bluuebunny/crossref_metadata_2025 huggingface dataset:
Overview of wavelets and applications
Authors: Lakey Joseph D.
Published: October 2005

Construction of orthogonal and biorthogonal wavelets as well as redundant wavelet frames will be reviewed. Fast computational wavelet-based algorithms will be outlines and their performance will be compared with Fourier-based algorithms. Various applications of wavelet analysis in speech compression and speech recognition, as well as broader applications in acoustic signal processing including denoising and transient analysis, will be discussed.
Effects of reverberation cues on distance identification in virtual audio displays
Authors: Brungart Douglas S. , D’Angelo William
Published: October 2005

Although reverberation is known to play an important role in the perception of distance, it is not possible to isolate the effects of early and late reflections in a real environment. A virtual audio display, however, can be used to examine the effects of early and late reflections on distance identification. In this experiment, a virtual audio display simulates distant sound sources under 4 conditions: Without reflections, with an early reflection (floor reflection) only, with late reflections (reverberation) only, and with both early and late reflections. In each trial, the subjects identify the distance of the simulated sound source from one of 5 possible distances: 2, 4, 8, 16, and 32 ft. Numbered targets are placed at the locations of the simulated sound sources, allowing the subjects to visualize the distances involved. White noise and speech are used as stimuli in the experiment, and their amplitudes are randomized over 24 dB to prevent identification based on intensity alone. The results will be analyzed to measure the percentage of correct responses at each distance and the information transfer in each of the 4 conditions.
Frequency discrimination in noise by untrained listeners
Authors: Werner Lynne A.
Published: October 2005

The frequency discrimination performance of adults, with no prior experience as listeners in psychoacoustic experiments, was examined for tones of 1000 and 4000 Hz presented in a background of broadband noise. The tones were presented at a signal-to-noise ratio expected to produce 80% correct detection. The level of the stimuli was either 45 or 60 dB SPL. The subjects were tested in a procedure similar to one used in infant psychoacoustics [Olsho etal., Devel. Psychol. 23, 627–640 (1987)]. Threshold values of Δf were found to be more similar to those of well-trained listeners at 4000 Hz than at 1000 Hz. The effects of stimulus level were similar to those reported by Dye and Hafter [ 1748–53 (1980)] for well-trained listeners: Threshold Δf increased with increasing level at 4000 Hz, but not at 1000 Hz. This result suggests that the effects of level on frequency discrimination in noise are robust enough to be replicated in subjects with little listening experience. Further, the effects of level on human infants’ frequency discrimination in noise may provide important information about why their frequency discrimination in quiet is more adultlike at high frequencies. [Work supported by NIDCD DC00396.]
A longitudinal investigation of children’s duration and temporal variability in speech production
Authors: Smith Bruce L. , Kennedy Mary Kay , Hussain Sarmad
Published: October 2005

A number of cross-sectional studies have observed that children’s speech segments tend to decrease in duration and also become less variable from younger to older groups of subjects. Because cross-sectional investigations have certain limitations when they are used to study children’s development, it is also important to conduct longitudinal analyses of speech production development. The present study provides data based on a longitudinal analysis of the speech of 12 children. When they were initially seen, the children ranged from 7–11 years of age; they were evaluated again after approximately 1–1/2 years. At both ages, the children were recorded as they produced 25 repetitions of each of several different words and short phrases, from which various segments and syllables were measured. Results indicate that, on average, segment and syllable durations decreased from the initial to the follow-up recordings by approximately 10%, whereas temporal variability was found to decrease by about 40%. Although the relative decrease in the children’s temporal variability was substantially greater than the decrease in their duration across the year-and-a-half time period, their durations were considerably more adultlike than their variability at both times they were studied.
Conversion of an SH wave into a Stoneley wave under weak distortion of the elastic isotropic space material of a crystal lattice
Authors: Rossikhin Yuriy A. , Shitikova Marina V.
Published: October 2005

The problem of the conversion of a volume SH wave propagating in an isotropic elastic space into a Stoneley wave as a consequence of the conversion of this space into a three-layered medium by small variations in material elastic moduli in a portion of the space is considered. Three-layered medium of two types have been investigated: A weakly anisotropic layer of cubic symmetry between two isotropic half-spaces and an isotropic layer between two slightly anisotropic half-spaces of cubic symmetry. The elastic moduli of the isotropic material and the isotropic parts of the moduli of the weakly anisotropic material are the same. Small anisotropic values added to the isotropic elastic moduli are introduced by various means, in such a manner that velocities of the SH waves in the slightly anisotropic materials with cubic symmetry may be smaller, bigger, or equal to the velocity of the SH wave in the corresponding isotropic material. It is shown that in cases when the Stoneley wave exists it refers to a weakly inhomogeneous quasitransverse wave of SH type, because among three displacement components weakly decaying with depth, the transverse one parallel to the interface of three mediums predominates.
Speed of sound in seawater as a function of salinity, temperature, and pressure
Authors: Wong George S. K. , Zhu Shi-ming
Published: October 2005

In view of the adoption of the International Temperature Scale of 1990 (ITS-90) which defines the International Celsius Temperatures t90, the dependence on temperature of the speed of sound in seawater is reexamined. The coefficients for two seawater sound-speed equations published previously, one by UNESCO (1983) which is also known as the Chen and Millero equation of 1977, and one by DelGrosso (1974) are revised for application with the new temperature scale ITS-90. It is found that the resulting change in seawater sound speed is within 0.024 and 0.017 m/s for the UNESCO and the DelGrosso equations, respectively. These changes are comparable to the numerical correction values suggested by Dushaw et al. (1993).
Analytical backplate removal in panel tests: An experimental demonstration
Authors: Piquette Jean C.
Published: October 2005

It is demonstrated that the influences of the support plate that is often used on sample panels can be eliminated using material properties obtained in ONION method measurements. The frequency interval of interest is 1–10 kHz.
Comparison of the anisotropy of apparent integrated ultrasonic backscatter from fixed human tendon and fixed human myocardium
Authors: Hoffmeister Brent K. , Wong Andrew K. , Verdonk Edward D. , Wickline Samuel A. , Miller James G.
Published: October 2005

The content and organization of collagen in the cardiac interstitium may represent significant determinants of the ultrasonic scattering properties of myocardium. This study was designed to investigate the anisotropic backscattering properties of a fibrous soft tissue exhibiting an ordered arrangement of fibers similar to myocardium, but possessing a substantially greater content of collagen. Human Achilles tendon was chosen for this study because it possesses a simple unidirectional arrangement of fibers and a high content of collagen compared to normal myocardium. Integrated (frequency-averaged) backscatter was measured from ten formalin fixed samples of tendon as a function of insonifying angle relative to the fiber axis of the tissue. The samples were insonified in a water bath using a 5-MHz center frequency piezoelectric transducer. Maximum backscatter occurred for insonification perpendicular to the fibers, and minimum backscatter occurred for insonification parallel to the fibers. The mean peak to nadir variation, or magnitude of anisotropy, of integrated backscatter for the ten formalin fixed samples of tendon was 36.3 dB. This compares to 14.5 dB for formalin fixed human myocardium measured in an earlier study by our laboratory.
Frequency selectivity and consonant recognition for hearing-impaired and normal-hearing listeners with equivalent masked thresholds
Authors: Dubno Judy R. , Schaefer Amy B.
Published: October 2005

Thresholds in notched-noise maskers (NN) and narrow-band maskers (NB) were measured for normal-hearing and hearing-impaired subject pairs who were listening in a background of spectrally shaped broadband noise (SSBB). Consonant recognition was also measured in SSBB. SSBB was adjusted so that thresholds in that noise for each normal-hearing/hearing-impaired subject pair were equal. Threshold and signal-level differences between subject pairs were minimized with the addition of threshold-elevating SSBB, and the presence of a noise background for both groups provided a comparable listening environment for all subjects. At signal frequencies outside masker passbands, thresholds in NN and NB for hearing-impaired subjects were higher than for normal-hearing subjects, although threshold differences were much smaller than observed between normal-hearing and hearing-impaired subjects without SSBB. No consistent differences in consonant recognition measured in SSBB were observed between groups. The pattern of results is comparable to that observed in a previous experiment [Dubno and Schaefer, J. Acoust. Soc. Am. 91, 2110–2121 (1992)] in which thresholds in NN and NB, and consonant recognition, for hearing-impaired listeners were compared to results obtained for normal-hearing subjects, but only normal-hearing subjects listened in SSBB. Using a modified power-law model of masking additivity, thresholds in combined-masker conditions were estimated. Masking effects for spectrally overlapping maskers were similar for normal-hearing and hearing-impaired listeners and suggest that residual differences between subject groups are not due to the presence of an additional background noise.
Reciprocity method with complex nonlinear fitting for primary vibration standards
Authors: Ge Li-Feng
Published: October 2005

The historical development of two basic types of absolute calibration methods for primary vibration standards, i.e., the reciprocity method and laser interferometry, are briefly reviewed. This paper presents a new reciprocity method with complex nonlinear least-squares fitting, which can be used to determine all basic parameters characterizing the behavior of an electromechanical transducer. For this purpose, the reciprocity calibration theory of electromechanical or electroacoustic transducers is generalized, and a universal calibration formula is derived from a three-parameter model established in this paper. Then the paper describes an application of the theory to improve the piezoelectric reciprocity method (PRM) suited to the high- and ultra-high-frequency vibration calibration, and meanwhile develops a corresponding complex nonlinear fitting program for data process. It is verified that the new method is a distinct improvement on the conventional PRM with three-pair data.
Discrete wavelet analysis of blade vortex interaction noise
Authors: Constantine W. , Pezeshki C. , Bamberger R. , Mosher M.
Published: October 2005

The discrete wavelet transform, implemented in a multirate filter bank scheme using conjugate quadrature filters, is used to analyze blade vortex interaction (BVI) noise from helicopter rotors in different environments. The discrete wavelet transform successfully isolates the bursty, nonstationary nature of this impulsive noise source. The sub-band coding scheme is then used for signal reconstruction of only the portion of helicopter noise related to blade vortex interaction by filtering in the frequency and time domains. By eliminating extraneous noise sources, the wavelet analysis can produce a more direct comparison between BVI noise generated in flight and in other environments such as a wind tunnel.
Predicted target strength analysis using computer techniques
Authors: Gay Gerard P. , Raichel Daniel R.
Published: October 2005

Target strength was predicted for various geometric objects by a computer ray tracing algorithm. The ray tracing theory assumes that the properties of sound at high frequencies, entailing wavelengths which are small compared with the size of the target objects, are analogous to light properties. This is a preliminary experiment still in progress. Four simple objects: Sphere, cylinder, cube, and disk, and two compound objects: Cylinder with spherical ends, I-beam frame structure, were investigated. The objects were created in an object-oriented ray tracing software package and rendered at various orientations to describe the reflective properties. A separate program was written to decode the ray traced images of the objects and determine their target strength. Current work will yield results to be compared with the empirical high-frequency target strength analysis results obtained at Naval Surface Warfare Center for Naval Research Labs and at Cooper Union’s Acoustical Research Center.
Localization of animal calls via hyperbolic methods
Authors: Mitchell Steve , Bower John
Published: October 2005

For over a decade the Cornell Bioacoustics Research Program has been using passive sparse acoustic arrays to locate calling marine mammals in the near field in shallow water, as well as birds and other animals in air. The techniques used have been cross correlation followed by all-pairs hyperbolic geometric positioning, using the simplest propagation model, and iterative nonlinear least-squares error minimization. This talk describes some of our experiences with this process, including the results of calibrated field tests. Applications to whale population censusing and research into the countersinging behavior of song sparrows will be discussed. Many bioacoustic passive array experiments depend on accurate locations at the extremes of the near field, where range is difficult to determine. Analysis techniques for passive near-field arrays have appeared in the literature over the past 50 years. Recently there has been much work devoted to using detailed propagation modeling to improve the accuracy of undersea localization of marine vessels. It is argued that, in the case of animal calls, there are also accuracy improvements to be had from improved signal modeling.
Structural and acoustic intensity analysis for a fluid-loaded elastic plate with a distributed inhomogeneity
Authors: Cuschieri J. M. , Feit D.
Published: October 2005

The solutions developed for the response and scattered pressure from a fluid-loaded plate with a distributed mass inhomogeneity, which were presented at the ASA 128th meeting in Austin, Texas, are extended to included distributed stiffness inhomogeneities. The same four types of distributions, with varying degrees of ‘‘smoothness’’ are considered for the stiffness distribution. The scattering characteristics between the mass and stiffness inhomogeneities are different, and while the scattering is dipolelike for the mass inhomogeneity, it is quadrupolelike for the stiffness inhomogeneity. The results for this presentation are presented in the form of structural and acoustic intensity maps, both as vector plots and streamline plots. For frequencies lower than the critical frequency of the fluid-loaded plate, the results show the constant exchange of power between the plate and the fluid. The streamline plots for the reactive intensity show a band very close to the plate surface. For higher frequencies, the characteristics of the intensity maps become dependent on the relative length and ‘‘smoothness’’ of the distributed inhomogeneity.
The use of high-intensity focused ultrasound for noninvasive surgery
Authors: Crum Lawrence A. , Law Wing
Published: October 2005

High-intensity focused ultrasound (HIFU) can be used to destroy tissue invivo; recent applications of this modality to the treatment of benign prostatic hypertrophy (BPH) have met with significant success. The lesions formed by focused ultrasound can be induced by both thermal and mechanical (cavitation) mechanisms. However, the relative contributions of these two mechanisms, under varied HIFU parameters, are often difficult to ascertain. Descriptions are presented of some simple experiments designed to elucidate the relative roles of cavitation and thermal effects in specific tissues; these tests were undertaken in turkey breast tissues, but seem to correlate well with previous invivo experiments in dogs and humans. The experiments indicate that cavitation, once induced, tends to shorten and broaden the thermally induced lesions, suggesting that the presence of free gas generated by the cavitation blocks passage of the ultrasound.
Semiclassical techniques for long-range, low-frequency propagation
Authors: Henyey Frank S. , Reynolds Stephen A. , Ewart Terry E.
Published: October 2005

The Chester, Friedman, and Ursell (CFU) uniform asymptotic expansion near caustics has been implemented as an adjunct to a ray-tracing code. The method is applied to the propagation of 400 Hz sound from a 200-m deep source in a Munk sound-speed profile through a range of 300 km. Making the parabolic approximation in the ray trace, the validity of ‘‘semiclassical’’ wave functions with the CFU expansion near caustics can be determined by comparison with a parabolic equation code. Good results for the semiclassical wave function are found. If the CFU expansion is not used, the field is badly inaccurate over hundreds of meters in the vertical. A video of the propagation comparing the Wigner function with the ray depth-angle plot is shown. [Work supported by ONR.]
Vortex sound: An alternative derivation of Möhring’s formulation
Authors: Powell Alan
Published: October 2005

In the 1964 theory of vortex sound by Powell the source strengths are the volume integrals of (ζΛu)′, [u=flow velocity, ζ=∇Λu=vorticity, ( )′≡∂( )/∂t], for dipole sound and of yx(ζΛu)″x for quadrupole sound (y=local coordinate, yx=y⋅x/x with x=far-field observation point). Möhring solved the same inhomogeneous wave equation by a Green’s function technique that transformed these to the volume integrals of 1/2(yΛζ″)x and of 1/3yx(yΛζ‴)x, respectively. By considering fixed vortex rings of variable strength the first of the latter pair was given in 1964 by a simple physical argument, apart from a trivial geometrical equivalence. By considering that the radial flow velocity at a spherical bounding surface due to a system of vortex rings (as given by the so-called Biot–Savart analogy for incompressible flow), fixed but of variable strength, drives the contiguous acoustic fields, simple physical arguments are presented that yield the results for dipole and quadrupole vortex sound in Möhring’s form.
The focal phase shift of waves of a circular membrane, applied to underexpanded supersonic jet structure
Authors: Powell Alan
Published: October 2005

It is pointed out that a convergent wave on a circular taut membrane undergoes a −π/2 phase shift at the focus that radically affects the ensuing pattern of waves. The case of a membrane initially uniformly displaced everywhere except close to the fixed perimeter is considered. From the normal modes solution, a purely periodic approximation (valid r/R≳0.7, r/R=nondimensional radius) in terms of traveling waves is derived: The motion has a period of 8R/c (c=wave speed), half of the period being taken up by waves that are the impulselike (finite) Hilbert transforms of the initial step wave. A better approximation valid for r/R≳0.2 uses a refined first term of the series solution. By Rayleigh’s analogy, the result can be applied directly to the spacewise pressure perturbation due to slight over- or underexpansion of an otherwise uniform supersonic circular jet. The first, sinusoidally varying, term then corresponds to Prandtl’s cell length, all the remaining terms explicitly describing the familiar diamond pattern of Mach waves. The pattern repeats after four diamond lengths (the first and third complete diamonds being transformed) in contrast to just two for the two-dimensional case (that lacks the transformed portions). The introduction of an empirical exponential downstream decay of the Fourier components results in good qualitative agreement with experimental results for the jet, validating the use of the linear theory.
Interference in detection of interaural delay in a sinusoidally amplitude-modulated tone produced by a second, spectrally remote sinusoidally amplitude-modulated tone
Authors: Heller Laurie M. , Trahiotis Constantine
Published: October 2005

Sensitivity to interaural time delays (ITDs) within high-frequency sinusoidally amplitude-modulated (SAM) target tones was measured in the presence of a second, spectrally remote diotic SAM tone (termed an interferer). Targets and interferers were 100% modulated at 250 Hz and each was presented at 77 dB SPL for a duration of 250 ms. The modulations of targets and interferers were either in-phase or out-of-phase. In the first experiment, when the target SAM tone was centered at 4 kHz, interferers were centered at either 500 Hz, 1 kHz, or 2 kHz. Threshold ITDs were substantially increased in the presence of the interferers as compared to when the targets were presented in isolation. The greatest effects were observed with interferers centered at 500 Hz and 1 kHz. In the second experiment, when the target SAM tone was centered at 2 kHz, interferers were centered at either 500 Hz or 4 kHz. Threshold ITDs increased in the presence of either interferer, but the greatest increase occurred in the presence of the 500-Hz SAM tone. In the third experiment, it was found that presenting the low-frequency SAM tones continuously resulted in less interference than did presenting the interferers and targets coincidently. In all three experiments, the effects produced by the interferers did not depend upon whether they were modulated in-phase or out-of-phase with the target. Taken together, the data argue against the notion that the interference could result from a peripheral, monaural interaction between target and interferer waveforms.
A basically monopole source formulation for vortex-generated sound
Authors: Powell Alan
Published: October 2005

Lighthill’s source term for aerodynamic sound generation can be expressed in terms of the squares of the vorticity and of the principal rates of strain of the sound-generating fluid, in the usual incompressible approximation. These represent local monopole source regions. When there are fairly discrete interacting vortices, the former has the physical interpretation of the sound emission being associated with the occurrence of pressure minima at vortex cores, while the latter may be imagined to be the emission associated with the pressure maxima in regions between colliding vortices. The quadrupole source volume integrals converge rapidly, so the whole source region may be considered to be compact, the poor convergence difficulties associated with the use of the ‘‘incompressible’’ pressure of previous ‘‘simple source’’ or ‘‘dilatational’’ theories being avoided.
Masked level discrimination: Deterring profile listening
Authors: Florentine Mary , Buus So/ren
Published: October 2005

Two experiments examined how level discrimination (also called intensity discrimination) between two successive three-tone complexes depends on the bandwidth and rove range of a notched-noise masker. The three-tone complex consisted of equally intense components at 0.84, 1, and 1.17 kHz set to 25, 55, or 85 dB SPL. The notch extended from 0.77 to 1.27 kHz for all masker bandwidths. The masker level changed randomly on each presentation to reduce profile cues. Results from five listeners showed that level-discrimination thresholds, ΔL’s (=20 log([p+Δp]/p), where p is pressure), increased somewhat as the rove range increased. In contrast to profile-discrimination experiments, the ΔL’s did not decrease with increasing masker bandwidth. In addition, when the rove range was 10 dB or larger, discrimination was generally better than the best possible performance by a profile observer. The results indicate that profile analysis is not essential for reasonably good level discrimination in the presence of notched-noise maskers.
Modulation detection interference using random and sinusoidal amplitude modulation
Authors: Mendoza Lee , Hall Joseph W. , Grose John H.
Published: October 2005

The detection of amplitude modulation (AM) of a target sound is made more difficult by the presence of a modulated sound some spectral distance from the target. This effect (modulation detection interference, or MDI) was examined for stimuli with random amplitude modulations (RAM) and for sounds with sinusoidal amplitude modulations (SAM) as a function of average modulation depth (m) of the interferer. In an experiment comparing comodulated and independent RAM targets and interferers, the amount of interference was not related to the modulation coherence of the target and interferer. Elevations in AM threshold increased as a function of m in a similar way for both conditions. The MDI for RAM and SAM targets and interferers was also compared. While no difference was found for AM detection of RAM and SAM, MDI was found to be greater for the RAM stimuli than for the SAM stimuli. A subsidiary experiment comparing RAM and SAM modulation depth discrimination indicated that RAM discrimination is more difficult than SAM discrimination. Taken together, these results are quantitatively consistent with a mechanism resembling AM discrimination as the underpinning of MDI in conditions where the target and interferer are synchronously gated.
Electrically evoked basilar membrane motion
Authors: Xue Shuwan , Mountain David C. , Hubbard Allyn E.
Published: October 2005

Electrically induced outer hair cell (OHC) motility, demonstrated by a number of investigators in isolated OHC preparations, has been considered to be a key mechanism in the active process which brings about the excellent sensitivity and frequency selectivity of the mammalian cochlea. In this study, electrical-to-mechanical transduction in the gerbil cochlea was demonstrated in vivo by direct measurement of basilar membrane motion evoked by sinusoidal electrical current injected into the scala media. The characteristic frequency (CF) of the measurement place was approximately 40 kHz as determined by the basilar membrane (BM) responses to acoustic stimulation. The results showed that basilar membrane motion could be evoked by electrical current of frequencies from below 10 Hz to exceeding 40 kHz. The magnitude and phase of the BM velocity response to constant current stimulation, from 100 Hz to 10 000 Hz, were similar to the acoustically driven BM velocity for constant umbo velocity. For frequencies in this range, the BM motion evoked by a current of 50 μA was comparable to the BM motion evoked by a 60 dB SPL acoustic stimulus. The phase of the electrically evoked BM motion indicates that positive current injected into the scala media caused the BM to move toward scala vestibuli for frequencies between 100 and 10 kHz. This result is consistent with the hypothesis that the electrically evoked BM motion is due to electrically evoked OHC length changes.
Within- and across-channel processes in modulation detection interference
Authors: Mendoza Lee , Hall Joseph W. , Grose John H.
Published: October 2005

Modulation detection interference (MDI) describes the effect of an amplitude-modulated sound on detection of amplitude modulation (AM) on a spectrally distant target sound. In MDI, AM detection is worsened by an AM interfering sound. Previous research has implicated both within-channel and across-channel processes as the basis for MDI. This study examined the detection of 10-Hz sinusoidal AM as a function of the spectral relationship, gating synchrony, and ear of presentation of the target and interfering sounds. Using a 993-Hz target sound, AM detection improved as the frequency of the interferer increased from 1250 to 2188 Hz, and as it decreased from 788 to 450 Hz. MDI was less for continuous interferers than for interferers gated synchronously with the target. In the continuous interferer conditions, however, MDI was still greatest for interferers most proximal to the target. The effects of frequency proximity and gating asynchrony were also evident using interferers presented to the ear contralateral to the target ear. While a 1250-Hz interferer led to more MDI than a 788-Hz interferer when the interferers were presented to the same ear as a 993-Hz target, no significant asymmetry was noted with dichotic stimulation. Taken together, the results of these experiments indicated that MDI is the result of across-channel, and to a limited extent, within-channel processes.
Discriminating coherence in spectro-temporal patterns
Authors: Kidd Gerald , Mason Christine R. , Dai Huanping
Published: October 2005

This study examined the ability of trained listeners to discriminate coherent components in randomly varying spectral patterns. In each observation interval, the listener was presented with a sequence of bursts of multitone complexes having a fixed number of tones (m) in each burst. In the standard interval, the frequency of each tone in every burst was chosen randomly between 200 and 5000 Hz. In the signal interval, the frequencies of n tones were repeated throughout the burst sequence while the remaining m–n tones were chosen at random. The n tones were coherent in the sense that they were perceived as ‘‘sticking together’’ to form a pattern. The listener’s task was to discriminate which burst sequence contained the n components. The results indicated that discrimination improved with increasing n/m, with increasing number of bursts per interval, and declined as the coherent components were increasingly perturbed in frequency. Further, for a fixed value of the ratio n/m discriminability was relatively independent of m. A model incorporating multichannel filtering and an optimum decision rule was reasonably successful in accounting for the experimental results.
Robust estimation of speech in noisy backgrounds based on aspects of the auditory process
Authors: Hansen John H. L. , Nandkumar Srinivas
Published: October 2005

A new approach to speech enhancement is proposed where constraints based on aspects of the auditory process augment an iterative enhancement framework. The basic enhancement framework is based on a previously developed dual-channel scenario using a two-step iterative Wiener filtering algorithm. Constraints across broad speech sections and over iterations are then experimentally developed on a novel auditory representation derived by transforming the speech magnitude spectrum. The spectral transformations are based on modeling aspects of the human auditory process which include critical band filtering, intensity-to-loudness conversion, and lateral inhibition. The auditory transformations and perceptual based constraints are shown to result in a new set of auditory constrained and enhanced linear prediction (ACE-LP) parameters. The ACE-LP based speech spectrum is then incorporated into the iterative Wiener filtering framework. The improvements due to auditory constraints are demonstrated in several areas. The proposed auditory representation is shown to result in improved spectral characterization in background noise. The auditory constrained iterative enhancement (ACE-II) algorithm is shown to result in improved quality over all sections of enhanced speech. Adaptation of auditory based constraints to changing spectral characteristics over broad classes of speech is another novel aspect of the proposed algorithm. The consistency of speech quality improvement for the ACE-II algorithm is illustrated over time and across all phonemes classified over a large set of phonetically balanced sentences from the TIMIT database. This study demonstrates the application of auditory based perceptual properties of a human listener to speech enhancement in noise, resulting in improved and consistent speech quality over all regions of speech.
Further tests of the ‘‘perceptual magnet effect’’ in the perception of [i]: Identification and change/no-change discrimination
Authors: Sussman Joan E. , Lauckner-Morano Valerie J.
Published: October 2005

The present study investigated the existence of a ‘‘perceptual magnet’’ effect [Kuhl, Percept. Psychophys. 50, 93–107 (1991)] in a speech perception experiment. Sixteen subjects experienced in phonetics, transcribed the [i] stimuli used by Kuhl (1991) or identified the stimuli as [i] or not-[i] in experiment 1. In experiments 2 and 3, 50 adults who were not trained in phonetics, participated in an identification task requiring them to decide whether the vowel sounds they heard were the ‘‘[i] in ‘peep’’’ or ‘‘not the [i] in ‘peep’.’’ They also completed a ‘‘change/no change’’ discrimination task with standards consisting of the ‘‘prototype’’ [i] and other nonprototype stimuli at 67, 75, and 120 mels away from the prototype. Results from the first study showed that listeners did not identify the 120-mel token previously used by Kuhl (1991) as the nonprototype standard stimulus in discrimination experiments as [i]. Sensitivity results from experiments 2 and 3, as measured with d-prime partially supported the ‘‘perceptual magnet’’ hypothesis as suggested by Kuhl (1991) whereas miss results did not. Findings indicated that d-prime, a nonbiased measure of subjects’ discrimination ability, better represented the perceptual magnet effect than misses alone. Thus results suggested that subjects were better able to discriminate stimuli surrounding a less ‘‘prototypical’’ [i] vowel as demonstrated by greater sensitivity, faster reaction times for hits and fewer number of misses. However, current results may also be explained by increased auditory resolution rather than prototype-based, ‘‘magnet’’ effects. It was concluded that whereas the perceptual magnet effect may exist for particular vowel categories, more data are needed to better understand the role of prototypes in speech perception.
Small-Molecule Inhibitor of
Vibrio cholerae
Virulence and Intestinal Colonization
Authors: Hung Deborah T. , Shakhnovich Elizabeth A. , Pierson Emily , Mekalanos John J.
Published: October 2005

Increasing antibiotic resistance requires the development of new approaches to combating infection. Virulence gene expression in vivo represents a target for antibiotic discovery that has not yet been explored. A high-throughput, phenotypic screen was used to identify a small molecule 4-[
N
-(1,8-naphthalimide)]-
n
-butyric acid, virstatin, that inhibits virulence regulation in
Vibrio cholerae
. By inhibiting the transcriptional regulator ToxT, virstatin prevents expression of two critical
V. cholerae
virulence factors, cholera toxin and the toxin coregulated pilus. Orogastric administration of virstatin protects infant mice from intestinal colonization by
V. cholerae
.
S-Phase-Dependent Enhancement of Dengue Virus 2 Replication in Mosquito Cells, but Not in Human Cells
Authors: Helt Anna-Marija , Harris Eva
Published: October 2005

Dengue virus (DEN) is the most prevalent cause of arthropod-borne viral illness in humans. We determined the influence of cellular growth state on DEN type 2 (DEN2) replication in mosquito and human cells, based on the hypothesis that manipulation of cellular growth state will facilitate identification of viral and cellular determinants of productive infection. Comparison of density-arrested and cycling C6/36Aedes albopictuscells infected with a low-passage DEN2 isolate revealed that cycling cells generated higher virus titers per cell. When C6/36 cells were stalled in S-phase via a thymidine (THY) block, titers of low-passage DEN2 isolates and a high-passage strain, 16681, were increased approximately 30-fold and 10-fold, respectively. Moreover, virus release was earlier in THY-treated cells than in asynchronously cycling cells. Adsorption, entry, genome uncoating, and translation were not responsible for increased titers of virus from S-phase C6/36 cells. In contrast to the 30-fold increase in virus titers, intracellular levels of viral RNA were increased approximately 2-fold, suggesting that the S-phase-responsive step is late in the DEN2 replication cycle. Analysis of viral RNA and protein released from the cells indicated that enhanced DEN2 assembly is largely responsible for increased virus titers produced during S-phase. In contrast to C6/36 cells, DEN2 titers from S-phase human hepatoma cells or primary human fibroblasts were not increased. These results demonstrate a differential response of DEN2 to the mosquito and human cell cycle and provide a framework for detailed studies into the mechanisms mediating virus assembly.
Complex Determinants in Human Immunodeficiency Virus Type 1 Envelope gp120 Mediate CXCR4-Dependent Infection of Macrophages
Authors: Ghaffari Guity , Tuttle Daniel L. , Briggs Daniel , Burkhardt Brant R. , Bhatt Deepa , Andiman Warren A. , Sleasman John W. , Goodenow Maureen M.
Published: October 2005

Host cell range, or tropism, combined with coreceptor usage defines viral phenotypes as macrophage tropic using CCR5 (M-R5), T-cell-line tropic using CXCR4 (T-X4), or dually lymphocyte and macrophage tropic using CXCR4 alone or in combination with CCR5 (D-X4 or D-R5X4). Although envelope gp120 V3 is necessary and sufficient for M-R5 and T-X4 phenotypes, the clarity of V3 as a dominant phenotypic determinant diminishes in the case of dualtropic viruses. We evaluated D-X4 phenotype, pathogenesis, and emergence of D-X4 viruses in vivo and mapped genetic determinants in gp120 that mediate use of CXCR4 on macrophages ex vivo. Viral quasispecies with D-X4 phenotypes were associated significantly with advanced CD4+-T-cell attrition and commingled with M-R5 or T-X4 viruses in postmortem thymic tissue and peripheral blood. A D-X4 phenotype required complex discontinuous genetic determinants in gp120, including charged and uncharged amino acids in V3, the V5 hypervariable domain, and novel V1/V2 regions distinct from prototypic M-R5 or T-X4 viruses. The D-X4 phenotype was associated with efficient use of CXCR4 and CD4 for fusion and entry but unrelated to levels of virion-associated gp120, indicating that gp120 conformation contributes to cell-specific tropism. The D-X4 phenotype describes a complex and heterogeneous class of envelopes that accumulate multiple amino acid changes along an evolutionary continuum. Unique gp120 determinants required for the use of CXCR4 on macrophages, in contrast to cells of lymphocytic lineage, can provide targets for development of novel strategies to block emergence of X4 quasispecies of human immunodeficiency virus type 1.
N-Linked Glycosylation of West Nile Virus Envelope Proteins Influences Particle Assembly and Infectivity
Authors: Hanna Sheri L. , Pierson Theodore C. , Sanchez Melissa D. , Ahmed Asim A. , Murtadha Mariam M. , Doms Robert W.
Published: October 2005

West Nile virus (WNV) encodes two envelope proteins, premembrane (prM) and envelope (E). While the prM protein of all WNV strains contains a single N-linked glycosylation site, not all strains contain an N-linked site in the E protein. The presence of N-linked glycosylation on flavivirus E proteins has been linked to virus production, pH sensitivity, and neuroinvasiveness. Therefore, we examined the impact of prM and E glycosylation on WNV assembly and infectivity. Similar to other flaviviruses, expression of WNV prM and E resulted in the release of subviral particles (SVPs). Removing the prM glycosylation site in a lineage I or II strain decreased SVP release, as did removal of the glycosylation site in a lineage I E protein. Addition of the E protein glycosylation site in a lineage II strain that lacked this site increased SVP production. Similar results were obtained in the context of either reporter virus particles (RVPs) or infectious lineage II WNV. RVPs or virions bearing combinations of glycosylated and nonglycosylated forms of prM and E could infect mammalian, avian, and mosquito cells (BHK-21, QT6, and C6/36, respectively). Those particles lacking glycosylation on the E protein were modestly more infectious per genome copy on BHK-21 and QT6 cells, while this absence greatly enhanced the infection of C6/36 cells. Thus, glycosylation of WNV prM and E proteins can affect the efficiency of virus release and infection in a manner that is cell type and perhaps species dependent. This suggests a multifaceted role for envelope N-linked glycosylation in WNV biology and tropism.
Recombinant Newcastle Disease Virus Expressing a Foreign Viral Antigen Is Attenuated and Highly Immunogenic in Primates
Authors: Bukreyev Alexander , Huang Zhuhui , Yang Lijuan , Elankumaran Subbiah , St. Claire Marisa , Murphy Brian R. , Samal Siba K. , Collins Peter L.
Published: October 2005

Paramyxoviruses such as human parainfluenza viruses that bear inserts encoding protective antigens of heterologous viruses can induce an effective immunity against the heterologous viruses in experimental animals. However, vectors based on common human pathogens would be expected to be restricted in replication in the adult human population due to high seroprevalence, an effect that would reduce vector immunogenicity. To address this issue, we evaluated Newcastle disease virus (NDV), an avian paramyxovirus that is serotypically distinct from common human pathogens, as a vaccine vector. Two strains were evaluated: the attenuated vaccine strain LaSota (NDV-LS) that replicates mostly in the chicken respiratory tract and the Beaudette C (NDV-BC) strain of intermediate virulence that produces mild systemic infection in chickens. A recombinant version of each virus was modified by the insertion, between the P and M genes, of a gene cassette encoding the human parainfluenza virus type 3 (HPIV3) hemagglutinin-neuraminidase (HN) protein, a test antigen with considerable historic data. The recombinant viruses were administered to African green monkeys (NDV-BC and NDV-LS) and rhesus monkeys (NDV-BC only) by combined intranasal and intratracheal routes at a dose of 10
6.5
PFU per site, with a second equivalent dose administered 28 days later. Little or no virus shedding was detected in nose-throat swabs or tracheal lavages following immunization with either strain. In a separate experiment, direct examination of lung tissue confirmed a highly attenuated, restricted pattern of replication by parental NDV-BC. The serum antibody response to the foreign HN protein induced by the first immunization with either NDV vector was somewhat less than that observed following a wild-type HPIV3 infection; however, the titer following the second dose exceeded that observed with HPIV3 infection, even though HPIV3 replicates much more efficiently than NDV in these animals. NDV appears to be a promising vector for the development of vaccines for humans; one application would be in controlling localized outbreaks of emerging pathogens.
A Major Determinant for Membrane Protein Interaction Localizes to the Carboxy-Terminal Domain of the Mouse Coronavirus Nucleocapsid Protein
Authors: Hurst Kelley R. , Kuo Lili , Koetzner Cheri A. , Ye Rong , Hsue Bilan , Masters Paul S.
Published: October 2005

The two major constituents of coronavirus virions are the membrane (M) and nucleocapsid (N) proteins. The M protein is anchored in the viral envelope by three transmembrane segments flanked by a short amino-terminal ectodomain and a large carboxy-terminal endodomain. The M endodomain interacts with the viral nucleocapsid, which consists of the positive-strand RNA genome helically encapsidated by N protein monomers. In previous work with the coronavirus mouse hepatitis virus (MHV), a highly defective M protein mutant, MΔ2, was constructed. This mutant contained a 2-amino-acid carboxy-terminal truncation of the M protein. Analysis of second-site revertants of MΔ2 revealed mutations in the carboxy-terminal region of the N protein that compensated for the defect in the M protein. To seek further genetic evidence corroborating this interaction, we generated a comprehensive set of clustered charged-to-alanine mutants in the carboxy-terminal domain 3 of N protein. One of these mutants, CCA4, had a highly defective phenotype similar to that of MΔ2. Transfer of the CCA4 mutation into a partially diploid MHV genome showed that CCA4 was a loss-of-function mutation rather than a dominant-negative mutation. Analysis of multiple second-site revertants of CCA4 revealed mutations in both the M protein and the N protein that could compensate for the original lesion in N. These data more precisely define the region of the N protein that interacts with the M protein. Further, we found that fusion of domain 3 of the N protein to the carboxy terminus of a heterologous protein caused it to be incorporated into MHV virions.
In Nasopharyngeal Carcinoma Cells, Epstein-Barr Virus LMP1 Interacts with Galectin 9 in Membrane Raft Elements Resistant to Simvastatin
Authors: Pioche-Durieu Catherine , Keryer Cécile , Souquère Sylvie , Bosq Jacques , Faigle Wolfgang , Loew Damarys , Hirashima Mitsuomi , Nishi Nozomu , Middeldorp Jaap , Busson Pierre
Published: October 2005

Nasopharyngeal carcinomas (NPC) are etiologically related to the Epstein-Barr virus (EBV), and malignant NPC cells have consistent although heterogeneous expression of the EBV latent membrane protein 1 (LMP1). LMP1 trafficking and signaling require its incorporation into membrane rafts. Conversely, raft environment is likely to modulate LMP1 activity. In order to investigate NPC-specific raft partners of LMP1, rafts derived from the C15 NPC xenograft were submitted to preparative immunoprecipitation of LMP1 combined with mass spectrometry analysis of coimmunoprecipitated proteins. Through this procedure, galectin 9, a beta-galactoside binding lectin and Hodgkin tumor antigen, was identified as a novel LMP1 partner. LMP1 interaction with galectin 9 was confirmed by coimmunoprecipitation and Western blotting in whole-cell extracts of NPC and EBV-transformed B cells (lymphoblastoid cell lines [LCLs]). Using mutant proteins expressed in HeLa cells, LMP1 was shown to bind galectin 9 in a TRAF3-independent manner. Galectin 9 is abundant in NPC biopsies as well as in LCLs, whereas it is absent in Burkitt lymphoma cells. In subsequent experiments, NPC cells were treated with Simvastatin, a drug reported to dissociate LMP1 from membrane rafts in EBV-transformed B cells. We found no significant effects of Simvastatin on the distribution of LMP1 and galectin 9 in NPC cell rafts. However, Simvastatin was highly cytotoxic for NPC cells, regardless of the presence or absence of LMP1. This suggests that Simvastatin is a potentially useful agent for the treatment of NPCs although it has distinct mechanisms of action in NPC and LCL cells.