bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of asymmetric vocal fold vibrations in a finite-element model
Authors: Berry David A. , Alipour Fari
Published: February 2014

Asymmetric vibrations of a finite-element model of the vocal folds were analyzed using the method of empirical eigenfunctions. In a previous study of symmetric vibrations from the model, periodic vibrations yielded two dominant eigenfunctions, which were related to the theoretical normal modes of the model. In a more recent study, the method of empirical eigenfunctions was applied to high-speed endoscopic imaging of vocal fold vibration on human subjects, suggesting several mechanisms of irregular vibration. However, in the in vivo study, the investigation of empirical eigenfunctions was limited to the superior view provided by endoscopy. The results of the present computational study were compared with the in vivo study, while providing additional information regarding vocal fold vibration along the medial surface of the folds. Moreover, the computational study allowed the asymmetric vibrations to be studied systematically as a function of tissue stiffness. [Work supported by Grant No. R29 DC03072 from the National Institute on Deafness and Other Communication Disorders.]
Prosody Workstation—Version 2
Authors: Allen George D. , Eulenberg John B.
Published: February 2014

The Prosody Workstation, Version 2 (PW2) is a low-cost, PC-based system for interactively teaching and researching prosody. This device does four different, inter-related jobs. On output from the host PC, it (1) synthesizes model utterances from stored LPCs and prosodic control parameters. On user input, it (2) extracts the F0 and intensity of the user’s productions, for comparison with the model as presented. The host PC then (3) visually displays the original model and the user’s response, with similarities and differences highlighted for the user’s information. Finally, it (4) resynthesizes either the original model or the user’s response for auditory comparison. Whereas PW1 used an expensive and no longer available signal processing board, PW2 runs on any PC running Windows and with SoundBlaster compatible sound I/O. PW2 features of interest are (a) scoring algorithms and visual displays are user selectable, permitting (e.g.) time and/or F0 normalization, selective focus on specific prosodic elements, and use of different F0 scales; (b) data acquisition is efficient, with one F0 and intensity estimate calculated for each 10 or 20 ms frame; (c) data extraction and resynthesis routines are coded as C++ DLLs, while the command modules are visual basic, permitting efficient extension of functionality. [Work supported in part by NIDCD and Michigan State University.]
Synthesis of nonperiodic features of pathological voices
Authors: Gabelman Brian C. , Kreiman Jody , Gerratt Bruce R. , Alwan Abeer
Published: February 2014

The question has been raised as to how successfully measures of nonperiodic vocal energy such as spectrally shaped aspiration noise, jitter, and shimmer can be used in modeling pathological voices, and how well listeners distinguish between these quantities. This work studies how two such quantities, spectrally shaped aspiration noise and jitter, can be used to synthesize pathological voices. Automatic algorithms for analyzing and modeling these measures are described. Tokens of the vowel [a] were inverse filtered and analyzed using a cepstral-domain comb filter algorithm to extract the aperiodic component of the vocal source. The pitch trajectory was established with an interpolating tracker and was high-pass filtered and analyzed to measure jitter. Synthetic tokens were then computed using the calculated levels of source noise alone, jitter alone, and a ratio of both, and the results compared with the original token in listening experiments. The success of each method at modeling the original token across a variety of voice samples will be described, as will implications for speech synthesis and voice perception. [Work supported by NIH/NIDCD.]
Comparison of in vitro growth and tissue behavior of two different fibroblast cell lines embedded on an artificial scaffold
Authors: Jaiswal Sanyukta , Titze Ingo R. , Martin James A. , Gray Steven
Published: February 2014

The molecular and cellular composition of the vocal folds and the relation of these to the biomechanical and physiological properties of the tissue have been of considerable interest in the current vocal fold research. The fibroblast cells establish and maintain the extra-cellular matrix of the vocal folds. These influence the visco-elastic properties of the tissue, and ultimately its functioning. The present study compares the in vitro tissue behavior of two fibroblast cell lines from the human vocal fold tissue and three from human foreskin tissue. Histological and biochemical analyses were used to investigate the inherent cytological differences between the two cell lines when cultured in a synthesized ‘‘matrixlike’’ scaffold. [Work supported by NIDCD.]
The application of M sequences to sonar
Authors: DeFerrari Harry , Birdsall Theodore
Published: February 2014

M sequences have long served as enabling technology for numerous basic research experiments to observe the fluctuations of acoustic propagation and for many acoustical oceanographic studies including ocean acoustic tomography. They provide coherent processing gain without loss of temporal resolution. Simply stated M sequences combine the energy of CW with the resolution of a pulse. In addition to processing gain, the M sequences can eliminate ping stealing and allow for environmentally friendly transmissions (lower peak pressure levels). Yet, early attempts (circa 1960) to apply M sequences to monostatic active sonar were unsuccessful. In hindsight, the inability to process Doppler and possibly an inappropriate application of a matched filter correlation are the reasons. Two approaches for M-sequence applications to sonar are discussed here, one for passive, whereby clandestine background experiments can evaluate sonar conditions, and the other for a multisource bistatic active. Ultrafast Hadamard transforms make possible full range Doppler processing for both applications and the combination of orthogonal sampling and cancellation by coordinate zeroing are applied to reduce the direct arrivals and some of the stable reverberation components for the active application. The same approach can be used to process and separate simultaneous transmissions from more than one source that transmit nearly orthogonal signals.
Intensity fluctuations of refracted bottom reflected arrivals in shallow-water propagation
Authors: DeFerrari Harry , Williams Neil , Nguyen Hien
Published: February 2014

Recent measurements of shallow-water acoustic propagation off the coast of south Florida have found persistent arrivals from low loss propagation paths. The environmental conditions that support this anomalous transmission are common at midlatitudes—specifically the combination of a downward refracting sound-speed profile with upward refracting bottom having a high critical angle, greater than 10 deg. When a source transmits from deep in the channel, refracted modes/rays are trapped above the bottom and reflect from the bottom with grazing incidence less than the critical angle. The combination accounts for low loss propagation. Further, the modes/ rays tend to reinforce and form lines of caustics at every range. The most intense caustic occurs for a receiver located at the source depth. Broadband pulse transmissions yield a single ‘‘focused arrival’’ at every range that is usually 25 dB more intense than other arrivals. Intensity fluctuations for the focused arrivals tend to have log-normal distributions with large scintillation even at short ranges (e.g., scintillation index, SI=8 at 10 km), whereas the fluctuations of intensity for other paths exhibit classical statistics with exponential distributions (Rayleigh) and SI=1. Fluctuations are analyzed for several frequencies of transmission and receiver depths.
Predictability of shallow water sound transmission in selected shallow water experiments
Authors: Carey William M. , Siegmann William L.
Published: February 2014

This paper summarizes our efforts to compare calculations in several shallow water areas using range dependent models with results from coherent sound transmission experiments. The approach is to use detailed environmental and geophysical measurements to determine acceptable ranges of input parameters for the range dependent calculations, and then to determine within these bounds the ability to calculate the pressure amplitude, the phase of the signal, and the modal wave number spectrum. In addition, the coherence of the transmitted signal and the measurement of relative array signal gain were estimated. Although shallow water is known for its variability, these investigations clearly demonstrate predictable metrics of sound transmission, provided a sufficient type and an amount of environmental data are known. These investigations also show the key factors in this variability for acoustic predictability and highlight the areas of uncertainty. These results further suggest that shallow water variability and sound transmission can be calculated deterministically with dynamic changing environmental oceanographic variables.
The PDF of intensity for Ocean WPRM—15 years later
Authors: Ewart Terry E.
Published: February 2014

Spatial intensity correlations for wave propagation in random media (WPRM) can be predicted in terms of the index of refraction space-time autocorrelation function, with scattering parameters Gamma (strength) and X (scaled range) in the iso-velocity case. In ocean WPRM the temporal intensity correlations are also well predicted from the modeled index of refraction spectrum for the lower path in sub-CZ propagation with a depth-dependent sound speed profile (Eastern Pacific). For both of these cases the intensity pdf’s have been shown [Ewart and Percival, 80, 1745–1753 (1986)] to be very well fit by generalized Gamma distributions. In that work quantile–quantile goodness of fit tests were used to test the generalized Gamma hypothesis. The upper path intensity correlations, in sub-CZ propagation, however, have not been predicted. The pdf’s of upper path data taken during MATE will be discussed. Several authors have proposed functional forms of intensity pdf’s, e.g., one distribution modulated by another. Quantile-quantile tests will be applied to see if such functions model ocean WPRM intensity pdf’s. [Work supported by ONR.]
A microphone array for hearing aids
Authors: Widrow Bernard
Published: February 2014

A directional acoustic receiving system is constructed in the form of a necklace including an array of two or more microphones mounted on a housing supported on the chest of a user by a conducting loop encircling the user’s neck. Signal processing electronics contained in the same housing receives and combines the microphone signals in such a manner as to provide an amplified output signal which emphasizes sounds of interest arriving in a direction forward of the user. The amplified output signal drives the supporting conducting loop to produce a representative magnetic field. An electroacoustic transducer including a magnetic field pick-up coil for receiving the magnetic field is mounted in on the user’s ear and generates an acoustic signal representative of the sound of interest. The microphone output signals are weighted (scaled) and combined to achieve desired spatial directivity responses. The weighting coefficients are determined by an optimization process. By bandpass filtering the weighted microphone signals with a set of filters covering the audio frequency range and summing the filtered signals, a receiving microphone array with a small aperture size is caused to have a directivity pattern that is essentially uniform over frequency in two or three dimensions. This method enables the design of highly directive hearing instruments, which are comfortable, inconspicuous, and convenient to use. The invention provides the user with a dramatic improvement in speech perception over existing hearing aid designs, and particularly in the presence of background noise and reverberation.
The relationship between the amount of information and the value of information in animal communication
Authors: Bradbury Jack
Published: February 2014

How much information should senders try to provide and receivers try to extract from signals? Using a simple but generalizable model of communication, it will be shown that the net payoff to either party for communicating, called the value of information, is not a linear, or even monotonic, function of the amount of information. Because receivers invariably have a default (no-signal) strategy that is better than chance, a signal must exceed a minimal threshold of accurate information before receivers should attend to it. Because costs of producing and analyzing increasingly accurate signals tend to rise faster than benefits above the minimal threshold, there is also an upper limit on how much information is worth the effort. These conclusions have important implications for how new signals are likely to evolve, and how much error we should expect to see in real animal communication systems.
Entropic structure of chickadee calls
Authors: Hailman Jack P.
Published: February 2014

Language-like ‘‘chick-a-dee’’ calls of the black-capped chickadee are combinations of four note types with repetitions but no permutations. Written English has higher values of entropy (bits/letter) than calls (bits/note) at all orders of a Markov chain because it has 26 elements compared with only four. More importantly, the values of bits/letter falls evenly with increasing orders of Markov chain, reflecting long-range dependencies, whereas values of bits/note drop noticeably from entropy based on probability of occurrence to that based on probability of transition to the next note. This latter structure has been called ‘‘semi-Markovian’’ and reflects the lack of permutation in this chickadee’s calls. The ‘‘entropic structure’’ of calls also differs from that of English words, which have a theoretically immense channel capacity. Nevertheless, constraints on English are so severe that actual words on the average have less than twice the source entropy of calls (11.8 bits/word vs 6.7 bits/call). English is far more informative than chick-a-dee calls, though, because words are themselves combined into meaningful sentences whereas successive chick-a-dee calls appear to be merely repetitive.
Role of beamwidth in lung hemorrhage induced in adult rats by exposure to pulsed ultrasound
Authors: Frizzell Leon A. , O’Brien William D. , Simpson Douglas G. , Zachary James F.
Published: February 2014

The objective of this study was to assess the role of beamwidth on ultrasound-induced lung hemorrhage in rats. A total of 144 10- to 11-week-old 257±21-g female Sprague–Dawley rats were randomly exposed to pulsed ultrasound at three exposure levels and four beamwidths (12 rats/group). The three in situ peak rarefactional pressures were 5.0, 7.4 and 10 MPa. Four 19-mm-diam focused transducers were used to obtain the −6-dB beamwidths of 470 μm (2.8 MHz, f/1), 930 μm (2.8 MHz, f/2), 310 μm (5.6 MHz, f/1), and 510 μm (5.6 MHz, f/2) at the pleural surface. Exposure durations were 10 s, pulse repetition frequencies were 1 kHz, and pulse durations were about 1 ms. The lesion surface area and depth were measured for each rat as well as the percentage of rats with lesions per group. Each lesion parameter exhibited a significant dependence upon beamwidth, but no dependence on frequency. Logistic regression analysis was used to determine an ‘‘effective dose’’ threshold for 5% (ED05) probabilities of lesions. The ED05 exhibited no dependence on the beamwidth. [Work supported by NIH Grant HL58218.]
Cavitation mediated rat lung bioeffects from diagnostic ultrasound
Authors: Holland Christy K. , Roy Ronald A. , Biddinger Paul W. , Disimile Christopher J. , Cawood Cheryl
Published: February 2014

Several animal models have exhibited petechial hemorrhage in the lung within the current FDA output limit of diagnostic ultrasound systems. To elucidate the mechanism of damage, seven rat lungs were simultaneously exposed or sham exposed in vivo to 6-MHz pulsed Doppler ultrasound and interrogated with a confocally aligned 30-MHz active cavitation detector (ACD) [R. A. Roy, S. Madanshetty, and R. E. Apfel, J. Acoust. Soc. Am. 20, 2451–2455 (1990)]. The right lung lobes of four 200 g rats were insonified with an ATL HDI 3000 6.0-MHz Doppler pulse for 1.5 min and three rats were sham exposed. At the termination of ultrasound or sham exposure, each animal was immediately euthanized with sodium pentobarbital (200 mg/kg IP) and lung tissues were removed intact, inflated with buffered formalin, and examined by a pathologist who was blind to the exposure conditions. Histologically, damage was observed in the lungs exposed to ultrasound as extravasation of erythrocytes into the alveolar spaces. The ACD signal received was analyzed for the presence of increased scattering and radiated noise from inertial cavitation. The variance of the sequentially obtained ACD received pulses correlated with the damage in the exposed lungs. We conclude that inertial cavitation mediated the damage from diagnostic ultrasound. [Work supported by NIH R29 HL58761-02.]
Magnetostrictive transducer performance characterization
Authors: Flatau Alison , Kellogg Rick A.
Published: February 2014

An overview of work done on the characterization of magnetostrictive materials and magnetostrictive transducers will be presented. Experimental results obtained from a test device sized for use with 0.25 in. diameter by 2.0 in. long samples will be presented. Tests were conducted at constant temperatures ranging from 0–75°C as the sample underwent cyclic magnetic fields and/or cyclic mechanical stresses. Test results include characterization of samples of Terfenol−D under varied temperatures, cyclic stress, and cyclic fields. The output force−−strain relationship typical of the performance of Terfenol−D transducers under varied operating conditions is examined to study transducer blocked force characteristics. The design and construction of a transducer for testing under controlled thermal, magnetic, and mechanical load conditions are described. Results of compression tests used to generate load lines and the blocked force characteristics of the transducer will be discussed. Comparisons of the transducer’s force and strain output are made with published data. This test data is also used to examine the variability in Young’s Modulus with applied magnetic field, strain, and stress. [Work supported by NSF and the Carderock Division of the Naval Surface Warfare Center is gratefully acknowledged.]
Investigation of eddy current losses in laminated TERFENOL-D drivers
Authors: Slaughter Julie
Published: February 2014

One of the most significant loss mechanisms in TERFENOL-D is eddy currents. Performance of the active material is reduced both by heating of the magnetostrictive element, and thus decreased magnetostrictive capability, and also by reduced magnetic field intensities in the active material. Accurate predictions of eddy current losses in TERFENOL-D are necessary to avoid too few laminations, which reduces performance, or too many laminations, which unnecessarily increases costs. Eddy current losses in TERFENOL-D drivers of different configurations were investigated for realistic operating conditions. Drivers of the same size with different lamination configurations were tested at frequencies from 10 Hz up to 8 kHz. At each frequency, energy loss per cycle per unit volume due to eddy currents was calculated. Comparisons were made between the experimental data, theory for infinite sheets, and finite element analysis. Very good agreement was achieved between the FEA and the experiments. Poor agreement was shown between theory and experiment. Eddy current losses are over-predicted by infinite sheet theory. In order to achieve accurate estimations of eddy current losses, more sophisticated analysis methods, such as finite element analysis, must be used.
Propagation of short pulse through arbitrary relaxing media with resonant properties. A new approach
Authors: Maksimov German A. , Larichev Vladimir A.
Published: February 2014

The new analytical representation of fundamental solution (Green’s function) describing the short-pulse propagation in medium with single process of resonant relaxation is presented in this report. This analytical solution is based on the generalized local response function of linear media [V. A. Larichev and G. A. Maksimov, Acoust. Phys. 44, 709–716 (1998)]. It contains well known Lorentz and Ziner models of relaxing media, as particular cases. The changing of pulse shape at propagation, described by obtained solution, shows a variety of forms of pulse propagation and general lows of pulse dynamics beginning from pure relaxation behavior and up to a resonant one. [Work supported by Russian Found Dasic Research (Project No. 00-02-16556).]
Acoustic stop bands and discrete transmission in slender tubes
Authors: Kushwaha M. S. , Akjouj A. , Djafari-Rouhani B. , Dobrzynski L. , Vasseur J. O.
Published: February 2014

Extensive band structures and transmission spectra for longitudinal (acoustic) wave propagation in a system made up of N′ dangling side branches (DSB) periodically grafted at each of the N equidistant sites on a slender tube have been computed. A periodic pattern of large stop bands is obtained for the airy DSB on a slender water tube. Noteworthy are the interesting results of huge gaps and discrete transmission spectrum due only to the DSB grafted at a single site (N=1) on the slender tube. Designing the system with open tubes allows achievement of the lowest gap below a threshold frequency and extending up to zero—thereby providing an entirely discrete band structure and transmission spectrum. This should have important consequences for the suppression of low-frequency noise and for designing filters and transducers.
Ultrasonic resonances in the presence of ray chaos
Authors: Ellegaard Clive
Published: February 2014

The work described here was inspired by quantum chaos and will in large part be discussed in terms of models based on random matrix theory. We study wave mechanics of a system very different from quantum systems, namely ultrasonic resonances of solid objects. We measure the frequency spectra—the eigenvalues—and the standing wave patterns—the eigenfunctions. We are mostly looking at freely vibrating plates. The plates can have regular or chaotic shapes, where regular and chaotic are defined in terms of whether we in the ray limit have chaos or not. By going to the acoustic system we will be testing the predictions of RMT on systems governed by a much more complex wave equation than the Schrödinger equation. In plates the acoustic waves can be either flexural, in-plane compressional, or in-plane shear. These will be mixed through mode conversion at the boundaries and other perturbations so there will in general be complex mixtures in the standing waves. We show different experimental techniques for separating the different modes. We measure transitions from regularity to chaos and show the effects of specific symmetry breaking, some of these unique to the acoustic system.
Random matrix theory, random point process theory, and natural frequency statistics
Authors: Langley Robin S.
Published: February 2014

There has been much recent interest in the application of random matrix theory to the dynamics of uncertain engineering structures. In particular, it has been found experimentally and numerically that the results arising from the Gaussian orthogonal ensemble (GOE) are applicable to natural frequency spacing statistics. The occurrence of natural frequencies can also be viewed as a random point process, and although there is much in common between random point process theory and random matrix theory, the two subjects appear to have been developed independently. It is shown here that the two approaches employ very similar mathematical functions, albeit under a different name: For example, the distribution function (point process theory) corresponds to the n-point correlation function (random matrix theory), and the cumulant function corresponds to the n-level cluster function. By recognizing this similarity, it is possible to apply a number of established results in random point process theory to the statistics of the eigenvalues of a random matrix. This leads to new insights into the statistics of natural frequency spacings, and helps to explain why the Wigner surmise (which states that the spacings have a Rayleigh distribution) is applicable to a much wider class of matrix than the GOE.
Spectral power variances for random matrix systems at moderate modal overlap
Authors: Rozhkov Igor , Weaver Richard L.
Published: February 2014

Recent work has established statistical equivalence between the spectra of generic undamped structures and those of typical members of the Gaussian orthogonal ensemble (GOE) of random matrices. This suggests that a kind of universal behavior may obtain for the statistics of the power transmission coefficient in weakly damped generic structures. Unfortunately modal statistics are modified by nonproportional damping, and the GOE is not directly applicable. The power transmission coefficient is the square of elements of the matrix inverse to [[H]−i[C]−E[I]] where [H] is a GOE matrix (effectively the stiffness of the structure), [C] is a (symmetric) damping matrix, E is frequency squared, and [I] is the identity. In the case that [C] is proportional to the identity (or more generally when C is diagonal in the natural basis), power transmission variances can be determined theoretically using the known properties of the GOE. Numerical simulation confirms that theoretical prediction. Further numerical simulation, in the case in which [C] is nonproportional, agrees with laboratory measurements in demonstrating a power variance that is significantly lower than the naive theory predicts. Possible modifications of the theory are discussed, including Efetov’s supersymmetry method and Mello’s statistical S matrix.
The relationship between production of suprasegmental speech characteristics and lung volumes in conversational speech
Authors: Bunton Kate , Petska Jill
Published: February 2014

‘‘Monopitch’’ and ‘‘monoloudness’’ are frequent descriptors of speech produced by people with dysarthria, these terms correspond to acoustic findings of flattened F0 contours, limited rms variability, and short phrases. Underlying reasons for these production characteristics, however, have not been investigated. The present study was designed to look at the relationship between use of lung volumes in conversational speech and the production of suprasegmental characteristics in healthy speakers versus those with Parkinson disease. Measures of the suprasegmental components of the speech signal included, F0 and rms variability, breath group duration, and number of syllables. Measures of starting and stopping lung volumes for each of the breath groups were also obtained. Results indicate a tendency for subjects to alternate a longer breath group, started at a higher lung volume, with exaggerated prosodic characteristics with a much shorter breath group. Although this pattern was seen in the disorder group, the length of their breath group, and F0 and rms variability were limited. The disorder group also tended to initiate utterances at lower lung volumes and continue speaking past resting expiratory level. [Work supported by NIDCD DC-01409.]
Schwas with and without active gestural control
Authors: Smorodinsky Iris
Published: February 2014

This study investigates whether some epenthetic vowels are targetless, that is, whether they can arise from the timing of the surrounding consonants [C. P. Browman and L. Goldstein, Papers in laboratory phonology II: Gesture, segment, prosody, 26–56 (1992)]. Specifically, the difference in targetlessness between past tense and lexical schwas in American English is examined. Articulatory data were collected from three speakers of American English using an electromagnetic midsagittal articulometer. The stimuli included phrases with past tense and lexical schwas embedded in a common environment: for example, ‘‘If cheated even once’’ (past tense schwa) and ‘‘If Cheetah’d even known’’ (lexical schwa). If the tongue body is assumed to be controlled continuously by the targetful vowels, the tongue body position ‘‘during a schwa’’ should not differ significantly from the tongue body position during the preceding vowel in the epenthetic schwa tokens while it would in the lexical schwa tokens. In addition, if the lexical schwas have tongue body gestures associated with them but the past tense schwas do not, a significant interaction between schwa type and vowel context is expected. These results would provide evidence of a difference in targetlessness between the past tense and lexical schwas in American English. [Work supported by NIH.]
Articulatory and acoustic relations during variations in speech rate and loudness
Authors: Green Jordan R. , Weismer Gary
Published: February 2014

Rate and loudness manipulations are standard treatment strategies used to recover speech intelligibility. Although numerous studies have characterized the articulatory changes that result from these manipulations, their influence on segmental aspects of the acoustic signal are not well understood. This preliminary investigation examines acoustic, electromyographic (EMG), and kinematic changes associated with elicited modulations of rate and loudness in typically speaking individuals. Participants were instructed to repeat a sentence five times while incrementally increasing or decreasing either their speaking rate or loudness with each repetition. Acoustic measures included total utterance durations, segment durations, vowel formant frequencies, and trajectories. Displacements of the upper lip, lower lip, and jaw were captured in three dimensions using a computerized video movement-tracking system. Surface EMG signals were recorded from the right masseter, right temporalis, and submental group. Data analyses were directed toward describing the degree of correspondence among parametric changes in muscle activity, articulatory kinematics, and segmental features of the acoustic signal that result from nearly continuous changes of rate and loudness. [Work supported by NIH-NIDCD.]
Developmental changes in the production of obstruents. II. An acoustic analysis of voiced obstruents
Authors: Frieda Elaina , Nissen Shawn L. , McGory Julie , Fox Robert A. , Rosenbauer Kim , Friedman Kelly
Published: February 2014

This is one of two papers measuring the acoustic structure of prevocalic obstruents in children and adults, examining age-related differences. This study looks at voiced consonants. The data will be drawn in part from a large scale acoustic database developed in collaboration with ATR and include word initial voiceless obstruents from real words (in a range of phonetic contexts) as well as a series of syllable initial intervocalic obstruents drawn from nonwords (in the constrained context [a —a]). Of particular interest are the intervocalic consonants, as there is a relatively limited amount of knowledge on the acoustic nature of obstruents produced by children in this position. Utterances elicited from speakers ranging in age from 3–70 years were recorded online in a quiet room environment using high quality microphones and direct analog-to-digital conversion to computer disk. Acoustic measurements collected include the spectral moments, formant transitions, VOT, percentage of voicing during consonant closure or approximation, closure duration (for stops), noise duration (for fricatives), and preceding vowel duration. Acoustic differences obtained will be discussed as a function of age group, gender, and phonetic context. [Work supported by an INRS Award from NIH and research funding from ATR (Fox, P.I.).]
Dialectal differences in vowel articulations in pre-consonantal contexts
Authors: Turk Alice , Scobbie Jim , Hewlett Nigel
Published: February 2014

Many varieties of English show the well-known pattern of longer vowels before voiced consonants, at least in monosyllabic words. Scottish English, however, shows a different pattern of adjacent-consonant conditioned vowel duration for the vowels /i,u,ai/: In this variety, short vowels are found before tautomorphemic voiceless stops, voiced oral and nasal stops, and voiceless fricatives. Long vowels are found before voiced fricatives and morpheme boundaries. For example, ‘‘bead,’’ ‘‘bean,’’ and ‘‘beat’’ and ‘‘peace’’ all contain short vowels, while ‘‘please,’’ ‘‘free,’’ and ‘‘freed’’ contain long vowels. This contextually conditioned durational pattern has been described by the Scottish vowel length rule (SVLR). We conducted an EMA study of the SVLR to examine the articulatory strategies speakers use to produce these well-documented acoustic durational patterns. We are particularly interested in (1) whether there is a single mechanism underlying all long duration vowels, i.e., those conditioned by tautomorphemic /z/ as compared to tautosyllabic but heteromorphemic /z/ and /d/, and (2) whether the strategy Scottish English speakers use to lengthen vowels in the SVLR conditioning environments is the same as that used by speakers of other varieties to produce longer vowels before voiced obstruents. [Work supported by ESRC.]
Analysis of acoustic telemetry signals in the surf
Authors: Stroud John S. , Commander Kerry W. , McDonald Robert J. , Wilbur JoEllen
Published: February 2014

The 2000 Surf Zone Acoustic Telemetry Experiment (SZATE) was conducted off of the Scripps Institute of Oceanography pier in La Jolla, CA. In this experiment, measurements were conducted in a very shallow-water/surf zone (VSW/SZ) region to investigate acoustic propagation and sound channel stability in the coastal area. These measurements utilized two receivers and a broadband source projecting shoreward toward the receivers. The data to be presented were acquired by a computer-controlled system designed and operated by Grant Deane of Scripps Institution of Oceanography. This system provided for 12 18-min data acquisition periods per day. The probative transmissions to be discussed consisted of a variety of linear frequency-modulated (LFM) and binary phase shift keyed (BPSK), as well as 4-ary frequency shift keyed (FSK) signals. Each of the types of signals was used during each data acquisition period, providing a record of propagation throughout the tidal cycle. Results of this acoustic measurement to be presented include the mean, variance, and probability density function of the integrated energy as well as the delay spread (duration) of the complex baseband impulse response of the channel. [Work supported by ONR.]
The effect of Doppler shift/spread on the performance of the phased locked loop for phase coherent underwater acoustic communications
Authors: Yang T. C.
Published: February 2014

Phase coherent acoustic communication systems, which employ joint adaptive channel equalization and phase-locking synchronization, have been shown to yield a much higher symbol rate (e.g., 1–2 kb/s at 2–5 kHz) by successfully tracking and updating time varying acoustic channels dominated by multipath components. While the decision feedback equalizer (DSE) can in principle adapt to the change of both the signal amplitude and phase, the adaptation rate (requiring typically 20–30 symbols) is in practice too slow compared with the phase rate, hence an additional phase locked loop (PLL) is required. However, the PLL has its limitations. It is found in data analysis that the failure of the PLL is responsible for the high bit error rate (BER) for many situations. This paper illustrates the effect of the phase shift/fluctuations (emulating the Doppler shift/spread) on the performance of PLL and BER, keeping the channel impulse response fixed in time. It is shown with at-sea data that the BER is significantly reduced by removing the phase wander after precise Doppler estimation. The residue phase is apparently below the tolerance threshold as determined by simulations. [Work supported by ONR.]
Temporal coherence: A critical function for phase coherent underwater acoustic communications
Authors: Yang T. C. , Al-Kurd Azmi
Published: February 2014

The temporal evolution of an acoustic channel can be characterized by its temporal correlation function from which temporal coherence (the value) and temporal correlation time (at coherence equal to, say, 0.5) can be deduced. Temporal coherence and correlation time have been experimentally measured in the past when the coherence time is much longer than the pulse duration. This is the intra-packet coherence. As frequency increases to tens of kHz or above, the coherence time can be shorter than the packet length. Under such circumstances, the channel coherence can impede the equalizer performance. In the extreme case when the coherence time is shorter than the multipath delay time, the later arrivals may travel through a channel that is different from the earlier arrivals. This paper presents the simulation of communications signals through a time-evolving channel including random media due to internal and turbulence for which temporal correlation time can be predicted for stationary source/receivers. For moving source/receivers, the temporal correlation time (the inverse of the Doppler spread) can be significantly shorter. The performance of the equalizer is found limited by the coherence value. Some at-sea data are presented that support the simulation predictions. [Work supported by ONR.]
Effect of vibration of porous absorbent layers in the cavity of a multiple-leaf structure on its acoustic properties
Authors: Sakagami Kimihiro , Yairi Motoki , Morimoto Masayuki , Minemura Atsuo , Andow Kei
Published: February 2014

Porous absorbent layers are often used in the cavity of multiple-leaf acoustic panels in buildings to reduce the sound power radiated by the panels or to enhance the panel absorption. It is known that bulk vibration of the porous layer can result in the reduced transmission loss of the multiple-leaf acoustic panel. This work presents a simple method to account for the effect of the bulk vibration of the layer on its acoustic resistance. In this method the ‘‘modified’’ flow resistance of the layer is defined as the real part of the parallel impedance in the electro-acoustical equivalent model. The model relates the impedance to the flow resistivity and the density of the porous layer. The ‘‘modified’’ flow resistance is then used to predict the propagation constant and the characteristic impedance of the material using the appropriate model for sound propagation in rigid-frame porous materials. As an application, the effect of a porous layer in the cavity of double-leaf panels on the radiated sound power is studied. Calculated examples show that the acoustic efficiency of the layer decreases at low frequencies. The reduction in the acoustic efficiency is more pronounced in the case of porous materials with high-flow resistivity.
Nonlinear behavior of poroelastic absorbing materials
Authors: Umnova Olga , Attenborough Keith , Cummings Alan
Published: February 2014

A theory for the non-linear acoustic behavior of porous materials with an elastic frame composed of incompressible grains or fibers has been derived. Johnson’s expression for complex flow resistivity [D. L. Johnson et al., J. Fluid. Mech. 176, 379–402 (1987)] has been combined with the dependence of dc flow resistivity on the amplitude of particle velocity (Forchheimer’s nonlinearity). The frame compressibility has been assumed to be linear. The system of coupled nonlinear equations for slow and fast planar compressional modes propagating in the material has been solved approximately by method of slow varying amplitudes. As a result of calculations the dependence of surface impedance on the amplitude of sound wave has been obtained for either fixed or moving surfaces. For all of the parameter values considered so far, it is predicted that the amplitude of the reflection coefficient increases with the incident sound intensity. This approach has been extended to allow for waves reflected from rigid backing of a layer of material. The influence of nonlinearity on the impedance of a sample of finite thickness has been estimated. [Work supported by USARSDG (UK), Contract No. R7D 8901-EN-01.]
The precedence effect in budgerigars (Melopsittacus undulatus)
Authors: Dent Micheal L. , Dooling Robert J.
Published: February 2014

When localizing sounds in a reverberant environment, the precedence effect allows us to localize direct sounds accurately while disregarding the many echoes in that environment. The precedence effect has been well studied behaviorally in humans and behaviorally and physiologically in other animals. Until now, however, precedence effect experiments in birds have been limited to barn owls. These birds have highly specialized auditory systems; nothing is really known about how unspecialized birds deal with competing sound sources. Budgerigars (Melopsittacus undulatus) are excellent subjects for this type of investigation since so much is known about their hearing. These birds have unremarkable sound localization abilities, but exhibit free-field binaural unmasking at amounts similar to those found in humans with much larger heads. We examined whether budgerigars exhibit the precedence effect, and if the phases of the precedence effect were similar to those found in humans and other animals. Psychoacoustic methods were used to measure the discrimination performance of click pairs from different locations separated by a short delay. The results suggest that budgerigars exhibit the precedence effect and that the time-courses are similar to those found in humans and other animals. [Work supported by NIH MH12698 to MLD and DC00198 to RJD.]
Underwater masked thresholds of the West Indian manatee
Authors: Gerstein Edmund R. , Gerstein Laura A. , Forsythe Steven E. , Blue Joseph E. , Forsythe Steven E.
Published: February 2014

Underwater acoustic masked thresholds at 0.5, 1.6, 3, 6, 12, 18, and 26 kHz were obtained from two test-sophisticated West Indian manatees using a forced-choice, two-alternative, paradigm and an up–down staircase psychometric method. Pure tones were presented under two different stimulus conditions: (1) as pulsed signals; and (2) as nonpulsed signals. Under both stimulus conditions the tones were presented against a 1/3 octave continuous white-noise masker. Three different masking intensities were used to simulate moderate ambient noise levels recorded from manatee habitats. Masked thresholds across frequencies increased in a linear fashion with increased masking intensity. Critical ratios for both stimulus conditions increased with higher frequencies, however, thresholds for pulsed signals were significantly lower than nonpulsed signals suggesting some attenuation or higher-order inhibitory process affected the perception of nonpulsed tones. Comparisons of critical ratios with other marine mammals suggest manatees have acute filtering abilities for detecting pulsed tones under continuous noise conditions. While manatees do not exhibit a rich vocal repertoire to account for acute filtering abilities, they are passive listeners which may be adapted to selectively filter out continuous noise in favor of detecting biologically significant sounds like their pulsed 200–500 ms species-specific calls.
Contrast agent-induced cardiac arrhythmias in rats: Exposimetry and clinical findings
Authors: Hartleben Sarah A. , O’Brien William D. , Frizzell Leon A. , Zachary James F.
Published: February 2014

Other than minor contraindications, no known meaningful health risks have been reported following the use of microbubble ultrasound echogenic contrast imaging agents in the United States. Recently, a report from the Netherlands has documented premature ventricular contractions during triggered second harmonic imaging of a contrast agent for myocardial perfusion in healthy male volunteers. Because of this report, we designed a study to characterize electrocardiogram conduction abnormalities in rat hearts exposed to pulsed ultrasound following injection of a contrast agent. We used a focused f/1 3.1-MHz, transducer that had in situ (at the heart) peak rarefactional and compressional pressures of 15.9 MPa and 36.1 MPa, respectively, 1.7-kHz PRF, 1.2-μs pulse duration, and MI of 5.8. Rats had no meaningful conduction abnormalities when exposed to ultrasound alone or contrast agent alone but developed premature atrial and ventricular complexes and polymorphic ventricular tachycardia when a contrast agent was administered intravenously and the heart exposed to pulsed ultrasound. When ultrasound exposure was concluded, cardiac arrhythmias ceased but reoccurred when ultrasound exposure was resumed. These results suggest that a microbubble contrast agent through its biomechanical interactions with pulsed ultrasound has the potential to induce conduction abnormalities leading to potentially hazardous cardiac arrhythmias. [Work supported by NIH Grant No. HL58218.]
Ultrasound assisted clot lysis for stroke therapy
Authors: Shaw George J. , Hahn Nancy L. , Wagner Kenneth R. , Kanter Daniel S. , Holland Christy K.
Published: February 2014

Thrombolytics such as tissue plasminogen activator (tPA) have advanced the treatment of ischemic stroke. To aid in the development of a transcranial ultrasound thrombolysis system (TUTS), the synergistic thrombolytic effect of tissue plasminogen activator (tPA) and 1-MHz ultrasound was assessed in vitro in a porcine clot model. Thirty clots were made by incubating 2-ml aliquots of citrated whole pig blood with 2 μl of bovine thrombin (1 NIH Unit/μl) at 37 °C for 3 h, refrigerated overnight, blotted, and weighed. Clots were placed in an acoustically transparent latex sample holder filled with porcine fresh frozen plasma and tPA at a clinically relevant concentration of 0.0126 mg/ml. The clots were either sham exposed to ultrasound (0.0-atm amplitude) or exposed to 1-MHz pulsed ultrasound over a range of duty cycles (10%–100%) at two amplitudes (1.9 and 11.4 atm) for 30 min in a 37 °C water bath, and were weighed to determine the efficacy of thrombolysis. Clots that received continuous wave ultrasound treatment exhibited significantly more thrombolysis than those that were sham exposed (p=0.001, students t-test). The TUTS technology promises to improve the effectiveness of thrombolytic drugs so that ultimately lower concentrations of drugs can be used for faster recanalization of blocked arteries. [Work supported by The Neuroscience Institute, University of Cincinnati Medical Center.]
Magnetostrictive transducer configurations and modeling
Authors: Butler John L.
Published: February 2014

The advent of the highly active magnetostrictive material, Terfenol-D (Tb0.27Dy0.73Fe1.9), by Clark and co-workers in the 1970s has yielded the realization of high power magnetostrictive transducers. The national and recent international availability of this material together with price reductions should spawn more common usage of Terfenol-D in transducers. However, the incorporation of this material requires additional design considerations including a different type of equivalent circuit than used in the piezoelectric models along with associated magnetic circuitry including eddy current losses and magnetic bias considerations. We present a review of some of these considerations including properties, fundamental theory, equivalent circuits, matrix representations, and other modeling tools. Along with this background, we present examples of transducer designs, which incorporate the Terfenol-D material in some interesting unconventional designs as well as in some conventional designs.