bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexure Design for Progressive Clearance Labyrinth Seal
Authors: Deo Hrishikesh , Zheng Xiaoqing
Published: September 2013

Turbo-machinery sealing is a challenging problem due to the varying clearances caused by thermal transients, vibrations or bearing lift–off. Conventional labyrinth seals have to be assembled with large clearances to avoid rubbing during rotor transients and this results in large leakage and lower efficiency. In our previous work, we have proposed a Progressive Clearance Labyrinth Seal which is mounted on flexures and employs progressively tighter teeth from the upstream to the downstream direction. The clearance progression gives rise to a feedback phenomenon whereby a small tip-clearance is maintained between the seal and the rotor. The flexures play a very important role in the design of this seal. They are required to have low radial stiffness relative to the fluidic feedback stiffness, so that the seal can move freely in response to the self-correcting forces. The axial stiffness has to be high to limit the displacement in that direction. Most importantly, the flexures need to provide extremely high twist stiffness, since a small twist can cause large changes in the clearance progression necessary for the self–correcting behavior. In this paper, we propose a novel zero–twist flexure architecture which preserves radial compliance and twist stiffness. We first create a simple analytical model to illustrate the design concept. An experimental setup is built and the design is validated on representative flexure geometry.
Characterization of Piezoelectric Nanofiber Composites Acoustic Emission Sensor for Structure Health Monitoring
Authors: Chen Xi , Shi Yong
Published: September 2013

A nanoscale active fiber composites (NAFCs) based acoustic emission (AE) sensor with high sensitivity is developed. The lead zirconate titanate (PZT) nanofibers, with the diameter of approximately 80 nm, were electrospun on a silicon substrate. Nanofibers were parallel aligned on the substrate under a controlled electric field. The interdigitated electrodes were deposited on the PZT nanofibers and packaged by spinning a thin soft polymer layer on the top of the sensor. The hysteresis loop shows a typical ferroelectric property of as-spun PZT nanofibers. The mathematical model of the voltage generation when the elastic waves were reaching the sensor was studied. The sensor was tested by mounting on a steel surface and the measured output voltage under the periodic impact of a grounded steel bar was over 35 mV. The small size of the developed PZT NAFCs AE sensor shows a promising application in monitoring the structures by integration into composites.
Large Amplitude Vibration Analysis of Shear Deformable FGM Cylindrical Shell
Authors: Younesian Davood , Askari Hassan , Esmailzadeh Ebrahim
Published: September 2013

The free vibration of shear deformable FGM cylindrical shell is analyzed by means of three analytical approaches including Hamiltonian Approach (HA), Energy Balance Method (EBM) and the Modified Energy Balance Method (MEBM). Firstly, dimensionless equation of vibration of shell is derived and using the Galerkin procedure, the associating ODE is constructed. The Voight model is employed and a parametric study is provided. Effects of different parameters such as the temperature, stiffness and material properties on the natural frequencies are studies. Accuracy and performance of different approaches are analyzed. Moreover the sensitivity of frequency ratio to the different parameters is investigated.
Effects of elasticity and porosity in modeling of the acoustic-to-seismic transfer function
Authors: Fokina Margarita S. , Fokin Vladimir N. , Sabatier James M.
Published: September 2013

Modeling sound interaction with the ground is important both for remote sensing techniques and the elimination of false alarms in the landmine detection application. Elastic and porous-elastic models of the ground are most frequently used for these studies. Though both of these models are well known, few comparisons have been made between the acoustic-to-seismic transfer functions (TF) calculated from these two models for the frequency range 100–1000 Hz, which is typical for geoacoustic applications. In this work, the matrix technique was exploited to solve boundary equations for porous-elastic layers. This technique allows one to obtain the TF and refraction indexes for arbitrary porous-elastic stratifications of ground layers. The results of test computations of original codes are presented. Effects connected with the slow wave in the porous-elastic model are analyzed. Effective parameters of the visco-elastic model are analyzed to give the best fit to frequency dependence of the TF calculated in the frame of porous-elastic layered model. Comparison between real and effective parameters demonstrates the possible accuracy for obtaining properties of porous-elastic ground in the frame of elastic models. [Work supported by ONR Grant N00014-02-1-0878.]
Dominance region for pitch: Effect of duration
Authors: Gockel Hedwig , Carlyon Robert P. , Plack Christopher J.
Published: September 2013

Frequency discrimination thresholds for pure tones increase with decreasing duration, more so at low than at high frequencies. The present study investigated the possible influence of this frequency-dependent effect on the dominance region for pitch (DRP) of complex tones (CTs). The DRP was determined for CTs containing the first seven harmonics with a fundamental frequency (F0) of 250 Hz, and a level of 65 dB SPL per component. The tones had a duration of 16 or 200 ms, including 8-ms ramps. Listeners were presented with a CT with one of the harmonics mistuned upwards or downwards by 3%, followed 500 ms later by a perfectly harmonic CT of the same duration. Listeners had to adjust the F0 of the harmonic tone so that its pitch matched that of the mistuned complex. For all five listeners, the DRP was higher in harmonic number for the short than for the long duration tones. The results are consistent with the idea that pitch is derived from a weighted sum of information from individual harmonics, the individual weights being dependent on duration and related to the discriminability of the harmonics. [Work supported by EPSRC Grant GR/R65794/01.]
Listening to a non-native speaker: Adaptation and generalization
Authors: Clarke Constance M.
Published: September 2013

Non-native speech can cause perceptual difficulty for the native listener, but experience can moderate this difficulty. This study explored the perceptual benefit of a brief (approximately 1 min) exposure to foreign-accented speech using a cross-modal word matching paradigm. Processing speed was tracked by recording reaction times (RTs) to visual probe words following English sentences produced by a Spanish-accented speaker. In experiment 1, RTs decreased significantly over 16 accented utterances and by the end were equal to RTs to a native voice. In experiment 2, adaptation to one Spanish-accented voice improved perceptual efficiency for a new Spanish-accented voice, indicating that abstract properties of accented speech are learned during adaptation. The control group in Experiment 2 also adapted to the accented voice during the test block, suggesting adaptation can occur within two to four sentences. The results emphasize the flexibility of the human speech processing system and the need for a mechanism to explain this adaptation in models of spoken word recognition. [Research supported by an NSF Graduate Research Fellowship and the University of Arizona Cognitive Science Program.] a)Currently at SUNY at Buffalo, Dept. of Psych., Park Hall, Buffalo, NY 14260, cclarke2@buffalo.edu
Issues in the measurement of perceptual assimilation
Authors: Harnsberger James , Wayland Ratree
Published: September 2013

This study examined the effect of methodological variables on the fit between predicted discrimination scores based on identification data and actual discrimination data in cross-language speech perception experiments. Such variables include (1) single versus multiple talkers in discrimination test trials; (2) different discrimination test types (e.g., AX, AXB, oddity); and (3) identification tests in which stimuli are presented individually versus stimuli being presented in the same context as they appear in discrimination tests. The optimal pair of identification and discrimination tests, yielding the best match between predicted and actual discrimination scores, can be used in subsequent studies examining perceptual category structure. These methodological variables were examined by presenting American English speakers with two Hindi contrasts, [b]–[p] and breathy voiced dental-retroflex, both in initial position and in an [i], [a], or [u] context. The stimuli appeared in a range of categorial discrimination and identification tests. Early results examining the third variable listed above demonstrate that identification tests that present stimuli in the same context as they appear in corresponding discrimination test trials correlate more strongly with discrimination scores (r=0.72, p<0.05) than identification tests that present stimuli in isolation (r=0.58, p<0.05).
Spoken word recognition in English by Japanese listeners: A case of Japanese-accented and unaccented English words
Authors: Yoneyama Kiyoko
Published: September 2013

The effect of acoustic mismatch between a listener’s phonological representations and speech input on spoken word recognition was examined with Japanese learners of English. Imai, Flege, and Walley (2003) recently found that native-Spanish listeners showed a larger neighborhood density effect for unaccented English words than Spanish-accented English words, whereas native-English listeners showed a larger neighborhood density effect for Spanish-accented than unaccented words. We hypothesized that phonological mismatches would occur when native-Japanese listeners respond to unaccented English words than Japanese-accented English words. Further, the effect of the mismatch would be expected to be greater for words from dense versus sparse neighborhoods because Yoneyama (2002) found that Japanese listeners showed neighborhood density effect when they listen to Japanese. This paper reports the results of the experiment where native-Japanese listeners were asked to write down English words that were presented in noise. The words differed in neighborhood density; half were Japanese-accented words that were produced by a Japanese learner of English at a beginner level, the other half were unaccented words that were produced by a native-English listener. The results replicated Imai et al.’s (2003) finding.
Effects of acoustic and semantic contexts when learning to identify L2 phonemes in words and sentences
Authors: Ikuma Yuko , Akahane-Yamada Reiko
Published: September 2013

Laboratory training experiment was conducted in order to examine the effect of acoustic and semantic contexts when learning second language phoneme perception. Fifty minimal pairs of English words contrasting in /r/ and /l/ were produced by native speakers of American English in three conditions; in isolation (WD), within semantically neutral carrier sentences (NS), and within semantically contextual carrier sentences (CS). Participants were native speakers of Japanese, and were divided into three groups; each was trained to identify /r/ and /l/ in one of above three conditions. In pretest, identification accuracy varied by condition in the order, NS<WD<CS, which replicated the previous study [Rothwell and Akahane-Yamada, J. Acoust. Soc. Am. 112, 2386 (2002)]. It was also shown that the group trained with CS stimuli improved the ability to identify CS stimuli from pretest to post-test, but not WD and NS stimuli. In contrast, the effect of training using WD or NS stimuli generalized to all the stimulus conditions. These results suggest that the perception training utilizing the auditory input, in which acoustic information is the only clue to identify phonemes, is effective in cultivation of aural comprehension. Implications for foreign language education will be discussed. [Work supported by TAO, Japan.]
Phonetic and phonological effects in production and perception of Croatian clear speech
Authors: Smiljanic Rajka , Bradlow Ann R.
Published: September 2013

This paper examines the interaction of language-general, signal enhancement strategies and language-specific, phonological enhancement strategies in clear speech production and perception in Croatian, a language with a phonemic vowel length contrast and a relatively small inventory of five vowel qualities. Two native speakers of Croatian (one male, one female) read 20 nonsense sentences in conversational and clear speech. In a sentence-in-noise perception test, native Croatian listeners more accurately recognized words produced in clear than in conversational speech by both talkers. However, this clear speech intelligibility benefit was greater for the male than the female talker. Acoustic analyses showed that in clear speech both talkers enhanced the overall acoustic salience of the signal (slower, more frequent pauses, wider pitch range) and expanded the vowel space, although the male showed slightly less extensive vowel space expansion. However, only the male talker enhanced the phonemic vowel length contrast, suggesting that the observed asymmetry in the clear speech intelligibility benefit between the talkers may be due to the contribution of this phonological enhancement feature of his (but not her) clear speech production. The results suggest that speech intelligibility is most effectively enhanced by acoustic-phonetic modifications that reflect a combination of acoustic-auditory and phonological factors.
Can Japanese listeners recognize phonemes as well as morae as word boundary cues?
Authors: Otake Takashi , Sakamoto Yoko
Published: September 2013

According to Shortlist (Norris et al., 1995), one of the most recent universal models in spoken word recognition, metrical segmentation strategy, provides us with important cues on word boundaries, which are determined by linguistic rhythm. If this model is applied to Japanese, the cue must be morae because it is a mora-timed language. One thing which is not fully understood yet is whether or not a phoneme boundary exists in Japanese. According to Shortlist, a possible word costraint (PWC) predicts that impossible words are inhibited, so that a phoneme boundary should not exist in Japanese. In order to test this hypothesis, two experiments were conducted using a modified version of word spotting task (search ase and hamu in nip♯ase and ri♯hamu) with three groups of Japanese subjects, 19 adults, 35 children, with or without Roman alphabet. The miss rates show that the subject groups could successfully find embedded words beyond both phoneme (adults:15%; children with alphabetic knowledge: 17%; children without it; 23%) and mora (adults:7%; children with alphabetic knowledge 9%; children without it; 13%) boundaries with high accuracy, suggesting that in fact Japanese could be sensitive to phoneme boundaries, but the PWC inhibits them because they are not possible words.
Production frequency effects in perception of phonological variation
Authors: Connine Cynthia M. , Ranbom Larissa J.
Published: September 2013

Two experiments were conducted that investigated the relationship between phonological variant occurrence frequency (based on a corpus analysis of conversational speech) and auditory word recognition. The variant investigated was an alternation between the presence of [nt] and a nasal flap (e.g., center, cen’er). The corpus analysis showed that 80% of productions are nasal flaps, with wide variability across words (from 0% for ‘‘enter’’ to 100% for ‘‘twenty’’). In a production goodness rating experiment, listeners rated [nt] productions as better than their nasal flap counterparts. For individual items, a strong positive correlation was found between nasal flap frequency and goodness ratings: words typically produced with nasal flaps were rated as better productions. A lexical decision experiment showed that nasal flap variants were recognized more slowly and less accurately than [nt] versions. The rated quality of the nasal-flapped production was strongly correlated with the results of the lexical decision task: nasal-flapped words considered highly acceptable were recognized more quickly and accurately than words rated as poor nasal flap productions. The results demonstrate a strong relationship between experienced variant frequency and auditory word recognition and suggest that phonological variation is explicitly represented in the mental lexicon.
Effects of syllable onset length in determining word-likeness
Authors: Brewer Jordan , Tucker Benjamin V. , Hammond Michael
Published: September 2013

Previous research on word-likeness has determined effects of neighbors, and frequency of word parts (Bailey and Hahn, 2001; Coleman and Pierrehumbert, 1997; Frisch et al., 2000). Holding those contributors constant, we conducted an experiment designed to determine if there is also an independent effect of syllable onset length in determining word-likeness. Twenty students, native speakers of English, participated in a lexical decision task in which they were asked to rank tokens, e.g., /vork/, /flork/ and /strork/ (with the syllable onset varied between one and three segments) from 1 to 7. A 7 indicated a word that does not sound at all like a possible English word and 1 indicated a word that sounds like it could be a real English word (that you never heard before). A significant effect was found of syllable onset length [F(3,20)=4.121; p<0.024]. Specifically, a significant effect was found by subject but not by item between onsets of one segment versus two [F(2,20)=6.362; p<0.021], as well as one segment versus three [F(2,20)=7.436; p<0.013], but there was no effect of two versus three [F(2,20)=0.019].
The timing of speech-accompanying gestures with respect to prosody
Authors: Renwick Margaret , Shattuck-Hufnagel Stefanie , Yasinnik Yelena
Published: September 2013

The question of how and whether the body movements that accompany speaking are timed with respect to the speech has often been studied, and investigators have reached different conclusions depending on the types of gestures and aspects of prosody attended to. The ToBI system for labeling pitch accents (phrase-level prosodic prominences) and intonational phrase boundaries, which provides a well-defined inventory of prosodic elements, was used to label several sound files from videotaped lectures in English. A particular type of gesture, i.e., discrete sharp rapid movements that reach a perceptually salient end point, was separately labeled for syllable location in the visual display of the same lecture samples. Preliminary analysis showed a strong correlation between this type of ‘‘stroke-like’’ gesture of the head or hands and pitch accented syllables. For example, for one speaker of Australian English, 168 of 195 strokelike gestures (86%) occurred with a pitch-accented syllable. If these observations from coarse-grained temporal labeling are confirmed by the frame-by-frame labeling now under way, it will suggest that the study of speech-accompanying gestures can provide evidence for the prosodic structure of spoken utterances, and raise the possibility that a complete model of speech production planning should include a gestural component.
Distinct relative F0 levels elicit categorical effects in F0 maximum and minimum alignment
Authors: Dilley Laura C. , Brown Meredith
Published: September 2013

A standard assumption in intonation research is that the presence and timing of fundamental frequency (F0) maxima and minima relative to segments are crucial phonetic characteristics of intonation patterns. The present experiment tests an alternative hypothesis that the representation of intonation patterns is based on the relative pitch levels of syllables in sequence. Synthetic stimuli were created using the phrase Some lemonade with an overall rising/falling or falling/rising intonation pattern. Cues to the presence and timing of F0 maxima and minima were eliminated by replacing the F0 across lemon- with level F0 contours and replacing the sonorant consonants before and after each target vowel nucleus with Gaussian noise. Four continua were created by shifting the F0 levels of one or both syllables in equal 0.5- or 0.75-semitone increments. Thirteen subjects imitated randomized stimuli presented over headphones. Results showed that alignment of maxima and minima in imitations was predictably related to relative F0 level: F0 maxima (minima) were aligned early in the segmental string when the first target syllable in the stimulus was higher (lower) than the following syllable; otherwise, maxima and minima were aligned late. These results provide support for models of intonation based on relative pitch levels.
Low-frequency sound speed reduction in unconsolidated sediments by grain rolling and sliding
Authors: Isakson Marcia , Chotiros Nicholas
Published: September 2013

In recent experiments in the Gulf of Mexico, measured low-frequency sound speeds in sandy ocean sediments were significantly less than those predicted by Woods equation, the theoretical lower limit for sound speed in unconsolidated sediment [Williams et al., IEEE J. Ocean Eng. 27(3), 413–428; Turgut and Yamamoto, J. Acoust. Soc. Am. 87, 2376–2382 (1990)]. Therefore, the conventional treatment of sound wave velocity is apparently overlooking processes necessary to describe wave propagation in unconsolidated sediments. One possible process is a partitioning of sound wave energy into grain rolling and sliding, which leads to additional terms in the kinetic energy equation for the sand grain frame. This additional kinetic energy can be treated as an incremental virtual mass. The virtual mass terms can be evaluated given the scintillation index of the distribution of the compressional and shear stiffness variability, Poisson’s ratio, and the number of contact points for a single grain. This work will present the derivation of the virtual mass terms, calculations based on likely parameter values and a comparison with the experimental measurements. [Work supported by ONR, Ocean Acoustics.]
Near-real-time geoacoustic characterization during the BOUNDARY 2003 experiment
Authors: Heaney Kevin D. , Nielsen Peter N.
Published: September 2013

During the SACLANT Center BOUNDARY 2003 experiment on the Malta plateau, the rapid geoacoustic characterization (RGC) algorithm was applied. This algorithm uses the slope and spacing of shallow-water striations as well as the slope of the received level with range from a passing surface ship to estimate an effective geoacoustic sediment. By searching over a small set of representative sediments, using empirical relationships between grain size and compressional speed, density, and attenuation, the inversion can be carried out in near-real time. Ambient noise measurements of passing surface ships in the Malta plateau lead to geoacoustic inversion results obtained at sea that are comparable to previous work in the area where the inversions were obtained using vertical line arrays and controlled towed sources.
The frequency dependence of the relative sensitivities of the Biot parameters
Authors: Isakson Marcia , Neilsen Tracianne
Published: September 2013

The frequency and angular dependence of the seabed reflection coefficients contain information about how the properties of the ocean bottom influence acoustic propagation. One description of the interaction between sound and sediment is the Biot–Stoll model, in which the sediment is parameterized by 13 properties. Some of these properties have a large influence on the reflection coefficients over a specific frequency band and little or no influence on reflection coefficients at other frequencies. The sensitivity of the reflection coefficients as a function of frequency to changes in the Biot–Stoll parameters are explored using a rotated coordinates inversion method. Rotated coordinates are eigenvectors obtained from an eigenvalue decomposition of the covariance matrix of gradients of the cost function to be optimized. In this case, the cost function is designed to minimize the difference between measured and modeled reflection coefficients. The resulting rotated coordinates and corresponding eigenvalues indicate the relative sensitivity of the reflection coefficients to changes in the parameters. The rotated coordinates inversion technique is applied to reflection coefficient data synthesized for a sandy bottom over subsets frequencies from 100 Hz to 1 GHz. [Work supported by ONR.]
Wedge assemblage modeling of SAX99 backscatter strengths
Authors: Keiffer Richard S. , Novarini Jorge C. , Richardson Michael D. , Briggs Kevin B.
Published: September 2013

In SAX99 (Sediment Acoustics Experiment 1999), a number of high quality acoustic and environmental measurements were made in support of an ONR Department Research Initiative on high–frequency sound interaction in ocean sediments [M. D. Richardson et al. and E. I. Thorsos et al., IEEE J. Ocean Eng. 26, 4–53 (2001)]. Supporting environmental measurements include digital stereo photography of the interface roughness which were converted [A. P. Lyons et al., IEEE J. Ocean Eng. 27, 515–524 (2002)] to digital elevation maps. Using these micro-bathymetry data sets, the measured backscatter strengths from SAX99 are modeled via an extension of the wedge assemblage model [R. S. Keiffer and J. C. Novarini, J. Acoust. Soc. Am. 107, 27–39 (2000)] that allows for density-contrast between the water and sediment but assumes no change in the sound speed. In particular, SAX99 data in which changes in the acoustic backscatter can be directly related to the time evolution of the fine-scale interface morphology will be modeled and compared. [Work supported by ONR, Program Element No. 61153N-32 and by the DoD High Performance Computing Shared Resource Center (Stennis). This document has been reviewed and approved for public release.]
Multisensory integration and the concert experience: An overview of how visual stimuli can affect what we hear
Authors: Hyde Jerald R.
Published: September 2013

It is clear to those who ‘‘listen’’ to concert halls and evaluate their degree of acoustical success that it is quite difficult to separate the acoustical response at a given seat from the multi-modal perception of the whole event. Objective concert hall data have been collected for the purpose of finding a link with their related subjective evaluation and ultimately with the architectural correlates which produce the sound field. This exercise, while important, tends to miss the point that a concert or opera event utilizes all the senses of which the sound field and visual stimuli are both major contributors to the experience. Objective acoustical factors point to visual input as being significant in the perception of ‘‘acoustical intimacy’’ and with the perception of loudness versus distance in large halls. This paper will review the evidence of visual input as a factor in what we ‘‘hear’’ and introduce concepts of perceptual constancy, distance perception, static and dynamic visual stimuli, and the general process of the psychology of the integrated experience. A survey of acousticians on their opinions about the auditory-visual aspects of the concert hall experience will be presented. [Work supported in part from the Veneklasen Research Foundation and Veneklasen Associates.]
Spectro-temporal interactions in auditory-visual perception: How the eyes modulate what the ears hear
Authors: Grant Ken W. , Van Wassenhove Virginie
Published: September 2013

Auditory-visual speech perception has been shown repeatedly to be both more accurate and more robust than auditory speech perception. Attempts to explain these phenomena usually treat acoustic and visual speech information (i.e., accessed via speechreading) as though they were derived from independent processes. Recent electrophysiological (EEG) studies, however, suggest that visual speech processes may play a fundamental role in modulating the way we hear. For example, both the timing and amplitude of auditory-specific event-related potentials as recorded by EEG are systematically altered when speech stimuli are presented audiovisually as opposed to auditorilly. In addition, the detection of a speech signal in noise is more readily accomplished when accompanied by video images of the speaker’s production, suggesting that the influence of vision on audition occurs quite early in the perception process. But the impact of visual cues on what we ultimately hear is not limited to speech. Our perceptions of loudness, timbre, and sound source location can also be influenced by visual cues. Thus, for speech and nonspeech stimuli alike, predicting a listener’s response to sound based on acoustic engineering principles alone may be misleading. Examples of acoustic-visual interactions will be presented which highlight the multisensory nature of our hearing experience.
Conceptual architectural/acoustical design
Authors: Marshall A. Harold
Published: September 2013

The thinking which characterizes acoustics as a branch of physics and engineering has difficulty with the architectural design process—the process that generates a room concept in the imagination and experience of the architect. The architect has learned to ‘‘sense’’ the visual properties of a room as the design develops in the interaction between mind and media. Phrases such as ‘‘wanting to be’’ express the architectural intention but too often such intentions are dismissed as arbitrary; acoustics may then be about fixing the design with acoustical add-ons. Occasionally there is a true meeting of minds—a creative and receptive architect and an acoustician able to communicate at the level of the architectural intention. There is evidently an auditory dimension of wanting to be which is one with the visual. This paper explores the idea in several examples and concludes with suggestions for the training of acousticians.
Responses of inferior colliculus neurons are shaped by inhibitory projections from lower nuclei
Authors: Pollak George , Xie Ruili
Published: September 2013

Bats are highly social animals that utilize a remarkably rich repertoire of signals for a variety of social interactions. This talk will explore how these signals are processed and represented in the inferior colliculus (IC) of Mexican free-tailed bats. Most IC neurons are selective for communication calls in that they respond only to some calls but not to others. The selectivity is due largely to inhibition. To evaluate the impact of the inhibitory projections from the dorsal or intermediate nucleus of the lateral lemniscus (DNLL and INLL), each nucleus was reversibly inactivated while responses of IC neurons to a suite of communication calls were recorded. Inactivation of both nuclei allowed these IC cells to respond to a larger number of calls, and thus become less selective than when the inhibitory innervation was intact. We therefore conclude that the inhibitory DNLL and INLL inputs to IC are functionally shaping the signal processing in the IC by suppressing some excitatory inputs. One consequence of the inhibition from these nuclei is that it shapes the selectivity of IC neurons for complex signals, allowing those IC cells to extract certain information from only some complex signals but not others. [Work supported by NIH Grant DC00268.]
Cognitive processes in bird song
Authors: Cynx Jeffrey
Published: September 2013

Anthropomorphic hypotheses can alter previous ethological concepts. Songbirds have been traditionally categorized as open- or close-ended learners. Open-ended learners such as canaries and starlings continue to learn new songs throughout life. Close-ended learners such as song sparrows and zebra finches appear to learn song once and then repeat this song in a stereotyped or crystallized manner for the rest of their lives. Research over the last dozen years or so has produced evidence that whatever is close-ended in songbirds may be more than a little ajar. It is clear that adult song is a highly dynamic and closely monitored act. In these regards, it has a number of cognitive processes similar to human speech. Birds appear to continually monitor their own song, being able to stop in midsong if necessary. They also regulate the song amplitude given environmental and social conditions, and show song perturbations when experiencing delayed auditory feedback. However, so far as is known, close-ended learners cannot learn new song elements from a model, although there are hints to the contrary, including both behavioral and physiological results.
Perturbative inversion method for range-varying seabed sound speed profile estimation
Authors: Souza Luiz L. , Frisk George V.
Published: September 2013

In a range-dependent, slowly varying medium, the acoustic field can be represented as a sum of modes that adapt to the local properties of the medium. Modal wavenumbers measured as a function of source-receiver range, as described, for example, by Souza and Frisk [J. Acoust. Soc. Am. 113, 2204 (2003)], can be used to estimate seabed geoacoustic properties. An algorithm for estimating the compressional sound speed profile as a function of range is described. The technique consists of solving a Fredholm integral equation relating the perturbation of a background sound-speed profile to the perturbation of the modal eigenvalues [Rajan et al., J. Acoust. Soc. Am. 82, 998–1017 (1987)] in conjunction with smoothing constraints based on the stochastic regularization method. The formulation leads to a Kalman filter based algorithm, where the sound speed profile is obtained by solving the perturbative equations sequentially in range. The technique is applied to synthetic and experimental data from the modal mapping experiments (MOMAX).
Simple single path calculations for MFP tomography
Authors: Tolstoy Alexandra
Published: September 2013

MFP tomography promises a strong computational advantage over other geoacoustic inversion methods in 3-D, variable environments. In particular, the method can simply and rapidly estimate bottom parameters in full 3-D given average individual path estimates of the unknown properties. The method can then perform a simple linear inversion to obtain the full volume values. But, how simple is it to estimate the individual path averages? Sometimes simple, sometimes less so. This presentation will explore this issue.
Vertical coherence of sound propagation and seabed geoacoustic inversion
Authors: Yang Jie , Zhang Xue-Zhen , Zhou Ji-Xun , Rogers Peter H.
Published: September 2013

Array processing techniques in shallow water often require knowledge of the spatial coherence of sound propagation. However, few wideband data sets on this subject have been published. As a part of the ASIAEX program in the East China Sea, wideband sound propagation measurements were conducted in June 2001 along three radial directions and along a circle with a radius of 30 km. An earlier related paper dealt with reverberation data from this experiment [J. X. Zhou and X. Z. Zhang, J. Acoust. Soc. Am. 113, 2204 (2003)]. This paper analyzes sound propagation vertical coherence (SPVC) as a function of frequency, range, and propagation direction. Then the SPVC is used to invert bottom sound speed and attenuation. The results show that the characteristics of the SPVC and the SPVC-inverted bottom acoustic parameters agree well with geological survey and sediment cores in the ASIAEX area. [Work supported by ONR and NNSF of China.]
Appraisal of an energy flux model for geoacoustic inversion of ambient noise coherence data
Authors: Thomson David J. , Desharnais Francine
Published: September 2013

The vertical directionality of the ambient noise field in a shallow-water waveguide is highly dependent on the local geoacoustic properties of the seabed and is directly related to the vertical noise coherence observed between two closely spaced hydrophones. As a result, a direct measurement of the broadband ambient noise coherence can be used to invert for sea-bottom properties that affect propagation. In previous work, an energy flux model [D. M. F. Chapman, Proc. Inst. Acoust. 9(4), 1–11 (1987)] for computing vertical noise coherence in shallow water was extended to include the effects of multilayered geoacoustic seabeds, refraction and absorption within the water column, sensor-pair tilt, and nondipolar radiation patterns due to near-surface but finite source depths. This modified flux-based coherence model was combined with a hybrid local/global nonlinear optimization scheme and used to estimate geoacoustic and source/sensor parameters for several synthetic data sets [F. Desharnais et al., J. Acoust. Soc. Am. 113, 2204 (2003)]. In this paper, the capability of the energy flux coherence model/geoacoustic inversion procedure is assessed for ambient noise data that were measured at several shallow-water sites over differing seabed types. Where possible, comparisons with geoacoustic properties estimated by other methods will be presented.
Bounds on errors in geoacoustic inversion: A second order analysis
Authors: Sanders William
Published: September 2013

Whereas bounding of errors in inverse problems is not generally possible, the problem has been shown to be tractable if the forward equation can be linearized about some (preferably the true) set of values and if, further, all errors are assumed Gaussian. Under these assumptions, the covariances of the a posteriori errors can be formulated, thus providing bounds on the uncertainty resulting from the inverse process. A previous effort analyzed the errors involved in benchmark cases and compared results to other published analyses. This surprisingly demonstrated the ability of a linearized relation to yield estimates of errors comparable to those achieved in Monte Carlo sampling. However, such a linear model neglects the interaction between model parameters. This current effort extends the analysis to second order. First and second derivatives of the acoustic field with respect to the environmental variables are calculated utilizing a parabolic equation propagation model. [Work supported by ONR.]
Acoustic radiation force impulse (ARFI) imaging: Characterizing the mechanical properties of tissues using their transient response to localized force
Authors: Nightingale Kathryn R. , Palmeri Mark L. , Congdon Amy N. , Frinkely Kristin D. , Trahey Gregg E.
Published: September 2013

Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 ms, and tissue displacements are typically several microns. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g., fat) displacing farther than stiffer tissues (e.g., muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies will be presented. [Work supported by NIH Grant R01 EB002132-03, and the Whitaker Foundation. System support from Siemens Medical Solutions USA, Inc.]
Elasticity imaging of arterial wall with transcutaneous ultrasound both in longitudinal-axis and short-axis planes
Authors: Kanai Hiroshi , Hasegawa Hideyuki
Published: September 2013

A method for measuring regional elasticity of tissue surrounding atherosclerotic plaque is described. An ultrasonic beam was scanned with a conventional linear-type probe, and multiple layers were preset from luminal surface to adventitia of the common carotid artery (CCA) with intervals of 375 μm. By applying the method [IEEE Trans. UFFC 46, 1229–1241 (1999)], a minute decrease of several tenths of a micrometer in thickness of each layer resulting from arrival of the pressure wave was determined. By assuming that the arterial wall is incompressible and that the blood pressure is applied normal to each layer, the elastic modulus in the circumferential direction of each layer was estimated at intervals of 75 μm in the radial direction and 150–300 μm in longitudinal direction. On the other hand, by designing the directions of ultrasonic beams so that each beam always passes through the center of the artery, the cross-sectional elasticity image in the short-axis plane was also obtained. Based on the elasticity library determined by comparing the elasticity distribution and their pathological images, each point was statistically categorized as lipid, a mixture of smooth muscle and collagen fiber, or other. By applying the method to the CCAs, soft inclusion of lipid was found for plaques.
Studying viscoelasticity in soft tissues with supersonic shear imaging
Authors: Bercoff Jeremy , Muller Marie , Tanter Mickael , Fink Mathias
Published: September 2013

In this work, a 3D analytical formulation of the mechanical Green’s function in a viscoelastic medium is derived and presented. Based on a Voigt model to take into account viscoelasticity, this mathematical formulation is validated experimentally using the supersonic shear imaging technique (SSI). Taking benefit of the ultrasonic remote generation of a moving shear source radiating low-frequency shear waves in the medium, this technique has been studied and validated for soft tissue elasticity mapping in previous works. It is shown here that the spatial and temporal shape of shear waves induced in soft tissues using SSI can be accurately modeled with the viscoelastic Green’s function. The influences of important parameters such as viscosity, elasticity, or diffraction on the shear wave shape are carefully studied and discriminated. In a second part, taking advantage of the previous modeling, the inverse problem consisting of recovering shear elasticity and viscosity is presented and validated using the Green’s function-based simulation tool. Experiments on tissue-mimicking phantoms presenting different viscoelastic properties are presented. The influence of out-of-plane shear propagation on the inversion algorithm is discussed.
Strain imaging with intravascular ultrasound: An in vivo study
Authors: Perrey Christian , Ermert Helmut , Bojara Waldemar , Holt Stephan , Lindstaedt Michael
Published: September 2013

The evaluation of mechanical properties of coronary plaques is of high interest for the assessment of coronary diseases. Intravascular ultrasound (IVUS) can be used to visualize strain in coronary tissue. In this study, strain imaging is performed using an IVUS system with a 40-MHz rotating single-element transducer. Radio frequency (rf) data are acquired during in vivo examinations and sampled at 100 MHz. Image frames are stored consecutively during 3 s at a frame rate of 30/s. Data are recorded at different levels of tissue compression. The required pressure difference is caused by natural pulsatile blood flow. The strain imaging algorithm estimates radial strain from rf data based on frame-to-frame correlation. Rotating transducers often show nonuniform rotational distortion (NURD), which leads to misaligned echo lines in consecutive frames. This results in lateral motion artifacts and causes decorrelation. This effect is reduced by lateral motion correction based on block-matching algorithms. Results show that strain imaging can successfully be performed in vivo with data acquired predominantly in diastole. Different coronary tissue regions can be identified by local strain variations. If NURD is present, strain image quality is degraded. In some cases NURD is reduced by repositioning the transducer.
Design and application of a perforator element muffler for reducing noise from fan-trays in telecommunication enclosures
Authors: Holness Hugh , Prasad M. G.
Published: September 2013

Generally the mufflers for reducing noise from fan-trays in telecommunication enclosures use sound absorptive materials in their design. Our objective in this work is to design a perforator element muffler that will produce similar acoustical performance without increasing pressure drop in the system as compared to a generally used muffler with sound absorptive material. The work includes parametric studies on the influence of perforated element on noise attenuation and pressure drop. The advantages and disadvantages of reactive perforator element mufflers over the dissipative mufflers in such applications will be studied. The studies include both design and experimental work.
Acoustic project for installation of motor generator group by means of computer simulation
Authors: Ferreira Jose C. , Zannin Paulo T.
Published: September 2013

This work presents an acoustical project for the installation of a motor generator group of electricity in a hotel by means of computer modeling. The noise levels at the site have been obtained without the motor generator group, and via the computer modeling it has been deduced how these levels would be after the installation of the equipment. A possible solution to mitigate the noise impact the equipment would cause on the neighborhood has been indicated, and it has been predicted how the impact would be reduced after the implantation of this solution.
Ground-penetrating radar for landmine detection applications
Authors: Bradley Marshall , Duncan Michael
Published: September 2013

The use of ground-penetrating radar (GPR) for landmine detection and its relationship to acoustic–seismic (A/S) techniques is discussed. While GPR is very effective against buried metal targets, modern plastic-cased landmines are much more difficult for GPR to detect. This difficulty is due to the low dielectric contrast between the landmine material and the soil itself. Recent advances in radar technology and signal-processing algorithms have improved GPR performance against buried plastic landmines. Several multichannel and synthetic aperture GPR systems have been developed that are capable of acquiring broad spectrum data over densely sampled spatial grids. Volumetric images of the subsurface produced by these systems are processed using automated-target-recognition (ATR) routines in order to determine the presence/absence of a landmine target. While GPR systems are capable of performing well on their own, the fusion of GPR data with data from an additional ‘‘orthogonal’’ sensor greatly increases the overall probability of detection (Pd) and reduces the false-alarm rate (FAR). Acoustic–seismic (A/S) sensors provide this orthogonality by exploiting mechanical properties of the target as opposed to the electromagnetic properties detected by GPR.
Laser Doppler vibrometer-based acoustic/seismic technique and GPSAR technique for co-located landmine detection
Authors: Xiang Ning , Bradley Marshall
Published: September 2013

Recent success in using a laser Doppler vibrometer (LDV) based acoustic-to-seismic landmine detection [J. M. Sabatier and N. Xiang, IEEE Trans. Geosci. Remote Sensing 39, 1146–1154 (2001); N. Xiang and J. M. Sabatier, J. Acoust. Soc. Am. 113, 1333–1341 (2003)] and a ground penetrating synthetic aperture radar (GPSAR) suggested a novel configuration of fused sensors comprised of a LDV-based A/S detection sensor and a GPSAR. Extensive field experiments revealed that these two technologies can be considered orthogonal. When used in concert, a fused configuration may significantly improve the probability of detection and reduce the false alarm rate. They function best against different types of landmines under different burial conditions because they exploit disparate phenomena to detect mines. In order to optimize the fused detection ability using the two modalities, co-located field experiments have been conducted using both LDV-based A/S sensor and a GPSAR sensor. This paper will discuss the comparative experimental study using the recent co-located field scanning results.