bluuebunny/crossref_metadata_2025 huggingface dataset:
Surf zone acoustic measurements from DUCK94
Authors: Livingston Ellen S. , Pasewark Bruce H.
Published: October 2005

Low-frequency (0–600 Hz) acoustic measurements were taken on a 20-element bottom mounted horizontal line array in the surf zone of Duck, NC, during the DUCK94 exercise of Oct 1994. These measurements of breaking wave noise comprise acoustic array data uniquely taken so close to shore. The array was oriented endfire to shore, at 500 m offshore in 6 m of water. The beamformed array data provide a space-time-frequency decomposition of the surf zone noise. In particular, comparisons of noise levels from inshore and offshore in low surf conditions and moderate surf conditions are shown. Individual hydrophone data show frequency versus time versus level dependence and indicates a correlation between breaking wave period and noise levels.
Characteristics of seismoacoustic propagation in a near-shore environment
Authors: Hodgkiss William S. , D’Spain Gerald L. , Kuperman William A.
Published: October 2005

MPL conducted the adaptive beach monitoring experiment, a near-shore, seismoacoustic experiment, over April–June 1995, at Camp Pendleton Marine Base north of San Diego, CA. Other participants included NRaD/NCCOSC, NRL, ARL/PSU, and ARL/UT. The objectives were to examine the generation and propagation of seismoacoustic energy from both signals of interest and ambient noise sources on land and in the ocean, and the signal processing structures needed to separate signals from noise. To help quantify the propagation characteristics, a series of controlled source tows was performed. Tow tracks included along-shore tows (at approximately constant depth of 20 m), upslope/downslope tows from the surf zone to 3.5 km offshore, and cross-slope runs. Four tones at 95, 145, 195, and 370 Hz were simultaneously broadcast by the source and received by two nearly orthogonal, 120-m-long, 64-element, horizontal bottom hydrophone arrays located 3.4 km offshore in 20-m water. For tows along a bottom depth contour, the acoustic field at the higher frequencies shows the classical two- or three-mode interference pattern, whereas those in the upslope/downslope and cross-slope directions are more complicated. Horizontal plane-wave beamforming techniques are used to examine the horizontal refractive effects of cross-slope propagation. [Work supported by ONR, Code 32.]
Deoxyribonucleic acid damage induced by a spark-gap lithotripter in vitro
Authors: Miller Douglas L. , Thomas Ronald M. , Thrall Brian D.
Published: October 2005

Chinese hamster ovary cells suspended at a concentration of 106 ml−1 were exposed at 37T°C in thin-walled chambers at the focus of a spark-gap lithotripter. Discharges of 20 kV, triggered at a 2-Hz rate, emitted bright flashes of light, and generated shock waves of 27-MPa peak positive and 3.3-MPa peak negative pressures. DNA damage in viable cells was assessed using the single-cell gel electrophoresis (comet) assay. After exposure to 500 discharges, DNA strand breaks were readily detected. This DNA damage approximated the damage seen either from 10-min treatment with 5-micromolar hydrogen peroxide, or from 37 J/m2 of 254-nm ultraviolet light. Cavitation caused by the shock waves reduced cellular viability (trypan-blue exclusion) to about 67% after 500 discharges. However, the cavitation generated less than 0.1 μM H2O2, far too little to account for the DNA damage. Placing an opaque plastic sheet between the gap and the chamber to block the flashes of light eliminated the DNA damage effect, but maintained the cavitation-induced viability reduction (to about 66% after 500 discharges). This finding suggests that the ultraviolet light, not the cavitation, associated with the spark discharge may be the mechanism responsible for the DNA damage observed. [Work supported by NIH Grant No. CA42947.]
Endolymph volume regulation mechanisms revealed by microinjections into scala media
Authors: Salt Alec N. , DeMott John E.
Published: October 2005

Longitudinal movements of endolymph were quantified invivo in the basal turn of the guinea pig cochlea during injections of artificial endolymph into the second turn at rates up to 70 nl/min. Flow measurements utilized the marker ion tertramethylammonium (TMA), which was iontophoretically injected into the basal turn. TMA dispersion was measured by two ion-selective microelectrodes, one placed 0.5 mm apical, and the other 0.5 mm basal to the TMA injection site. Longitudinal endolymph movements were calculated from the recorded TMA time courses. Prior to injections, endolymph flow rates were extremely low. Volume injection into the second turn induced basally directed flows in the basal turn. The relationship between the measured rate and the injection rate was nonlinear, in which low-injection rates produced proportionately less flow than higher rates. These data show that for injections at low rates, volume disturbances have primarily local effects, presumably generating local distension or being compensated by local homeostatic mechanisms. At higher rates, basally directed endolymph flow becomes increasingly significant. These findings suggest that two independent processes may be involved in the regulation of endolymph volume. [Work supported by NIH Grant No. DC01368.]
The influence of sound direction on frequency tuning of inferior collicular neurons of the big brown bat, Eptesicus fuscus
Authors: Chen Yi-Wen , Tang Ka-Choi , Jen Philip H.-S.
Published: October 2005

The influence of sound direction on frequency tuning of 64 inferior collicular neurons of the big brown bat was studied by comparing the best frequency and Q10-dB, Q30-dB, and Q50-dB values of each neuron determined from five sound directions between ±70° in azimuth. Sound direction did not affect the BF of all but three neurons by more than 5 kHz but it affected at least one Q value of 51 (80%) neurons by more than 50%. Whereas sound direction affected all three Q values of 9 (14%) neurons, it afected no more than two Q values of the remaining 42 (66%) neurons. Sound direction also affected the shape of frequency tuning curves in 21 (32.8%) neurons. Frequency tuning of 30 collicular neurons to different sound directions was also studied before and after ionophoretical application of bicuculline to each recorded neuron. Bicuculline application not only lowered the minimum threshold of 20 (67%) neurons in all sound directions, it also shifted the lowest MT of 10 (33%) neurons to a different sound direction. In addition, it reduced the Q10-dB values of 18 (60%) neurons and changed the shape of the frequency tuning curves of 21 (70%) neurons.
Source spectrum recovery at different spatial locations
Authors: Macpherson Ewan A.
Published: October 2005

The directional filtering of sound by the pinnae is vital to localization, but distorts the spectrum of the signal reaching the eardrum. Sounds do not appear to change character dramatically as a function of direction, so listeners might have some ability to deconvolve pinna effects from the received signal. A three-interval profile analysis task measured listeners’ ability to recover source spectra. The stimuli were wideband noise bursts in which the levels of 1/3-octave bands were adjusted to control spectral shape. They were filtered by listeners’ measured head-related transfer functions (HRTFs) and delivered via headphones. Listeners discriminated between various nonflat spectra and perturbed versions of them. HRTFs were selected randomly for each interval, and localizability was controlled by varying the correspondence of the left and right HRTFs. Thresholds were highest when HRTFs were imposed diotically, and lowest in an unfiltered diotic baseline condition. Accurate spatialization improved recovery, but applying independent near-ear HRTFs dichotically was more effective. However, deconvolution was imperfect in both conditions. The results suggest that the ability to disregard HRTF filtering and achieve some timbre constancy over direction depends on having two independent, wideband ‘‘looks’’ at the source spectrum, rather than on accurate localization.
The role of temporal factors in pitch perception
Authors: Ciocca Valter
Published: October 2005

This study investigated how pitch perception mechanisms integrate acoustic information over time. The pitch matching procedure developed by Moore etal. [J. Acoust. Soc. Am. 77, 1853–1860 (1985)] was used in order to measure pitch shifts in a harmonic series (target complex) produced by mistuning a harmonic that either preceded or followed the target complex. In the first experiment, the mistuned component could either stop as the target complex started (pretarget condition) or start as the target stopped (post-target condition). The results showed that pitch shifts were significantly larger in the post-target than in the pretarget condition. In the second experiment, the duration of the silent period, which separated the mistuned component and the target complex, was varied in both the pre- and the post-target conditions. Pitch shifts were virtually eliminated by a delay longer than 20 ms in the pretarget condition. By contrast, a delay of 160 ms was necessary to eliminate pitch shifts in the post-target condition. These results suggest that pitch perception mechanisms take into account the order of occurrence of acoustic information for calculating the pitch of a complex sound. [Work supported by Hong Kong RGC, Grant HKU 362/94M.]
Glide difference limens as a function of center frequency, duration, and transition size
Authors: Madden John P.
Published: October 2005

The study determined glide difference limens for up and down glides in several conditions. Signal durations were 50, 100, and 400 ms, and the average stimulus center frequencies were 2 and 6 kHz. The standard, or comparison, signals changed in frequency by 0, 500, and 1000 Hz. These transition sizes were chosen to cover the range of F2 formant transitions. The subject’s task was to distinguish between the standard and a target signal with a greater or lesser change in frequency, depending on the experimental condition, in a 2-alternative, forced-choice task. To avoid the confounding effect of between-stimuli static pitch cues, the center frequencies of the standard and target stimuli were ‘‘roved’’ about the center frequencies [Neill and Feth, J. Acoust. Soc. Am. Suppl. 1 87, S23 (1990)]. The data were analyzed using a level-detection model consisting of a filter bank, a nonlinearity, a temporal integrator, and a detection device. The question of whether the results support a rate place or temporal mechanism of frequency coding is discussed. [Work supported by NIDCD.]
Time domain simulation and visualization of fuzzy structures
Authors: Sparrow Victor W.
Published: October 2005

Fuzzy structure formulations divide a complicated structure into a well-known master structure and an imprecisely known fuzzy substructure. The loss of energy from the master structure, now known in the fuzzy structures literature as apparent damping, is simply a transfer of energy into the internal degrees of freedom of the attached fuzzy substructure. Some energy in the substructure is not returned to the master structure if either the internal damping of the substructure is non-negligible or there are a large number of degrees of freedom in the substructure with closely spaced resonances. This paper will demonstrate such effects using transverse wave pulses propagating on simple master structures, strings, and rods. Sets of one degree of freedom (dof) oscillators, drawn from particular statistical distributions, are attached as the fuzzy substructure. Finite-difference models for the strings and rods are solved simultaneously with the dynamics of the attached one dof oscillators in the time domain. Videotape animations show both the displacements of the master structure and the attached oscillators. Quantitative comparisons are made to the recent results of Russell [J. Acoust. Soc. Am. 97, 3414–3415(A) (1995)]. [Work supported by ONR.]
Nonlinear localization in mistuned periodic structures
Authors: Layne Philip , King Melvin E.
Published: October 2005

A characteristic phenomenon encountered in weakly coupled repetitive systems (systems composed of identical, repetitive substructural elements) is mode localization. Such localized modes have been investigated widely in the literature, in which it has been shown that eigenvalue veering in mistuned linear systems and mode bifurcations in perfectly tuned nonlinear systems give rise to motions during which a system’s vibrational energy may be spatially confined to a small subset of its elements. In the present work, a systematic investigation of the combined effects of nonlinearities and structural mistunings is discussed. The method of multiple scales is utilized to compute localized modes for an n degree-of-freedom nonlinear cyclic system with structural mistunings. Strong and weak localized motions are computed for various structural parameters, and it is shown that the presence of nonlinearities and mistunings can enhance the localization effect for some modes, while simultaneously diminishing the effect for others. Sample calculations will be presented for systems composed of two, three, and four degrees of freedom. The implications of nonlinear mode localization for vibration isolation are also discussed.
Anomalous attenuation in disordered networks
Authors: Dickey J. , Maidanik G. , D’Archangelo J.
Published: October 2005

A two-dimensional ‘‘jungle gym’’ is modeled as a network of connected dynamic systems, each characterized by a propagation wave number, loss factor, and length. The response of the network to an out-of-plane harmonic drive is calculated as a function of frequency. When the systems are all identical (i.e., a regular lattice) the modes are well defined and identifiable as being either modes of the individual systems or global modes of the network. Further, the pass and stop band structure in the network is distinct. When the system lengths are not regular, and in particular when they are randomly distributed, the modes are not easy to classify and the transmission of waves through the network is profoundly affected. This tends to destroy both pass and stop bands giving rise to an attenuation which is an average of the pass and stop bands, i.e., an ‘‘amber’’ band (since pass bands are green, stop bands are red and amber bands lie in between). In other words, perturbing the lengths gives rise to a structure whose attenuation (and transmission) from one point to another far exceeds that which would be expected based on the propagation loss of the constituent systems.
Vowel formant discrimination
Authors: Kewley-Port Diane
Published: October 2005

This series of experiments examines the relation between the basic capabilities of the peripheral auditory system to process speech and the classification of speech at more central levels. Psychophysical techniques have been applied to determine listeners’ abilities to detect, discriminate, and identify speech sounds. The current series of experiments established that thresholds for the discrimination of vowel formants are constant in the F1 region with a value of F=14 Hz and in the F2 region increase linearly with increasing frequency. This presentation describes three directions of our recent research. First, the effects of various stimulus parameters, including fundamental frequency and consonantal context, on thresholds were explored. Second, excitation pattern models have been shown to account for the significant effects of vowel formant frequency and fundamental frequency on F thresholds. Third, an initial experiment compared formant discrimination to vowel identification for listeners with normal hearing and moderate hearing impairment. Results demonstrated that for the impaired listeners, reduced ability to identify vowels was partially predicted by elevated discrimination thresholds in the F2 region. [Work supported by NIDCD.]
Vowel recognition: Formants, spectral peaks, and spectral shape
Authors: Hillenbrand James , Houde Robert A.
Published: October 2005

The purpose of this presentation will be to review some recent research on the acoustic characteristics of American English vowels, and to discuss some issues related to the auditory mechanisms underlying vowel recognition. Evidence from studies using traditional formant frequency representations will be reviewed to address issues such as talker normalization and the role of dynamic features in vowel identification. A long-standing debate in phonetic perception theory concerning whether phonetic quality is controlled by formant frequencies or the overall shape of the spectrum will also be addressed. While formant theory has tended to dominate much of vowel perception research, some compelling arguments have been leveled against formant representations; however, there are also some very important problems with whole-spectrum representations. A new method of representing speech will be described which is believed to address some of the limitations of both formants and overall spectral shape. The masked peak representation (MPR) was designed to: (1) show maximal sensitivity to spectral peaks, (2) show minimal sensitivity to spectral shape details in nonpeak regions, and (3) avoid explicit formant tracking. Preliminary results will be described from an experiment in which listeners are asked to identify /hVd/ utterances that were synthesized from MPR spectra.
Talker variability in vowel perception
Authors: Johnson Keith
Published: October 2005

Individual differences in the speech acoustic waveform create complications for theories of human speech perception, and auditory word recognition, as well as for automatic computer speech recognition systems. Theories of vowel perception, often taking the form of scatter reduction techniques more or less related to possible auditory or cognitive mechanisms, have been proposed to deal with individual differences. Word recognition theorists are also beginning to grapple with the problem of talker variability and implicit memory for talker-specific acoustic patterns. Talker variability is also one of the central problems in automatic computer speech recognition, where the dichotomy between speaker-dependent and speaker-independent systems has recently been augmented by new hybrid speaker-adaptive systems. Recently it has become apparent that all three of these areas of research are converging on the same conclusion—that speaker variability is best handled by rich, speaker-specific representations. In speech perception, this viewpoint has been called ‘‘indirect’’ speaker normalization. In the theory of word recognition, exemplar-based models of memory have been proposed to account for talker variability, and in automatic speech recognition a similar strategy is evident in multimodel systems and data augmentation approaches to speaker adaptation.
Quantification of nonlinear phenomena in laboratory-generated random sea waves
Authors: Powers Edward J. , Im Sungbin , Park In-Seung , Duggal Arun , Johnson Peter
Published: October 2005

In this paper higher-order statistical signal processing and Volterra series models of nonlinear phenomena are utilized to quantify the role of nonlinear second-order effects in laboratory-generated random seas. It is indicated how higher-order moment spectra may be utilized to determine a frequency-domain Volterra model of the linear and second-order wave physics occurring between two closely spaced points at which the random wave field is sampled. It will be shown that although the amount of ‘‘energy’’ associated with second-order effects is very small, such second-order phenomena play an important role in the generation of large amplitude waves. By inverse Fourier transforming the outputs of the linear and quadratic Volterra filters, it is demonstrated that the generation of large amplitude waves is due to momentary phase locking of the first- and second-order components. All of the phenomena mentioned above will be demonstrated with the aid of experimental data collected at the Offshore Technology Research Center’s Model Basin. [This study was supported by the National Science Foundation Engineering Research Centers Program Grant Number CDR-8721512 through the Offshore Technology Research Center (OTRC). The Volterra modeling techniques were developed under ONR Grant N00014-92-J-1046 and the Joint Services Electronics Program AFOSR F-49620-92-C-0027.]
Multilag high-order ambiguity function for multicomponent polynomial phase signals
Authors: Giannakis Georgios B. , Barbarossa Sergio
Published: October 2005

The analysis of polynomial phase signals using the recently developed polynomial phase transform suffers from spurious harmonics when dealing with multiple components having identical high-order coefficients. It is illustrated that such a model appears in synthetic aperture radars (SAR) imagery and transmission of polynomial phase signals through multipath channels. Analytical expressions for the spurious peaks are derived first, followed by algorithms for estimating the parameters of multicomponent polynomial phase signals taking advantage of the overdeterminacy introduced by the so called multilag high-order ambiguity function. An algorithm will be presented based on the projection of the observed signal onto a subspace estimated as the intersection of signal subspaces obtained using different sets of lags. Fast suboptimal algorthms will also be presented for suppressing interference terms and removing ambiguities. Autofocusing of real SAR imagery and mitigation of multipath when acoustic signals arrive at moving receivers, will be used to illustrate the usefulness of the proposed techniques.
Hot topics in animal bioacoustics
Authors: Au Whitlow W. L.
Published: October 2005

The field of animal bioacoustics is a diverse one involving a wide variety of species varying from insects and birds to terrestrial and aquatic animals. Some of the interesting research being performed with different species will be highlighted. Recent research has uncovered a possible new mechanism for sound localization in the parasoidal fly. Acoustics is being used to solve agricultural problems associated with insects. The U.S. Air Force is conducting a comprehensive program to study the effects of loud sounds and noise on different birds and terrestrial mammals. The availability of the U.S. Navy Integrated Undersea Surveillance System for detecting, localizing, and tracking whales has contributed significantly in the understanding of the seasonal distribution and movements of these large mammals. The ATOC program has generated considerable controversy on the possible effects of the ATOC source on marine animals. Several research programs have been initiated to investigate this particular issue.
Analysis and perception of voice similarities among family members
Authors: Kushner Rachel E. , Bickley Corine A.
Published: October 2005

The similarities of voice between members of the same family were found to be high when measured both perceptually and acoustically. The recordings of nine subjects (two mothers, two daughters, two sisters, two brothers, and an unrelated male) were made using sentences of different stress and reiterant syllable combinations. The recordings were paired into related and unrelated sets. Unfamilar listeners were instructed to listen to the recordings and rate their similarity on a numerical scale. Results showed that paired voices of those who were related showed a significant number of high scores as opposed to the voiced pairs of individuals who were unrelated. It was also found that voice similarity was more easily detected when the listeners heard whole sentences as opposed to reiterant syllables and individual words. Other influential factors associated with high scores (similar sounding voices) were equal prosody and volume. Related pairs who had similar prosody scored higher than unrelated pairs with similar prosody. Acoustic measurements of individual voices found that the difference in amplitude of the first and second harmonic as well as the spectral tilt were related to the listener’s judgment about voice similarities.
Voice quality: Listener identification of African-American versus Caucasian speakers
Authors: Trent Sonja A.
Published: October 2005

Although relative contributions of dialect and voice quality are difficult to tease apart, previous research has shown that listeners can perceive the gender and ethnicity of speakers at better than chance performance from recorded speech samples. The present study attempted to mitigate dialect cues and measure the resulting effects on perception by screening for dialect and by varying stimulus length. In experiment I, passages produced by ten African-American males, ten African-American females, ten Caucasian males, and ten Caucasian females were presented to 40 listeners with the same gender/ethnic distribution. In experiment II, sentence and citation /hVd/ stimuli produced by five of the speakers from each of the gender/ethnic groups were presented to 40 listeners. Both experiments required listeners to categorize the speakers by gender and ethnicity. Listeners were able to identify speaker gender and ethnicity at far better than chance performance. Accuracy of identification increased with stimulus length. Accurate identifications were made even in the citation condition, suggesting a unique contribution of voice quality apart from dialect. Caucasian male speakers were most accurately identified, while African-American females were least accurately identified. No listener gender/ethnic group performed more accurately than another. [Work supported by NIDCD.]
Acoustic study of acted emotions in speech
Authors: Wang Rong , Strong William J.
Published: October 2005

An extensive set of carefully recorded utterances provided a speech database for investigating acoustic correlates among eight emotional states. Four actors and four actresses simulated the emotional states of anger, joy, neutral, nervousness, hate, fear, sadness, and depression. Many acoustic parameters were extracted from analyses of the 64 (8×8) emotion portrayals. A reduced set of acoustic parameters was obtained by eliminating some highly correlated parameters. The talkers realized ‘‘unique’’ emotions, such as anger, with consistent values of the parameters. Different talkers realized ‘‘ambiguous’’ emotions, such as neutral and nervousness, with different values of the parameters. Emotion ‘‘pairs,’’ such as sadness and depression, had similar parameter values. The acoustic parameters tended to correlate strongly with ‘‘unique’’ emotions but less well with ‘‘ambiguous’’ emotions.
Vocal expression of emotion is associated with formant characteristics
Authors: Bachorowski Jo-Anne , Owren Michael J.
Published: October 2005

Acoustic properties of speech likely provide external cues about internal emotions, a phenomenon called ‘‘vocal expression of emotion.’’ Most empirical work in this area has emphasized global measures, such as pitch, speech rate, and overall amplitude. In this work, associations between induced positive and negative emotions and more fine-grained formant characteristics were tested. Subjects were 120 undergraduates who completed a questionnaire measuring their typical intensity of emotional experience and thereafter performed a challenging lexical-decision task during which noncontingent feedback occurred. On each of 10 baseline and 20 on-task trials, subjects spoke the words ‘‘Test n test’’ (n referred to next trial or trial block). The intent was to induce positive and negative emotions by providing success and failure feedback, and to measure the expression of emotion during the experience of those states. Analysis focused on the backward eh phoneme from the first ‘‘test.’’ Frequency and amplitude of F1, F2, and F3 were examined with MANOVAs that examined changes between baseline and on-task trials, as well as differences associated with the feedback conditions. Subjects who reported experiencing emotions intensely were found to show statistically significant changes in formant characteristics between baseline and on-task trials in both feedback conditions.
Sound propagation through a bubbly wake
Authors: Burch Holly , Buckingham Michael , Vagle Svein
Published: October 2005

The presence of bubbles in the near surface layer of the ocean causes significant reduction of the sound speed (A. B. Wood, 1957). The result is an upward-refracting sound-speed profile which acts as an acoustic waveguide. An experiment was performed in Saanich Inlet off the south east coast of Vancouver Island to investigate the spectral structure of sound which had propagated through a bubble layer. A motorboat, driven in a circle, created a bubbly wake which advected through the experimental region. Acoustic measurements were obtained at depths of 1.5 and 3.5 m at a range of 10 m from a broadband source. The spectral structure of the data depends on depth, but in both cases, shows a regular positioning of the peaks. The Green’s function solution for an isovelocity sound-speed profile (Lloyd’s mirror) and an upward-refractng inverse-square profile were fitted to acoustic spectra. The bubble-free records are well fitted by the Lloyd’s mirror theory, and good inverse-square fits were found for acoustic ‘‘snapshots’’ of the bubbly field at 2 and 8 min after field generation. It is possible to invert for the sound-speed profile in the near-surface bubble layer by fitting the spectral structure predicted by the inverse-square theory to that of sound that has propagated through the bubbly field.
The physiology and psychophysics of the acoustic startle reaction
Authors: Ison James R.
Published: October 2005

Intense noise bursts elicit in many animals, including humans, an abrupt and graded contraction of the flexor muscles called the ‘‘acoustic startle reflex’’ (ASR). Response vigor is determined in part by the acoustic properties of the eliciting stimulus, and in part by organismic factors such as biological rhythms, habituation, and emotion. Additionally it is powerfully affected by diverse and apparently irrelevant momentary shifts in the stimulus surround occurring just prior to the eliciting stimuli. These stimuli, called ‘‘prepulses,’’ can variously inhibit (‘‘PPI’’) or facilitate (‘‘PPF’’) the ASR, the general effect being ‘‘reflex modification.’’ The major variables affecting the strength of RM are prepulse salience and lead time, and, for short lead times, whether prepulses are increments or decrements in background level. Reflex modification has obvious intrinsic interest, and is being used to study sensory, perceptual, and cognitive processes in laboratory animals and in humans. The short brain-stem pathway responsible for ASR elicitation is simple and reasonably understood, with few remaining unknowns. In contrast, reflex modification consists of a set of less well understood semi-independent phenomena, which may variously call on different levels of the neuraxis, from brain stem to cortex, in processing stimulus input. [Work supported by NIH.]
Attentional factors in the elicitation and inhibition of the startle reflex
Authors: Hoffman Howard S.
Published: October 2005

More than a century ago, Helmholtz noted the ‘‘curious fact’’ that by mere conscious effort one can focus attention on any portion of the visual field and that the process ‘‘is entirely independent of the position and accomodation of the eyes.’’ A sequence of experiments in the Bryn Mawr laboratory, provided strong support for Helmholtz’s assertion. When eyeblinks were elicited by a tap between the eyebrows, the response was inhibited by a light flash (i.e., a prepulse) presented in various parts of the visual field. Subjects were able to modify the amount of inhibition engendered by the flash by shifting their attention toward or away from its impending location and they were able to do so without moving their eyes. A second experiment examined the effects engendered by foreknowledge as to the modality (auditory versus tactile) of an impending startle eliciting stimulus. Foreknowledge was found to reduce response amplitude. In other experiments foreknowledge as to when a startle eliciting signal would occur also reduced response amplitude. Overall the results imply that foreknowledge acts selectively with respect to the modality of a given sensory input and it also acts selectively as to where in the nervous system that input is directed.
The neural mechanism for directional escape in the goldfish
Authors: Eaton Robert C. , Guzik Audrey L. , Casagrand Janet L.
Published: October 2005

In response to sudden sound, many fishes rapidly accelerate away from the stimulus. This complex behavior, or C-start, is mediated by a network of brain-stem neurons that receive acoustic input and connect to motoneurons in the spinal cord. In the brain-stem network, the bilateral pair of Mauthner cells (M-cells) play the major role in determining the initial direction of the C-start. Each M-cell axon crosses the brain and connects to motoneurons on the opposite side of the body, so that the animal turns away from the side of the activated M-cell. M-cells receive primary acoustic afferents and inhibitory input from a network of ‘‘PHP’’ cells. PHP cells have a very short latency response to sound and operate in a feedforward mode to regulate M-cell firing threshold. These studies suggest that the PHP cells receive specific combinations of pressure- and displacement-sensitive auditory afferents that inhibit the M-cell to sounds coming from the side of the body opposite the stimulus. Thus only the correct M-cell fires, while its opposite counterpart is inhibited by PHP cells. Present studies involve an electrophysiological, behavioral, and neurocomputational analysis of this hypothesis. [Work supported by NIH and ONR.]
Effects of helicopter noise on spotted owls: Methodology
Authors: Pater Larry L. , Delaney David K. , Grubb Teryl G. , Beier Paul , Reiser M. Hildegard
Published: October 2005

The Endangered Species Act requires federal agencies to assess impacts of their activities on threatened and endangered species and to carry out programs for the conservation of listed species. In some cases activities, including military training, are curtailed because of potential impacts. There is currently no known published research on the possible impact of noise on the spotted owl. The present research addresses the question of the noise impacts of low level helicopter flights and ground activities such as chain saws and motorcycles on Mexican spotted owls (Strixoccidentalislucida). This research will characterize the effect of anthropogenic activity on breeding Mexican spotted owls by developing a dose-response threshold model that quantifies animal response relative to sound stimulus levels and approach distances. Consideration is given to the hearing range and sensitivity of the Mexican spotted owl, the sound level received at roost and nest sites, flight response of nonbreeding owls, effects on nest attentiveness of breeding females and on the rate of prey delivery by breeding males, and development of disturbance-specific management guidelines to minimize potential audio and visual impacts from helicopter and ground activities.
The effects of the acoustic thermometry of ocean climate signals on dolphins and small whales
Authors: Au Whitlow W. L. , Nachtigall Paul E. , Pawloski Jeffrey L.
Published: October 2005

The acoustic thermometry of ocean climate (ATOC) program of Scripps Institute of Oceanography and the Applied Physics Laboratory, University of Washington, will broadcast a low-frequency 75-Hz phase-modulated acoustic signal over ocean basins in order to study ocean temperatures on a global scale. One of the major concerns is the possible effect of the ATOC signal on marine life, especially on dolphins and whales. In order to address this issue, the hearing sensitivity of a false killer whale (Pseudorcacrassidens) and a Risso’s dolphin (Grampusgriseus) to the ATOC sound was measured behaviorally. A staircase procedure with the signal levels being changed in 1-dB steps was used to measure the animals’ threshold to the actual ATOC coded signal. The results will be used to examine how the ATOC sound will affect the hearing capability of these small cetaceans. The relative effect of the ATOC sound will also be compared with effects from other sources of noise such as aircraft, ocean going ships, pleasure craft, and other whales.
Ambient noise measurements of selected fish environments
Authors: Clark Joseph A. , Bart Amrit N. , Young Jane A.
Published: October 2005

A survey of ambient noise levels in a variety of environments, where fish are found or raised, has been conducted. Included in the survey were regions in the open water of the Chesapeake Bay, fish pens used by aqua farms in several states, and closed cycle tanks used for aqua-culture research and for public exhibitions. One-third octave-band and narrow-band measurements of the ambient noise levels will be presented. Sound recordings will also be played to demonstrate other characteristics of the noise at the different sites. [Work partially supported by Dual Use Technology Program, NAVSEA.]
A DSP-based neural computing system for acoustical signal processing
Authors: Zhang J. W. , Ma Y. L.
Published: October 2005

An artificial neural network (ANN) can be implemented by many methods, such as electronic hardware or simulation on digital machines. Hardware implementation of an ANN cannot provide network size and computation flexibility because its topology is difficult to change once it is implemented in the hardware. Simulation of an ANN on commercial parallel computers is not cost effective because their architectures are not optimized for ANN computation, while software approaches need a large amount of execution time. The solution to these problems is to use the special parallel-processing architectures. Based on studying existing methods, this paper concentrates on the DSP-based virtual implementation of ANN. A parallel processing system composed of TMS320C30 has been designed and configured, which meets the needs of ANN application to acoustical signal processing in the real world. It is a multiprocessor system with shared multiport memories. In this paper, the architecture of the system is described, and its performance is evaluated. The scalibility and communication method are also studied. The simulation results show that parallel efficiency of the system has reached a high level 80% when running a BP algorithm for classification of acoustical signals.
High-frequency threshold processes for leaky waves on cylinders of variable thickness: Fluid shell case
Authors: Morse S. F. , Feng Z. W. , Marston P. L.
Published: October 2005

To develop an understanding of high-frequency scattering processes by complicated elastic objects, it is helpful to identify benchmark problems which exhibit new kinds of leaky wave scattering contributions. It is found that scattering by a nonconcentric circular cylinder exhibits scattering processes not present in the simple case of uniform thickness. By application of a cylindrical harmonic addition theorem, the scattering was computed for a right circular fluid cylinder with a circular off-set vacuum core. The speed of sound in the fluid corresponded to the longitudinal velocity for steel and exceeded the speed for the outer fluid (water). For a uniform-thickness cylinder of sphere, previous calculations show a backscattering signature as the frequency was raised above the propagation threshold for the leaky waveguide mode analogous to the s1 Lamb wave [P. L. Marston, Phys. Acoust. 21, 1–234 (1992), Sec. 4.11]. When the thin part of a variable thickness shell is on the shadow side, the vicinity of the s1 mode threshold exhibits a new backscattering process due to mode cut off in the thin region and reversal of the associated ray. The local decrease in backscattering due to the thickness resonance is also affected. [Work supported by ONR.]
Wave propagation on coated cylindrical shells
Authors: McDaniel J. Gregory
Published: October 2005

This presentation describes methods of using an approximate elasticity formulation to compute natural wave numbers of waves in coated cylindrical shells. The efficient computation of these wave numbers is critical to coating design. A previously developed displacement-based variational formulation for coated shells [J. G. McDaniel and J. H. Ginsberg, J. Appl. Mech. 60, 463–469 (1993)] retains the accuracy of analytical formulations, but avoids the computational burdens associated with special functions of complex argument. This formulation, which was previously applied to two-dimensional problems, is extended to address wave propagation in the axial coordinate for each circumferential harmonic. Because the formulation is energy based, one has ready access to the strain energy distributions of each wave. For a specified real axial wave number, one obtains an easily solvable generalized eigenvalue problem for complex natural frequency. For a specified real frequency, the search for complex axial wave number is iterative. A fast algorithm for finding the complex axial wave numbers, which facilitates the design process, will also be discussed.
Vocal tract shapes and area functions from magnetic resonance imaging (MRI)
Authors: Story Brad H. , Titze Ingo R. , Hoffman Eric A.
Published: October 2005

There have been considerable research efforts in acoustic modeling of speech but there is still only a small body of information regarding direct three-dimensional measurements of the vocal tract shape. The purpose of this study was to acquire, using MRI, an inventory of three-dimensional vocal tract airway shapes that correspond to a particular set of vowels and consonants. The MR imaging was carried out for one subject (29-yr-old male, native of the midwestern United States) using a GE Signa 1.5-T scanner. The images were reconstructed and analyzed with a general display and quantitation package. The resulting three-dimensional (3D) vocal tract shapes were analyzed to find the cross-sectional areas perpendicular to the centerline extending from the glottis to the mouth to produce an ‘‘area function.’’ These area functions were then used as input to a wave-reflection type model of one-dimensional acoustic-wave propagation in the vocal tract. 3D reconstructions and area functions of the vocal tract shapes will be shown and the corresponding simulations of the speech sounds will be demonstrated.
A three-dimensional solution of the wave equation in a model of the vocal tract
Authors: Alipour Fariborz , Story Brad H.
Published: October 2005

The wave equation was solved in a cylindrical coordinate system for models of the vocal tract corresponding to vowels, /a/, /i/, and /u/. A straight cylindrical model of vocal tract was built upon area function data for each vowel. Using boundary fitted coordinates, the vocal tract shape and its boundary conditions were simplified to a straight tube. However, this simplification in geometry resulted in a complicated wave equation in the new coordinate system. The transformed wave equation was discretized in space over a 91×21 grid and solved in time using a finite difference method. Preliminary results indicate that pressure contours are typically planar, however, higher-order mode propagation is possible with this model. The results of the model have been compared and validated against the open–open and closed–open uniform tubes with good accuracy. The predicted frequency response of this model was also compared with a wave-reflection type of model. [Work supported by NIDCD Grant No. DC00831-04.]
Determination of chaos in human vowels
Authors: Winkel Casey R. , Vaidya P. G.
Published: October 2005

Human speech is a topic of much study today and many aspects of human speech are still unknown. The existence of chaos in a sustained vowel is one example. An analysis of the time series data generated by human speakers will be performed to determine if the data are chaotic. A set of pseudostate vectors will be created and used to analyze the time series data. From this analysis the largest Lyapunov exponent and the fractal dimension will be estimated. Also, support of a nonlinear origin of speech will be provided.
Variability in tongue kinematics in stop production
Authors: Lofqvist Anders , Gracco Vincent L.
Published: October 2005

The focus of this study is individual differences in tongue kinematics in the production of sequences of vowel–stop consonant–vowel. Four subjects produced VCV sequences with all possible combinations of the vowels /i, a, u/, and the stop consonants /p, t, k, b, d, g/. A magnetometer system was used to track vertical and horizontal movements of receivers placed on four points on the tongue. Individual variations were found for the influences of stop consonant voicing and vowel quality on tongue kinematics. In addition, in sequences with an alveolar consonant /t, d/ occurring between two high vowels /i, u/, some speakers lowered the rear portions of the tongue for the consonant closure, while other subjects maintained a tongue configuration that closely resembled that for the high flanking vowels. Possible accounts for these differences, such as oral anatomy, speaking rate, and speaking style will be discussed, as well as the acoustical consequences of the different articulatory patterns. [Work supported by NIH.]
Local and global effects of the pyriform fossa on speech spectra
Authors: Dang Jianwu , Honda Kiyoshi
Published: October 2005

The pyriform fossa consists of two bilateral cavities located behind the laryngeal ventricle. The fossa is known to act as a branch of the vocal tract by Fant’s study (1960) based on x-ray data. This study investigates acoustic characteristics of the fossa using hardware models, which replicated the portion from the vocal folds to the velum based on volumetric MRI data, and using human subjects. Acoustic measurement was performed on the models by filling and emptying the fossa. The results confirmed that the fossa contributes local zeros to speech spectra at about 4 kHz. Further, it was shown that the effects of the fossa extend down to the first and second vowel formants. This global effect of the fossa on formant pattern has been confirmed by this simulation as being dependent on the location of the fossa close to the sound source. An invivo experiment was performed by injecting water into the fossa of human subjects, and identified the antiresonance frequencies of the fossa as the frequencies increase with decreasing the volume. The zeros obtained from these experiments were found to be consistent with those in natural speech. The relatively stable acoustic properties are thought to provide one of the individual characteristics of speech sounds.
Open-loop acoustic-to-articulatory mapping
Authors: Zussa F. , Lin Q. , Richard G. , Sinder D. , Flanagan J.
Published: October 2005

A new design is presented for open-loop estimation of articulatory parameters from an acoustic speech signal. Previous systems for acoustic-to-articulatory mapping generally involve an optimization loop which adapts synthetic speech to an arbitrary speech input. The open-loop method (i.e., without any optimization), aims to provide an accurate estimation of articulatory parameters at a low computational cost. The technique is used as a component of an adaptive voice mimic system. Model shapes corresponding to the natural signal are found by searching a precomputed table. The table associates vocal tract shapes to their corresponding spectra obtained by linear acoustic simulation. A new metric based on poles from linear predictive analysis is proposed to compare the natural spectrum to the precomputed synthetic spectra. Nearly real-time processing is achieved on a workstation by introducing a two-step search strategy. The resulting representation is known to provide an efficient parametrization of the speech signal which can be used for speech synthesis, low-bit-rate coding, and speech recognition. Further, the open-loop method also provides an accurate initial guess for traditional closed-loop adaptation. Initial results of speech coding using this open-loop estimation are presented and discussed. [Research supported by ARPA-DAST 63-93-C-0064.]