bluuebunny/crossref_metadata_2025 huggingface dataset:
A new kind of multiple-droplet levitator
Authors: Tian Yuren , Apfel Robert E.
Published: October 2005

Many different kinds of levitators are used to study liquid drops. In most of them, only a single drop can be levitated. Under some circumstances, however, it is desired to levitate multiple drops simultaneously. An acoustical levitator has been modified for the purpose of multiple-droplet levitation. During the experiments, a liquid is poured on the surface of the acoustic transducer and is ultrasonically atomized. By applying a static electric field on the surface of the liquid, the atomized drops are electrically charged. After the drops are dispersed into the levitator, they can be contained together and levitated by acoustic radiation force. Coalescence among the drops is prevented by the forces of electric repulsion. The separation distance between the drops, the droplet size, and the number of levitated drops can be controlled by the intensity of the acoustic and electric fields. Preliminary experimental results will be reported, including the observation of mass transfer among the levitated drops. [Work supported by NASA through JPL, contract 958722.]
Nonlinear acoustics of bubbly liquids: Traveling waves in a quadratic approximation
Authors: Goldman Daniel , Nadim Ali , Barbone Paul E.
Published: October 2005

An important aspect of underwater acoustics is the effect of trapped clouds of air bubbles. Recently, an approach to wave propagation in dilute bubbly liquids was described in which the Rayleigh–Plesset equation is used to derive a nonlinear equation of state for the gas bubble-liquid mixture [Nadim etal., Bull. Am. Phys. Soc. 39, 1976 (1994)]. In this formulation, the pressure in the mixture depends in a highly nonlinear way on the local density and its first and second time derivatives. Linearization leads to the standard acoustic equation for bubbly liquids. Here the quadratic approximation to the nonlinear equation of state is examined, along with the related nonlinear wave equation. The high- and low-frequency limits are then analyzed, and traveling wave solutions are sought in each case. Comparison is made with existing results for nonlinear waves in bubbly media.
Feasibility of low-frequency single-bubble sonolumin- escence
Authors: Apfel Robert E. , Shi Tao , Jankovsky Joseph , Ketterling Jeffrey , Chen Xiaohui
Published: October 2005

The potential to perform single-bubble sonoluminescence (SBSL) at low frequencies is motivated by the payoff of greatly enhanced energy concentration during collapse. Yet it is also known that bubbles undergoing such catastrophic collapse tend to be unstable. Experimental apparatus has been designed and computer simulations have been performed to test the feasibility of low-frequency, single-bubble sonoluminescence. The experimental apparatus consists of a cylindrical cell that is driven by an aluminum, half-wavelength resonator with fundamental resonance of less than 15 kHz. The cell is designed to be pressurized up to 5 atmospheres to allow levitation without significant spurious cavitation in the liquid. To complement this experimental work, our computer simulations of this phenomena are continuing [T. Shi and R. Apfel, 3253 (1994)] in order to follow the shape distortion of collapsing bubbles for varying parameters, including acoustic frequency. The basic characteristics of our low-frequency resonator and the results of experimental work and computer simulations will be reported.
A dynamic, psychophysical model of adaptation in localization experiments
Authors: Shinn-Cunningham Barbara
Published: October 2005

Previous psychophysical models have described how resolution depends upon the range of physical stimuli employed in a given experiment; however, these models generally assume that subject performance is stable over time. The current work extends the context-coding model of Durlach and Braida [ 372–383 (1969); Braida and Durlach, 483–502 (1970)] to account for changes in subject performance that occur when feedback is used to retrain subjects during the course of an experimental session. In the current model, observed changes in performance are accounted for by assuming a single exponential adaptation process. This process, which describes the adaptive state of the subject, determines the decision criteria and context (effective stimulus range) used in the model at a given point in time. From the dynamic decision criteria and effective range, and knowledge of the underlying sensitivity to localization cues, the model predicts mean response, bias, and resolution. The model predictions are in good agreement with results from a relatively large body of experiments, including experiments in which the number and range of stimuli were varied.
Model simulations of masked thresholds for tones in dichotic noise maskers
Authors: Holube Inga , Colburn H. Steven , van de Par Steven , Kohlrausch Armin
Published: October 2005

The study of masked thresholds in dichotic noise maskers is important for understanding the processing in binaural hearing. To simulate these thresholds a psychoacoustically motivated perception model was used [T. Dau etal. (1995). ‘‘A quantitative model of the ‘‘effective’’ signal processing in the auditory system: I. Model structure,’’ submitted to J. Acoust. Soc. Am.]. This model, which has been successfully applied to several monaural psychoacoustical experiments, was extended by an additional binaural processing unit. It consists of a filterbank, half-wave rectifier, low-pass filter, and adaptation loops, which model the temporal processing. The binaural processing unit detects the interaural correlation and makes decisions based on the difference between the signals from both ears. Masked thresholds in the NoSπ and NπSo configurations, obtained as a function of noise masker frequency and bandwidth, were simulated and compared to new experimental measurements. The dependence on interaural delay and interaural decorrelation of the noise masker was also modeled and compared to data in the literature. In general, model simulations agree well with the main features seen in the measurements. [Work supported by DFG (Ho 1627/1-1) and by NIDCD (Grant DC00100).]
Lateralization of high-frequency FM tones and frequency sweeps
Authors: Saberi Kourosh
Published: October 2005

Lateralization thresholds were measured in three experiments. In experiment I, thresholds measured for sinusoidal FM with carriers of 3 or 4 kHz and modulation rates from 50 to 800 Hz were comparable to those measured for sinusoidal AM stimuli. Lowest thresholds (at 71% correct) were about 100 μs, obtained at modulation rates of 300–350 Hz. In experiment II, a 300-ms tone was linearly swept in frequency from 2 to 5 kHz. The slope and intercept of the time-frequency function were randomized by 10% on each observation. Lateralization thresholds were about 50 μs. Unequal time-frequency slopes at the two ears produced a sense of motion. In experiment III, a sinusoidal FM was presented to one ear and a sinusoidal AM to the other ear. When the FM and AM had the same modulation rate (250 Hz), a single image was perceived. Observers were sensitive to the interaural modulation phase with near perfect discrimination of homophasic from antiphasic conditions. Results are discussed in terms of an FM-to-AM transduction mechanism. [Work supported by NIH and AFOSR.]
The segregation of SAM 4-kHz targets from SAM 2-kHz distractors on the basis of interaural envelope delay
Authors: Dye R. H.
Published: October 2005

A stimulus-classification paradigm was used to examine the extent to which judgments of the laterality of 4-kHz targets, sinusoidally amplitude modulated at 200 Hz, were influenced by 2-kHz distractors that were modulated at rates ranging from 50 to 400 Hz. On each trial, the target was presented with one of ten envelope delays (ranging from −250 to +250 μs in 50-μs steps), as was the distractor. Each test interval was preceded by a diotic presentation of the target alone. The duration of the signals was 200 ms. During a block of 100 trials, each combination of target-distractor delay was presented once. The relative salience of the envelope delays carried by the target and the distractor was assessed by the slope of the best linear boundary between left and right responses. Two listeners gave increasing weight to the target as the difference between the target and distractor modulation frequencies increased, but weighed that target and distractor equally when both were modulated at 200 Hz. Two other listeners gave increasing weight to the 2-kHz distractor as modulation frequency increased, as though its relative salience increased with ‘‘number of looks.’’ These data will be compared to measures of binaural interference that have been obtained for similar stimuli. [Work supported by NIH.]
Precision of sound localization measured by a reaching task
Authors: Ashmead Daniel H. , Yang Xuefeng , Wall Robert , Ebinger Kiara
Published: October 2005

This study validates a reaching measure of sound localization for subsequent application to children. Seven adults reached for broadband sound sources while hand position was measured to within 2 mm. Sounds came from 18 regions in frontal reaching space, with the loudspeaker moved away just after stimulus offset. In the ‘‘visual’’ condition subjects watched until the sound ended, then closed their eyes and reached. In the ‘‘auditory’’ condition subjects were blindfolded. Precision of sound localization was estimated by comparing variability in the visual and auditory conditions: s=√s2A−s2V. Estimates were computed for horizontal angle, vertical angle, and distance for each target location. Results agreed reasonably well with conventional measures. For targets straight ahead at ear level, horizontal s=2.6°, vertical s=5.0°, and distance s=9.5%. Systematic variations occurred across target locations. This reaching task is a rapid, naturalistic way of measuring three-dimensional sound localization. [Work supported by DOE and NIH.]
Virtual auditory reality reduced to the bare essentials
Authors: Hartmann William Morris , Wittenberg Andrew
Published: October 2005

Successful imaging of real sound sources by headphones can be done by measuring free-field head-related transfer functions (HRTF) using small microphones in the ear canals and then inverse filtering by the headphone response. A simpler alternative to this standard procedure is described where a listener, with small microphones in the ear canals, wears open-air headphones throughout the experiment. A synthesized vowel is played, first from a loudspeaker and then from the headphones. The headphone signal is adjusted so that the amplitudes and phases of the harmonics measured with the small microphones are the same as those found when the loudspeaker is sounding. The technique is successful in that listeners cannot distinguish between real and virtual sources. It lacks the flexibility of the HRTF technique, but it allows an experimenter to study the most interesting psychoacoustical questions about sound localization and externalization using an experimental technique that is simpler and probably more reliable. [Work supported by the NIDCD and by the NSF Research Participation for Undergraduates Program.]
Modeling distortion product otoacoustic emission fine structure in humans
Authors: Talmadge Carrick L. , Tubis Arnold , Piskorski Pawal , Long Glenis R.
Published: October 2005

The presence of fine structure in distortion product otoacoustic emissions (DPOAEs) in humans and other species provides important clues concerning the underlying mechanisms which give rise to this structure. Recent experimental findings of our group indicate that (i) synchronous evoked emissions, hearing threshold microstructure, and the fine structure of DPOAES in each ear appear to correspond, (ii) the fine structure of higher-order DPOAEs, i.e., f1−n(F2−f1), n≳2 depends on the DPOAE frequency, and (iii) DPOAEs with n<−1 do not have well-formed fine structure. These data will be used to contrast and compare two distinct models of DPOAE generation, one in which the fine structure arises from the interactions in the strong overlap region of the f1 and f2 activity patterns (near the f2 tonotopic place), and one in which the fine structure arises from reflections of the distortion product near its tonotopic location. The data strongly favor the later model.
Fine structure of 2f1−f2 acoustic distortion product: Effect of L1/L2 ratio
Authors: He Ning-ji , Schmiedt Richard A.
Published: October 2005

The fine structure of the 2f1−f2 acoustic distortion product (ADP) was measured in a group of normal-hearing subjects with different combinations of primary levels (L1 and L2). The frequency ratio (f2/f1,f2≳f1) was 1.2, and the f2 frequency was swept from 1781 to 2300 Hz in 1/32 octave steps. In condition 1, L1 was fixed at 50 dB SPL while L2 varied from 30 to 75 dB SPL in 5-dB steps. In condition 2, L2 was fixed at 50 dB SPL and L1 was varied as in condition 1. For a fixed L1, an upward frequency shift was evident in the ADP fine structure as the L2 level increased, whereas for fixed L2, a downward frequency shift in the ADP pattern was observable with an increasing L1. These results support a vector sum computer model for the ADP fine structure [Sun etal., 2166–2174, 2175–2183 (1994)], suggesting that ADP fine structure is largely generated in the overlap area of the traveling waves for the primary tones, and the effects of reemissions from the 2f1−f2 area are minimal. A large variance was observed in the best L1/L2 ratio, ranging from −7.5 to 20 dB both across and within subjects. [Work supported by NIDCD.]
Spontaneous and click-evoked otoacoustic emissions of the frog inner ear: Spectral characteristics and temperature dependence
Authors: Maat Bert , van Dijk Pim , Wit Hero P.
Published: October 2005

Spontaneous otoacoustic emission (SOAE) and click-evoked otoacoustic emission (CEOAE) measurements were performed in frogs (Ranaesculenta). The SOAE and CEOAE measurements followed each other repeatedly, while the frog’s body temperature was changed at a rate of approximately 0.1 °C/min. In some sessions, only SOAE measurements were performed. The SOAE and CEOAE spectra were closely related: The spectra of CEOAE contained the same peaks as those observed in the related SOAE spectrum. It seems that click evoked emissions in the frog are synchronized spontaneous emissions. The click-evoked responses show a nonlinear compressive amplitude growth with the stimulus intensity. As function of temperature, various emission modes, and complex amplitude patterns were observed for both types of emissions.
Enhanced cochlear responses after sound exposure
Authors: Szymko Yvonne M. , Zwislocki Jozef J.
Published: October 2005

Hensen’s cell alternating potentials were recorded in the gerbil cochlea by means of the approach developed previously in this laboratory. An intensity series of magnitude and phase transfer functions (TFs) and cochlear microphonic (CM) TFs from 125 Hz to 16 kHz were obtained at 40–90 dB sound pressure level (SPL) by means of frequency sweeps. Subsequently, the same frequency sweeps at either 80, 90, or 100 dB SPL were delivered to the ear for 10–40 min. CM, Hensen’s cell TFs, and EP were monitored periodically post-exposure. Hensen’s cell responses showed enhancement within 40–50 min post-exposure and a phase lead. There was no correlation between changes in peak response and changes in receptor potential or EP. The response enhancement and its associated phase lead is explained with the help of Zwislocki’s cochlear model [MechanicsandBiophysicsofHearing, edited by P. Dallos (Springer-Verlag, Berlin, 1990)]. Since Hensen’s cells cannot generate receptor potentials by themselves, and their AC potentials have been shown to be directly proportional to those of OHCs, the measured enhancement appears to reflect enhanced OHC responses. [Work supported by NIDCD.]
Representation of sinusoid ‘‘ramps’’ and ‘‘damps’’ in auditory-nerve fibers of the goldfish
Authors: Fay R. , Chronopoulos M. , Patterson Roy
Published: October 2005

Earlier, behavioral data was presented showing that goldfish perceive repeated, asymmetrically shaped 400-Hz tone bursts (ramps and damps) qualitatively as humans do: Ramps are more tonelike than damps [R. Fay and R. Patterson, 2941 (A) (1994)]. Ramps have slow rise and relatively fast fall envelopes. Damps are ramps played backward. Single auditory-nerve fibers were recorded in response to the same ramp and damp stimuli used in the behavioral studies. Spike times were recorded for two presentations of six, 3-s stimuli: Ramps with 25-, 35-, and 45-ms rise times and 5-ms fall times, and these stimuli played backward (damps), presented at several levels. Tuning was described using REVCOR analysis and by spike count functions of frequency at several levels. Responsiveness was defined using the coefficient of synchronization (R) over the carrier period, the number of spikes evoked (N), and the statistic Z where Z=R2N. For most fibers, R, N, and Z were greater for ramps than for the corresponding damps. This neural behavior is quantitatively similar to the behavioral results. The differential perception of ramps and damps is represented within individual primary afferents. The origins of these physiological differences will be discussed. [Work supported by the NIDCD.]
Polynomial correlation used to estimate the degree of nonlinearity of the frog inner ear system
Authors: van Dijk Pim
Published: October 2005

The nerve fiber response to Gaussian noise was measured in the American bullfrog (RanaCatesbeiana). By cross correlating the stimulus and the response, Wiener kernels of the frog inner ear system were obtained. The first- and second-order Wiener kernels were fully calculated, while for the 3rd- to 10th-order kernels only the diagonals (also known as polynomial correlation functions) were computed. The data for fibers above 500 Hz could be described by a BPNL sandwich model. A new least-squares method was used to determine both filter functions in the model from the Wiener kernels. Preliminary analysis showed that response components could be found in kernels up to the order of 5. This suggests that the degree of the nonlinearity of the frog inner ear is at most 5.
Binaural lateralization and discrimination in MS and CVA patients
Authors: Aharonson Vered , Furst Miriam , Korczyn Amos D.
Published: October 2005

Most previous studies on MS patients’ binaural performance reported similar performance according to intensity and time cues, or abnormality only for interaural time differences. In this study, combined lateralization and discrimination tests on both MS and CVA patients detected other phenomena. Lateralization and discrimination ability were measured during the same session for each patient, with clicks, high, and low narrow-band noises. Lateralization tests arbitrarily presented interaural time and intensity changes in 9 levels scale across the head. Adaptive 2I2AFC procedure determined jnd’s. Ten CVA and 5 MS patients performed abnormally in some of the tests, and can be crudely divided into three groups: The first group performed normally in response to clicks and low frequencies, and failed only in high frequencies stimuli, in both lateralization and jnd. The second group performed abnormally in both tests and for all stimuli. The third group had normal jnd’s for all stimuli. However, for some stimuli, those patients failed in the lateralization tasks, only in one of the interaural changes—either time or intensity. These results indicate that criteria used for jnd tasks are not applicable in lateralization and that time and level differences are estimated independently along the auditory pathways.
An asymptotic analysis of the added damping effect of a distribution of fuzzy attachments with steady state excitation
Authors: Russell Daniel A. , Sparrow Victor W.
Published: October 2005

In the current state of fuzzy structure theory, it is recognized that the primary effects of a fuzzy substructure are a frequency-dependent effect added damping and a frequency-dependent effective added mass. In this paper the fuzzy substructure is modeled, in accordance with current practice, as a system of independent 1-DOF oscillators whose masses are distributed with respect to natural frequency. The exact form of the distribution is shown to be relatively unimportant as long as it is smooth and continuous. The effects of the system of attachments, in response to steady-state excitation of the master structure to which they are attached, are obtained through an analysis of the input mechanical impedance. The real part of this impedance represents the effective added damping. Two asymptotic limits are investigated. In the first limit, the number of attachments becomes very large (N→∞), and the impedance sum approaches an asymptotic integral. In the second limit, the damping ratio of the attachments becomes very small (ζ→0), and the asymptotic integral reduces to a simple algebraic expression. Comparison of the impedance sum and the asymptotic expression, in light of the product Nζ, suggests that the simple asymptotic expression is valid for steady-state excitation, as long as ζ≲0.01, and the product Nζ≳2. [Work supported by ONR.]
From a ‘‘sound observatory’’ to a ‘‘sound city’’ masterplan
Authors: Bosshard Andres
Published: October 2005

‘‘Sound sculptures,’’ ‘‘sound installations,’’ and ‘‘telematic media network links’’ can be considered as observatories as soon as they look for resonances, reverberations, and other spatial qualities of the actual site and if they are composed to look for possible interaction with the ongoing stream of sounds of the real environment. Time structures of human perception and behavior help to find a basis for ‘‘sound perspectives’’ and ‘‘territorial sound fields’’ and ‘‘tidal sound spheres,’’ which can be stimulated, simulated, and modified by advanced electroacoustic networks. The ‘‘Klangturm’’ inSt. Pölten, Austria and the ‘‘AdiSrvya’’ soundgalleryinNewDelhi, India are two house-sized musical instruments under construction; both will be opened in fall 1996. Field research of the indigenous ‘‘Santal’’ population in WestBengal, India, shows very sophisticated and complex ‘‘natural’’ sound architectures for entire towns. The acoustic tuning of the ‘‘Santal’’ villages is a basic model for an acoustic and electronic study to prepare a ‘‘sound city’’ masterplan.
Understanding individual differences in response to environmental noise: An essential step in determining health risk
Authors: Staples Susan L.
Published: October 2005

Evidence is reviewed indicating that psychological and social factors render people more or less susceptible to stress-related health effects from noise. Factors such as appraised meaning, personality traits, and perceived control are considered in terms of their relationship to physiological variables and in terms of the mechanisms underlying adverse effects. The limitations of epidemiological and dose-response methods for determining and understanding health effects are discussed. Modifications in these approaches are suggested to clarify the role of intervening psychological factors, to understand the physiological mechanisms implicated, and to delineate public health risks.
Characterization of the sound quality of vacuum cleaners
Authors: Frédérique Guyot , Christine Piron , Michèle Castellengo , Benoit Fabre
Published: October 2005

The intensity level is not the only parameter responsible for noise disturbance. The basis of the perceived world is the categorization process which permits recognition and qualitative appreciation. This study is based on Rosch’s categorization concept. [E. Rosch, Cognitive Psychol. 7, 573,605 (1975)]. In order to estimate the pleasantness features of a set of 23 vacuum cleaner noises and to characterize the prototype of ‘‘the pleasant aspirator noise,’’ a free categorization method was adopted. The subjects are asked to group, in a free number of categories, the noises according to the comfort sensation they evoke. By analyzing the results the role played by the typicality and the gradation phenomenon in the structures relative to these noises quality can be estimated. Finally, the organization of these categories is analyzed by estimating on one hand the relative importance of parameters coming exclusively from noises physical content, and on another hand, the significance given to the stimuli by each subject.
Resonant photoacoustic measurements of optical absorption in solids
Authors: Lin Wei-li
Published: October 2005

For glasses and crystals the optical absorption near the infrared is much lower than that in the visible. While the previous noncontact resonant photoacoustic (PA) measurement is several orders of magnitude more sensitive than that of conventional PA in the visible for a piezoelectric sample, it was further developed to apply to nonpiezoelectric materials in the near infrared. The noncontact interdigital capacitor transducers were replaced by lithium niobate disks and PVDF films. By supporting the sample between transducers only at its corners, the quality factor has been improved and is comparable to that of a noncontact system, while the separate supports and the precise positioning of the sample are avoided. An optical absorption coefficient on the order of 10−7 cm−1 at 1.06 μm has been measured with a 20 signal-to-noise ratio. Recent results on single crystals of quartz and calcium fluoride, using different piezoelectric transducers, will be discussed. [Work supported by NSF Grant No. DMR-9000549 and by the Office of Naval Research.]
Resonant photoacoustic measurements of optical absorption in gases
Authors: Wright Wayne M.
Published: October 2005

The use of the photoacoustic (or optoacoustic) effect in spectroscopy gives a valuable tool for examining weak optical absorption features of gases. It is inherently a more sensitive detector of light absorption than other techniques, which attempt to measure a small attenuation of an intense beam. Instead, absorption by the gas of periodically interrupted optical energy, from either a tunable or fixed-wavelength laser, results in the production of sound at the same frequency. Device optimization has followed a number of different paths. The particular approach emphasized here uses a cylindrical gas cell, driven at its 1st azimuthal acoustic resonance, to increase signal amplitude. Experimental concerns include enhancement of the signal relative to acoustic and electronic noise. Examples are presented of what can be learned through application of this technique. These include results for the absorption of visible light by nitrogen dioxide and aerosol particles, as well as from a study of the profiles of oxygen absorption lines in the infrared region.
Across session temporal stability of the lip–jaw complex in bilabial closure
Authors: Alfonso Peter J.
Published: October 2005

Movements of the tongue, lips, and jaw were transduced by electromagnetic midsagittal articulography. A single session included 20 repetitions of /pap/, /tat/, and /sas/ imbedded in a carrier phrase at normal, slow, and fast speech rates. Seven talkers completed three sessions at 1 week intervals. Reported here are across session comparisons of temporal ordering and relative timing of the movement of the lips and jaw for labial closure at normal rates. The predominant sequence patterns are those in which either upper or lower lip movement occurs first and jaw movement occurs last. Across-subject comparisons show that either lip lead sequence is equally likely to occur. Within-subject across-session comparisons show no clear preference for either lip lead sequence for some subjects, and reversals in dominate lip lead sequences for other subjects. Across-session stability of temporal order is related to interarticulator relative time: Subjects who demonstrate tight coupling of the upper and lower lips have a higher probability of producing both lip-lead sequences, whereas subjects who demonstrate longer interarticulator relative timing produce consistent sequence patterns across sessions. Temporal measures representing the central tendencies of the complete set of session closure gestures are most stable across sessions. [Work supported by NIH DC-00121 to Haskins Laboratories and University of Illinois research grant.]
Three-dimensional visualization of human jaw motion in speech
Authors: Guiard-Martigny Thierry , Ostry David J.
Published: October 2005

With the development of precise 3-D motion measurement systems and powerful computers for 3-D graphical visualization, it is possible to record and fully reconstruct jaw motions. In this paper, a video demonstration of a visualization system for displaying 3-D jaw movements in speech will be presented. Kinematic records of jaw motion and the corresponding speech signal are recorded using an optoelectronic measurement system. The three orientation angles and three positions which describe the motion of the jaw as a rigid skeletal structure and derived from the empirical measurements. These six kinematic variables, which account fully for jaw motion kinematics, are used to drive a real-time 3-D animation of a skeletal jaw and upper skull. The visualization software enables the user to view jaw motion from any orientation and to change viewpoint in the course of an utterance. Selected portions of an utterance may be re-played and the speed of the visual display may be varied. The user may also display, along with the audio track, individual kinematic degrees of freedom or several degrees of freedom in combination. The system is now being integrated into a 3-D audio-visual articulatory speech synthesizer. [Work supported by NIH Grant DC-00594.]
Functional data analyses of lip motion
Authors: Ramsay J. O. , Munhall K. G. , Gracco V. L. , Ostry D. J.
Published: October 2005

The vocal tract’s motion during speech is a complex patterning of the movement of many different articulators according to many different time functions. Central issues are the accurate description of the shape of the vocal tract and determining how each articulator contributes to this shape. Techniques are described that provide useful tools for describing multivariate functional data such as the measurement of speech movements. The choice of data analysis procedures has been motivated by the need to partition the articulator movement in various ways: movement start- and end-effects separated from shape effects, effects due to different syllables, and the splitting of within-sensor variation from between-sensor overall variation. The techniques of functional data analysis seem admirably suited to the analyses of phenomena such as these. Familiar multivariate procedures such as analysis of variance and principal components analysis have their functional counterparts, and these reveal in a way more suited to the data the important sources of variation in lip motion. Finally, it is found that the analyses of acceleration were especially revealing in considering the character of possible control mechanisms. [Work supported by NIH Grant DC-00594.]
A computational model using formant space planning of articulator movements for vowel production
Authors: Guenther Frank H. , Johnson Dave
Published: October 2005

It is often hypothesized that articulator movements are planned within a coordinate frame whose variables correspond to key vocal tract constrictions [e.g., E. Saltzman and K. G. Munhall, Ecol. Psych. 1, 333–382 (1989)]. However, recent evidence suggests that speakers may utilize a more acoustic-like space for planning vowel movements [J. Perkell etal., 2948–2961 (1993)]. Previous work has verified the capacity of a computational speech production model called DIVA to explain a wide range of experimental data using a constriction planning space. The current work extends the model to allow formant space planning of vowel movements. The model learns target regions for F1 and F2 for each vowel during a babbling cycle. A mapping between desired formant changes and articulator movements that achieve these changes is also learned. After babbling, the model successfully reaches all vowel targets from any initial vocal tract configuration, even in the presence of constraints such as a blocked jaw, and the resulting synthesized vowels are easily recognizable. Although vowel targets specify only formant ranges with no articulatory information, articulator configurations used by the model to produce vowels are similar to human configurations. [Work supported by AFOSR F49620-92-J-0499.]
Sound scattering by a single air bubble and by a cloud of air bubbles near the sea surface
Authors: Gaunaurd G. C. , Huang H.
Published: October 2005

Sound scattering by an air bubble in a boundless fluid is an old classical problem [i.e., R. Y. Nishi, Acustica 33, 65–74 (1975)]. If the air bubble is near, and strongly interacting with the surface of a liquid half-space, then the scattering cross section (SCS) of the bubble is quite different from its value far away from the boundary. The exact solution for this scattering problem is given which is valid for any incidence direction of the (plane) sound waves, and for any bubble depth, obtained by the method of images. This benchmark solution is found by means of the addition theorems for the spherical wave functions. The resulting SCS contains contributions from the interface, the bubble, and from its image, and it is expressible in terms of coupling coefficients containing products of Wigner 3-j symbols. The formulation is illustrated with many computed plots and it is finally extended to the case of a round, low-concentration cloud of equal size bubbles, just beneath the sea surface. This generalization is possible by replacing the individual bubble properties by those of an ‘‘effective medium’’ describing the bubble cloud just as we found them earlier [i.e., 541–554 (1989)]. [Work supported by NSWC’s IR Program.]
Low-frequency sea surface scatter and horizontal bistatic angle dependence utilizing short coherent pulses
Authors: Chester John B. , Christian Raymond J.
Published: October 2005

A comprehensive low-frequency (<1000-Hz) low grazing angle (<30°) sea surface acoustic scatter experiment was conducted during February/March 1992 in the Gulf of Alaska. During data collection, wind speeds ranged from 3–17.5 m/s and sea states from 2–6. cw waveforms less than 500 ms in length at 250, 380, 900, and 935 Hz were transmitted by three collinear vertical towed source arrays. Surface scattered energy was received in 17 cosine-spaced beams by a horizontal source-ship-towed line array. This experimental geometry allowed measurement of surface scattering strength as a function of mean grazing angle, frequency, and horizontal bistatic angle. Analysis of these measurements in terms of these dependencies is presented along with comparison to current surface scattering strength model predictions.
On the correlation of ambient noise levels and other parameters with backscattering strengths observed during the acoustic surface reverberation experiment (ASREX)
Authors: Williams Neil J. , Nguyen Hien B. , Monjo Charles L. , Deferrari Harry A.
Published: October 2005

Preliminary results from a surface reverberation experiment performed in the North Atlantic during the winter of 1993–94 indicate that ambient noise levels may prove to be a convenient and accurate indicator of surface backscattering strengths. Backscattered energy from coherent sources ranging in frequency from 100 to 800 Hz were observed over a three month period. Both the backscattered returns and ambient noise were recorded by a 64-element vertical array while simultaneous measurements were made of a variety of environmental parameters, including: wind speed and direction, wave spectra, air and sea temperature and current fields, bubble plumes, etc., by investigators from SIO, WHOI, and IOS/BC, Canada. The nature of the data set lends itself to time series analysis techniques. Multivariate analysis of backscattering strengths as a function of ambient noise and various other environmental parameters will be presented and discussed. [Work supported by ONR.]
Backscattering from the ocean surface: Observations from the acoustic surface reverberation experiment (ASREX) December ’93–March ’94
Authors: Monjo Charles L. , Nguyen Hien B. , Williams Neil J. , Deferrari Harry A.
Published: October 2005

Preliminary results from a surface reverberation experiment that was performed in the North Atlantic Ocean during the winter of 1993–94 will be presented. Observations of acoustic backscatter from the ocean surface were made from a moored vertical array at frequencies ranging from 100 to 800 Hz at 12-min intervals during a 3-month period. Simultaneous measurements were made by other investigators (from SIO, WHOI, and IOS-BC, Canada) of a variety of environmental parameters, including wind speed and direction, wave spectra, air and sea temperature and current fields, and the presence and nature of bubble clouds were observed with devices that detected anomalies in the near surface sound speed and using high-frequency side scan sonars. Variation of backscattering strengths with changes in the environment will be presented and comparisons with results from other recent observations [P. M. Ogden and F. T. Erskine, 746–761 (1994)] will be made. [Work supported by ONR.]
Numerical studies of the small slope approximation for rough surface scattering using a Pierson–Moskowitz spectrum
Authors: Broschat Shira L. , Thorsos Eric I.
Published: October 2005

The small slope approximation (SSA), introduced by Voronovich in the mid-1980s [A. G. Voronovich, Sov. Phys. JETP 62, 65–70 (1985)], has been shown to be a very promising method for modeling wave scattering from rough surfaces. The theory gives a systematic series which is manifestly reciprocal at each order, reduction to perturbation theory is intrinsic to the formulation, and reduction to the Kirchoff approximation occurs under the appropriate conditions when the first two terms of the series are retained [E. I. Thorsos and S. L. Broschat, 2082–2093 (1995)]. In this paper numerical results are presented for scattering strengths for one-dimensional, pressure release surfaces satisfying a Pierson–Moskowitz power law spectrum. Results are given for incident angles varying from grazing to normal over the full angular range of scattering. Comparisons with Monte Carlo integral equation results show that the SSA is extremely accurate over a large range of scattering angles including low forward grazing angles.
A physically motivated model for sea surface backscattering in the low to moderate frequency regime
Authors: Keiffer Richard S. , Novarini Jorge C.
Published: October 2005

Based on the refractive properties of the bubble clouds and the background (uniform) bubble layer and resonant scattering at the sea surface, a simple model is presented to estimate the backscattering from the ocean surface for frequencies below 1 kHz. This new model yields a dependence on the three fundamental variables, wind speed, grazing angle, and frequency, that is in general agreement with trends observed in reverberation-derived backscattering data. [Work supported by ONR.]
Modeling sea surface scattering with a finite difference method
Authors: Stephen R. A.
Published: October 2005

A numerical scattering chamber based on the finite difference solution of the two-way elastic wave equation is applied to the sea surface scattering problem. For a reference model, the method gives excellent agreement in amplitude and phase with the solution obtained by an integral equation method [Eric Thorsos, personal communications]. This problem demonstrates a number of issues in numerical modeling of wave scattering: (1) the spreading of Gaussian beams (even in homogeneous media) has implications for (i) defining the surface footprint or scattering area and (ii) for generating approximate Gaussian beams by tapered vertical arrays; (b) the treatment of a rough, free, fluid surface in a Cartesian grid scheme; (c) solving continuous wave (cw) problems in the time domain; (d) diffraction of waves from roughness elements with scale lengths on the order of a wavelength; (e) multiple scattering effects between roughness elements; and (f) omni-directional scattering including low angle backscatter. [Work supported by Office of Naval Research.]
Macromolecular absorption: The roles of molecular size, structure, solvation, and solute interactions
Authors: Kremkau Frederick W.
Published: October 2005

Attenuation of ultrasound in tissues is due primarily to macromolecular absorption. Biomacromolecules have higher absorptions than the constituent molecules of which they are made [F. W. Kremkau and W. Cowgill, 1330–1335 (1984)]. Absorption dependencies on structure [F. W Kremkau and R. W Cowgill, 1217–1221 (1985)] and solvation [F. W. Kremkau, 2410–2415 (1988)] are probably interrelated. Underlying absorption processes are enhanced or new processes are added under conditions of high concentration, aggregation, or cross linking [F. W. Kremkau etal., 1448–1451 (1973)].
Major accomplishments in development of acoustic instrumentation for biomolecular studies
Authors: Sarvazyan Armen P.
Published: October 2005

A great potential of acoustics in the thermodynamic characterization of biomolecular systems, studies of conformational transitions and hydration of proteins and nucleic acids and drug–biopolimer interactions has been revealed in the last decade mainly due to advances in the instrumentation for ultrasonic measurements in small volumes of liquids. The methods and devices reviewed in this talk are based upon the fixed path interferometer method, also known as a ‘‘resonator method.’’ It is the only method which can provide measurements of ultrasound velocity and attenuation in the sample volume of the order of 10–100 microliters with sufficient precision. The requirement of small sample volume is a major precondition for applicability of the method to the most of the problems in biomolecular studies. Different types of resonators will be described in detail including a new type of micro-volume cylindrical standing wave resonators with a chamber volume of about 3 microliters. The electronic circuits for high precision measurement using acoustical resonators are usually based on the phase-locked loop which provides the oscillation in the system at the chosen resonance. Fields of applications and prospects of future development of instrumentation will be reviewed. a)Permanent address: Inst. of Theoret. and Exp. Biophys., Russian Acad. of Sci.
Passive acoustic fetal heart rate monitoring with a parallel redundance approach
Authors: Zahorian Stephen A. , Zhou Zongyao , Brewton Charles
Published: October 2005

Acoustic methods for monitoring fetal heart rate are potentially advantageous over ultrasound methods, since, eventually, long-term low-cost monitoring would be possible for high risk mothers, with no concern for fetal damage due to the monitoring device. However, sensor design and signal processing requirements are very demanding in this low signal-to-noise ratio environment. The present approach is patterned after that by Zuckewar etal. [IEEE Trans. Biomed. Eng. 40-9, 963–969 (1993)] using a third-generation sensor belt, and enhanced signal processing strategies. In the new method, each of seven differential sensor signals is scanned continuously and processed in parallel with a PC-hosted DSP system. The processing of each channel includes FIR bandpass filtering, Teager energy calculations, autocorrelation, and ‘‘intelligent’’ peak picking. ‘‘Candidates’’ for fetal heart rate are computed every 0.5 s and evaluated with a figure of merit which incorporates both measures of peak quality and continuity constraints. Clinical testing indicates that the new method of signal processing is able to reliably track fetal heart rate for most fetuses with a gestation age of at least 30 weeks. The multiple-channel approach results in a significant improvement over a single-channel method.
Sound in context: Acoustic communication and soundscape research at Simon Fraser University
Authors: Truax Barry
Published: October 2005

Research activities at Simon Fraser University over the past 25 years that bridge environmental acoustics and music are summarized, including soundscape studies, acoustic communication, soundscape composition, and the granulation of sampled sound. Gaps in traditional disciplinary approaches in dealing with environmental sound are identified, and an acoustic communicational model is proposed as an interdisciplinary alternative. Sound examples drawn from the author’s compositions, and the work of R. Murray Schafer, Hildegard Westerkamp and the World Soundscape Project will be included.
Acoustic hygiene: The importance of protecting ears, lungs, and other organs from acoustic insult
Authors: Zagorski Michael A.
Published: October 2005

While the importance of controlling noise is widely accepted, the major concern has been with annoyance. The public is not generally aware of the potential severity of even a few noise exposures. Most people do not realize the extent to which they use acoustic cues in daily life, nor the extent of debilitation associated with recruitment or loss of binaural abilities. Similarly, most do not realize that a flyover producing short-term noise measurement of a little over 130 dBA can have the same effect on the lung as 2 lbs. of TNT exploding a meter or two from the body. It is argued here that to promote acoustic hygiene the public must be made aware that hearing loss is a complex and serious handicap that is not generally corrected with hearing aids. To do this emphasis must be placed on the importance of acoustic cues in everyday activities even without speech, the handicap produced by not being able to localize, the difficulty of hearing in crowds, and the annoyances of hearing aids. A number of methods for illustrating the effects of hearing loss and the value of normal hearing will be presented and demonstrated. [Work partially supported by the National Research Council of Canada.]
Dispersion of longitudinal waves in periodic septate liquid–elastic waveguides
Authors: Sheiba L.
Published: October 2005

The propagation of longitudinal waves in a composite liquid–elastic waveguide is analyzed. The waveguide is a periodic structure consisting of alternating liquid–elastic cylinders joined by rigid septa. The elastic material (Lamé constants: μ≪λ, Poisson relation σ→0.5) and the liquid material (μ=0, σ=0.5) are assumed to have low compressibility, and the septa are rigid and weightless. Consequently, the boundary between the cylinder and the septum’s radial displacement is absent, and the axial displacements are planar. The admittance matrix Y of the unit cylinder is initially constructed within a framework of the hypothesis of plane cross sections, neglecting strains induced by hydrostatic stress. Hydrostatic stress waves are approximately included by adding to the unit cylinder admittance matrix correction ΔY associated with the strains of hydrostatic stress in the cylinder. The transfer matrix of the liquid–elastic waveguide and its elements, expressed through the waveguide sections elastic parameters, have been obtained. It has been shown that damping in a waveguide with a periodic structure is much greater in comparison with a regular waveguide, even when the latter is made with a high-loss material.