bluuebunny/crossref_metadata_2025 huggingface dataset:
A parametric study of broadband noise generation by small centrifugal blowers
Authors: Konieczny P. , Bolton J. S.
Published: October 2005

An experimental program has been conducted to identify the influence of several design elements on the broadband noise generated by small centrifugal blowers having impeller diameters of about 0.15 m. The design parameters considered in this study include: blade type, axial and radial inlet clearance, scroll development angle, scroll development length, and cutoff clearance. The noise generated by each blower was measured using the INCE plenum in a reverberation room (as standardized in ANSI S12.11 1987), and the aerodynamic performance of each was determined using a test tank built according to AMCA Standard 210-85. Pure tones generated by blade-cutoff interaction and by the driving motor were removed during data acquisition so that the A-weighted and 1/3 oct, broadband sound-power levels associated with each blower configuration could be established. In addition, a scaling procedure was developed to adjust blower sound-power levels to compensate for level differences resulting simply from aerodynamic performance differences. In this way, it has been possible to identify “design-related” noise differences unequivocally. Design guidelines for low-noise centrifugal blowers have been developed and will be summarized.
Acoustic segmentation and labeling of speech: Contribution from knowledge of articulatory nature
Authors: Autesserre D. , Meunier C. , Vigouroux N.
Published: October 2005

Numerous experts in human speech are facing problems relating to acoustic segmentation and labeling tasks. It is commonplace knowledge that labeling consists of aligning phonetic symbols onto portions of vocal signal that have been conventionally isolated, without establishing in all certitude the phonic substance they are supposed to support. Therefore, can it not be argued that the occurrence of co-articulatory phenomena questions the very possibility of segmenting at all a phonic sequence? Associating various instances of acoustic phonetic segmentation and labeling to a physiological segmentation and labeling are proposed. To achieve this, markers spotting various acoustic events become associated to remarkable physiological events, the latter being defined on the basis of amplitude variations in the movements of lips and velum. Both a manual and an automatic fine segmentation and labeling are carried out, to bring out phonetic events within sequences involving a stop between two nasal vowels. The data collected are set in comparison with the temporal evolution of both articulators retained in this experiment. The results, thus obtained, shed a new light upon the question of interpreting the meaning of the boundaries placed along an acoustic signal, in terms of production phases incurred by both consonantic and vocalic articulators.
Recent study of a microphone with range-dependent sensitivity
Authors: Date Hikaru
Published: October 2005

The spatially selective multimicrophone system, whose principle was first introduced at the 115th ASA meeting, can be easily modified into a directional microphone with range-dependent sensitivity by appropriately selected distribution of gains of microphone pairs located on a virtual spherical surface. An optimum choice for realizing a super close-talking microphone with this range-dependent microphone is investigated by systematic change of gain distribution through computer program, while keeping the spherical boundary shape. The effect of deviation on sensitivity and position of microphone pairs located on the boundary are also analyzed. Furthermore, the simulation study is also extended to the spheroidal shape of the boundary surface and it is made clear that the ratio of major and minor axes up to 2 is allowable without significantly disturbing the spatial characteristics of the multimicrophone system. The experimental results on the first model, occasionally equipped with an analog signal processing part, is also reported.
Use of the group velocity concept in acoustical resonances studies
Authors: Quentin G. , Derem A. , Poirée B.
Published: October 2005

The authors first review the fundamental notions involved in the group velocity concept. Then, they discuss how this concept may be usefully applied to the study of Regge trajectories. In acoustical scattering, the group velocity is related very simply to the frequency spacing between two consecutive resonances of the same wave. The group velocity appears also in the determination of resonance's widths and consequently of acoustic radiation. Finally, they discuss briefly the relationships between resonances, Regge trajectories, and group velocity in nuclear physics and elementary particles physics [J. Phys. France 50, 1943–1952 (1989)].
SAW sensors and their application to sense stresses in turbulent flows
Authors: Rob Yongrae , Shanker B. , Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

The potential of the SAW devices as sensors has not been fully exploited. New SAW sensors are developed to sense the shear stress and the normal stress in turbulent flows. These devices are extremely sensitive to changes in the environment. The surface wave velocity is hence changed when forces are applied on the sensor. The direction of the surface wave can be changed and by suitable manipulation, the effect of each stress can be isolated. Experiments are conducted with a low-frequency SAW oscillator sensor and the frequency shift is measured. The values obtained agree with the expected values for the experimental setup. As the frequency of operation is increased, the sensors become smaller and the values can be determined more accurately eliminating the effect of spatial variation of the stresses.
The design of an intelligent vibration absorber using numerical optimization techniques
Authors: Walsh Patricia L. , Lamancusa John S.
Published: October 2005

The tuned absorber is an effective method of vibration reduction for systems that operate at constant frequency. However, the tuned absorber adds an additional low-frequency resonance through which the system must pass during startup or shutdown conditions, thereby creating potentially excessive noise or vibration. An intelligent vibration absorber that will be effective during these periods has been designed. The mechanical system is modeled as a lumped mass, two-degree-of-freedom system driven by a rotating unbalance that accelerates from rest to a constant driving frequency. The absorber has constant mass and damping but variable stiffness. The optimal value of absorber spring stiffness as a function of time was found using the optimization routine CONMIN. The time response was discretized and the optimization was performed on each successive time interval. The cost function and design variable used were the root-mean-squared displacement of the main mass and the absorber stiffness during each time interval. The process was repeated for several mass ratios, damping ratios, and accelerations. The intelligent absorber is shown to be superior to the tuned absorber for all cases.
Fiber optic sound and strain measurements employing newly developed digital demodulators
Authors: Houston Brian H. , Bucaro J. A. , Kraus Larry A.
Published: October 2005

Fiber optic interferometric sensor systems for “smart” materials and structures applications offer a number of advantages including minimal electrical interference, geometric flexibility, and multisensor capability. Demodulation of these interferometric sensor signals typically is carried out by analog hardware. However, accuracy, bandwidth, and linearity are hampered by limitations in available electronic components and low-performance analog filters. A high-precision off-line digital demodulator has been developed and the techniques with fiber optic strain gauges and hydrophones are demonstrated. The measurement system is unique and represents an advancement in the state-of-the-art. A real-time implementation for control applications based on the Texas Instruments Inc. TMS 320C25 signal processing chip set is also proposed.
A bistatic, high-frequency, under-ice, acoustic scattering model and the space-time properties of high-frequency, under-ice acoustic scattering
Authors: Bishop Garner C.
Published: October 2005

A model is described that has been developed to calculate the scatter produced by a high-frequency acoustic pulse that originates from a stationary and arbitrarily located source, is incident on and is scattered from the under-ice surface characteristic of pack-ice regions of the interior Arctic, and is detected by a stationary and arbitrarily located receiver. A variety of measured data and model results are shown, which demonstrate the validity of the model as well as many of the unique scattering properties of the under-ice surface. In particular, spatial and temporal horizontal and vertical covariance functions as well as several types of acoustic images are calculated from modeled reverberation, target strength, and pressure field spatial phase time series produced by scattering from ice keels as well as from ensembles of under-ice scatterers. Some effects of various geometric and physical quantities on spatial and temporal covariance are indicated.
Arctic acoustic databases
Authors: Ingram Richard D.
Published: October 2005

Over the past 5 years, four acoustic field programs have been conducted by the Applied Research Laboratory (ARL) at Penn State Univ. These tests have been conducted from both stationary and moving platforms under the Arctic pack ice. The measurements include multiple signal waveforms to study the reverberation generated by both smooth and rough ice. The forward scattering versus ice type has been measured as a function of the depth of the source and the receiver. The basis of these measurements is to quantify the acoustic medium in the Arctic to ascertain what information about the environment can be extracted using state-of-the-art acoustic sensors within certain physical limitations. The effects of multipath and out-of-plane scattering will be discussed along with its effects upon direct path propagation. Ambient noise effects on acoustic processing will be discussed.
Anatomies of oceanic fronts
Authors: Mooers Christopher N. K.
Published: October 2005

Oceanic fronts have attributes in common with atmospheric fronts: for example, strong horizontal gradients in temperature and/or salinity and strong horizontal velocity shears and convergences. Their forcing mechanisms include tidally induced mixing, the advection of plumes, atmospherically driven upwelling, and deformation fields in oceanic flows. Some fronts are confined to the surface or bottom turbulent boundary layers; others exist as internal features of the ocean. Some are thousands of kilometers long, extend to great depth, and are semipermanent; others occur over short horizontal and vertical distances for brief durations. Due to strong convergences often found at fronts, strong vertical velocities can be induced. Also, internal gravity waves are often intense near fronts, and the consequent shear instabilities induce turbulent mixing and fine structure. Thus fronts can be major foci for vertical transfers, including between the surface mixed layer and the ocean interior, especially in situations where a surface front is an outcrop of an oceanic pycnocline. Due to their convergences, fronts are biologically significant: They concentrate nutrients and phytoplankton, and, consequently, zooplankton, fish, marine mammals, marine birds, and probably “marine snow.” Hence, oceanic fronts can be expected to scatter, as well as refract, acoustic energy.
Lagrangian studies of ocean currents using SOFAR
Authors: Rossby T.
Published: October 2005

Acoustically tracked neutrally buoyant floats are being used to study two extremes of ocean motion: the very energetic flows of the Gulf Stream off the east coast of the U.S. and Canada, and the very weak flows of the deep South Pacific. In the first case, where the particle velocities are much greater than the phase velocity of the meandering current, there is a strong tendency for the floats to remain in the stream. This has allowed the study of the advective properties of the current and the pathways of fluid exchange to both sides. In the deep ocean, where the particle velocities are much smaller than the phase velocity of the planetary wave field, the floats tell us about the time scales of deep ocean motions, and how particles move and disperse with time. Linear FM at 260 Hz (1.5-Hz bandwidth) and a few watts power (with moored sound sources built by Webb Res. Corp.) give a useful (off-axis, shallow) range of 1000 km in the Gulf Stream and somewhat more (off-axis, deep) in the deep South Pacific. A new high-powered resonant pipe projector is expected to give ocean basin scale tracking capabilities.
Measurements of zooplankton biomass with acoustic Doppler current profilers
Authors: Flagg Charles N.
Published: October 2005

Acoustic Doppler current profilers, ADCPs, arrived on the oceanographic scene a decade ago as a development of ship-mounted Doppler speed logs to measure vertical profiles of horizontal water velocities. Backscattered acoustic intensity is one of the parameters that can be recorded and early anecdotal observations indicated that intensity variations had distinctly biological characteristics such as diel zooplankton migrations. These early observations led to an ongoing study of the conditions under which ADCPs might be able to make quantitative estimates of zooplankton biomass. The attraction of ADCPs, and the motivation for the study, is not so much the ADCPs' ability to discern details about zooplankton populations but rather their ease of use and general availability. The results of the study to date, with operating frequencies of 150 and 300 kHz, have shown that ADCPs produce biomass estimates to within ± 15% throughout their acoustic range when the individual transducers have been calibrated and proper care is exercised in processing the results. ADCPs provide the ability to conduct nonintrusive large-scale surveys, in either time or space, of zooplankton biomass providing input, for example, to ecological models and as guides to more conventional sampling schemes.
Investigations into biological/water mass interactions in the Alaskan Beaufort Sea using hydroacoustic techniques
Authors: Thorne Richard E. , Johnson Gary E.
Published: October 2005

Hydroacoustic techniques were used to study the biological activity associated with water mass boundaries. Both fish and zooplankton were found to be most abundant along the boundary between a cold, high-salinity water mass and a warmer, low-salinity water mass in the nearshore region. Biological abundance was found to be greatest where the boundary between the water masses intersected the bottom.
An acoustical technique to detect and possibly classify fish in confined reverberant environments
Authors: Patrick P. H. , Kowalewski J. J. , Christie A. E. , Jennette B. L.
Published: October 2005

Investigations were conducted in the laboratory on the potential of using acoustical resonance as a technique to detect and possibly classify fish in shallow, fast flow environments. Present high-frequency acoustical approaches are limited in these situations because of reverberation. An initial experiment with bubble packing material indicated an insertion loss of approximately 26 dB. Further experiments involving live walleye and rainbow trout showed similar results. For rainbow trout, there was a direct relationship between an increase in insertion loss with a corresponding increase in fish density. The estimated resonant frequency for each density of fish was approximately 412 Hz. Insertion loss ranged from approximately 7 dB for 3 fish to approximately 32 dB for 65 fish. These preliminary results were encouraging and indicated the potential of using this technique in highly reverberant environments. Research activities involving high-frequency acoustics will also be discussed. [Work supported by Ontario Hydro.]
Atmospheric gravity waves and turbulence study with acoustic Doppler sounders
Authors: Weill A.
Published: October 2005

Work undertaken at CRPE about gravity waves and turbulence indentification and characterization using acoustic remote sensing is presented. In a first part the techniques of measurement and methods of determination of wayes and turbulence parameters and their representativeness are described. Hence the elements are prepared to discuss, in a second part, observations showing interactions between inertial-gravity waves and turbulence. In particular, the advantage of acoustic remote sensing to localize critical levels related to gravity waves is demonstrated. The mechanism of wave formation related to wind and reflectivity profiles is also interpreted. Vertically propagating gravity waves and their relationship with entrainment at the level of the inversion layer are also analyzed. As elements of a gravity wave field locally observed are generally studied, rather than the field itself, in the third part, observations of a gravity wave field using a Doppler Sodar network are considered. A discussion is then open about relations between the field characteristics and the local properties of the flow. Adjustment of the wavenumber of the gravity waves field to the “most unstable” wavenumber is discussed, which is important in estimating fluxes and momentum associated with the waves. In the conclusion, the generality of the different observations is considered with special emphasis on the problem of interaction between atmosphere and ocean.
A simulation of a turbulent mesoscale current by eddy and current superposition to predict sound velocity variations
Authors: Childs McCarthy Emily
Published: October 2005

Ocean mesoscale currents display large-scale turbulence, clearly evident in remotely sensed imagery and in situ XBT casts. Deducing water velocity from remotely sensed data is a topic of ongoing research. The relationship of geostrophic water velocity and the acoustically relevant water column parameters has been expressed in the quasigeostrophic equation. Two general solutions of this equation, the uniform current [J. G. Watson, W. L. Siegmann, and M. J. Jacobson, J. Acoust. Soc. Am. 60, 355–364 (1976)] and the symmetrical eddy [R. F. Henrick, W. L. Siegmann, and M. J. Jacobson, J. Acoust. Soc. Am. 62, 860–870 (1977)], are analyzed and combined into one dynamical model. A scheme to reduce the three-dimensional temperature and velocity distributions of a turbulent current to simple eddies superimposed on a current is presented. The dynamical model is then used to predict the variations in sound speed across the current. A simulation of the North Pacific Current is given and the predicted sound velocity profiles are compared to data collected from the region [W. J. Emery et al., J. Acoust. Soc. Am. 66, 831–841 (1979)].
Active control for the acoustic radiation of a vibrating structure using a superposition formulation
Authors: Koopmann Gary H.
Published: October 2005

A new, computational approach provides a methodology for specifying how the acoustic power radiated from a complex, three-dimensional vibrating structure may be controlled. The method uses a superposition principle to transform the surface of a vibrating structure into a discrete distribution of acoustic sources interior to the boundary surface of the structure. The transformation is carried out by requiring that the interior sources produce the same or nearly the same normal velocities as those prescribed on the surface of the vibrating structure. Based on this transformation, the total time-averaged, acoustic power output from the vibrating structure can be expressed in terms of the strengths of the equivalent sources. To control the radiated acoustic power, one or more secondary point sources is then placed on or near the surface of the vibrating structure. By using the total power radiated from the vibrating structure and the secondary sources as an objective function for an optimization operation, the optimal strengths and locations of the secondary sources are found that lead to a maximum reduction in the acoustic power radiated from the vibrating structure. The significance of this approach is that it provides design guidelines for applying active control techniques to complex vibrating structures.
The current status of the development of an active noise control microphone
Authors: Warnaka Glenn E. , Kulikauskas Joseph A. , Hoover Lawrence M.
Published: October 2005

This paper describes the current status of the development of a simple unitary active microphone that provides superior noise cancellation. The microphone, based on active noise control principles, is small and does not require an independent sample of the ambient noise. At the same time, there is no requirement for locating the microphone near the speaker's mouth, as required with conventional passive noise canceling microphones. Instead, the microphone under development can be placed several feet, or more, from the speaker, since superior performance of the new microphone can still be realized. The microphone element can discriminate between the voice and noise even at a distance without voice recognition algorithms, and all kinds of noises, including random noise, can be canceled. A simple electronic control unit can be used to produce commercial systems.
Onset dominance in the perception of binaural information
Authors: Houtgast Tammo , Aoki Shigeaki
Published: October 2005

This contribution extends the paper presented by Aoki and Houtgast. Besides interaural time difference and interaural cross correlation, two additional types of binaural information are considered: interaural level difference and free-field localization. Listening experiments are performed with brief signals, subdivided into a leading and a trailing part with durations T1 and T2, and the measuring paradigm aims at assessing the critical ratio T1/T, for which both parts contribute equally to the overall sensation of the signal. Onset dominance is reflected by a critical ratio T1/T, < 1. The signal was either broadband noise or octave-band-filtered noise around 500 or 2000 Hz. With total signal duration as a parameter (5, 10, 20, or 40 ms), the data on the critical ratio T1/T, can be summarized in a single weighting function: the perceptual weight as a function of time after onset. These weighting functions show a high peak at onset, followed by a typical “rarefaction dip.” In this respect, all four types of binaural information show qualitatively very similar results.
Computational model of monaural localization
Authors: Zakarauskas Pierre , Cynader Max S.
Published: October 2005

This paper attempts to supply a computational theory of monaural localization. It is well established that monaural localization capacities for pure-tone stimuli are very poor. Broad spectrum stimuli are localized with far greater accuracy. This paper explores the spectral characteristics that a sound source must have in order for it to be localized accurately. In previous work, it has been shown that monaural localization is possible if the source spectrum is locally flat. In that case, one looks for points or intervals of the received spectrum with a high slope, and this effect is assumed to be due solely to the interferences induced by the pinna. Here, it is shown that the spectrum need not necessarily be flat for monaural localization to be possible. The spectrum can have any slope, and the only restriction is that this slope be more or less constant over a small frequency interval. This assumption leads to the conclusion that one may be able to extract the position of the source by using information about spectral curvature. The conditions under which this is possible are laid out. Possible neural implementations of this process are considered.
The articulatory kinematics of accent
Authors: Beckman Mary E. , Edwards Jan
Published: October 2005

Two recent kinematic studies of syllables with bilabial consonants suggest different dynamic accounts of the durational increase associated with stress: Kelso et al. [J. Acoust. Soc. Am. 77, 266–280 (1985)] interpret regression curves for peak velocity against displacement as evidence that lower-lip gestures in stressed syllables are less stiff, whereas Nittrouer et al. [J. Acoust. Soc. Am. 85, 1653–1661 (1988)] show that the upper-lip closing gesture begins at a later phase relative to the jaw opening gesture. Preliminary results from a kinematic study of accented syllables suggest a resolution of the discrepancy. Jaw opening and closing gestures for pop and poppa embedded in sentences that varied the placement of the nuclear pitch accent (sentence stress) were looked at. When accented, gestures were substantially longer, but the velocity-displacement regression curve showed no decrease in slope, contra Kelso et al. Also, a comparison of observed syllable durations to those predicted by the velocity-displacement ratios showed that this stiffness index alone cannot account for the greater length. Rather, an accented syllable is longer probably because the closing gesture is later, in accordance with Nittrouer et al. The seemingly contradictory pattern in Kelso et al. may be an artifact of including reduced syllables with unaccented full syllables in a single “unstressed” category. [Work supported by the NSF.]
The effect of the amplitude of the spectral envelope on P-center location in speech and nonspeech analogs
Authors: Turk Alice E.
Published: October 2005

This paper discusses a study of P-center locations in the equal duration syllables [a], [ba], and [ma]. The syllables were chosen because, in articulatory terms, the onsets of [ba] and [mal are quite similar, and acoustically the beginnings of the syllabics vary in their amplitude envelopes. The nonspeech analogs are single-formant stimuli that vary only in how low the first 60 ms was low-pass filtered: [a] had no low-pass filtering; [ma] had an intermediate amount, and [ba] had the most extreme amount. The purpose of the experiment is to determine whether the resulting spectral differences alone can affect the location of the P center. Stimuli consist of five syllables and include all nine possible pairs of the three-syllable types. The silent interval between the second and third syllables and between the fourth and fifth syllables is varied along a continuum from 0 to 250 ms in 25-ms steps (the interval between the first and second syllables and the third and the fourth syllables is always 150 ms). Subjects judge the relative isochrony of these strings. Results from a preliminary experiment show that the location of the P center in nonspeech analogs of [ba] and [ma] are not significantly different, while the P center of the nonspeech analog of [a] differs from that of both [ba] and [ma]. Fowler (1979) found that the P-center location of prevoiced and nonprevoiced allophones of homorganic stops did not differ significantly. She argues from this result that the location of P centers is determined by the underlying articulation and not by the spectrum of the acoustic signal. The fact that the nonspeech analogs of [ba] and [ma] (with no underlying articulations) did not differ in P-center location suggests instead that the spectrum of the signal alone may after all underlie P-center location; specifically, like the analogs of [ba] and [ma], the prevoiced and nonprevoiced stops in Fowler's study may have so little energy in the closure that their spectra do not differ significantly during that interval. In light of this study's nonspeech results, a reevaluation of Howell's (1984) claims that spectral differences do determine P-center location is in order.
Multidimensional imaging of the heart with ultrasound
Authors: Greenleaf James F.
Published: October 2005

The heart is a three-dimensional structure that performs its function by undergoing complex deformation. Current clinical evaluation of the heart is limited to silhouettes, outlines, projections, or tomograms, obligating the clinician or investigator to sequentially evaluate a series of two-dimensional images using mental assimulation of data. To provide more easily understandable three-dimensional images, techniques have been developed for acquiring data in sequential planes through the heart to display the beating heart in three dimensions. Analysis of such data on a user-friendly workstation can be accomplished using an extensive set of software tools developed at our institution. Three-dimensional imaging can be used as an effective means of teaching interrelationships of volume, contents, and function, in addition to the physiologic and anatomic interrelation-ships. Three-dimensional images of the beating human heart obtained in vivo using new data acquisition techniques will be shown. Evaluation of the method using balloons and excised hearts has shown that software and geometry of scanning are appropriate for high-accuracy measurements of surfaces.
A characterization of wave-front distortion in ultrasonic imaging
Authors: Waag Robert C. , Smith James F. , Sumino Yoichi
Published: October 2005

The influence of wave-front distortion in ultrasonic imaging is examined using a model that represents the signal in the imaging system aperture in terms of the aperture, the scattering source, and a distortion function. This model, along with assumptions that the beam pattern factors into the product of axial and lateral functions and that the distortion is represented by a time shift that is either a sinusoid or Gaussianly distributed, permits the development of expressions for the correlation function of the aperture and, thus, the intensity of the beam pattern. Although these assumptions are idealizations, the approach yields relatively simple expressions that show the way time delay couples into beamwidth to degrade resolution. Further simplifications follow from assuming that the distortion is small or that the axial and lateral beam functions have specific forms such as Gaussian shapes. The analysis indicates that compensation of distortion using time delays estimated from cross correlation of signals on adjacent elements of an aperture maximizes overall average intensity in an image of uncorrelated scatterers. The results provide representations of distortion in ultrasonic imaging systems and may be used to study the relationship between techniques that compensate for wave-front distortion.
Suppression of reverberation artifact by subtraction imaging
Authors: Kling Terry A. , Shung K. Kirk
Published: October 2005

Reverberations in ultrasound pulse-echo signals are the result of parallel specular reflectors that are perpendicular to the incident sound beam. The multiple reflections within the space between the reflectors cause a decaying pulse train of echoes to be superimposed on the returned echoes due to other structures. In a medical ultrasound B-scan, these reverberant signals obscure detail in the underlying tissue. One method to suppress these reverberation artifacts may be to subtract the images obtained at two different frequencies. This approach was tested in a water bath on a phantom of two parallel thin plastic plates in front of a foam sponge. A 5- and a 7.5-MHz transducer with similar beam profiles in the region of interest were used to create the B-mode images. The results showed that subtraction imaging resulted in a significant decrease in the reverberation artifact. Application of this method to the phantom without the sponge indicate a 7- to 13-dB decrease in the reverberant signal level.
Acoustic scattering from ocean microstructure
Authors: Goodman Louis , Forbes Michael J.
Published: October 2005

An examination has been made of the scattering cross section per unit volume per unit solid angle, σ, for the case of acoustic scattering from ocean microstructure. Both monostatic and bistatic geometries have been considered. Diffraction has been explicitly included in the formalism, resulting in an expression for σ that accounts for finite scattering volume size effects associated with vertically anisotropic microstructure. Vertically anisotropic microstructure results in σ a maximum at reflection with respect to the horizontal plane with an angular bandwidth of order the maximum of the beamwidth angle and the anisotropy slope angle. Two models of ocean temperature microstructure, a classical turbulence model and an empirical model based on recent field observations, have been used as input into the acoustic formulations. Specific functional forms have been obtained for σ in term of environmental parameters. A complimentary laboratory experiment has been undertaken. [Work supported by ONR and NUSC Independent Research Program.]
Scatter of high-frequency acoustic wave fields from ocean turbulence
Authors: Orr Marshall H.
Published: October 2005

Space and time coincident 200-kHz acoustic backscattering records, CTD, and zooplankton distribution data were taken during an interdisciplinary study of the internal wave packets that propagate through Massachusetts Bay [L. R. Haury, M. G. Briscoc, and M. H. Orr, “Tidally generated internal wave packets in Massachusetts Bay, U.S.A.; preliminary physical and biological results,” Nature 278, 312–317 (1979)]. The data strongly support the contention that acoustic wave fields can be backscattered from temperature and salinity fluctuations caused by turbulent mixing processes associated with the internal wave packets. Sections of the data records will be presented.
Increasing the intelligibility of speech through multiple phonemic restorations
Authors: Reiner Keri R. , Bashford James A. , Warren Richard M.
Published: October 2005

When gaps in speech are filled with noise, phonemic restorations (PhR's) may occur. Multiple PhR's follow rules governing “auditory induction” of nonverbal sounds, so that for maximal extent of illusory continuity of speech interrupted by noise, the noise must have the spectrum and amplitude corresponding to a potential masker of the speech. In addition, maximal illusory continuity occurs for speech with normal syntactic and semantic context [Bashford and Warren, Percept. Psychophys. 42, 114 (1987)]. The current study examines the effect of multiple PhR's upon speech intelligibility. When narrow-band CID (“everyday speech”) sentences were interrupted by periodic gaps, insertion of louder narrow-band noise into the gaps increased intelligibility, the greatest increase occurring when the noise band matched the speech in center frequency. A second experiment employed broadband speech with varying amounts of linguistic context (monosyllabic word lists, sentences with low predictability, and sentences with high predictability). Filling gaps with louder broadband noise improved the intelligibility of sentences, with the more predictable sentences showing the greatest restoration. However, noise did not restore intelligibility of word lists even when illusory continuity occurred. [Work supported by NIH and AFSOR.]
Phonetic integration and nonphonetic fusion with spectral discontinuities in duplex perception
Authors: Nygaard Lynne C.
Published: October 2005

When a synthetic syllable is split so that the third-formant transition is presented to one ear and the rest of the syllable (the base) is presented to the other ear, listeners report hearing a dual percept in which the isolated third-formant transition contributes to both phonetic and nonphonetic percepts. A previous study [L. C. Nygaard and P. D. Eimas, J. Acoust. Soc. Am. Suppl. 1 85, S26 (1989)] investigated a variation of this phenomenon by reintroducing the third-formant transition back into the base component of the duplex syllable while leaving the isolated third-formant transition in the other ear. In this case, the redundant information provided by the third-formant transitions appears to fuse to form a chirp percept centered in the listener's head and a clearer syllable in the ear presented the base. By varying the acoustic properties of the isolated third-formant transition relative to the base, the conditions necessary for phonetic integration and nonphonetic fusion were investigated. It was found that phonetic inegration remained intact at larger differences in fundamental frequency, amplitude, and onset asynchrony between components than did nonphonetic fusion. In the present study, the spectral composition of the isolated transition was varied relative to the base. In general, both phonetic integration and nonphonetic fusion remained remarkably intact even with large differences in spectral composition between components. However, as spectral differences increased, syllable identification of the modified stimuli fell toward chance, suggesting that listeners were integrating phonetic information across cars even when that information began increasingly to conflict.
Contribution of duration and intensity to the perception of prominence
Authors: Lehiste Ilse , Fox Robert Allen
Published: October 2005

In a comparison of word stress perception in Estonian and Russian, Arvo Eek showed that the stress judgments of Estonians were mostly associated with F0 patterns, while for Russians, duration was the leading parameter [In Honor of Ilse Lehiste, edited by R. Channon and L. Shockey (Foris, Dordrecht, Holland, 1987)]. Intensity played a negligible role for listeners with either language background. The current experiment describes perception of prominence by English and Estonian listeners under conditions where no F0 is present. Listeners heard sequences of four “noise” tokens created by randomly changing the polarization of individual samples of a digitized [ba]. The basic token was 400 ms in duration. However, in the experimental trials, one token in the sequence could be lengthened to 425, 450, or 500 ms and/or one token could be increased in intensity by 3 or 6 dB—the duration and intensity changes were independent. Listeners were required to indicate which token was “more prominent.” Listening tests were given to 24 native speakers of English in Columbus, Ohio and to 38 native speakers of Estonian in Tallinn, Estonia. The responses showed that for English listeners, intensity cues overrode duration cues, while Estonian listeners were more responsive to duration cues. [Work supported partly by NSF.]
Point load response of a finite cylindrical shell with a convected internal fluid
Authors: Leyrat G. , Cuschieri J. M.
Published: October 2005

In this paper, the response of a simply supported baffled cylindrical shell excited by a point force, with an internal constant flow speed, is investigated. The solution to this problem is obtained by using the normal modes of the in vacuo finite shell and the Kirchhoff-Helmholtz equation derived for a fluid moving at a constant flow speed and bounded by a perfectly rigid cylinder. Numerical results for the input accelerance of a copper pipe of radius 0.025 m, wall thickness 1.5 mm, and various lengths are presented. It is found that the decrease of the natural frequencies of the shell due to the flow is dependent on the circumferential and axial mode numbers. Also investigated are the effects of the circumferential mode number, length to radius ratio, and thickness to radius ratio on the critical flow velocity at which the motion of the pipe becomes unstable.
Acoustic radiation loading on cylindrical vibrators in an inviscid fluid with axial flow
Authors: Ebenezer D. D. , Stepanishen Peter R.
Published: October 2005

A wave-vector-time domain (k̄-t) method is presented to evaluate the acoustic radiation loading on cylindrical shells vibrating in an inviscid fluid with axial flow. The method is based on the use of the in vacuo modes of vibration of the shell that has infinite rigid extensions. The solution to the differential form of the acoustic wave equation for the pressure is first obtained in wave-vector-time space. The time-dependent modal forces are then expressed as a sum of the modal radiation impulse responses of the finite cylinder convolved with the time-dependent modal velocities. The modal radiation impulse responses are obtained by using the impulse responses of an infinite cylinder and the modes in wave-vector space. The approach can thus be easily used to obtain the radiation impulse responses for various boundary conditions, length to radius ratios, and arbitrary space- and time-dependent surface velocities. Numerical results are presented for a wide range of Mach numbers and length to radius ratios of simply supported cylindrical shells.
Acoustic radiation from rib-reinforced infinite cylindrical shell
Authors: Burroughs Courtney B. , Becker Kenneth J.
Published: October 2005

The acoustic radiation from rib-reinforced cylindrical shells is effected by the interaction between the shell and reinforcing ribs. This interaction includes normal, shear, and moment reactions of the rib to shell motion. An analytic model for the farfield acoustic radiation from a fluid-loaded infinite circular cylindrical shell with periodic rib supports is developed. The ribs are modeled as circular rings where the reactive forces, moments, and shears are applied by the shell at the outer edge of the ring. Approximate solutions for the force, moment, and shear impedances of the ribs are developed and incorporated into the acoustic radiation model to explore the dependence of the acoustic radiation from ribbed cylindrical shells on rib/shell interaction.
Low-frequency sound radiation from a line force excited, fluid-loaded, baffled strip
Authors: Kauffmann Chris
Published: October 2005

The two-dimensional problem of a fluid-loaded, baffled elastic strip (width 2a) excited by a time-harmonic line force (circular frequency ω) is analyzed theoretically. A Green's integral representation for the plate velocity distribution is used and boundary conditions are met by a system of two integral equations along the plate edges [P. Filippi, J. Sound Vib. 100, 69–81 (1985)]. For the case of clamped edges, results for the farfield pressure are presented for several values of koa, where k0 = ω/co is the wavenumber in the fluid. It is shown that at low frequencies, i.e., for koa ≪ 1, the strip radiates like a monopole with a strength equal to the net volume velocity of the strip. This monopole behavior of the finite strip differs from the well-known dipole radiation at low frequencies for a line force excited, infinite plate. The results are compared with similar results published by Filippi. The connection is discussed of the present problem to the case of an infinite plate with two parallel clamped line joints. [Work supported by the TNO Institute of Applied Physics, Delft, The Netherlands.]
Sound radiation from structural discontinuities
Authors: Keltie Richard F.
Published: October 2005

A useful method for analyzing the vibration response of structures with abrupt changes in property or dimension is to separate the vibration field into the incident, reflected, and transmitted components. These components will, in general, include both propagating waves and nonpropagating nearfield constituents. Utilizing this method, the specific contributions of each portion of the vibratory response to the resulting sound radiation are quantified for planar radiators. The general methodology is developed and results are given for the particular cases of subsonic bending waves incident upon elastic supports and rigid masses. The relative role of each portion of the vibratory response in scattering energy into the supersonic wavenumber domain, and contributing to the sound field, is discussed as a function of the wavenumber ratio, k/kB, of the incident bending wave.
A boundary element approach to weak radiator analysis—Preliminary results for a plate
Authors: Cunefare Kenneth A. , Koopmann Gary
Published: October 2005

Weak radiator analysis attempts to answer the question how should a structure respond at a given frequency such that it radiates sound least efficiently? Use of the boundary element method leads to a quadratic expression for the total radiated power from a structure formulated in terms of the surface velocity distribution on the structure. This quadratic power expression, formulated at the surface, represents the basis for the technique. Constrained optimization applied to the expression for power leads to that response shape that radiates sound least efficiently. The constraint considered here corresponds to a nonzero velocity at some point on the surface, equivalent to a drive point. More general constraints are possible, such as nonzero mean-square velocity. Weak radiator analysis is demonstrated through its application to a centrally driven, 760 × 610 mm plate, forming one side of a box. The resulting weak radiator shapes are unique, i.e., they do not correspond to the mode shapes of either a simply supported or clamped plate.
Estimating changes in biological properties across biogeographic boundaries using high-frequency acoustics
Authors: Wiebe P. H.
Published: October 2005

The use of high-frequency acoustics to study biogeographic boundaries is entering a new phase with the development of hardware and software that enable estimates of total biomass, number of scatterers, and individual size, all as a function of distance from the echo sounder. For macrozooplankton and micronekton, the relationship between target strength (TS) and the physical size of the scatterer in terms of length, wet weight, or dry weight is of crucial concern. Recent study of a variety of zooplankton taxa has revealed relationships that indicate TS increases as a function of organism volume, not cross-sectional area, as usually assumed. New models of sound scattering from plankton appear to be required as recent work illustrates [T. K. Stanton, J. Acoust. Soc. Am. 86, 1499–1510 (1989)]. Although more specific information about the identity of sound scatterers is presently difficult to extract from the acoustic returns, ongoing studies of the size frequency distribution of oceanic zooplankton suggest that in particular geographic regions and depths, specific taxa occupy a specific range of sizes. Accurate estimates of a number of organisms, in particular, size categories can, in such cases, be used to estimate numbers of individuals in these taxonomic groups. [Work supported by ONR.]
Approaches to the assessment of function in the four cutaneous mechanoreceptor channels
Authors: Bolanowski Stanley J. , Gescheider George A. , Verrillo Ronald T.
Published: October 2005

Normal cutaneous tissue has been shown to contain four distinct populations of mechanoreceptors. Psychophysical experimentation has demonstrated that these receptor populations may be identified with four independent channels that mediate the sensation of touch originating from stimulation of the surface of the skin. To be discussed will be a variety of approaches for making differential assessments of the integrity of each of the four channels.
Acoustics and the arena
Authors: Paoletti Dennis A.
Published: October 2005

This paper will present an overview of the relationship between acoustics and arena facilities during the past 20 years. There are three general categories of facilities: small (5000 seats), medium (20 000 seats), and large (50 000 seats). There are two acoustic sources: speech and music. There are many different architectural building and roof types (fabric in tension, air inflated, concrete dome, and wood and steel trusses). There are a number of other interrelated factors that inherently become considerations during the design process leading to the final constructed building. This includes heating, ventilation and air conditioning, score boards/advertising, major uses/home teams, and of course economics. Acoustic consultants have fared well in being able to recognize and implement the necessary design solutions to help attain arena facilities that perform well acoustically and serve the public for sports, cultural arts, and public assembly.