bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of attenuation and speed of sound in soils for the purposes of imaging buried objects
Authors: Oelze Michael , Darmody Robert , O’Brien William
Published: February 2014

The speed and attenuation of sound vary in different soil types and with different levels of water saturation. Imaging techniques make use of speed and attenuation to range targets and compensate for loss in echo magnitude with depth. Signals from an acoustic source over the range of 2–6 kHz were passed through soil and detected by a coupled hydrophone. Six soil samples were used to represent a range of properties expected to influence acoustic response. Clay ranged from 2%–38%, silt from 1%–82%, sand from 2%–97%, and organic matter from 0.1%–11.7%. The attenuation and propagation speed were determined in the soil as a function of soil moisture and compaction. Attenuation coefficients ranged from 0.12–0.96 dB cm−1 kHz−1. Correlation coefficients were 0.35 (P=0.01) and 0.31 (P=0.03) between attenuation and soil water content and soil bulk density. Propagation speeds ranged from 86 to 260 ms−1. The correlation coefficient with speed was −0.28 (P=0.05) for soil water content and 0.42 (P=0.002) for porosity. Given the attenuation, it is theoretically possible to image objects in soils to 40 cm in depth. [Work supported by U.S. Army Construction Engineering Research Laboratory, Champaign, IL.]
Psychophysical studies of auditory sensory traces
Authors: McKeown Denis , Wellsted David , Green Tim
Published: February 2014

The evidence is impressive, using an evoked potentials paradigm, that detailed internal models of recent sound stimulation are formed and compared with incoming sounds: Changes are incorporated, it is supposed, in order to update those models or sensory traces. Here psychophysical studies are reported. The first experiment poses the question of how recent tone stimulation affects ongoing performance in a discrimination task. Briefly, it is assumed that such a tone, or cue, may provide a highly frequency-specific sensory trace equivalent to sensory enhancement at that frequency. In a discrimination task two complex sounds occur in successive intervals. A single component of one complex is decreased in intensity: The task is to report whether this is in the first or second interval. Now, prior to each trial a tone cue is introduced: This is at the same frequency as the decreased component, or at a different frequency. The reasoning is that if the cue tone produces sensory enhancement, then it should effectively remove the decrement when cue and decrement are at the same frequency, impairing performance on these trials. This was the result obtained. Other experiments ued a detection task in examining the time source of the presumed sensory trace.
Variations in coda sonorants at different speaking rates
Authors: Bray Jodi P.
Published: February 2014

Despite sonority’s role in phonological accounts of syllable structures in the world’s languages, phonetic correlates of sonority remain controversial. This study is part of a larger project designed to examine possible phonetic cues to sonority. Specifically, this paper reports on acoustic characteristics (i.e., duration, amplitude, and F0) of sonorants [r, l, m, n] occurring word finally or before an obstruent. The goal is to examine (a) whether these acoustic characteristics vary across speaking rate: slow, casual, and rapid; (b) whether these characteristics vary across speakers. Preliminary results based on data from one male native English speaker suggested that sonorant duration did not seem to vary at different speaking rates. Moreover, the ratio of sonorant to rhyme duration is greatest in rapid speech suggesting that sonorants require duration for their perceptibility. Additional speakers will be analyzed to confirm these findings. A perception experiment designed to examine degree of perceptibility of sonorants at different speaking rates and in different degrees of noise will also be conducted. Perceptual data will be examined and discussed in relation to production data.
What happens to segment durations at the end of a word?
Authors: Schwarzlose Rebecca , Bradlow Ann R.
Published: February 2014

Coda consonant clusters of monosyllabic words were studied to determine what durational modifications occur at the segment level as a function of the number, the order, and the morphemic status of segments in the coda. We focused on the segment /s/ because it has the fewest constraints in terms of position in coda clusters, allowing reversals such as tax (/tæ ks/) and task (/tæsk/), and because /s/ can also be a separate morpheme, allowing us to compare segment durations for tax and tacks (/tæ ks/). Preliminary results from four talkers reaffirm previous findings that segment durations decrease as the number of segments increases, although all segments do not decrease to the same extent. Our data also reaffirm previous claims that morphemic /s/ has a longer duration relative to the overall word duration than its nonmorphemic counterpart. In addition to these factors, position at the right-edge boundary of a word seems to play a special role in determining the relative durations of segments within a coda cluster. Specifically, we found that the balance between segment durations in /sk/ and /ks/ coda clusters in monomorphemic words tended to tip in favor of the word-final segment and against the word-internal member of the cluster.
Use of formant movement detail in vowel identification
Authors: Neel Amy T. , Krishnan Ananthanarayan , Collins Kent J.
Published: February 2014

Many studies have shown that American English listeners identify vowels with dynamic formants better than flat-formant vowels. The amount of formant movement detail used by listeners, however, is not known. This study examined use of formant movement detail in vowel identification and discrimination using five sets of Klatt-synthesized vowel stimuli modeled after natural vowels. One-point stimuli consisted of flat-formant vowels with formant values taken from the center of the natural vowels. The other four sets consisted of tokens with two, three, five, or eleven points having formant values taken from the natural vowels with the remainder of the values being linearly interpolated. Two-point vowels, with sloping formants, were least well identified by listeners, whereas the most detailed stimuli, the five- and eleven-point vowels, were the best identified tokens. Listeners had difficulty discriminating between the five- and eleven-point representations of vowels. Results indicate that listeners may have an intermediate level of formant movement detail representation — more detailed than a simple slope from onset to offset, but less detailed than natural vowel patterns. In addition to behavioral data, frequency-following responses (FFRs), electrophysiologic measures of neural encoding of formant movement patterns, will be presented. [Work supported by 2001 Research Grant in Speech Science, ASHF/ASA.]
Acoustic and articulatory characteristics of Korean affricates
Authors: Chung Hyunjoo , Schmidt Anna Marie
Published: February 2014

The purpose of this study was to examine the three voiceless Korean affricates in terms of differing acoustic and articulatory characteristics which might determine three-way lax, aspirated, and tense distinctions. In previous studies, the three-way stop distinction and the two-way fricative distinction (lax and tense) were investigated. Yet little is known about how the three distinctions are implemented in affricates. The three Korean affricates in CV and VCV syllables produced by two female and one male native Korean speaker were compared. Duration, amplitude, and fundamental frequency in six vowel contexts for each affricate were measured on spectrograms. In addition, temporal and spatial characteristics of lingual gestures during production of affricates such as seal duration and skewness of articulatory movement were measured from electropalatographic data. Endoscopic and air flow data for two different subjects were also examined for differences in measures such as glottal width and air flow. Finally, measurements of affricates will be reported and discussed in comparisons to previous findings on stops and fricatives with respect to the three-way distinctions. [Speech Communication Best Student Paper Award.]
Some acoustic cues for categorizing American English regional dialects
Authors: Clopper Cynthia G. , Pisoni David B.
Published: February 2014

The perception of phonological differences between regional dialects of American English by naive listeners is poorly understood. Using the TIMIT corpus of spoken sentences produced by talkers from a number of distinct dialect regions in the United States, an acoustic analysis conducted in Experiment I confirmed that several phonetic features distinguish between the dialects. In Experiment II recordings of the sentences were played back to naive listeners who were asked to categorize each talker into one of six geographical dialect regions. Results suggested that listeners are able to reliably categorize talkers into three broad dialect clusters, but have more difficulty accurately categorizing talkers into six smaller regions. Correlations between the acoustic measures and both actual dialect affiliation of the talkers and dialect categorization of the talkers by the listeners revealed that the listeners in this study were sensitive to acoustic-phonetic features of the dialects in categorizing the talkers. Taken together, the results of these experiments suggest that naive listeners are aware of phonological differences between dialects and can use these differences to categorize talkers by dialect. Implications for the study of variation and variability in speech will be discussed. [Work supported by NIH.]
Color rendering of range in passive acoustic displays
Authors: Boyle Frank A. , Phipps Thomas H.
Published: February 2014

Techniques for mapping image color to range in passive time-bearing displays were explored. They included (1) a range-focusing method wherein images focused at multiple ranges were combined; and (2) a parallax technique wherein images were formed with different subarray apertures. In both cases, a Hough transform based image processing method was used to enhance features and to compensate for degradation associated with combination of multiple images. Colormapping techniques were employed to render source ranges in color. The presentation will include a description of the methods and a discussion of their effectiveness under various conditions. [Work funded under ARL:UT IR&D program.]
A reconstruction technique for passive acoustic imaging through a turbulent atmosphere
Authors: Benson Jonathan W. , Swenson George W. , Bresler Yoram
Published: February 2014

Interferometric passive acoustic imaging through the near-ground atmosphere is hampered by the effects of turbulence. Traditional techniques aimed at removing the effects of the atmosphere, such as self-calibration and phase-closure, cannot be applied in this case where the distortion is a function of the source coordinates. A method was developed to remove the distortion due to the atmosphere within the context of interferometric imaging. A discrete complex-valued distorting screen was used to model the atmosphere. This type of model is routinely used to model propagation through turbulent media and in this case was found to adequately model the distortion effects seen in field data.Reconstruction is accomplished by joint estimation of the source intensity distribution along with the parameters of the distorting screen. Multiple short integration period images or snapshots are used. The parameters of the screen are allowed to change from one snapshot to another, while the source distribution is assumed constant. The Cramer–Rao bounds of the problem were computed and found to be very favorable. The estimation problem was solved using both maximum likelihood and least-squares methods. Near-perfect reconstruction was obtained for simulated data, and significant image quality gains were obtained with experimental data.
Performance bounds of atmospheric acoustic arrays operating in a turbulent medium
Authors: Collier Sandra L. , Wilson D. Keith
Published: February 2014

The performance bounds of an atmospheric acoustic array operating in a turbulent medium with fluctuations described by von Kármán’s spectrum are investigated. This treatment considers a single monochromatic source and no multiple-path effects. The Cramer–Rao lower bounds of the azimuthal and zenith angles of arrival (AOAs) are calculated. The normalized range (to wavelength), turbulence parameters, and signal-to-noise ratio are introduced as additional unknowns. It is found that the Cramer–Rao lower bounds of the AOAs increase significantly in strong turbulence at large values of the normalized range. For weak turbulence and moderate values of the normalized range, the signal-to-noise ratio is the dominating factor. For an incident plane wave, the estimates of the AOAs will decouple from the estimates of the other parameters with the appropriate choice of array geometry; however, the estimates of the azimuth and zenith are coupled to one another due to the constraints of the turbulence model.
Issues of analytical continuation of the field interior to the target surface and a more general T-matrix for submerged fluid targets
Authors: Werby M. F.
Published: February 2014

The T-matrix or extended boundary condition method developed by P. Waterman for wave scattering from classical targets and extended by a host of researchers is a marvelous generalization of normal mode solutions allowed for separable geometries to extend to nonseparable geometries by means of mode coupling. The method is based on Huygens’ principle and partial wave expansions of physical quantities. In general the expansions don’t obey orthogonality and one must take care in the way expansions are made. One must never take expansions of a quantity and then represent expansions of their differential forms in terms of the partial wave differential forms using the same expansion coefficients lest one violate a mathematical principle (the Rayleigh hypothesis). One may circumvent any issues without resort to analytical continuation of interior solutions by including all solutions subject to interior and exterior Greens functions. This leads to matrix relations (constraining matrices) between the expansion terms which when used lead to new forms of the fluid T-matrix, for example. The new form differs from Waterman’s T-matrix for the case when the constraining matrices are not symmetric. Otherwise the original expression by Waterman is valid. These issues are discussed and examples are presented.
The contributors of sound scattering in stratified flows
Authors: Prokhorov Victor
Published: February 2014

It is generally assumed that marine biomass dominates the backscattering everywhere in the ocean. However, stratified flows form both aggregated and solitary scatterers whose scattering levels are close to those of biologicals. The present work deals with theoretical and laboratory study of scattering phenomena in stratified flows of different types and regimes. Microscale clusters, flat and curved discontinuities, and solitary vortex rings were modeled and examined with both monostatic and bistatic acoustic schemes. Simultaneously they were optically visualized and photographed to provide their direct identification and computation of spatial spectra, and to extract characteristic scales being responsible for scattering. The average scattering levels converted to dimensionless backscattering cross section are of the same order or above those obtained in field measurements. Theoretical study seeks to reveal the mechanisms producing acoustic contrasts and to examine temporal characteristics of scattering. The scattering dynamics essentially depends on whether salinity or temperature stratification dominates the condition under which the scattering inhomogeneities arise. Also, attached internal waves contribution to produce the scattering interfaces was theoretically and experimentally confirmed. Shadowgraphs of scattering structures followed by synchronous scattering profiles, spatial and temporal characteristics of scattering, data of theoretical modeling are presented.
Early reflection energy in concert halls: how much, how early, and from where
Authors: Gade Anders Chr.
Published: February 2014

Today, the importance of distributing early reflection energy to listeners and performers in concert halls is well understood and accepted—also among architects. Still, implementation in the practical design of a large hall is not easy, partly because we still have difficulties quantifying precisely the demands in detail (how much, how early, and from where) due to limitations in our acoustic knowledge—and often also due to little response from the clients regarding their preferences when decisions between alternative demands must be made. Therefore, in general it is up to the acoustician to decide how far to promote the good cause on the basis of his/her experience, taste, and talent in influencing the decision process. The aural presentation will focus on the current limitations in our knowledge regarding the musicians’ need for early reflections, which is a special challenge in the design of terraced, ‘‘surround’’ concert halls. In the case of the listeners, knowledge has reached a much higher level, and recent results regarding how room shape influence the objective acoustic parameters monitoring the early energy will be presented.
The nervous spatial behavior of early-energy measures in auditoria
Authors: de Vries Diemer , Hulsebos Edo M.
Published: February 2014

Most commonly used room acoustical measures are defined as the ratio between the energies in two time windows of the impulse response. In the Clarity Index and the Lateral Energy Fraction—supposed to be indicators for transparancy and spaciousness, respectively—the time window 0–80 ms plays a predominant role. When impulse responses are recorded along an array of closely spaced microphone positions and the above measures are calculated for each position, it appears that large fluctuations, up to a factor of 2, occur on a small spatial scale, e.g., in front of one and the same seat. These fluctuations are due to interference of early relections and can be physically well understood. It makes clear that the acoustic quality of a seat or row should not be based on one single measurement but on some spatial average, or that the measures should be redefined such that interference, to which our hearing mechanism apparently is not sensitive, is eliminated.
Effects of seating arrays on subjective quality in auditoria
Authors: Morimoto Masayuki , Hirose Sachio , Ishida Koji
Published: February 2014

Listening tests were performed to clarify the subjective effects of seating arrays. First, a qualitative assessment was made of the subjective effects introduced by the seating array. Test signals were prepared by convolving dry music with impulse responses measured in a scale model consisting of a stage, a floor with audience but no walls or ceiling. The measured impulse responses showed that the seating array caused an increase in amplitude below 80 Hz as well as a large dip at 150–200 Hz. The results of listening tests demonstrated that the seating array affected not only bass perception but also loudness. Second, it was investigated whether reflections from the ceiling and walls can compensate for an excess or deficiency of perceived bass caused by the seating array. In addition, the relation between the frequency characteristics of sound fields and bass perception is discussed. Test signals were prepared by adding a ceiling reflection and reverberation to test signals used in the first test. The results indicated that to a certain extent they can compensate for an excess or deficiency of perceived bass. It is suggested that bass perception should be evaluated according to the frequency characteristics of sound fields within the first 100 ms or so after the direct sound.
A synopsis of state-of-the-art high-frequency sonars for water column measurements
Authors: Trevorrow Mark V.
Published: February 2014

In recent years there has been a dramatic surge in the use of high-frequency (10 kHz–2 MHz) backscatter sonar systems for oceanographic and bioacoustic measurements in oceans, lakes, and rivers. These applications have generally focused on measuring the distribution of scatterers, such as bubbles, particulates, microstructure, fish, and zooplankton. Additionally, oceanographic flows and wave motions can be illuminated using these scatterers as tracers, using both the intensity and Doppler signals. Advances in electronics, data storage, signal processing, and transducer materials technology have made, and will continue to make, HF sonars smaller yet more capable in terms of bandwidth, resolution, and endurance. Some novel applications of simple echo sounders and sidescan sonars will be reviewed, showing examples of near-surface bubble distributions, internal hydraulic flows, and fish and zooplankton detection. Newer developments in multifrequency, volumetric multibeam and parametric sonars will be discussed.
Expanding capabilities of acoustic instruments: Benefits of calibrated output signals, bandwidth, midwater signals, and dynamic range
Authors: Foote Kenneth G.
Published: February 2014

Echo sounders, multibeam sonars, acoustic Dopper current profilers (ADCPs), and other acoustic instruments are widely used, if often for quite specific applications. Sometimes, these applications have been pursued at the design stage to the detriment of general system performance and versatility. Availability of a calibrated output signal in a fishery echo sounder, for example, may enable this to be used in quantitative applications. The availability of bandwidth may enable scientific echo sounders to classify and quantify multispecies assemblages of zooplankton. The provision of midwater signals may enable multibeam bathymetric sonars to be used for imaging scatterers in the water column. Extension of the dynamic range of ADCPs may enable a single unit to be used as four synchronous echo sounders with noncollinear beams. In general, the capacities of most underwater acoustic systems can be expanded significantly by attention to issues such as those mentioned here. Resulting opportunities for new applications are described, with justification in the physics of scattering. [Work supported by the Alfred P. Sloan Foundation.]
Instantaneous target strength measurement of live squid with synchronized video image
Authors: Mukai Tohru , Iida Kohji
Published: February 2014

The TS is a complex function of the fish’s size, shape, orientation, behavior, and internal structure, as well as of the acoustic wavelength employed. Therefore, for practical purposes, it is necessary to measure the TS experimentally. There is a considerable amount of knowledge about the TS of fish. Information about the TS of squid, however, is much less. Through previous studies over the past 6 years at our experimental field, acoustic equipment has been modified and gradually stabilized. It was also possible to use live squid in our specially designed experimental barge equipped with two underwater video cameras which look at the side view and upward. Preliminary TS and orientation measurements were done on single tethered live squid Todarodes pacificus. The live squid was suspended with monofilament nylon string near the acoustic beam axis and positioned 3.5 m below the transducers. The echo signals of the squid at six frequencies were converted to amplitude modulated signals in audible frequency, then they were recorded on audio channels of video tape with a video image simultaneously. Afterward, the echo envelopes were demodulated to analyze the relationship between TS and the swimming aspect of live squid by synchronized video image. Preliminary results from this measurement will be presented.
Proof of existence of monopole-type sound generation mechanism in a centrifugal blower
Authors: Nagi Ashnapreet , Wu Sean
Published: February 2014

Previous studies have shown that sound radiation from a centrifugal blower is primarily of the dipole and quadrupole characteristics, which describe the effects of fluid-structure interaction and turbulence generated by rotating blades. However, in many engineering applications the sound powers from centrifugal blowers are found to be proportional to the speed to the power of 4–6, which implies the existence of a monopole-type sound according to the Lighthills acoustic analogy [Lighthill, Proc. R. Soc. London, Ser. A 222, 564–587 (1952)]. This paper demonstrates that such a monopole sound generation mechanism indeed exists in a centrifugal blower used in an HVAC unit of a passenger vehicle. LDV measurements show a velocity fluctuation at the trailing edge tangential to the blade surface of an impeller. Laser tachometer measurements further indicate a fluctuation in shaft speed for all models of blowers tested. The resulting sound powers from these blowers show a predominant dependence of the speed to the power of 4, indicating the characteristic of a monopole. When these blowers are installed on a nonfluctuating shaft, however, the flow fluctuations are significantly reduced and the resulting sound powers are found to be proportional to the speed to the power of 6, which implies that the monopole sound generation mechanism is effectively eliminated.
Computational investigation of acoustic streaming in a two-dimensional duct
Authors: Erskine W. R. , Selamet A.
Published: February 2014

The present work investigates the nonlinear phenomenon of Rayleigh streaming characterized by acoustically driven flows attenuated by wall friction, resulting in nonzero average streaming velocities and circulation zones within the duct. A two-dimensional, long and narrow duct is considered in the present study with one end closed and the other subject to a sinusoidal acoustic velocity of varying frequency and amplitude, leading to a standing wave within the duct. A computational fluid dynamics code is used to solve the unsteady, compressible Navier–Stokes equations in two dimensions with turbulence modeling. Since the formation of streaming depends on the velocity profile within the Stokes layer, a high resolution grid is employed near the walls. The effect of inlet conditions is examined in terms of the circulation patterns, including the number of zones per wavelength and penetration depth into the fluid, as well as the mean velocity profiles.
On the sound sources of the screech tone radiated from a choked circular jet
Authors: Umeda Yoshikuni , Ishii Ryuji
Published: February 2014

In this experimental study, the generation of the screech tone in the dominant helical oscillation mode C was investigated by using a series of instantaneous Schlieren photographs and it was observed that the moving sound source for mode C appears to be the prominent point on the helical-shaped coherent vortical structure. This sound source is generated by the interaction between the helical-shaped vortical structure and the oblique shock at the rear edge of the third shock cell. The sound source rotates about the jet axis in the plane perpendicular to the jet axis at a constant supersonic speed and forms a Mach cone. The envelope of the Mach cone widens upstream and downstream as the sound source moves along the circular orbit and forms two helical-shaped wave-fronts of the screech tone propagating in upstream and downstream directions.
Ultrasound propagation in random, two-phase media with application to damage detection in concrete
Authors: Turner Joseph A. , Dugan Sean P. M. , Yang Liyong
Published: February 2014

The scattering of ultrasonic waves in a random two-phase medium, such as concrete, is discussed. Explicit expressions are derived for the attenuation of longitudinal and shear waves in terms of the statistics of the density and Lam parameter fluctuations. The derivation is based upon diagrammatic methods. The problem is posed in terms of the Dyson equation, which is solved for the mean field response. The attenuation results are given here in a straightforward manner. The general description is further simplified in accord with assumptions representative of a random, two-phase material. The medium is assumed statistically homogeneous and statistically isotropic, with a single correlation length. With these assumptions, the attenuations reduce to simple integrals on the unit circle. Expressions for mean free paths and elastic diffusivity follow from the general scattering theory. Applications to diffuse ultrasound experiments in concrete are then discussed. In particular, the appropriate form of the two-point spatial correlation function is examined and compared with experimental results from digitized concrete images. These results show that the assumed form of the correlation function describes the spatial statistics well. Finally, damage detection prospects relevant for concrete inspection are discussed. [Research supported by NSF Grant No. CMS-99-0078707.]
A crack model for nonlinear wave modulation spectroscopy
Authors: Gommerstadt Boris , Sutin Alexander
Published: February 2014

Nonlinear wave modulation spectroscopy is a novel technique for damage and crack evaluation based on the effect of modulation of ultrasonic waves by vibration. This technique was developed as an experimental approach and our goal is to discuss some mathematical models simulating these phenomena. The first model describes variation of resonance frequencies of the ultrasonic wave by breathing crack oscillation under low frequency vibration. This model considers an opened crack with the length changing under the action of vibration. The second model is concerned with plastic deformation in the vicinity of the crack tips that develops a hysteretic stress–strain relationship leading to the increase of ultrasonic wave damping. The Dugdale model is employed to describe ultrasonic wave damping and its variation under the vibration. These models relate modulation parameters to crack size and position. The suggested models explain the basic features of the observed modulation phenomena and could be used for characterization of the dimension and localization of cracks and crack-like damage.
‘‘What’’ and ‘‘where’’ in the auditory cortex
Authors: Rauschecker Josef P.
Published: February 2014

Several cortical fields have been defined in the superior temporal gyrus (STG) of the rhesus monkey. These ‘‘belt’’ areas are further characterized by their responses to spatially localized, species-specific vocalizations. Neurons in the caudal belt are more specific for spatial location, whereas neurons in the rostral belt are more selective for communication calls. Furthermore, the caudal and rostral belt project to distinct regions of the prefrontal cortex previously identified as subserving roles in visual spatial analysis and object recognition, respectively. Functional neuroimaging in humans also supports the existence of dual streams for the processing of sound content and location. Complex sounds generally activate a larger area in the belt region of the STG than tones. Consonant–vowel combinations give rise to activity distributions anterior to Heschls gyrus, which are organized into ‘‘phonetic maps.’’ If visual input is added in a McGurk-type fusion experiment, these maps are found to shift in individual subjects. Virtual auditory space stimuli administered via headphones activate two regions in the posterior parietal cortex. When this activation is compared with that by a visual spatial task, no overlap is found in the inferior parietal cortex, whereas convergent input is present in a superior parietal region.
Cognitive and sensory influence on the perception of complex auditory signals
Authors: Eddins Ann , Eddins David , Coad Mary Lou , Lockwood Alan , Watson Charles
Published: February 2014

Using positron emission tomography (PET), we have been studying the relationship between psychophysical performance and cortical activation during auditory discrimination tasks. In one experiment, we studied normal hearing listeners who had markedly different perceptual performance on a battery of auditory discrimination tasks. Changes in regional cerebral blood flow (rCBF) were measured while subjects discriminated changes in a tonal sequence or a temporally analogous syllable sequence. The results showed that behavioral performance was correlated with cortical activation in auditory sensory areas as well as cognitive areas related to attention and memory, depending on the demands of the task. To evaluate further whether attention to specific features of complex auditory signals influences the recruitment of cognitive processing areas of the cortex, we studied changes in rCBF when subjects attended to different features of a 1-octave band signal that varied in spectral envelope frequency (i.e., ripple frequency) or carrier frequency. The results showed that when subjects attended to ripple frequency relative to carrier frequency, activation in the thalamus increased. Moreover, when they discriminated ripple frequency in a low-carrier versus a high-carrier frequency, there was increased activation in the anterior cingulate gyrus, which is known to be involved in attention function.
Some neural correlates of speech and nonspeech perception
Authors: Binder J. R. , Liebenthal E. , Kaufman J. N. , Piorkowski R. L. , Remez R. E.
Published: February 2014

In a series of functional magnetic resonance imaging experiments aimed at examining the perceptual boundary between speech and nonspeech stimuli, brain activation signals were measured while subjects listened passively to a continuum of sounds ranging from noise to speech, detected speech signals in varying levels of noise, and perceived the same sinewave speech replicas as either nonspeech or speech while performing an auditory discrimination task. Activation at the anterolateral aspect of left Heschl’s gyrus increased with signal-to-noise ratio in the passive listening and noise masking experiments, and was higher when subjects heard sinewave speech as nonspeech than when they heard the same stimuli as speech while performing an auditory task that conflicted with the speech percept. Activation in this area was correlated with behavioral measures of phoneme perception and was unrelated to attentional demands. The data suggest a key role for this region in the representation of spectrotemporal information underlying phoneme recognition.
The functional anatomy of tinnitus
Authors: Lockwood Alan H. , Salvi Richard J. , Burkard Robert F. , Reyes Samuel A.
Published: February 2014

We have used positron emission tomography to map the neural systems that mediate subjective tinnitus. In two studies, subjects altered their tinnitus by voluntary jaw muscle contraction or sustained lateral gaze. In the third, tinnitus was altered by intravenous lidocaine. These experiments all linked the loudness of tinnitus with unilateral spontaneous neural activity in auditory cortex. This unilaterality contrasts with the bilaterality of cortical responses during acoustic stimulation, evidence for a noncochlear central origin for tinnitus. Plasticity in the central auditory system, thought to be associated with deafferentation, was demonstrated in hearing-impaired or unilaterally deaf patients by the greater extent of auditory cortex activation by tonal stimuli when compared to normals. Other sensory and motor systems may interact with these aberrant pathways, further upsetting the balance of auditory system activity. This is manifested by patients’ reports of transient voluntary loudness and/or pitch control. In controls, lateral gaze suppressed auditory cortical activity: this cross-modal inhibition was absent in the patients. Subjective tinnitus appears to be due to spontaneous neural activity in aberrant central auditory pathways that have abnormal interactions with other sensory and motor systems. This complexity may explain the unresponsiveness of tinnitus to pharmacological interventions.
A computational model for detecting and perceiving dynamic properities of speech
Authors: Niyogi Partha
Published: February 2014

We investigate many aspects of a computational framework for detecting phonetically salient dynamic properties of the speech signal from continuous speech input. As a prototypical example of this problem, we consider frameworks for the detection of the transition from closure to burst for stop consonants in continuous speech. We formulate the problem as an optimal non-inear filtering problem. This involves the mapping of the dynamic acoustic data into a low dimension Riemannian manifold in an infinite dimensional Hilbert space. This leads to many kinds of metrics that can now be imposed on the dynamic speech signal and we explore these metrics in the context of the perceptual magnet effect. An extensive discussion of the robustness of the strategy, the nature of the errors made, the relationship to acoustic phonetis and distinctive features and to categorical perception will be conducted. Related problems that have a similar structure include nasal detection using transitions from vowels into adjacent nasals, transitional models of vowels and so on. Results of automatic speech recognition experiments using these dynamic features will be presented.
Auditory context effects for nonequivalent sources
Authors: Holt Lori L. , Lotto Andrew J.
Published: February 2014

One of the most compelling examples of the symmetry in speech perception and production is the ability of the perceptual system to maintain phonetic constancy despite the context sensitivity in acoustic realization of the phonetic segment arising from coarticulation. It may be suggested that the perceptual system is able to accomplish this compensation for coarticulation by recovering the dynamic information in the surrounding acoustic context of the segment. We will present previous data and novel demonstrations that suggest that the contextual information need not come from the same source nor even resemble speech. For example, combinations of pure tones, which are not heard as speech, can shift the identification of neighboring consonants. These nonspeech effects can be described as cases of general auditory contrast. Whereas it is typical in dynamic theories of speech to refer to information specific to vocal tracts in accounting for speech perception phenomena, we feel that the present data are not completely inconsistent with a dynamic approach. The presence of contrast effects suggest to us that the perceptual system respects the dynamic nature of the environment by enhancing sudden canges in kinematics, which are presumed to be caused by application of novel forces.
The perception of rate induced resyllabification in English
Authors: de Jong Kenneth , Lim J. Byung-jin , Nagao Kyoko
Published: February 2014

Stetson (1951) noted that, when repeated, singleton coda consonants (VC) appear to modulate into onset consonants (CV) as the rate of repetition increases. The current study examines whether nave listeners perceive such resyllabifications, and whether such perceptions are affected by the voicing of the resyllabified consonants. Stimuli were extracted from production experiments in which talkers repeatedly produced singleton voiced and voiceless stops in the CV or VC position. Speakers entrained to a metronome which increased tempo from 450 to 150 ms/syllable. Open-set identification revealed that (1) while slow VCs are identified as such, fast VCs are identified as CVs a majority of the time and (2) CVs are rarely identified as VCs; however (3) both CVs and VCs at fast rates are often identified as CVCs, especially when the consonant is voiceless. A forced-choice identification task indicates that fast VCs and CVs, while clearly differentiated at slow rates, are both identified as CVs 80% of the time at fast rates. These results support Stetson’s observations, but like previously reported production results, indicate that fast rate tokens are partially ambiguous between CV and VC forms, an ambiguity which can get resolved by splitting the consonant in question. [Work supported by NIDCD and NSF.]
Perceptual experiment on Korean number production
Authors: Yang Byunggon
Published: February 2014

Acoustic parameters of the nine Korean numbers were analyzed by praat, a speech analysis software, and synthesized by sensynppc, a Klatt formant synthesizer. The overall intensity, pitch, and formant values of the numbers were modified dynamically by a step of 1 dB, 1 Hz, and 2.5%, respectively. This study explored the sensitivity of listeners to changes in the three acoustic parameters. Twelve male and female subjects listened to 390 pairs of synthesized numbers and judged whether the given pair sounded the same or different. Results showed that subjects perceived the same sound quality within the range of 6.6 dB of intensity variation, 10.5 Hz of pitch variation, and 5.9% of the first three formant variations. The male and female groups showed almost the same perceptual ranges. Also, an asymmetrical structure of high and low boundary was observed. The ranges may be applicable to the development of a speaker identification system while the method of synthesis modification may apply to its evaluation data. [This work was supported by a grant from the Interdisciplinary Research Program (Contract No. 1999-2-302-106-5) of the KOSEF.]
Perceptual metathesis of obstruent clusters
Authors: Makashay Matthew J.
Published: February 2014

This study examined acoustic and perceptual cues of obstruent clusters in order to test the hypothesis that metathesis can be a process that maintains identification of the consonants involved. In an auditory lexical decision task, there were effects of both optimality of cues, and lexical frequency of clusters. Nonword targets were created by metathesizing medial obstruent clusters in English words (e.g. [nækpI n] for napkin). For the clear listening level group, there was a slow rejection of nonword targets with optimal clusters that occur with higher frequency in the lexicon. For the speech reception threshold group, nonword targets with optimal clusters were more likely to be perceptually metathesized and realized as words than nonword targets with nonoptimal clusters were, presumably because subjects are more likely to hear both consonants in optimal clusters. Clusters with fricatives and stops were less likely to be perceptually metathesized than clusters containing only stops, since the continuity of manner features in a stop cluster hinders perception of consonant order. Whether some listeners are more adept than others in the ordering of temporal acoustic events will be investigated as well. [This material is based upon work supported under a National Science Foundation Graduate Fellowship.]
Backward masking in speech perception by children and adults
Authors: Sussman Joan , Laczi Elizabeth
Published: February 2014

The current investigation measured discrimination and identification of tone-noise and [b]-[a] stimuli by adults, children with normally developing language, and children with language impairment. The children were aged 4–6 years. These tasks were chosen instead of the more traditional two alternative forced choice (2AFC) technique because it was believed possible that task difficulty influenced previous results (e.g., Wright et al., 1997). The stimuli in the current set of experiments had longer tones (40 ms) than prior studies but used higher masker levels (52 dB spectrum level). However, results showed that all the participants discriminated the stimuli containing the tone or [b] signal significantly above chance, contrary to previous findings. More difficulty was found in the identification task, similar to prior backward masking results. [Supported by an Individual Development Award, NYS/UUP.]
Bandpass filtered faces and audiovisual speech perception
Authors: Munhall Kevin , Kroos Christian , Vatikiotis-Bateson Eric
Published: February 2014

The visual system processes images in terms of spatial frequency-tuned channels. However, it is not clear how complex object and motion processing are influenced by this early visual processing. In two studies this question was explored in audiovisual speech perception. Subjects were presented with spatial frequency filtered images of the moving face during a speech in noise task. A wavelet procedure was used to create five bandpass filtered stimulus sets. The CID Everyday sentences were presented with a multivoice babble noise signal and key word identification accuracy was scored. Performance varied across the filter bands with peak accuracy being observed for the images containing spatial frequencies spanning 7–14 cycles/face. Accuracy for higher and lower spatial frequency bands was found to be lower. When viewing distance was manipulated no change in the overall shape or peak in the key word accuracy function was observed. However, at the longest viewing distance the performance in the highest spatial frequency band decreased markedly. The results will be discussed in terms of visual information processing constraints on audiovisual integration.
Neighborhood effects in Japanese word recognition
Authors: Yoneyama Kiyoko , Johnson Keith
Published: February 2014

This paper reports on the results of a naming experiment that investigated lexical neighborhood effects in Japanese word recognition. A naming experiment was conducted with 28 Japanese adult listeners. Each participant responded to 700 words that had varying neighborhood density (in terms of Greenberg–Jenkins’ phoneme substitution, deletion, and insertion rules). The lexicon used for this calculation consisted of only nouns from the NTT Japanese psycholinguistic database [Amano and Kondo (1999)]. A preliminary regression analysis showed that such neighborhood density was negatively correlated with naming reacting time. The words with higher neighborhood density were responded to faster than those with lower neighborhood density. We plan to report further analyses that (1) include prosodic information as another dimension of the neighborhood calculation in order to reflect the finding that prosodic information has a vital role in Japanese word recognition, and that (2) calculate neighborhood density based on the auditory properties of the words in the lexicon. Neighborhood density is measured by comparing similarity of audio files in the Amano and Kondo database. Altogether, we plan to discuss which level of lexical representation (a lower-level acoustic-auditory representation or a higher-level abstract phonemic representation) is used to calculate phonological similarity within the lexicon.
Experimental paradigm for examining the formation of complex auditory categories
Authors: Lotto Andrew J. , Holt Lori L.
Published: February 2014

Phonetic perception is at its essence a categorization task involving multiple imperfectly valid cues to category membership. To examine the general cognitive processes underlying the formation and utilization of complex auditory categories such as speech, we have created a set of stimuli crafted from 300-m bursts of white noise. These stimuli vary in onset duration (or attack) and the center frequencies of two spectral gaps. Categories of varying complexity can be created from this stimulus set and input distributions can be strictly controlled. In addition, category formation can be observed ‘‘online’’ in this microgenetic design as subjects make responses (identification and discrimination) while learning the categories. In one such task, subjects were trained with categories defined by boundary values across three attributes. After 10 h of training, the subjects demonstrated extensive learning despite the fact that the categories suffered from ‘‘lack of invariance;’’ that is, no cue could be relied on exclusively to determine category membership. This demonstrates the viability of this paradigm for examining complex categorization. Implications for speech categorization and phonetic acquisition will be discussed. [Work supported by NSF.]