bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthetic aperture sonar imaging in a random ocean
Authors: Chang Enson
Published: October 2013

The maximum achievable aperture of a coherent imaging sonar is normally considered to be limited by the horizontal coherence length of the medium, which is on the order of several tens to several hundred wavelengths. Synthetic aperture sonar results from the past several years, however, have clearly exceeded this limit by an order of magnitude or more. It appears that the horizontal coherence length alone does not describe some important aspects of the phase errors present in real data. In particular, we suggest that underlying structures in the phase errors are exploitable in processing algorithms and are responsible for these results. We give a number of numerical examples from sub-kHz to tens of kHz, including new results on subcritical imaging of buried objects.
Motion compensation technique for wide beam synthetic aperture sonar
Authors: Fernandez Jose E. , Cook Daniel A. , Christoff James T.
Published: October 2013

Optimal performance of synthetic aperture sonar (SAS) systems requires accurate motion and medium compensation. Any uncorrected deviations from those assumed during the SAS beam formation process can degrade the beam pattern of the SA in various ways (broadening and distortion of the main lobe, increased side lobes and grating lobes levels, etc.). These would manifest in the imagery in the form of degraded resolution, blurring, target ghosts, etc. An accurate technique capable of estimating motion and medium fluctuations has been developed. The concept is to adaptively track a small patch on the sea bottom, which is in the order of a resolution cell, by steering the SAS beam as the platform moves in its trajectory. Any path length differences to that patch (other than the quadratic function product of the steering process) will be due to relative displacements caused by motion and/or medium fluctuations and can be detected by cross-correlation methods. This technique has advantages over other data driven motion compensation techniques because it operates in a much higher signal-to-noise beam space domain. The wide beam motion compensation technique was implemented in matlab and its performance evaluated via simulations. An overview of the technique, simulation, and results obtained are presented.
Comparison of ASIAEX South China Sea acoustic fluctuations with oceanographic variability
Authors: Duda Timothy F. , Lynch James F. , Newhall Arthur E.
Published: October 2013

During May 2001, signals were transmitted from five moored 16- to 100-Hz-bandwidth sources to colocated horizontal and vertical receiving arrays in 120-m-depth water on the continental slope. The site was in the northern portion of the South China Sea. Transmissions were nominally 20 km cross slope to the receiver from a site with three closely spaced sources, and 32 km up-slope to the receiver from a site with two sources, although the bathymetry was complex. Signal frequencies ranged from 210 to 550 Hz. A broad spectrum of water column variations was observed during the 17-day acoustic experiment with our array of moorings at 20 sites, including the source and receiver locations. Internal tides were consistently present, as were nonlinear internal waves of moderate amplitude. Nonlinear internal waves of larger amplitude propagating from the eastern South China Sea were present only episodically. Subtidal frequency water-mass variations also occur. Correlation between various measures of the acoustic signal variability and the water column variability will be examined. [Work supported by ONR.]
Sound scattering in shallow water in presence of internal solitons
Authors: Katsnelson Boris G. , Pereselkov Serguey A. , Petnikov Valery G.
Published: October 2013

Sound scattering by localized inhomogeneity (object) in a shallow-water waveguide is studied. Influence of internal solitons (IS) traveling in the sea, on the scattered field is considered. The problem is analyzed within the framework of theory of the sound scattering in the waveguide developed by the authors, where the scattering matrix is expressed through modal decomposition including the scattering amplitude of the object in free space. The peculiarity of the given work is the taking into account of additional modes conversion due to IS. The waveguide and IS are modeled on the basis of experimental data (sound-speed profile, bottom relief, IS parameters, etc.) collected in the Japan Sea. The inhomogeneity is selected in the form of soft spheroids with dimensions characteristic of gray whales (eschrichtius). Calculations of amplitude fluctuations of the low-frequency sound field at the receiving point are carried out for moving spheroid and different orientations of acoustic track with respect to direction of propagation of IS. It is shown that sound fluctuations have essentially different characteristics for longitudinal and transversal propagation of IS. [Work supported by RFBR, Grant No. 00-05-64752.]
Impacts of internal tides on acoustic propagation at sonar frequencies and their effects on sonar system performance
Authors: Rajan Subramaniam D. , Lewis James K. , Rudzinsky Jason , Stein Peter J.
Published: October 2013

Temperature oscillations triggered by ocean tides can be found along nearly all shelf-slope regions throughout the world’s oceans. It is of interest to ascertain how these internal tides impact acoustic propagation for operational purposes. Internal tides have been observed around the Hawaiian Islands, and these tides result in large fluctuations in temperature on a semidiurnal basis. Ocean models are presented that reproduce tidally induced sound speed variations (through model-predicted variations in temperature and salinity) around the islands of Oahu and Kauai, Hawaii. The model provides sound-speed structure and variability, and this is used as input to acoustic propagation models. Model-predicted sound-speed structures are functions of space and time. We present results of studies carried out to investigate the effect of the internal tides on the performance of sonar systems. We quantify these effects by studying the impact of internal tides on factors such as the detection range to target in active systems and source localization errors in passive systems. A means of quantifying uncertainty in the performance of the sonar systems due to the presence of the internal tides is investigated by studying the performance of the sonar system by varying the strength of the internal tidal field.
Challenges and possible solutions to acoustic tomography in shallow-water areas
Authors: Rudzinsky Jason , Stein Peter J. , Rajan Subramaniam D. , Lewis James K.
Published: October 2013

The Pacific Missile Range Facility off the island of Kauai in the Hawaiian chain is equipped with a large number of bottom-mounted sources and receivers. This instrumentation provides an immense opportunity for the ocean acoustic community to create an ocean acoustic laboratory. Such a laboratory can be used to monitor the changes in the three-dimensional sound-speed structure in the region using acoustic tomography. An ocean model developed for the region predicts the sound-speed structure of the region given the atmospheric, tidal, and mesoscale circulation forcing functions. This information, supplemented by acoustic tomography results, can be used to develop a consistent picture of the sound-speed field of the region. We present the challenges involved in successful implementation of tomography. The challenges are posed by the location of the sources and receivers, the bathymetry of the region, the nature of the ocean/bottom interface, the limitation on the bandwidth of the source signal, and the factors affecting the acquisition of data. We will also present approaches that can be taken to overcome some of the problems. Preliminary results of a field experiment conducted to assess the feasibility of tomography in the region will be presented.
30 MHz backscatter and Doppler signals from individual microbubbles undergoing inertial cavitation
Authors: Yoon Johanna M. , Everbach E. Carr
Published: October 2013

Short pulses (1–2 microseconds duration) of 30 MHz ultrasound were used to interrogate individual OptisonTM and PESDA microbubbles convected in a coaxial jet flow or adhering to a thin MylarTM window. Backscattered signals were recorded as the bubbles were forced into symmetrical or asymmetrical collapse by application of 1 MHz ultrasound pulses from a focused source in water. Peak-to-peak amplitudes of the backscattered signal were converted to radius–time curves via comparison with similar signals from a monodisperse population of polystyrene spheres of known diameter. Additionally, backscattered signals were mixed with reference sinusoids at 30 MHz and low-pass filtered to yield Doppler signals. Results are consistent with theoretical models and provide a possible method to quantify asymmetrical bubble collapse via Doppler signature.
High frequency ultrasonic scattering by biological tissues
Authors: Shung K. Kirk , Maruvada Subha
Published: October 2013

High frequency (HF) diagnostic ultrasonic imaging devices at frequencies higher than 20 MHz have found applications in ophthalmology, dermatology, and vascular surgery. To be able to interpret these images and to further the development of these devices, a better understanding of ultrasonic scattering in biological tissues such as blood, liver, myocardium in the high frequency range is crucial. This work has previously been hampered by the lack of suitable transducers. With the availability of HF transducers going to 90 MHz, HF attenuation and backscatter experiments have been made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range for frequencies, from 30 to 90 MHz and on bovine tissues for frequencies from 10 to 30 MHz using a modified substitution method that allow the utilization of focused transducers. These results will be reviewed in this talk along with relevant theoretical models that could be applied to interpreting them. The relevance of the parameter that has been frequently used in the biomedical ultrasound literature to describe backscattering, the backscattering coefficient, will be critically examined.
Cuts with negative Poisson’s ratio in alloys and rocks
Authors: Tokmakova Svetlana P.
Published: October 2013

Stretching of material with negative Poisson’s ratio leads to an unexpected transverse expansion. Stretching of anisotropic material can cause expansion in one direction and contraction in another direction. For example it is possible for Poisson’s ratio in crystals to be negative in one direction and highly positive in another direction. In the paper a set of hexagonal, monoclinic and cubic crystals of rocks, minerals and alloys were investigated. The stereographic projections of Poisson’s ratio were computed for each crystal. From these stereographic projections the Poisson’s ratio for any directions of stretch and lateral strain in crystal were calculated and orientations of stretch and lateral strain with extremes values of Poisson’s ratio were obtained. By analysis of the above results cuts with negative values of Poisson’s ratio were revealed in zinc, molybdenum sulfide, polypropylene, graphite, carbon, natural precious minerals labradorite and augite, complex silicate and in copper, zinc, iron, nickel, indium, silver and gold alloys. For these crystals the angular dependence of stretched orientations corresponding to negative Poisson’s ratio were determined. Elastic modules of crystals from the manual of Landolt–Bornstein were applied in calculations. Some simple models with negative Poisson’s ratio are considered and some possible applications of materials with negative Poisson’s ratio basing on their unusual acoustic properties are discussed.
Piezoelectric control of sculptured thin films
Authors: Wang Fei , Lakhtakia Akhlesh , Messier Russell
Published: October 2013

It shows that the Bragg center wavelength of a polymeric chiral sculptured thin film (STF) can be shifted by the axial tension generated in a co-bonded piezoelectric disk by a dc voltage. This attractive possibility can be exploited for tunable optical filters as well as lasers made of chiral STFs, and can be extended to other types of STFs.
A counterexample of spatial unmasking in multitalker speech perception
Authors: Brungart Douglas S. , Simpson Brian D.
Published: October 2013

In listening tasks that involve more than one competing talker, substantial improvements in performance can usually be obtained by moving the target speech signal to a different location than the interfering speech signal. However, recent results in our laboratory suggest a possible listening configuration where informational and energetic masking effects might cause performance to decrease when an interfering speech signal is moved from the same ear as the target speech to the opposite ear. In this experiment, listeners were asked to respond to a color and number coordinate in a target phrase that was presented in two different listening configurations. In the first configuration, a high-level interfering talker and a low-level interfering talker were presented in the same ear as the target speech; in the second configuration, a high-level interfering talker was presented in the same ear as the target speech and a low-level interfering talker was presented in the ear opposite the target speech. The results confirm that the low-level interfering talker sometimes produced more interference when it was presented in a different ear than the target speech than when it was presented in the same ear.
On the ability of human listeners to detect dispersion in head-related transfer functions
Authors: Constan Zachary A. , Hartmann William M.
Published: October 2013

Because of dispersion around the head, the interaural time difference (ITD) depends on frequency. However, virtual reality experiments have shown that human listeners cannot distinguish between veridical head-related transfer functions (HRTFs) and HRTFs with a carefully chosen constant ITD. A reasonable explanation for this result is that listeners are insensitive to the kind of dispersion created by the head. This explanation was tested in headphone experiments using incident angles and particular noise bands chosen to give listeners the best opportunity to detect dispersion. The dispersive ITD was modeled using Kuhn’s equations for pressure on a spherical surface due to an incident plane wave [J. Acoust. Soc. Am. 62, 157–167 (1977)]. Listeners were required to distinguish between noise with dispersive ITD and noise with constant ITD. Experiment 1 varied the ITD and found a pronounced minimum in the percentage of correct responses at an optimal value of ITD. Experiment 2 used optimal ITDs only in order to remove lateralization cues. Experiment 3 reversed the sign of the dispersion, causing the ITD to increase with increasing frequency rather than decrease. All experiments led to the same conclusion: listeners cannot detect head-related and similar dispersion. [Work supported by NIDCD.]
Discrimination of interaural envelope correlation for high- and low-standard correlations
Authors: Stellmack Mark A. , Viemeister Neal F.
Published: October 2013

This experiment examined the cues that listeners use in discriminating interaural envelope correlation. Thresholds for discriminating normalized interaural envelope correlation [r; see L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 100, 1754–1763 (1996)] were measured for a sinusoidally amplitude-modulated 4-kHz tone. The parameter r was manipulated by varying the interaural phase difference (IPD) of the signal envelope. Using a method of constant stimuli that measured percent correct, threshold Δr (ΔIPD) was estimated for standard r=1 (IPD=0 deg) and r=0.4235 (IPD=180 deg), with modulation frequencies (fm) of 4–256 Hz and modulation index=0.9. For low fm, thresholds expressed as Δr were from 10–60 times larger for the small standard correlation than for r=1. However, when expressed in terms of difference in the peak interaural level difference (ILD), thresholds were within several dB across standards. Furthermore, thresholds were comparable to those for discrimination of fixed ILDs. For high fm, discrimination thresholds were smaller than those at low fm. The difference at high fm may be due to processing of the interaural envelope differences as fixed interaural time differences rather than dynamically varying ILDs. [Work supported by NIDCD DC00683.]
Loudness for tone underwater
Authors: Cudahy Edward , Schwaller Derek
Published: October 2013

The loudness for pure tones was measured by loudness matching for 1-s pure tones from 100 to 50000 Hz. The standard tone was 1000 Hz. Subjects were instructed to match the loudness of the comparison tone at one of the test frequencies to the loudness of the standard tone. The standard was presented at one of five sound pressure levels (SPL) for each set of frequencies. The standard SPL was varied randomly across test series. The subjects were bareheaded US Navy divers tested at a depth of 3 m. All subjects had normal hearing. The tones were presented to the right side of the subject from an array of underwater sound projectors. The SPL was calibrated at the location of the subject’s head with the subject absent. The loudness increased more rapidly as a function of standard SPL at mid-frequencies than at either high or low frequencies. The most compact loudness contours (least SPL change across range of standard SPL) were at 50000 Hz. The underwater loudness contours across frequency are significantly different from in-air measurements and have a minimum in the 1000 Hz region rather than the 2–4 kHz region observed for in-air measurements. [Work supported by ONR.]
Modulation rate-discrimination and frequency modulation detection thresholds in the amplitude modulation domain
Authors: Füllgrabe Christian , Lorenzi Christian , Demany Laurent
Published: October 2013

The present study tested the existence of modulation filters by transposing the concept of excitation pattern to the amplitude modulation (AM) domain. In the first experiment, AM rate-discrimination thresholds (DLFs) for white-noise carriers with AM reference rates of 4, 16, and 64 Hz were measured in five normal-hearing listeners. AM depth was either (i) fixed at 0.2, 0.6, or 1.0, or (ii) varied randomly between 0.2 and 1.0. Randomization of the modulation depth occurred either between trials or between the two intervals of the same trial. In a second experiment, detection thresholds of slow (1 or 4 Hz) frequency modulation (FMDLs) applied to the AM carrier (of identical rates as in the previous experiment) were measured, with and without the presence of a slow sinusoidal modulation applied to the depth of the AM carrier. Overall, the data show that DLFs are less affected than FMDLs by variations in the depth of AM. The results are discussed in light of current models of AM perception.
Detection and discrimination of second-order sinusoidal amplitude modulation (SAM)
Authors: Füllgrabe Christian , Lorenzi Christian
Published: October 2013

The perception of complex temporal envelopes has been recently studied using second-order SAM [Lorenzi et al., J. Acoust. Soc. Am. 110, 1030 (2001)]. In these stimuli, the modulation depth of a SAM signal (of rate fm) is sinusoidally amplitude-modulated at a rate fm′, thereby generating two additional components at fm±fm′ in the modulation spectrum, and a slow beat at fm′ in the temporal envelope. The present study investigates the respective contribution of these two cues to the perception of second-order SAM. In four normal-hearing listeners, second-order SAM detection and rate-discrimination abilities are measured at a high ‘‘carrier’’ (fm=256 Hz), but low beat rates (fm′≤128 Hz), as a function of stimulus duration (250 ms to 2 s). The data are compared to first-order SAM detection and rate-discrimination thresholds measured in similar conditions at 1≤fm≤128 Hz. At common modulation rates (fm=fm′), the results show that (i) first- and second-order thresholds increase similarly when stimulus duration decreases, and (ii) first- and second-order SAM rate-discrimination thresholds are basically identical. The data therefore indicate that detection and discrimination of second-order SAM are mainly based on the slow temporal envelope beat cue.
Amplitude modulation perception for people with normal hearing
Authors: Koopman Jan , Plasmans Niels , Dreschler Wouter
Published: October 2013

Our experiments focus on the perception of amplitude modulation. In total, four experiments were carried out. In the first experiment, the sensitivity for amplitude modulation was determined. In the other three tests, amplitude modulation has been matched for signals that differ with respect to one of the following parameters: bandwidth, center frequency, and sensation level. The equally perceived modulation depth (EPMD) was approximately equal to the reference depth for signals with a 15 dB difference in sensation level. For the bandwidth and center frequency, we generally found an interference of the internal fluctuations on the perceived modulation depth. Data can be described reasonably well by determining the differences in sensation depth (i.e., the amplitude modulation depth [in dB] above the threshold for modulation detection). An alternative way to model the results of this study is to determine the standard deviation of energy values for a sliding temporal integrator. Both models can be improved significantly by taking into account the differences in growth of loudness functions for the two conditions.
Differential auditory signal processing in an animal model
Authors: Lim Dukhwan , Kim Chongsun , Chang Sun O.
Published: October 2013

Auditory evoked responses were collected in male zebra finches (Poephila guttata) to objectively determine differential frequency selectivity. First, the mating call of the animal was recorded and analyzed for its frequency components through the customized program. Then, auditory brainstem responses and cortical responses of each anesthetized animal were routinely recorded in response to tone bursts of 1–8 kHz derived from the corresponding mating call spectrum. From the results, most mating calls showed relatively consistent spectral structures. The upper limit of the spectrum was well under 10 kHz. The peak energy bands were concentrated in the region less than 5 kHz. The assessment of auditory brainstem responses and cortical evoked potentials showed differential selectivity with a series of characteristic scales. This system appears to be an excellent model to investigate complex sound processing and related language behaviors. These data could also be used in designing effective signal processing strategies in auditory rehabilitation devices such as hearing aids and cochlear implants. [Work supported by Brain Science & Engineering Program from Korean Ministry of Science and Technology.]
Measuring the performance of personal hearing protectors for high-noise environments
Authors: Ahroon William A. , Ostler Dale A. , Robinette Martin B.
Published: October 2013

The American National Standards Institute currently identifies two real-ear attenuation at threshold (REAT) methods for measuring the performance of hearing protective devices (HPD). The experimenter-supervised-fit method (Method A), employed in earlier standards, permits the subject nearly unlimited assistance from the experimenter in fitting an HPD under test. Conversely, the subject-fit method (Method B) allows no experimenter assistance and the only fitting instructions that are available to the subject are those published by the manufacturer of the HPD and included in the HPD packaging. It is assumed that the Method A procedure provides a best-case estimate of the HPD performance while the Method B procedure provides a better estimate of the performance that can be reasonably obtained in real-world industrial settings. While measurements using the subject-fit method are preferred, there are questions as to whether this method is appropriate for measuring HPD performance in very high-noise environments such as those experienced in some military vehicles (i.e., rotary-wing aircraft and tracked vehicles). Comparisons of REAT measurements using different fitting methods are presented from studies of single- and double-protection hearing protection strategies. The preference of the ANSI S12.6-1997 subject-fit method of measuring the performance of HPDs for hearing protectors in high-level noise environments is questioned.
Specific features of thickness resonance in finite elastic plate
Authors: Grinchenko Victor T.
Published: October 2013

The notion of the thickness resonance in the theory of oscillation of elastic elements has been formed in the scope of the two-dimensional model for infinite elastic plate. It is presumed that the corresponding frequency is eigenfrequency for the finite plate and motion in corresponding natural mode is pistonlike. The natural modes of a finite plate are formed as a result of interaction of wave motion in plane and in thickness. Contrary to the case of ideal compressible fluid these types of motion in elastic body are tightly coupled. The interaction of two types of motion results in the essential complication of the eigenforms and spectrum of eigenfrequencies in a vicinity of the thickness resonance frequency. One of the interesting phenomena is that some eigenforms have frequencies growing together with an increase of the size of the plate. The quantitative characteristics of the eigenforms and eigenfrequency spectrum in relative high-frequency domain are presented for the case of the circular plate and finite cylinder. The distribution of displacement on the surfaces of the plate for various values of Poisson’s ratio are submitted. Comparison of experimental data with results of numerical calculation is given.
Reconstruction of transient acoustic radiation from a thin disk
Authors: Bajwa Manjit , Wu Sean
Published: October 2013

The HELS method [Wu, J. Acoust. Soc. Am. 107, 2511–2522 (2000)] is extended to reconstruction of transient acoustic radiation from a highly nonspherical structure. The test object is a thin disk subject to an impulsive acceleration in an unbounded fluid medium. Since the HELS method allows piecewise reconstruction of acoustic quantities on the source surface, it is possible to focus on one side of the disk at a time. Also, since the origin of coordinates is arbitrary, one can set the spherical coordinates in such a way that the spherical surface looks almost flat locally. This treatment legitimizes the Rayleigh hypothesis and facilitates reconstruction of the normal surface velocity on the disk front surface. Reconstruction of normal surface velocity on the opposite side of the disk can be done in a similar manner. The input acoustic pressure signals are collected using an array of microphones in front of the disk and reconstructed acoustic quantities are compared with the analytic results [Wu, J. Acoust. Soc. Am. 94, 542–553 (1993)]. Results show that the accuracy of reconstruction depends on that of input signals, and convergence of the reconstructed normal surface velocity improves with an increase in the cutoff frequency of input data. [Work supported by NSF.]
Stress shift in rhythmical speech
Authors: Quené Hugo , Port Robert
Published: October 2013

In phrases like thirteen men, stress in thirteen is often shifted forward from its canonical final position. Presumably, the occurrence of this optional stress shift may be partly controlled by the rhythm of speech. Work on rhythmic speech production has demonstrated that given a repetition cycle, T, its harmonic fractions like T/2 attract stressed vowel onsets. Comparing phrases like ceMENT thirTEEN and GALaxy thirTEEN, differing in the number of weak syllables between strong ones, it was predicted that, during rhythmic production, the harmonic locations would attract shifted stress. Since shifting stress results in more even distribution of syllables through the cycle, we expected that faster repetition rates would also result in more stress shift. Dependent variables were the relative stress in the second word of each pair, and the location of onset of the nuclear vowel of the stressed syllable. Results confirmed the predictions, first, that with more intermediate unstressed syllables, stress was shifted forward more often (thereby locating the stressed vowel onset closer to T/2) and, second, that stress shifted forward more often at faster speaking rates. [Work supported by Fulbright Visiting Scholar program and by Utrecht University, The Netherlands.]
Dynamic synapse neural networks with a Gauss–Newton learning method for speech processing
Authors: Heidari Namarvar Hassan , Afshordi Dibazar Alireza , W. Berger Theodore
Published: October 2013

A continuous implementation of the biologically-based dynamic synapse neural network (DSNN) (H. H. Namarvar et al., 2001) is created by replacing the discrete nonlinear function of the synaptic cleft mechanism, which represent the neurotransmitter release in the discrete DSNN, with a continuous nonlinear function. A Gauss–Newton learning algorithm is introduced and is shown to efficiently determine the optimal parameters of a continuous DSNN being applied to a nonlinear problem in nonstationary speech processing. The continuous DSNN incorporates a new feedback architecture to model biological inhibitory mechanisms. Optimality is determined by an objective error function on the continuous DSNN output. This network has been successfully applied to the task of phoneme recognition in continuous speech. Preliminary results demonstrate that a phoneme recognizer utilizing a continuous DSNN may be successfully used as a phone recognition module in future automatic speech recognition systems. [Work supported by DARPA CBS, NASA, and ONR.]
Voice quality variations in English sentences
Authors: Epstein Melissa
Published: October 2013

This study examines the predictability of changes in voice quality at the sentence level in English. Sentence-level effects can only be isolated once the effects of linguistic factors (e.g., glottalization before a glottalized consonant), social or dialectal, and individual factors have been eliminated. In this study, these effects were controlled by obtaining a baseline value for each measurement for each word of the corpus. Voice quality variations were tracked using quantitative measurements derived from the LF model of the glottal source, and also qualitative descriptions of the waveforms. Preliminary results indicate that there are consistent voice quality differences at the sentence level and that pitch contours and sentence accent also produce predictable effects on voice quality.
Spectral moments analysis of stops in tracheoesophageal speakers
Authors: Rosenbauer Kimberly , Obert Kerrie , Fox Robert Allen
Published: October 2013

Optimal speech intelligibility is naturally of primary concern for individuals who have had their larynxes removed due to cancer and are now using tracheoesophageal (TE) speech as their primary mode of communication. The current study examines the acoustic characteristics associated with the oral stops /pbtdkg/ produced by TE speakers as compared to normal speakers. Of particular interest are the acoustic differences between these two sets of speakers in oral stop bursts and in the aspiration frication for the voiceless stops. A set of utterances in which these six stops occur in both initial position (CV) and intervocalic position (VCV) before a wide range of English vowels were recorded for each set of speakers. Appropriate acoustic measurements were then made for each stop. These measurements included the spectral moments of the burst and aspiration, VOT, closure duration (for intervocalic stops), and the relative and normalized amplitude levels of the burst and aspiration. Acoustic differences obtained will be discussed as a function of speaker type, phonetic context and, in the case of the TE speaker, experience with the device.
Adaptive interface for spoken dialog
Authors: Dusan Sorin , Flanagan James
Published: October 2013

Speech has become increasingly important in human–computer interaction. Spoken dialog interfaces rely on automatic speech recognition, speech synthesis, language understanding, and dialog management. A main issue in dialog systems is that they typically are limited to pre-programmed vocabularies and sets of sentences. The research reported here focuses on developing an adaptive spoken dialog interface capable of acquiring new linguistic units and their corresponding semantics during the human–computer interaction. The adaptive interface identifies unknown words and phrases in the users utterances and asks the user for the corresponding semantics. The user can provide the meaning or the semantic representation of the new linguistic units through multiple modalities, including speaking, typing, pointing, touching, or showing. The interface then stores the new linguistic units in a semantic grammar and creates new objects defining the corresponding semantic representation. This process takes place during natural interaction between user and computer and, thus, the interface does not have to be rewritten and compiled to incorporate the newly acquired language. Users can personalize the adaptive spoken interface for different domain applications, or according to their personal preferences. [Work supported by NSF.]
Vowels in clear and conversational speech: Talker differences in acoustic characteristics and intelligibility for normal-hearing listeners
Authors: Hargus Ferguson Sarah , Kewley-Port Diane
Published: October 2013

Several studies have shown that when a talker is instructed to speak as though talking to a hearing-impaired person, the resulting ‘‘clear’’ speech is significantly more intelligible than typical conversational speech. Recent work in this lab suggests that talkers vary in how much their intelligibility improves when they are instructed to speak clearly. The few studies examining acoustic characteristics of clear and conversational speech suggest that these differing clear speech effects result from different acoustic strategies on the part of individual talkers. However, only two studies to date have directly examined differences among talkers producing clear versus conversational speech, and neither included acoustic analysis. In this project, clear and conversational speech was recorded from 41 male and female talkers aged 18–45 years. A listening experiment demonstrated that for normal-hearing listeners in noise, vowel intelligibility varied widely among the 41 talkers for both speaking styles, as did the magnitude of the speaking style effect. Acoustic analyses using stimuli from a subgroup of talkers shown to have a range of speaking style effects will be used to assess specific acoustic correlates of vowel intelligibility in clear and conversational speech. [Work supported by NIHDCD-02229.]
Wave phase conjugation of the second harmonic in a focused ultrasonic beam
Authors: Brysev A. P. , Bunkin F. V. , Klopotov R. V. , Krutyansky L. M. , Yan X. , Hamilton M. F.
Published: October 2013

Wave phase conjugation of the second-harmonic component generated nonlinearly in a focused beam of ultrasound is investigated experimentally and theoretically. The incident field in this case is radiated from an extended volume of the fluid between the acoustic source and the phase conjugation system. A tone burst of frequency f=3 MHz was radiated into water and focused at a point midway between the source and the conjugator. Phase conjugation of the second harmonic 2f was performed inside a magnetostrictive ceramic modulated by a magnetic pump field at frequency 4f. The conjugate beam at frequency 2f reproduces quite accurately the incident second-harmonic beam everywhere between the focal plane and the conjugator. The agreement deteriorates somewhat between the focal plane and the acoustic source, because it is mainly in this region where second-harmonic generation occurs. Experimental observations are supported by analytical and numerical results. Phase conjugation using the nonlinearly generated second harmonic possesses some advantages over conventional phase conjugation of the sound beam at the source frequency. The obtained results may provide a basis for applications employing phase conjugation of harmonics in acoustic imaging and nondestructive evaluation, such as second harmonic imaging in tissue. [Work supported by RFBR, CRDF, and ONR.]
Mapping high power ultrasonic fields using a scanned scatterer
Authors: Cunitz Bryan , Kaczkowski Peter
Published: October 2013

The conventional method used to map the field of high intensity focused ultrasound (HIFU) transducers displaces a hydrophone over a grid of points in the zone of interest and provides a direct measure of the ultrasound pressure at each point. The approach has several major limitations: (1) the hydrophone is likely to be damaged while repeatedly measuring high intensity fields, (2) the resolution of the field map is limited to the size of the active area of the hydrophone which is typically on the order of 0.5 mm and large compared to some wavelengths of interest, and (3) cavitation can limit the accuracy of measurements. By placing a small scatterer in the HIFU field and measuring the scattered wave with a sensitive hydrophone from a safe distance, the field can be measured at full power without harm. We have used this technique to acquire single frequency field maps of HIFU transducers at high intensities without any damage to the hydrophone. We also have been able to improve the spatial resolution of the field map by an order of magnitude. In addition, this technique permits measurement of some non-linear behavior (e.g., harmonic content) at the focus at high intensities.
A study of angular spectrum and limited diffraction beams for calculation of field of array transducers
Authors: Cheng Jiqi , Lu Jian-yu
Published: October 2013

Angular spectrum is one of the most powerful tools for field calculation. It is based on linear system theory and the Fourier transform and is used for the calculation of propagating sound fields at different distances. In this report, the generalization and interpretation of the angular spectrum and its intrinsic relationship with limited diffraction beams are studied. With an angular spectrum, the field at the surface of a transducer is decomposed into limited diffractions beams. For an array transducer, a linear relationship between the quantized fields at the surface of elements of the array and the propagating field at any point in space can be established. For an annular array, the field is decomposed into limited diffraction Bessel beams [P. D. Fox and S. Holm, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 85–93 (2002)], while for a two-dimensional (2-D) array the field is decomposed into limited diffraction array beams [J-y. Lu and J. Cheng, J. Acoust. Soc. Am. 109, 2397–2398 (2001)]. The angular spectrum reveals the intrinsic link between these decompositions. [Work supported in part by Grant 5RO1 HL60301 from NIH.]
Cyclic and radial variation of the echogenicity from human carotid artery and porcine blood
Authors: Paeng Dong-Guk , Cao Pei-Jie , Shung K. Kirk , Chiao Richard Y.
Published: October 2013

The cyclic and radial variation of the echogenicity from human blood and porcine blood was investigated using a linear M12L transducer with a GE LOGIQ 700 Expert system. The bright collapsing ring phenomenon, a bright echogenic ring converging from the periphery to the center of the tube wall and eventually collapsing during a pulsatile cycle from the cross-sectional B mode images, was observed from porcine blood in a mock flow loop with a diameter of 0.95 cm at certain flow conditions. The bright ring phenomenon from porcine blood was stronger as the peak speed increased from 19 to 40 cm/s while the mean echogenicity decreased. As the stroke rate increased from 20 to 60 beats/minute, the phenomenon was weaker. As the hematocrit increased from 12 to 45%, the phenomenon became obvious. The black hole phenomenon was also observed at certain flow conditions. The well-known nonlinear hematocrit dependence on echogenicity was observed near the wall but the dependence pattern was changed at the center of the tube. The similar bright ring phenomenon was also observed at the harmonic images in vivo on 10 human carotid arteries. Aggregation due to the shear rate and acceleration is thought to be the explanation of the phenomena.
Detection of thrombosis and restenosis in an endovascular stent
Authors: Wu Junru , Weissman Eric
Published: October 2013

Endovascular stents that are implanted in an artery are often used in the interventional treatment of coronary artery disease. Its widespread applications are, however, limited by the development of subacute thrombosis (clot forming inside of the stent). Ex vivo experiments with pigs have shown that the broadband A-mode ultrasound is quite effective in detection thrombosis and restenosis in an endovascular stent. [Work supported by BFGoodrich and Noveon, Inc.]
A robust roughness quantification technique using a standard imaging array transducer
Authors: Samuel Stanley , Adler Ronald , Meyer Charles
Published: October 2013

Our goal is to measure cartilage roughness using intra-articular ultrasound imaging, thus providing a useful diagnostic tool for the early detection of osteoarthritis. Measuring the effectiveness of possible chondroprotective pharmacological or mechanical interventions depends on the availability of such a device. We have developed an empirical model of roughness using sandpaper for angles ranging from 20 degrees to 60 degrees at distances ranging from 25 mm to 80 mm. Roughness quantification is achieved using a scattering replacement normalization technique. An ultrasound imaging system employing a broadband 7 MHz multi-element transducer was used for insonifying the flat sandpaper surface. Dynamic focusing was performed at all distances and angles. The broadband transducer facilitates the selection of select bandwidths during analysis, which is beneficial for studying surfaces of varying roughness scales. Sandpaper of 150-, 400-, and 600-grit were examined for this study. The normalized average backscattered power (normalized with 150-grit) for 7–8 MHz frequency band provides well-behaved roughness characteristics. The students t test showed that the backscattering results for the 150- and 400-grit are significantly different with 0.025<p<0.05. We are extending this work to in vitro cartilage and will report these results as well. [Research supported by NIH R01-AR42667-01A2.]
Design and construction of a high frame rate imaging system
Authors: Wang Jing , Waugaman John L. , Liu Anjun , Lu Jian-yu
Published: October 2013

A new high frame rate imaging method has been developed recently [Jian-yu Lu, ‘‘2D and 3D high frame rate imaging with limited diffraction beams,’’ IEEE Trans. Ultrason. Ferroelectr. Freq. Control 44, 839–856 (1997)]. This method may have a clinical application for imaging of fast moving objects such as human hearts, velocity vector imaging, and low-speckle imaging. To implement the method, an imaging system has been designed. The system consists of one main printed circuit board (PCB) and 16 channel boards (each channel board contains 8 channels), in addition to a set-top box for connections to a personal computer (PC), a front panel board for user control and message display, and a power control and distribution board. The main board contains a field programmable gate array (FPGA) and controls all channels (each channel has also an FPGA). We will report the analog and digital circuit design and simulations, multiplayer PCB designs with commercial software (Protel 99), PCB signal integrity testing and system RFI/EMI shielding, and the assembly and construction of the entire system. [Work supported in part by Grant 5RO1 HL60301 from NIH.]
Correlations between vowel and the subsegments of an obstruent in CV and VCV sequences
Authors: Park Hansang
Published: October 2013

It is well known that there is a significant negative correlation between a consonant and the preceding or following vowel. However, it has seldom been specified what relationship lies between the subsegments (closure, frication, and aspiration) of an obstruent and the preceding or following vowel in Korean. This work investigates the relationship between the vowel and the subsegments of a Korean coronal obstruent in CV and VCV sequences. There was a significant negative correlation between the gap and vowel (r=−0.900) in utterance initial CV sequence but no significant correlation between frication and vowel. On the other hand, there was a significant negative correlation between the preceding vowel and closure (r=−0.510) in the VCV sequence but no significant correlation between the preceding vowel and other subsegments. There was a significant negative correlation between the following vowel and gap (r=−0.545) but no significant correlation between the following vowel and other subsegments. Generally, there was a significant correlation between the vowel and an immediately adjacent segment than between the vowel and remote segments. Correlation was stronger in the CV sequence than in the VCV sequence for the same pair of variables. Speech Communication Best Student Paper Award.
Acoustics and noise control curriculum development at Wayne State University
Authors: Wu Sean
Published: October 2013

This paper presents an overview of the curriculum development on acoustics, vibration, and noise control at Wayne State University. Special attention is given to the applications of acoustics and noise control principles to NVH (noise, vibration, and harshness) problems that are vital to the automotive industry. This emphasis is important in the curriculum development, given the fact that Wayne State is an urban university and many students are practicing engineers working at the local industries. Many hands-on experience and laboratories are included in the courses. Computer projects on the simulation of sound radiation from finite objects and on the designs of enclosures with specified transmission losses are incorporated in the course development. Research topics carried out at the Acoustics, Vibration, and Noise Control Laboratory are also integrated into the curriculum.
Helmholtz resonator with an extended neck
Authors: Lee Iljae , Selamet Ahmet , Tallio Kevin V.
Published: October 2013

The present analytical, computational, and experimental work investigates the effects of length and shape of an extended neck on the acoustic attenuation performance of a concentric circular Helmholtz resonator with a fixed cavity. For an extension with constant cross-sectional area, a 2-D analytical approach is developed to determine the acoustic behavior, while a 3-D boundary element method is employed when the cross-sectional area is allowed to vary. These results are compared with: (1) the experimental data obtained from an impedance tube setup, and (2) the classical lumped analysis to illustrate the effects of wave propagation and higher-order modes. The impact of extension and its geometry on shifting the resonance frequency is emphasized.
Application of feedback control design to improve the vibrator distortion
Authors: Lee Bai-Tang , Liu Yun-Hui
Published: October 2013

In the beginning, the power amplifier with vibrator combination of the low frequency primary vibration calibration system has total harmonic distortion (THD) of acceleration higher than 2% at most frequencies. To get better calibrated values and to meet the requirements of the International Organization for Standardization (ISO) 16063-11; a method has been developed to reduce the THD. The feedback control method is designed to reduce the signal distortion from the vibrator. The vibrator signal is measured by an accelerometer located on a moving platform that is driven by the vibrator. This signal is fed into a controller at which the difference between the signal and a pure sine wave is calculated and a modified waveform is obtained. After signal processing on the controller, this modified signal is fed back as the input signal of the vibrator to reduce the THD. As expected, the THD measured is below 2%.