bluuebunny/crossref_metadata_2025 huggingface dataset:
Integral equation approach for analyzing acoustic interactions with wrinkled flame fronts
Authors: Wu Lei , Lieuwen Tim
Published: October 2013

Flame-acoustic wave interactions play an important role in the characteristic unsteadiness of turbulent combustion processes. They arise because acoustic waves incident from other parts of the flame or from external sources impinge upon the flame and are scattered because of the significant change in sound speed and density at the flame front. The characteristics of the scattered waves are complex, due to the fact that they are interacting with a dynamic flame surface that is convoluted over a broad range of length and time scales. Over a wide range of frequencies (e.g., up to about 20 kHz), such turbulent flames may be treated as nonpassive (i.e., the flame acts as a source of acoustic energy) temperature discontinuities. We describe here an integral equation approach, similar to the development of the Ffowcs Williams–Hawking (FWH) equation, that is suitable for analysis of acoustic-flame interactions. This FWH equation is generalized for the case of interest where the surface is penetrable, not passive, and whose area varies in time. The integration surface consists of the time varying flame front that divides two homogeneous regions. The wave motions in these two regions are coupled by appropriate mass, momentum, and energy conservation conditions.
Decentralized structural acoustic control of a launch vehicle payload fairing
Authors: Frampton Kenneth D.
Published: October 2013

The development of smart structures and active noise and vibration control technologies promised to revolutionize the design, construction and, most importantly, the performance of many complex engineering. However, the early promise of these technologies has not been realized in large-scale systems primarily because of the excessive complexity, cost, and weight associated with centralized control systems. Now, recent developments in MEMS sensors and actuators, along with networked embedded processor technology, have opened new research avenues in decentralized controls. Such a control system consists of numerous nodes, possessing limited computational capability, sensors, and actuators. Each of these nodes is also capable of communicating with other nodes via a wired or wireless network. This results in a dramatic shift in the control system paradigm from that of a single, centralized computer to that of numerous decentralized, networked processors. This work describes the application of such a control system to the reduction of structural acoustic radiation in a launch vehicle payload fairing. A JAVA-based simulation tool is employed to simulate the interactions of the physical system with the networked embedded controllers. Results will indicate the potential for such a control system as well as the limitations imposed by the networked embedded processor hardware.
The role of language experience in word segmentation: A comparison of English, French, and bilingual infants
Authors: Polka Linda , Sundara Megha , Blue Stephanie
Published: October 2013

English-learning and French-learning 7.5-month-old infants were tested using the headturn preference procedure on their ability to segment bisyllabic words in both English and French. In the English condition infants were familiarized with trochaic bisyllables, the predominant stress pattern found in English, and then presented English passages with and without the familiarized words. In the French condition, infants were familiarized with iambic bisyllables, the characteristic word stress pattern found in French, and were then presented French passages with and without the familiarized words. Findings indicate that by 7.5 months of age, infants’ learning either a syllable-timed (French) or a stressed-timed language (English) can segment bisyllabic words with the predominant stress pattern of their native language. However, French infants fail to segment English trochaic words from English passages; data on English infants’ segmentation in the French condition are forthcoming. If both groups fail to segment in a rhythmically different non-native language, it will confirm that word segmentation abilities of 7.5-month-old infants are influenced by the prosodic structure of the native language. Preliminary results obtained from infants who are regularly exposed to both languages will also be reported.
Recent advances in synthetic aperture sonar for proud and buried object detection
Authors: Pinto M. , Bellettini A. , Hollett R. , Wang L.
Published: October 2013

This paper presents a comprehensive research program into synthetic aperture sonar (SAS) for proud and buried object detection. Experimental results are presented, which demonstrate the accuracy achievable with data-driven micronavigation (motion estimation) techniques, such as the displaced phase center antenna (DPCA) as well as aided inertial navigation systems (AINS). The combination of both methods is shown to provide a marked improvement in SAS performance compared with either method used alone. The impact of shallow and very shallow water environments is also discussed, using experiments specifically designed to study the effect of multipath and acoustic fluctuations. Finally, the issue of fast SAS image formation algorithms is addressed in the context of wideband/widebeam systems, nonlinear platform tracks, and sound velocity changes (as when sound penetrates into sediments). Preliminary results are presented for fast-factorized backprojection (FFBP), a promising algorithm derived for low-frequency SAR applications. [This work is done within the framework of a multinational Joint Research Program on Mine Detection and Classification and the authors would like to acknowledge the participation of all the Nations involved, in particular the UK and Norway.]
Extending the capabilities of synthetic aperture sonars (multiaspect and multiband) in the overall objective of buried mines classification
Authors: Hetet Alain P. , Zerr Benoit , Challande Pascal
Published: October 2013

Low- and medium-frequency sonars are more adequate for long-range detection and classification operations needed for mine hunting. In addition, with low frequencies the acoustic waves can penetrate into the sediment. With such a technique, detection of buried mines is possible. But, in real conditions, at sea, the number of alarms and false alarms is important. One of the problems is to find solutions to reduce those false alarms. One technique developed in this presentation is the multiband technique in association with large-bandwidth acoustical arrays. The aim of this technique is to reduce the speckle effect with noncoherent summation of multiband coherent SAS images. This technique has been focused, at the moment, on mines laying on the seabed, and is expected to be used on buried mines. The second technique discussed in the presentation is the multiaspect SAS processing applied in the low-frequency case for buried mines detection and classification. This technique is intended to help during the echo classification process of buried mines, limiting the false-alarm rate and reconstructing the shape of the object by following the echo along the shape of the objects.
Influence of environmental parameters on mid-to-high frequency acoustic signal propagation in coastal regiona)
Authors: Lenain Luc , Badiey Mohsen , Forsythe Steve E.
Published: October 2013

Broadband mid-to-high frequency (0.6–18 kHz) acoustic wave propagation in shallow coastal waters (20 m) is influenced by a variety of oceanographic conditions. Physical parameters such as temperature and salinity as well as hydrodynamic parameters such as surface waves, tide, and current can influence amplitude and travel time of acoustic transmissions. While some of these physical parameters can be extracted from the acoustic wave propagation, understanding the forward model is vital to a fundamental understanding of the inverted parameters in shallow coastal waters. A unique set of simultaneous ocean and acoustic observations that reveal interesting temporal behavior of the acoustic signal and its correlation with environmental variability are presented. Some forward modeling using full-wave and ray-based methods is employed to investigate the time-frequency-angle characteristics of the measured acoustic field. Results of acoustic inversion for current, salinity, and sea-surface roughness, as well as the limitations of such inversions when using broadband signals in very shallow water regions, are also discussed. [Work supported by ONR and Sea Grant.] a)For Underwater Acoustics Best Student Paper Award.
Propagation of sound in the surf zone
Authors: Sammelmann Gary , Deane Grant , Vagle Svein , Farmer David
Published: October 2013

This presentation focuses on the effects of a time-varying sea surface and bubble clouds due to breaking waves on the propagation of sound in the surf zone. The rough sea surface generates caustics corresponding to Bragg diffraction due to the focusing of sound by the rough surface as described by the specular point method. A comparison with experimental data taken by Grant Deane is presented. Time evolution of bubble clouds in the surf zone is modeled by the algorithms developed by Svein Vagle, David Farmer, and Grant Deane. Bubbles in the surf zone alter both the attenuation of sound and the sound-velocity profile in the ocean. [Work supported by Codes 321OE and 32MIW of the ONR.]
Cavitation bubble cluster activity in the breakage of stones by shock wave lithotripsy
Authors: Pishchalnikov Yuriy A. , Sapozhnikov Oleg A. , Williams James C. , Evan Andrew P. , McAteer James A. , Cleveland Robin O. , Colonius Tim , Bailey Michael R. , Crum Lawrence A.
Published: October 2013

High-speed photography was used to investigate cavitation at the surface of artificial and natural kidney stones during exposure to lithotripter shock pulses in vitro. It was observed that numerous individual bubbles formed over virtually the entire surface of the stone, but these bubbles did not remain independent and combined with one another to form larger bubbles and bubble clusters. The movement of bubble boundaries across the surface left portions of the stone bubble free. The biggest cluster grew to envelop the proximal end of the stone (6.5 mm diameter artificial stone) then collapsed to a small spot that over multiple shots formed a crater in that face of the stone. The bubble clusters that developed at the sides of stones tended to align along fractures and to collapse into these cracks. High-speed camera images demonstrated that cavitation-mediated damage to stones was due not to the action of solitary, individual bubbles, but to the forceful collapse of dynamic clusters of bubbles. [Work supported by NIH DK43881.]
Linking theoretical predictions of backscatter from biological media with experimental estimates
Authors: Miller James G. , Trousil Rebecca L. , Handley Scott M. , Holland Mark R.
Published: October 2013

Medical ultrasonic imaging is based on scattering processes that arise because of the inhomogeneous nature of biological media. In laboratory-based investigations, reduction of experimental rf data to the true backscatter coefficient is accomplished by compensating for measurement system, attenuation, and diffraction effects. In clinical imaging, image brightness is qualitatively related to local values of the backscatter coefficient after operator-adjusted compensation for attenuation (Time Gain Compensation). Clinical backscatter-based approaches to tissue characterization typically provide semi-quantitative data in regions-of-interest somewhat larger than the resolution cell of the image. This spatial averaging can improve the stability of the backscatter estimates. In addition, averaging over a range of frequencies can also improve the signal-to-noise ratio, as in the case of Integrated Backscatter. The sophisticated post-processing of backscattered data to form images poses an additional layer of complexity in compensating clinical data for imaging system-dependent effects. The objective of this talk is to address some approaches, and the corresponding approximations and compromises required, for comparing the results of laboratory and clinical estimates of backscatter with theoretical predictions of the backscatter coefficient (i.e., the differential scattering cross section per unit volume at 180 degrees). [Work supported in part by R37HL40302.]
The effect of hemolysis on acoustic scattering from blood
Authors: Coussios Constantin-C. , Ffowcs Williams Shon E.
Published: October 2013

In an attempt to develop a direct method for measuring the extent of red cell damage in vitro, the effect of the degree of hemolysis on ultrasonic scattering from blood was investigated. Starting with a suspension of 30% hematocrit, a series of suspensions containing different relative concentrations of healthy and damaged red cells in saline were prepared, with the total number of cells present in any one suspension being constant. For each sample, a suspension of equal concentration of healthy cells, but no lyzed cells, was also produced. Using a specially designed container, all samples were exposed to 15 MHz ultrasound in pulse-echo mode and measurements of backscattering were obtained. At high hematocrits, the samples containing damaged cells were found to scatter substantially more than the suspensions containing exclusively healthy cells. This indicates that damaged cells contribute significantly to the overall backscattered intensity. Below a concentration of 13% per volume of healthy cells, scattering levels from healthy and hemolyzed suspensions were comparable. A theoretical model, which treats healthy cells as weak-scattering spheres and damaged cells as hard thin disks, is proposed to interpret the observed scattering behavior.
Effects of mixing He and Ar on single bubble sonoluminescence (SBSL)
Authors: da Graça Julio , Kojima Harry
Published: October 2013

When a large pressure gradient is imposed in a gas mixture, a segregation of different species is expected to occur. Preliminary result of our search for segregation effects on the SBSL in ensonified water containing mixtures of 4He (partial pressure=pHe), Ar (pAr) and N2 (pN) gases will be presented. Deionized and initially degassed water was mixed with pHe+pAr=1.5 Torr and pN=148.5 Torr. The emitted light intensity I and the bubble radius dynamics (via Mie scattering) were measured as a function of the imposed 17.3 kHz acoustic drive amplitude for mixtures with varied x=pHe/(pAr+pHe). The acoustic pressure amplitude (Pa) at the bubble and the ambient bubble radius were extracted by fitting the Mie scattering data using Rayleigh–Plesset equation. In the range where SL occurs [Plo(x)<Pa<Phi(x)], the measured I increased linearly with Pa for x=0, 0.5, 0.75 and 1. The slope dI/dPa decreases with x. The results will be compared with expectations of homogeneous mixing of 4He and Ar and segregation in the SL bubbles.
Optical observations of single droplets during acoustic vaporization
Authors: Kripfgans Oliver D. , Carson Paul L. , Fowlkes J. Brian
Published: October 2013

It has been shown previously that Acoustic Droplet Vaporization (ADV) causes bubbles to form from small droplets. This paper shows that prior to vaporization the droplets undergo translatory (dipole) oscillations when exposed to tone bursts. A high speed video system was used to monitor droplets in a flow tube when single-element focused transducers (3.5 and 10 MHz) were used for ADV on individual droplets. Single sinusoidal tone burst (<3.3 μs) were sufficient for ADV of droplets with 5 to 25 micrometer diameter. Dipole oscillations of 1.3 μm independent of diameter were found. Variations in the droplet diameter of up to 15% were observed during the onset of acoustic irradiation. The pressure threshold for ADV decreased with increasing droplet diameter. The onset of vaporization was seen either as a localized event within or homogeneously throughout the imaged droplet (possibly due to the temporal resolution of the imaging system). Localized nucleation was solely observed along the direction of dipole motion of the droplet, which is the same as the direction of the propagating acoustic wave. Typically, sites on ‘‘north and/or south poles’’ were observed. [Research supported by PHS Grant No. R01HL54201 and US Army Grant No. DAMD17-00-1-0344.]
Active damping of capillary oscillations on liquid columns
Authors: Thiessen David B. , Wei Wei , Marston Philip L.
Published: October 2013

Active control of acoustic radiation pressure and of electrostatic stresses on liquid columns has been demonstrated to overcome the Rayleigh–Plateau instability that normally causes long liquid columns to break [M. J. Marr-Lyon et al., J. Fluid Mech. 351, 345 (1997); Phys. Fluids 12, 986–995 (2000)]. Though originally demonstrated for liquid–liquid systems in plateau tanks, the electrostatic method also works on columns in air in reduced gravity [D. B. Thiessen, M. J. Marr-Lyon, and P. L. Marston, ‘‘Active electrostatic stabilization of liquid bridges in low gravity,’’ J. Fluid Mech. (in press)]. In new research, the electrostatic stresses are applied in proportion to the velocity of the surface of the column so as to actively dampen capillary oscillations of the surface. The mode amplitude is optically sensed and the rate-of-change is electronically determined. Plateau tank measurements and theory both show that the change in damping rate is proportional to the feedback gain. The results suggest that either active control of electrostatic stresses or of acoustic radiation stresses can be used to suppress the response of interfaces to vibration. [Work supported by NASA.]
Inferring pore size distributions in cast metals from ultrasonic attenuation
Authors: Mozurkewich George , Ghaffari Bita , Godlewski Larry A. , Zindel Jacob W.
Published: October 2013

The frequency dependence of ultrasonic attenuation in cast metals has previously been shown to contain information about the volume fraction and size of pores. While direct metallographic examination shows that the actual size distribution can be quite broad, previous investigations have analyzed ultrasonic attenuation data on the assumption that all pores have the same, or nearly the same, size. That restriction can be eliminated by analyzing the data using the concept of maximum entropy. Pore sizes are divided into discrete bins, each containing a fraction fi of all the pores, and the entropy, obtained by summing −filn(fi) over all bins, is maximized subject to the constraints of the frequency-dependent attenuation data. The resulting pore size distributions for cast aluminum samples containing various levels of porosity are often found to be approximately log-normal. Volume fractions of pores deduced from these distributions are in excellent agreement with determinations using the Archimedes method.
Phase-locked onset detectors for monaural sound grouping and binaural direction finding
Authors: Smith Leslie
Published: October 2013

Locating sound sources is an important task for animals. IIDs and ITDs are normally used to provide information about the instantaneous direction of sound received at the ears. In a reverberating environment, this may differ from the direction of the sound source. However the IID and ITD always provide information about sound source direction at onset, since onsets always arrive from the shortest, direct path. Binaural recordings were filtered using a gammatone filterbank, converted to a phase-locked spike code, and passed to a leaky integrate-and-fire neuron through a rapidly depressing synapse. This provides a phase-locked onset detector in each bandpassed channel. Nearly coincident onsets from different channels in each ear were grouped. IIDs and ITDs were computed when grouped onsets in both ears occur at almost the same time. ITDs were converted to azimuth geometrically: IIDs were converted using the impulse response at each ear. The results show that even in a reverberating environment, sound direction can be found from a single onset. Wideband and long sounds provide better results. Multiple sound sources can be accommodated. The system exhibits the precedence effect since a second onset (without intermediate offset) will be ignored because the depressing synapses will not have recovered.
A new account of monaural phase sensitivity
Authors: Carlyon Robert P. , Shamma Shihab
Published: October 2013

Phase differences between partials of complex tones are detectable only when they interact within an auditory filter. This is consistent with auditory models whereby across-channel timing information is explicitly discarded. However, these models (e.g., the autocorrelogram) fail to account for listeners’ ability to detect across-channel phase differences for some sounds. For example, when two groups of unresolved harmonics are filtered into different frequency regions and presented concurrently, listeners can detect a 1- to 2-ms ‘‘pitch pulse asynchrony’’ between the peaks of the waveforms of the two groups. We attribute phase insensitivity for resolved partials to the rapid phase transition near the peak of the traveling wave, causing auditory neurons responding to each partial to do so at a variety of phases. In contrast, a group of unresolved harmonics does not produce a sharp traveling-wave peak, and all neurons responding do so synchronously. We propose a model whereby ‘‘auditory spectrograms’’ are processed by cortical filters tuned to characteristic frequency, modulation rate, and spectral ‘‘scale.’’ The model accounts quantitatively for detection of envelope phase disparities between AM tones, discrimination of AM from QFM, and discrimination of Huffman sequences. We argue that auditory models should not discard all across-channel phase information.
Phase effects in simultaneous and forward masking
Authors: Lerner Elizabeth A. , Weber Daniel L. , Harward Brian J.
Published: October 2013

We estimated masked thresholds for a 20-ms (two 10-ms ramps), 1-kHz sinusoid as a function of its temporal relation to a 400-ms, 1-kHz sinusoid in the transition from simultaneous to forward masking conditions (signal center minus masker offset times of −200, −20, −10, −3.75, −2.40, −1.25, 0.00, 1.25, 2.40, 3.75, 10, and 20 ms). In simultaneous masking conditions, thresholds for signals presented in phase with the masker were lower than for signals added in quadrature, but there was no such phase effect in forward masking conditions. When there was partial overlap of signal and masker, the phase effect was apparent until +3.75-ms center-offset time, where the phase effect disappeared and thresholds decreased. Thresholds for just the portions of the 20-ms signal that occurred during the masker (simultaneous partial signals) and for the portions of the 20-ms signals after the masker (forward partial signals), generally were consistent with results for whole (20-ms) signals: when thresholds for the whole signal appeared to be determined by simultaneous masking, thresholds for the simultaneous partial signals matched those of the whole signal and also showed a phase effect, whereas thresholds for the forward partial signals were higher and showed no phase effect.
Discriminating change in the envelope phase spectrum
Authors: Sheft Stanley , Yost William A.
Published: October 2013

Models of a modulation filterbank retain envelope phase information for only the lowest rates. To evaluate model predictions, the ability to discriminate change in the envelope phase spectrum of modulated wideband noise was measured. Modulators were narrow-band noises with bandwidth ranging from 5 to 160 Hz. The contrasting envelopes were generated by manipulating the modulator phase spectrum while leaving the amplitude spectrum unchanged. Modulator phase spectrum was varied by either reversing the modulator waveform, randomizing or zeroing phase arguments in the modulator spectrum, or generating a minimum-phase reconstruction through cepstral analysis. For time reversal and randomization, discrimination ability decreased as modulator bandwidth increased, indicating both a loss of phase information with increasing rate and masking of the low-rate information by higher-rate modulation. For zero- and minimum-phase modulators, at some point performance improved with bandwidth. This result implies a sliding temporal window to preserve power fluctuations in the filterbank output. Comparable performance was obtained when equal-bandwidth zero-phase regions were restricted to either a low- or higher-rate region. This result may reflect nonlinearity in modulation processing whereby intermodulation of high-rate components introduces perceptible low-rate modulation. [Work supported by NIH.]
Plasticity of loudness perception
Authors: Formby Craig , Sherlock LaGuinn P. , Gold Susan L.
Published: October 2013

Evidence from the management of tinnitus and hyperacusis suggests that loudness perception is plastic and adaptable. We have undertaken a study to evaluate this idea. The motivation followed from clinical observations suggesting that the magnitude of perceived loudness and, in turn, the rate of loudness growth can be manipulated either upward or downward by prolonged reduction or enhancement in the level of background sound to which a listener is exposed. Accordingly, volunteers were fitted bilaterally with in-the-ear noise instruments (NI treatment) or sound-attenuating earplugs (EP treatment). Both treatments produced audibility threshold shifts, mainly above 1000 Hz. The effects of each treatment were evaluated after 2 weeks of continuous use relative to pretreatment loudness response data obtained using the Contour Test of loudness perception. The resulting loudness data for warble tones revealed opposite patterns of plasticity for the two treatments, with steeper and shallower (than pretreatment) loudness growth functions measured, respectively, for the EP and NI treatments. These effects were significantly different for loudness response categories judged to be comfortably loud or louder at both 500 and 2000 Hz. Possible mechanisms for this apparent plasticity of loudness will be discussed. [Research supported by NIDCD.]
Second-order temporal modulation transfer functions (TMTFs) in normal-hearing, hearing-impaired, and cochlear implant listeners
Authors: Lorenzi Christian , Sibellas Jerome , Garnier Stephane , Gallego Stephane
Published: October 2013

‘‘Second-order’’ TMTFs are obtained by measuring detection thresholds for second-order modulation (that is, sinusoidal modulation applied to the modulation depth of a sinusoidally amplitude-modulated tone or noise carrier), as a function of fm′, the rate of second-order modulation. Here, the modulated tone or noise acts as a carrier stimulus of rate fm. Such TMTFs may be viewed as descriptions of the attenuation characteristics of the envelope beat component produced by second-order modulation at rate fm′. Second-order TMTFs assessed in normal-hearing listeners, listeners with moderately-severe cochlear damage, and cochlear implantees are similar (i.e., low pass) in shape. Overall, detection thresholds are higher in hearing-impaired than normal-hearing listeners. However, the differences in thresholds are small (5 dB). In cochlear implantees, detection thresholds are generally improved when amplitude compression is applied to the stimuli. However, the increase in sensitivity produced by compression is modest (4 dB). Taken together, these results may be accounted for in terms of modulation filters, under the following assumptions: (i) a weak distortion product is generated by the peripheral auditory system at the envelope beat rate fm′, and (ii) a salient envelope beat cue appears at the output of modulation filters tuned near the carrier rate fm.
The influence of practice on the detectability of auditory sinusoidal amplitude modulation
Authors: Fitzgerald Matthew B. , Wright Beverly A.
Published: October 2013

The capacity to detect fluctuations in sound amplitude influences the perception of many everyday sounds, including speech. Here, the influence of practice on this ability was investigated. Between two testing sessions, one group of nine listeners who were tested on the detection of sinusoidal amplitude modulation (SAM) improved by about 0.7 dB on each of five conditions (300 trials/condition). Nine other listeners participated in these same sessions, but between them, practiced 4320 trials detecting the presence of 80-Hz SAM with a 3- to 4-kHz narrow-band carrier. Only three of these listeners, who had among the highest initial detection thresholds on the trained condition, improved during this training phase. These learners subsequently improved at untrained modulation rates (30 and 150 Hz) with the trained carrier, but not at the trained modulation rate with untrained carriers (0.5–1.5 kHz and 0–5 kHz). These data suggest that (1) at some stage, modulation processing is more linked to the carrier spectrum than to the modulation rate, and (2) while most normal-hearing listeners reach their best modulation-detection performance with minimal experience, listeners with high initial thresholds benefit from extended practice. Thus, training may aid populations that have difficulty detecting amplitude modulation. [Work supported by NIDCD.]
Internal noise invariance across two informational masking tasks
Authors: Tang Zhongzhou , Richards Virginia M.
Published: October 2013

The detectability of a 1000-Hz signal tone added to a six-tone masker was measured using a two-interval, forced-choice task. The frequencies of the masker components were randomly drawn either within a trial (different maskers in two intervals; within condition) or between trials (same maskers across two trials; between condition). Using a linear channel model with channel variances that are unaltered across conditions, weights for different frequency regions were estimated using individual responses in the within condition. Additionally, estimates of total decision variance were estimated using psychometric functions. For two observers, thresholds in the within- and between conditions were approximately the same, indicating a failure of the linear model. For a third observer the data were sufficiently variable that the psychometric functions and the linear model were poorly fitted. For the remaining five observers, thresholds in the within condition were on average 7 dB higher than in the between conditions. However, for these observers estimates of internal noise did not reliably differ across conditions. Provided the modeling assumptions are reasonable, this result suggests that for these five observers the change in threshold can be accounted for by the change in stimulus uncertainty.
Evaluation of interval-based and beat-based timing mechanisms for duration discrimination
Authors: Berens Melody S. , Pastore Richard E.
Published: October 2013

An important topic in music perception is how people track time or judge duration [E. W. Large and M. R. Jones, Psychol. Rev. 106(1), 119–159 (1999)]. Two typically proposed duration judgment timing mechanisms are interval-based timing (judgment of discrete events) and beat-based timing (judgments of beat regularity) [S. W. Keele, N. Nicoletti, R. I. Ivry, and R. A. Pokorny, Psychol. Res. 50, 251–256 (1989)]. Models were developed for several different versions of these hypothetical timing mechanisms. Predictions from these models were then evaluated in experiments that estimated thresholds for judging difference in judgment of interval duration. Musicianship of participants was also evaluated. Each trial began with an initial training sequence of intervals that enhanced the stored interval or established the internal rhythm or beat. The training interval was followed by a specific delay that varied across conditions. Each trial ended with a target and a comparison interval. Participants judged whether the comparison interval was equal to or longer in duration than the target interval. Results were systematic, but not consistent with simple, straightforward versions of either timing mechanism.
Mode excitation and imaging by the radiation force of ultrasound
Authors: Fatemi Mostafa , Zeraati Mohammad R.
Published: October 2013

A method for noncontact excitation and displaying the vibration mode shapes in solids is introduced. This method utilizes the radiation force of amplitude-modulated focused ultrasound to remotely excite a resonant mode in the object. The ultrasound transducer is driven by a sinusoidally modulated continuous wave signal to produce an oscillatory radiation force on the object and drive it into one of its natural resonance modes. The acoustic field resulting from object vibration is detected by a hydrophone. A theoretical model has been developed that describes the relationship between the force, mode shape, and the acoustic field. It is shown that the acoustic field amplitude is proportional to the value of the mode shape at the focal point of the ultrasound beam. By scanning the ultrasound beam across the object it is possible to map the acoustic data into an image that represents the mode shape of the object. Experiments have been conducted on small steel, aluminum, and glass beams. The first five resonant modes were excited and imaged by the present method. Experimental results have shown remarkable agreement with the theory and computer simulation. Beam deflections in the order of tens of nanometers can be detected by this method.
Local/global homogenization (LGH) applied to sound reflection from a flexible barrier with impedance discontinuities
Authors: Bliss Donald , Franzoni Linda , Danilov Pavel
Published: October 2013

A new homogenization method for complex structures has been developed. The method utilizes a local/global decomposition to separate the low and high parts of the wave number spectrum. The low wave number global problem has an infinite-order structural operator, and structural discontinuities are replaced by an equivalent distributed suspension. The rapidly varying local problem, which provides transfer function information for the global problem, is solved separately. Once formulated for a specific structure, the self-contained global problem is solved first, and the local solution can be reconstructed afterwards. The LGH reformulation, which applies over the entire frequency range, allows the global problem to be solved at much lower resolution than the length of flexural waves on the original structure. To demonstrate the approach, the problem of sound reflection from a flexible barrier with impedance discontinuities in a channel is described. The effects of radiating acoustic modes are transferred entirely to the smooth global problem, whereas evanescent acoustic modes are contained within the global structural operator. Sample calculations are presented comparing the method with the exact solution.
Structural and acoustic intensities of an infinite, point-excited fluid-loaded elastic plate
Authors: Won Jungyun , Hayek Sabih
Published: October 2013

In this paper, the active vibrational structural intensity (VSI) in and the radiated acoustic intensity (AI) from an infinite elastic plate in contact with a heavy fluid is modeled by the Mindlin plate theory. This theory includes the shear deformation and rotatory inertia in addition to flexure. The plate is excited by a point force, which generates a vector active VSI field in the plate. The active VSI has two components; one depends on the shear force, and the other depends on the moment. The resulting acoustic radiation generates an active AI in the fluid medium. First, the Green’s functions for the plate with and without fluid loading were developed. These were then used to develop expressions for VSI and AI vector fields. The displacement, shear deformation, VSI vector map, radiated acoustic pressure, and the AI vector map are computed for frequencies below and above the coincidence frequency. Below coincidence, a significant portion of the point force input power is trapped in the plate in the form of VSI. Above coincidence, a significant portion of the input source power is leaked to the fluid in the form of AI, with a small portion propagating to the far-field VSI.
Vibration modeling of beam reinforced plates using a direct image method
Authors: Cuschieri Joseph , Sarda Alexandre , Lenzi Arcanjo
Published: October 2013

Plates reinforced by beams are the main components of offshore structures as used in oil prospecting and production industry. The vibration generated by machinery on these platforms propagates through the structure and can generate high noise levels in the accommodation areas. To determine the power flow through the beam reinforced plates, models that include the effect of the web and flanges’ resonance in the beam and in-plane waves in all the structural components are necessary, since both of these are important especially when considering relatively high frequencies for such large structures. This work presents a model to determine the response and power flow through beam reinforced plates using a direct image method to obtain the component mobility functions for arbitrary boundary conditions. This approach is very efficient computationally and can generate accurate results up to relatively high frequencies. The results obtained using this method are compared with an exact solution using 3-D stress equations for a free rectangular parallelepiped.
Computing multipole expansions numerically
Authors: Fahnline John B.
Published: October 2013

Multipole expansions have long been used to classify and better understand sound fields. They are easily computed up through the quadrupole term using standard formulas found in basic acoustic texts. Here, the formulas are adapted for numerical computations of radiated acoustic power from vibrating structures. To perform the calculations, the normal surface velocity and pressure must be known in advance and are computed using a boundary element analysis. Several examples are given to demonstrate the utility of the calculations, including a baffled circular plate clamped around its periphery and a bass-reflex loudspeaker. The results show how the expansion is useful as a way of identifying radiation mechanisms and separating out the radiating component of the surface velocity profile from the nonradiating component.
Reaction time of voluntary modulations in voice F0 during sustained pitch vocalizations
Authors: Bauer Jay J. , Larson Charles R. , Eckstein Kathryn C.
Published: October 2013

In an attempt to more clearly understand the neural control of voice, a reaction time study was designed to investigate how rapidly normal subjects, i.e., nontrained singers, can voluntarily increase or decrease their voice fundamental frequency (F0) during sustained vocalizations when cued with a 1000-Hz auditory tone stimulus. Results revealed that overall reaction times (RTs) (F=21.9, df=2, 150, p=0.01) for upward F0 modulations occurred faster (range: 138–176 ms) than downward responses (range: 196–234 ms). In contrast to the reaction time findings, slightly higher peak velocities were observed for downward responses compared to upward responses. Shorter RTs observed for F0 elevation are therefore possibly related to central mechanisms involved in the planning of or execution of the direction in which F0 is to be modulated instead of muscle biomechanics. The fastest RTs obtained from the present study (138 ms) are slightly longer than the reflex latencies of the initial pitch-shift reflex response (100–130 ms) [Burnett, J. Acoust. Soc. Am. 103 (1998)], and provide additional evidence that subjects normally respond to inadvertent changes in their voice F0 with a fast, but limited reflex, followed by a secondary voluntary response. [Research supported by NIH Grant No. DC07264.]
A physically informed glottis model for real glottal flow wave form reproduction
Authors: Drioli Carlo
Published: October 2013

A physically informed model of the glottal source is proposed. The model relies on a lumped mechanoaerodynamic scheme based on the mass-spring paradigm. The vocal folds are represented by a mechanical resonator plus a delay line which takes into account the vertical phase differences. The vocal fold displacement is coupled to the glottal flow by means of a nonlinear subsystem, based on a general parametric nonlinear model. The principal characteristics of the flow-induced oscillations are retained, and the overall model is suited for an identification approach where real (inverse filtered) glottal flow signals are to be reproduced. A data-driven identification procedure is outlined, where the parameters of the model are tuned in order to accurately match the target wave form. A nonlinear regression algorithm is used to train the nonlinear part. A set of inverse-filtered glottal flow wave forms with different pitch, open phase/closed phase ratio, and shape of the glottal wave form period, are used to test the effectiveness of the approach. The results demonstrate that the model can reproduce a wide range of target wave forms. Moreover, the flow wave forms generated by the trained model are characterized by spectral richness and are perceived as natural. [Work supported by EU.]
Stress clash: Frequency and strategies of resolution
Authors: Levey Sandra , Raphael Lawrence J.
Published: October 2013

The hypothesis that speakers establish a strong–weak stress pattern to resolve stress clash (the adjacency of two primary stressed syllables, e.g., racCOON COAT) was investigated through perceptual and acoustic analysis. Three hypotheses were tested: that primary stress is relocated to an earlier syllable of the sequence (e.g., RACcoon COAT); that stress is reduced on the final syllable that bears primary stress in the first word of the sequence; that stress clash is avoided by pitch accent assignment to an early and to a late-occurring stressable syllable in a sentence. Ten speakers produced iambic target words in stress clash and non-clash contexts with target words placed in early and late-sentence position. Stress clash was resolved in less than 30% of the utterances but also occurred in non-clash contexts. Pitch accent was assigned to an early syllable for words placed in an early sentence position, increasing the frequency of stress shift judgments in both clash and non-clash contexts. Acoustic analysis showed that the information most likely to underlie shifts in stress location was located in the first syllable of target words and that fundamental frequency was the most probable of the potential cues.
Effects of subglottal and supraglottal acoustic loading on voice production
Authors: Zhang Zhaoyan , Mongeau Luc , Frankel Steven
Published: October 2013

Speech production involves sound generation by confined jets through an orifice (the glottis) with a time-varying area. Predictive models are usually based on the quasi-steady assumption. This assumption allows the complex unsteady flows to be treated as steady flows, which are more effectively modeled computationally. Because of the reflective properties of the human lungs, trachea and vocal tract, subglottal and supraglottal resonance and other acoustic effects occur in speech, which might affect glottal impedance, especially in the regime of unsteady flow separation. Changes in the flow structure, or flow regurgitation due to a transient negative transglottal pressure, could also occur. These phenomena may affect the quasi-steady behavior of speech production. To investigate the possible effects of the subglottal and supraglottal acoustic loadings, a dynamic mechanical model of the larynx was designed and built. The subglottal and supraglottal acoustic loadings are simulated using an expansion in the tube upstream of the glottis and a finite length tube downstream, respectively. The acoustic pressures of waves radiated upstream and downstream of the orifice were measured and compared to those predicted using a model based on the quasi-steady assumption. A good agreement between the experimental data and the predictions was obtained for different operating frequencies, flow rates, and orifice shapes. This supports the validity of the quasi-steady assumption for various subglottal and supraglottal acoustic loadings.
Lexical and phonotactic effects on the perception of rate induced resyllabification
Authors: de Jong Kenneth , Nagao Kyoko , Lim Byung-jin , Okamura Kyoko
Published: October 2013

Stetson (1951) noted that, when repeated, singleton coda consonants (VC) appear to modulate into onset consonants (CV) as the rate of repetition increases. de Jong et al. (2001) found that naEe listeners robustly perceive such resyllabifications with labial consonants, and in a later study, that such perceptions broadly corresponded to changes in glottal timing. In the current study, stimuli included labial, coronal, and velar stops, creating mixtures of real words (such as ‘‘eat’’), and nonwords (such as ‘‘ead’’). A comparison of the perception of real and nonreal words reveals no robust effect of lexical status. In addition, vowels in the corpus were either tense or lax, so that the CV combination is phonotactically illegal in half of the corpus. The perception of resyllabification also does occur with these lax vowels, though only for voiced coronal and labial stops. Other stops did not exhibit resyllabification. Analyses of glottal and acoustic recordings are currently underway. [Work supported by NIDCD and NSF.]
Speaker adaptation of HMMs using evolutionary strategy-based linear regression
Authors: Selouani Sid-Ahmed , O’Shaughnessy Douglas
Published: October 2013

A new framework for speaker adaptation of continuous-density hidden Markov models (HMMs) is introduced. It aims to improve the robustness of speech recognizers by adapting HMM parameters to new conditions (e.g., from new speakers). It describes an optimization technique using an evolutionary strategy for linear regression-based spectral transformation. In classical iterative maximum likelihood linear regression (MLLR), a global transform matrix is estimated to make a general model better match particular target conditions. To permit adaptation on a small amount of data, a regression tree classification is performed. However, an important drawback of MLLR is that the number of regression classes is fixed. The new approach allows the degree of freedom of the global transform to be implicitly variable, as the evolutionary optimization permits the survival of only active classes. The fitness function is evaluated by the phoneme correctness through the evolution steps. The implementation requirements such as chromosome representation, selection function, genetic operators, and evaluation function have been chosen in order to lend more reliability to the global transformation matrix. Triphone experiments used the timit and arpa−rm1 databases. For new speakers, the new technique achieves 8 percent fewer word errors than the basic MLLR method.
The use of functional data analysis to study variability in childrens speech: Further data
Authors: Koenig Laura L. , Lucero Jorge C.
Published: October 2013

Much previous research has reported increased token-to-token variability in children relative to adults, but the sources and implications of this variability remain matters of debate. Recently, functional data analysis has been used as a tool to gain greater insight into the nature of variability in children’s and adults’ speech data. In FDA, signals are time-normalized using a smooth function of time. The magnitude of the time-warping function provides an index of phasing (temporal) variability, and a separate index of amplitude variability is calculated from the time-normalized signal. Here, oral airflow data are analyzed from 5-year-olds, 10-year-olds, and adult women producing laryngeal and oral fricatives (/h, s, z/). The preliminary FDA results show that children generally have higher temporal and amplitude indices than adults, suggesting greater variability both in gestural timing and magnitude. However, individual patterns are evident in the relative magnitude of the two indices, and in which consonants show the highest values. The time-varying patterns of flow variability over time in /s/ are also explored as a method of inferring relative variability among laryngeal and oral gestures. [Work supported by NIH and CNPq, Brazil.]