , Evan Andrew P. , Denman Dax D. , Mallett Coleen , Cleveland Robin O. , Averkiou Michalakis A. , Crum Lawrence A. , Lingeman James E. , Lifshitz David
Published: October 2005

This laboratory is involved in studies to determine the mechanism(s) responsible for cellular injury to the kidney during shock wave lithotripsy for the treatment of upper urinary tract stones. The studies are performed using an electrohydraulic lithotripter (Dornier HM3) and injury to isolated, cultured renal tubular epithelial cells was assessed. In this demonstration our experiences with the practical aspects of performing in vitro SW exposures are shared. Issues to be discussed and/or demonstrated include the following: (a) choice of cultured cell models and the handling of isolated cells, (b) factors that influence in vitro cell injury, (c) selection and preparation of specimen vials, (d) lithotripter setup and operation, (e) positioning the specimen and control of exposure parameters, (f) electrode performance and variability, (g) characterization of waveforms and determination of SW pressures, (h) markers of cell injury and cell response to SW insult, and (i) safety in the lithotripsy suite. [Work supported by NIH Program Project Grant No. PO1 43881: Role of SWL in renal injury and stone comminution.]
Numerical solutions of a prototypical master structure/fuzzy substructure system.
Authors: Weaver Richard L.
Published: October 2005

The transient response of a single degree of freedom master oscillator attached to a simple undamped N degree of freedom ‘‘fuzzy substructure’’ is studied numerically and theoretically. Results at early times are found to be in accord with the predictions of the Pierce–Sparrow–Russell theory; in particular, the master oscillation manifests an apparent damping. At later times, however, the energy is returned from fuzzy to master. The precise manner in which the energy is returned and the time taken to do this depend on the details of the mass and frequency distribution within the fuzzy and, in particular, on the distribution of spacings between the fuzzy resonances. For the case of irregularly positioned fuzzy resonances the energy returns immediately and the master then oscillates randomly. For the case of regularly spaced fuzzy resonances the energy returns after a longer time, and does so coherently. Theory is presented which supports the accuracy of the Pierce–Sparrow–Russell result at short times. Other arguments (for the case of random fuzzy resonances) predict the root-mean-square level of the subsequent random oscillations. Still others (for the case of regularly spaced fuzzy resonances) predict the return time. [Work supported by ONR.]
Forced localization in mistuned nonlinear repetitive structures.
Authors: King Melvin E.
Published: October 2005

The presence of localized modes in repetitive structures (i.e., systems composed of identical substructural elements) often gives rise to motions during which vibrational energy becomes spatially confined to a subset of elements. Such modes have been shown to be generated through eignevalue veering in weakly mistuned linear systems and mode bifurca- tions in perfectly tuned nonlinear systems. Recent work by the author has investigated the combined influences of weak nonlinearities and weak structural mistunings in generating localized modes. In the present work, the forced response of nonlinear cyclic systems with structural mistunings is investigated via the method of multiple scales. Under harmonic excitations, strongly and weakly localized motions will be shown to exist for various structural parameters. Sample calculations will be presented for systems composed of two, three, and four degrees of freedom. Additionally, motion confinement characteristics of such systems will be demonstrated for transient loading conditions, and the implications for novel vibration isolation designs will be discussed.
A musical history of architectural acoustics.
Authors: Herr Christopher , Siebein Gary W.
Published: October 2005

A brief multimedia presentation explaining the mutual developments of acoustics, music, and architecture was developed to illustrate the relations among art, science, culture, and music in the evolution of western architecture. Throughout much of the history of the western world there has been a clearly discernible connection between the development of music, musical instruments, ensembles, and the design of spaces for musical performances. This multimedia presentation was developed to illustrate the creative potential of understanding music and acoustics in the history of architecture. The acoustical rationales for musical and architectural phenomena are studied in the context of composers and musical works. The musical pieces have been convolved with the acoustical properties of the spaces in which they were originally performed to allow people to aurally experience a simulated acoustical history of architecture. Examples studied include chants in large cathedrals; Gabrieli’s music composed for St. Mark’s; comparisons of Haydn’s works written early in his career for small orchestras in small rooms and those written later in his career for larger orchestras in larger rooms; the operatic works of Wagner and the unique environment at Bayreuth; and the exploration of tone color and experimental music and architecture in the 20th century among others [Work supported by NSF.]
The effects of special coatings on the Sabine–Guastavino Rumford acoustical tiles.
Authors: Pounds Richard , Raichel Daniel R. , Weaver Martin
Published: October 2005

Wallace C. Sabine and Rafael Guastavino developed the Rumford tiles specifically to lessen the reverberation times inside ecclesiastical edifices. These tiles are used in a number of churches, including St. Bartholomew and St. Thomas, both in New York City, and the Duke University Chapel in Durham, NC. In recent times, those responsible for musical programs have been demanding greater reverberation times, even at the expense of clarity of spoken words. Accordingly sealers are being applied to a number of church interiors in order to increase the reverberation times. Because of the limited samples available, the tone burst method was applied at the Cooper Union Acoustics Research Center to measure the effect of applying special coatings to decrease sound absorption coefficients. The absorption coefficients were measured for the naked tiles, provided by the First Congregational Church of Montclair, NJ, and after the consolidator was sprayed on. The test was also repeated for each application of the sealer. The results of the test indicate that a considerable amount of coating will be necessary to decrease the sound absorption coefficient to the proper degree.
Song displays, song dialects, and lek mating systems in hummingbirds.
Authors: Gaunt S. L. L.
Published: October 2005

Males of some hummingbirds, including Colibri (violet-ears), congregate and display from traditional areas, leks, to attract mates. Hummingbirds use a vocal display. Males on a lek share the same song, i.e., nearest neighbors share song; males on distant, acoustically isolated, leks have different songs, i.e., there are dialects. Dialects have been used as evidence for song learning in birds, and, although song learning is usually ascribed to oscines and parrots, hummingbirds share vocal organ (syrinx) structures with them consistent with song learning ability. Digital spectrogram cross correlation was used to objectively determine degree of song similarity; this statistic was used in cluster analysis to describe relationships between birds and with the Mantel method to test hypotheses about associations. Further, males of a lek deliver their song cooperatively, i.e., without interference. The resultant is a lek signal that, from a distance, sounds as one song. If, as in other cooperative lekking systems, there is a skew in benefits, i.e., few obtain mates, then other males may gain benefits indirectly through relatedness (kin selection). Results from preliminary, DNA ‘‘fingerprinting’’ do not support this hypothesis, and alternative explanations are suggested. [Work supported, in part, by NSF.]
Sperm whale codas in the northwestern Gulf of Mexico.
Authors: Sparks Troy D. , Evans William E. , Benson Robert H.
Published: October 2005

Sperm whale (Physeter macrocephalus) coda patterns from the northwestern Gulf of Mexico have been examined. Recordings were collected via a towed passive hydrophone array. Sperm whales are known to produce a characteristic ‘‘hammering’’ click. Codas are rhythmic patterns of clicks [W. A. Watkins and W. E. Schevill, J. Acoust. Soc. Am. 62, 1485–1490 (1977)]. Two types of codas have been proposed: identity codas and general use or shared codas [Watkins et al., Cetology 49, 1–15 (1985)]. Identity codas are patterns that are unique to an individual for at least a few hours, and general use codas are vocalizations that seem to be shared among groups of whales. In the southeast Caribbean, it was found that 50% of the codas analyzed were made up of two patterns; therefore, it was proposed that shared codas may have a function other than individual identity [Moore et al., Mar. Mam. Sci. 9, 1–9 (1993)]. There also appears to be geographical differences in codas’ spacing and composition between the Galapagos and the southeast Caribbean [L. Weilgart and H. Whitehead, Can. J. Zoo. 71, 774–752 (1992)].