bluuebunny/crossref_metadata_2025 huggingface dataset:
Tunability and Sub- and Superharmonic Entrainment of Limit Cycles in CW Laser Driven MEMS
Authors: Blocher David B. , Zehnder Alan T.
Published: September 2013

The nonlinear dynamics of nanoscale mechanical oscillators driven both inertially and by CW laser light are explored experimentally. The oscillators are singly and doubly-supported beams, 200 nm thick with lengths up to 40 microns. The optically thin beams, suspended over a Si substrate, form a Fabry-Pérot interferometer. The net effect is that the fractions of absorbed and reflected light are periodic functions of the gap. Thus, monitoring the reflected signal allows the motion to be measured. In addition, motion of the device through the interference field modulates the temperature and hence thermal stress of the oscillator. The thermal stress provides a thermo-mechanical drive to the beam, resulting in nonlinear feedback that can drive the beam into limit cycle oscillation. The laser power needed for the onset of limit cycles is studied as a function of beam geometry, and laser placement. The oscillators show both hardening and softening behaviors, sub- and superharmonic entrainment and wide frequency tunability.
Marking emergency exits and evacuation routes with sound beacons utilizing the precedence effect
Authors: van Wijngaarden Sander J. , Bronkhorst Adelbert W. , Boer Louis C.
Published: September 2013

Sound beacons can be extremely useful during emergency evacuations, especially when vision is obscured by smoke. When exits are marked with suitable sound sources, people can find these using only their capacity for directional hearing. Unfortunately, unless very explicit instructions were given, sound beacons currently commercially available (based on modulated noise) led to disappointing results during an evacuation experiment in a traffic tunnel. Only 19% out of 65 subjects were able to find an exit by ear. A signal designed to be more self-explanatory and less hostile-sounding (alternating chime signal and spoken message ‘‘exit here’’) increased the success rate to 86%. In a more complex environment—a mock-up of a ship’s interior—routes to the exit were marked using multiple beacons. By applying carefully designed time delays between successive beacons, the direction of the route was marked, utilizing the precedence effect. Out of 34 subjects, 71% correctly followed the evacuation route by ear (compared to 24% for a noise signal as used in commercially available beacons). Even when subjects were forced to make a worst-case left–right decision at a T-junction, between two beacons differing only in arrival of the first wave front, 77% made the right decision.
Allowable floor-impact sound levels in apartment buildings
Authors: Jeon Jin Yong , Jeong Jeong Ho
Published: September 2013

The purpose of this study is to review the sound-isolation efficiencies of structural materials in multistory residential buildings, in which floor-impact sound was considered as the major source of residents’ complaints. Floor, walls, and ceiling were selectively treated, and the floor-impact sound was measured using standard noise sources such as the impact ball, the bang machine, and the tapping machine. The noise from the impactors was analyzed and the relationship between the sound levels and the subjective responses was investigated. Results showed that the overall sound level of the impact ball is slightly higher than that of a bang machine, although the impact ball has a lower impact force. It was also found that the noise from the impact ball is similar to the noise of children running and jumping. In addition, when the noise from the impact ball was evaluated in both laboratory and in situ conditions, the allowable noise level was found to be 54 dB (Li, Fmax, AW).
Investigation of comfort related aspects of noise in an aircraft cabin simulator
Authors: Weber Reinhard , Baumann Ingo , Freese Nils , Mellert Volker
Published: September 2013

In the frame of the multinational European project HEACE Health effects of aircraft cabin environment [www.heace.org] experiments have been carried out to investigate the effects of different environmental factors in an aircraft on performance, comfort and health of flight and cabin crew. Tests were run in aircraft cabin simulators where temperature, humidity and sound could be adjusted in a controlled manner because only limited possibility exists of systematically changing these factors in-flight. In a multi-factorial 3×3×3 design these tests simulated real flights with real cabin crew that was hired for the test and passenger. The research on passengers responses was done in cooperation with the European FACE Technology Platform (FACE Friendly aircraft cabin environment). This paper focuses on the effects of noise on the comfort on the cabin crew. It presents unexpected order effects of noise assessments and reports on the dependency of the ratings of noise and of other environmental factors on the assessed comfort. [The investigation is granted by the EU-Commission under HEACE G4RC-CT-2001-00611.]
Some recollections of D. R. Griffin as a young man
Authors: Galambos Robert
Published: September 2013

In 1939 Don Griffin invited me to join him in his earliest bat echolocation experiments. I will tell a few stories about what we two graduate students did together, and show the sound movie in which, for the first time, we recorded their cries as they flew and avoided obstacles.
Current and future innovations in high-frequency ultrasonic transducers and arrays
Authors: Shung K. Kirk
Published: September 2013

High-frequency ultrasonic imaging is considered the next frontier in ultrasonic imaging. Commercial high-frequency scanners often termed ultrasonic backscatter microscope (UBM) all use scanned single element transducers at frequencies higher than 30 MHz with a frame rate lower than 30 frames/s. The engineering of single element transducers and linear arrays at these frequencies has been problematic and may be addressed from the end of developing better piezoelectric materials and from the end of developing novel fabrication methodologies. The further improvement of UBM can be benefited greatly by the availability of superior single element transducers of wider bandwidth and higher sensitivity. Various novel piezoelectric materials, including 2-2 composites, fine grain materials, high or low dielectric constant materials, and fabrication methods that utilize conventional dice and fill, thick film, and MEMS have been explored to fulfill this need. Prototype linear arrays higher than 30 MHz have been developed and tested and preliminary images obtained. These recent developments will be discussed in this talk. [Work supported by NIH.]
Ultrasound biomicroscopy in mouse cardiovascular development
Authors: Turnbull Daniel H.
Published: September 2013

The mouse is the preferred animal model for studying mammalian cardiovascular development and many human congenital heart diseases. Ultrasound biomicroscopy (UBM), utilizing high-frequency (40–50-MHz) ultrasound, is uniquely capable of providing in vivo, real-time microimaging and Doppler blood velocity measurements in mouse embryos and neonates. UBM analyses of normal and abnormal mouse cardiovascular function will be described to illustrate the power of this microimaging approach. In particular, real-time UBM images have been used to analyze dimensional changes in the mouse heart from embryonic to neonatal stages. UBM-Doppler has been used recently to examine the precise timing of onset of a functional circulation in early-stage mouse embryos, from the first detectable cardiac contractions. In other experiments, blood velocity waveforms have been analyzed to characterize the functional phenotype of mutant mouse embryos having defects in cardiac valve formation. Finally, UBM has been developed for real-time, in utero image-guided injection of mouse embryos, enabling cell transplantation and genetic gain-of-function experiments with transfected cells and retroviruses. In summary, UBM provides a unique and powerful approach for in vivo analysis and image-guided manipulation in normal and genetically engineered mice, over a wide range of embryonic to neonatal developmental stages.
A small-scale, thermoacoustic-Stirling electric generator for deep-space applications
Authors: Backhaus Scott , Petach Michael , Tward Emanuel
Published: September 2013

Although thermoacoustic-Stirling hybrid engines (TASHE) have not been previously coupled to transducers to produce useful electric power, they have demonstrated high thermal-to-acoustic power conversion efficiencies. Electric generation is investigated by coupling a small TASHE to an electrodynamic linear alternator with an emphasis on satisfying NASA’s need for a small, lightweight, efficient electric generator for deep-space missions. The combined goals of low mass and high efficiency require the TASHE to have the largest acoustic power output possible from a minimum enclosed volume, which imposes a relation between various impedances of the TASHE’s lumped-element loop. The design of the TASHE and alternator used in this generator will be reviewed, performance data presented, and possible improvements discussed. [Work supported by NASA.]
Characterization of regenerator materials for thermoacoustic refrigeration
Authors: Liu Jin , Garrett Steven
Published: September 2013

A bellows bounce test apparatus using a mechanically resonant gas-filled metal bellows, coupled to moving-magnet linear motor, contained within a pressure vessel, has been developed for the testing of porous regenerator materials that might be useful for thermoacoustic refrigeration. The apparatus provides a combination of operating pressures, gases, amplitudes, and frequencies that can cover a large range of Reynolds numbers and Lautrec numbers (ratio of the hydraulic radius to the thermal penetration depth). We will report initial results obtained with this apparatus using two ceramic Celcor samples (400 and 600 cells/in*in) over four orders-of-magnitude in Reynolds number. The experimental results were in good agreement with the linear acoustic approximation at low Reynolds numbers, but deviate at higher Reynolds numbers for the viscous component of the pressure drop. For low Lautrec numbers, the dimensionless pressure drop depends on both Lautrec and Reynolds numbers. For Lautrec numbers greater than one (Poiseuille flow regime), there is no frequency (Lautrec) dependence. Similitude analysis collapses all data on both viscous (in-phase) and inertial (quadrature) pressure drops suggesting that introduction of the Lautrec number (or some dimensionless variable related to penetration depth) was required and measurements on samples of more complicated geometries should provide reliable results.
Magnetic resonance measurement of dynamics of cavitating fluid
Authors: Mastikhin Igor , Newling Benedict , Balcom Bruce J. , Green Derrick
Published: September 2013

The prevalent methods used in studies of cavitation are optical and acoustical. They are sensitive to changes in optical and/or acoustical transparency and are not applicable to studies of opaque media. Magnetic resonance (MR) methods, on the other hand, can be applied to arbitrarily opaque media, providing both dynamic and molecular information. A hindrance to implementation of MR methods in cavitation research is their relatively long measurement time: they cannot compete with optics or acoustics when a researcher needs a snapshot technique to study quickly changing processes on a microsecond scale. There are also some experimental problems with compatibility of MR scanners and acoustical equipment. However, if one is interested in longer time-scale processes, MR can provide data on velocity distribution, evaluate the turbulent processes in cavitating fluid, and measure correlations between the directions of flow on a microsecond scale. In this work, we show feasibility of an application of MR to studies of dynamics of cavitating fluid, with measurements of spatially resolved velocity spectra and other above-mentioned parameters.
Seismic sonar for landmine detection and confirmation
Authors: Muir Thomas G. , Zakharia Manell , Grill Aurore , Gestat de Garambé Emanuel
Published: September 2013

Impulsive vibration of the ground can generate seismic interface waves of the Rayleigh type. They decay exponentially with depth into the soil, and spread cylindrically with lateral range. At useful frequencies around 100 Hz, they typically travel at speeds around 100 m/s, with wavelengths around a meter. Rayleigh waves can be made to propagate in sonar-like pulses to buried targets, reflect, and return to the sonar for reception and signal processing, providing range, bearing, and information as to target type. We have conducted new experiments and analyses with seismic sonar in a clay soil. A focused array of ten sources and eight receivers (triaxial seismometers) were deployed at a range of 4.5 m to examine a 20-lb. landmine as well as a clump of rocks, and other false targets. After vector polarization processing, the amplitude of the mine target echo was 28 dB above the environmental backscatter. Mine-like target confirmation was provided by Wigner–Ville transformation, which allows separation of manmade from natural targets, by providing unique and identifiable time–frequency–amplitude signatures for each. The potential for target detection as well as a level of target type classification, at relatively long ranges, was demonstrated. [Work supported by the U.S. Army Night Vision Laboratory.]
Soil effect on landmine vibrations
Authors: Zagrai Andrei , Ekimov Alexander , Donskoy Dimitri
Published: September 2013

Field tests of the seismo-acoustic landmine detection techniques revealed strong dependence of mines’ vibration signatures on the burial depth, soil physical properties, and environmental conditions. This study discusses the mines’ linear and nonlinear signatures as a function of burial depth, soil type, and moisture content. Experimental results show that the resonance frequency of soil–mine system initially decreases with burial depth and then anomalously increases at greater depths. Soil moisture further amplifies this anomaly. Soil type and moisture content influence mines’ nonlinear signatures as well. It was found that the quadratic nonlinear (Q) and cubic nonlinear (C) intermodulation mine vibrations respond differently to the presence of moisture in soil. While Q response diminished in wet soil (after rain), the C response was still highly evident and used for mine visualization. These observations revealed complex behavior of soil–mine system, which is not completely understood or explained. [Work supported by ONR.]
Spectral profile discrimination ability using cochlear implants: Effects of number of active electrodes and pulse rate
Authors: Drennan Ward R. , Pfingst Bryan E.
Published: September 2013

The ability of cochlear implant users to discriminate a change in spectral shape was investigated in listeners with Nucleus CI24M and CI24R(CS) implants. A primary independent variable was the number of active electrodes. Listeners were asked to detect a current increment to one of 3, 7, 11, and 21 active electrodes. Intensity discrimination on one electrode was also evaluated. Stimulation was achieved using a monopolar configuration with 75μs/phase biphasic pulses and a 24 μs interphase gap presented at 250 pps per channel. The pulses were swept in rapid succession from the base to the apex such that the overall rate increased with the number of active electrodes. Sensitivity to differences in spectral shape decreased with increasing number of electrodes. Next, the pulse rate was reduced to 159 pps per channel for the 11 and 21 active electrode conditions. Sensitivity to spectral shape at the slower pulse rate was better than that at the higher rate given the same number of active electrodes. The improvement in sensitivity with the slower rate suggests that forward masking of one pulse over a successive pulse diminishes listener’s ability to hear an intensity increment in the spectral profile.
Effects of N-acetylcysteine on noise-induced temporary threshold shift and temporary emission shift
Authors: Robinette Martin
Published: September 2013

Animal research has shown that antioxidants can provide significant protection to the cochlea from traumatic noise exposure with some benefit when given after the exposure. Similar results in humans would have a significant impact on both prevention and treatment of noise-induced hearing loss. The current study evaluates the effectiveness of N-acetylcysteine (NAC) on temporary threshold shift (TTS) by using both behavioral and physiological measures. Sixteen healthy, normal-hearing subjects were given NAC or a placebo prior to exposure to a 10-min, 102-dB narrow-band noise, centered at 2 kHz. This exposure was designed to induce a 10–15-dB TTS. Following the noise exposure, pure-tone thresholds (Bekesy) and transient-evoked otoacoustic emissions (TEOAE) were measured for 60 min to monitor the effects of NAC on TTS recovery. Postexposure measures were compared to baseline data. [Work supported by American BioHealth Group.]
Perceiving a change in a nonperceived pitch
Authors: Demany Laurent , Ramos Christophe
Published: September 2013

Listeners were presented with 300-ms ‘‘chords’’ of five synchronous pure tones, followed after a 0.5–8-s silence by a single pure tone. The frequencies of each chord’s components were selected randomly, but spaced by intervals of between 6 and 10 semitones. In one condition (‘‘up/down’’), the single tone following a chord was 1 semitone higher or lower than one of the chord’s three intermediate components; on each trial, the corresponding component was selected randomly and the task was to indicate the direction in which its pitch changed. In another condition (‘‘present/absent’’), the single tone following a chord was either identical to one of the three intermediate components or halfway in frequency between two components; the task was to indicate if the single tone was present in the chord or not. Performance was much better in the up/down condition than in the present/absent condition, even though the opposite trend was predictable for an ideal ‘‘analytic’’ listener. Ten listeners reported that, in the up/down condition, they could often perceive the appropriate pitch change without having heard out the relevant component of the chord. These results provide strong evidence for the existence of pitch change detectors in the auditory system.
Evaluating the effects of bilingual dominance and language mode on overall degree of foreign accent
Authors: Imai Satomi , Flege James E. , MacKay Ian R. A.
Published: September 2013

This study evaluated the influence of bilingual dominance and language mode on overall degree of perceived foreign accent. Three groups of Italian–English bilinguals (n=12 each) were selected according to their ratio of self-rated English/Italian proficiency: English-dominant, balanced, or Italian-dominant. Language mode was manipulated by having participants repeat English phrases before and after similar Italian phrases (E1, E2) and then intermixed with Italian phrases (E3). Native English (NE) listeners rated four English phrases spoken by the bilinguals and 12 age-matched NE controls using a scale that ranged from 1 (strong foreign accent) to 9 (no foreign accent). We hypothesized that if switching into the native language (here, Italian) adversely affects pronunciation of the second language (English), the third repetitions of the English phrases (E3) should be more strongly foreign-accented than the first repetitions (E1). The foreign accent ratings decreased significantly in the following order: NE > English-dominant > balanced > Italian-dominant. That is, all three bilingual groups had detectable foreign accents, and strength of accent depended on bilingual dominance. The language mode effect was significant only for one of the four phrases examined, perhaps because it (mozzarella cheese) has distinctly different phonetic renditions in English and Italian. [Work supported by NIH.]
A cross-language study on perception of Taiwanese stops by non-native listeners
Authors: Chang Yueh-chin , Best Catherine T. , Halle Pierre A.
Published: September 2013

Few reports exist on perception of three-way stop voicing distinctions by non-native listeners whose languages have two-way distinctions that vary phonologically and phonetically. We examined perception of Taiwanese stops by French, Mandarin, and American English listeners. Taiwanese has three voicing categories: unaspirated voiceless (U), aspirated voiceless (A) and voiced (V). Phonologically, English and French have voiced-voiceless contrasts, so these listeners should have similar difficulties with Taiwanese /U-A/. Phonetically, however, English and Mandarin distinguish voiceless unaspirated versus aspirated stops, in which case these listeners should have equivalent difficulties with Taiwanese /U-V/. American and Mandarin listeners’ discrimination supported the second prediction. French listeners discriminated /U-A/ better than /U-V/ for velar stops, but the opposite for labials, possibly because French velar stop VOTs preceding high vowels are longer than Mandarin and American ones. Mandarin listeners discriminated better than French listeners overall. American listeners’ discrimination was poorest. The discrimination results are consistent with identification patterns for the three groups. The findings suggest that speakers of languages with phonologically unaspirated versus aspirated contrasts (Mandarin) can distinguish three voicing types more easily than speakers of languages with a voiced versus voiceless contrast (French, English), especially when the phonetic realizations differ from the phonological distinction (English).
Language-specific relevance of formant transitions for fricative
Authors: Wagner Anita , Ernestus Mirjam
Published: September 2013

Although the consonant inventories of Dutch, German, English, and Spanish are similar in size, the fricative inventories differ: English and Spanish distinguish labio-dental versus dental fricatives, whereas Dutch and German do not. Three phoneme-monitoring experiments investigated whether the relevance of formant transitions varies across languages, and whether it depends on the types of fricatives in a language. Native Dutch, German, English, and Spanish listeners detected a target fricative, /s/ or /f/, in nonwords. Half of the nonwords were cross spliced to produce misleading formant transitions: an /s/ replaced an /f/, or vice versa. Dutch and German listeners were unaffected by the misleading formant transitions, whereas Spanish listeners missed significantly more fricatives surrounded by misleading formant transitions; these results were obtained whether stimuli were originally spoken by a Dutch or Spanish speaker. English listeners showed the same sensitivity to formant transitions as the Spanish. Despite previous reports that formant transition cues are of negligible significance for fricative identification (Klaassen-Don, 1983), the present findings show that formant transitions are indeed relevant for listeners whose native language distinguishes labio-dental versus dental fricatives. Listeners relied on the transitions even though no dental fricatives occurred in these stimuli, and independently of the speaker’s native language.
Vowels in clear and conversational speech: Talker differences in intelligibility for elderly hearing-impaired listeners
Authors: Ferguson Sarah Hargus
Published: September 2013

Several studies have shown that when a talker is instructed to speak as though talking to a hearing-impaired person, the resulting clear speech is significantly more intelligible than typical conversational speech. A recent study of 41 talkers [S. H. Ferguson and D. Kewley-Port, J. Acoust. Soc. Am. 111, 2482 (2002)] demonstrated that for normal-hearing listeners identifying vowels in noise, the amount of improvement talkers achieve by speaking clearly varies widely. Acoustic analyses of 12 of these talkers suggested that the amount of clear speech vowel intelligibility benefit was related to specific clear speech acoustic strategies adopted by the talkers. However, an earlier paper [S. H. Ferguson and D. Kewley-Port, J. Acoust. Soc. Am. 112, 256–271 (2002)] suggested that clear speech acoustic strategies that improve vowel intelligibility for normal-hearing listeners may not be beneficial for the group of listeners for whom clear speech is actually intended: listeners with hearing loss. The current project will explore this issue by assessing vowel intelligibility in clear and conversational speech for older hearing-impaired adults, using materials from the 12 talkers cited above. [Work supported by the University of Kansas Center for Research New Faculty General Research Fund and by NIHDCD-02229.]
Verbal transformation effect and the neighborhood activation model: Exploring the boundaries of the neighborhood
Authors: Lenz Peter W. , Warren Richard M. , Bashford James A.
Published: September 2013

A recorded word repeating over and over undergoes a succession of illusory changes to other words and syllables in the listener’s lexicon, as well as to nonwords. This verbal transformation effect (VTE) appears to involve successive satiations of a dominant representation and serial replacements by competing representations. Early during the presentation of a VTE stimulus, reported illusory forms are typically lexical and nonlexical neighbors of the veridical stimulus (i.e., forms differing from the stimulus by a single phoneme). Interestingly, presentation of a lexical stimulus initially evokes far more reports of nonlexical neighbors while a nonlexical stimulus evokes predominantly lexical neighbors. After 6 to 7 min, the perceived forms are no longer immediate neighbors of the veridical stimulus, and differ by two phonemes on average. The neighborhood activation model (NAM) considers that identification of spoken words involves the activation of competing, phonetically similar lexical and nonlexical representations. Activation of one of these competitors reaches a critical level and that competitor enters awareness. The VTE polls the population of activated representations, providing a means of defining the functional boundaries of neighborhoods as well as the dynamics of competitor interaction. [Work supported by NIH.]
Adult perceptions of phonotactic violations in Japanese
Authors: Fais Laurel , Kajikawa Sachiyo , Werker Janet , Amano Shigeaki
Published: September 2013

Adult Japanese speakers ‘‘hear’’ epenthetic vowels in productions of Japanese-like words that violate the canonical CVCVCV form by containing internal consonant clusters (CVCCV) [Dupoux et al., J. Exp. Psychol. 25, 1568–1578 (1999)]. Given this finding, this research examined how Japanese adults rated the goodness of Japanese-like words produced without a vowel in the final syllable (CVC), and words produced without vowels in the penultimate and final syllables (CVCC). Furthermore, in some of these contexts, voiceless vowels may appear in fluent, casual Japanese productions, especially in the Kanto dialect, and in some, such voiceless vowels may not appear. Results indicate that both Kanto and Kinki speakers rated CVC productions for contexts in which voiceless vowels are not allowed as the worst; they rated CVC and CVCC contexts in which voiceless vowel productions are allowed as better. In these latter contexts, the CVC words, which result from the loss of one, final, vowel, are judged to be better than the CVCC words, which result from the loss of two (final and penultimate) vowels. These results mirror the relative seriousness of the phonotactic violations and indicate listeners have tacit knowledge of these regularities in their language.
Asking questions with focus
Authors: Liu Fang , Xu Yi
Published: September 2013

This study investigates how different interrogative meanings interact with focus in determining the overall F0 profile of a question. We recorded eight native speakers of Mandarin producing statements, yes–no questions with and without a question particle, wh questions, incredulous questions, and confirmation questions. In each sentence, either the initial, medial, final, or no word was focused. The tonal components of the sentences are all high, all rising, all low, or all falling. F0 contours were extracted by measuring every complete vocal period in the initial, medial, and final disyllabic words in each sentence. Preliminary results show that in both statements and questions, the pitch range of the focused words is expanded and that of the postfocus words suppressed (compressed and lowered). However, postfocus pitch-range suppression seems less extensive in questions than in statements, and in some question types than in others. Finally, an extra F0 rise is often observed in the final syllable of a question unless the syllable is the question particle which has the neutral tone. This is indicative of a high or rising boundary tone associated with the interrogative meaning, which seems to be superimposed on the tone of the sentence-final syllable. [Work supported by NIDCD DC03902.]
Acoustic correlates of perceived rhythm in spoken English
Authors: McAuley J. Devin , Dilley Laura C.
Published: September 2013

Two experiments examined the relationship between speech timing and perceived rhythm for a corpus of approximately 900 spoken sentences. In experiment 1, trained listeners applied an annotation system for perceptual isochrony to the corpus. For each sentence, listeners assigned beats to syllables and judged whether the intervals between successive beats were equal or unequal, permitting the identification of perceptually isochronous speech fragments (or beat chains). For each such beat chain, the intervals between vowel onsets of successive beat syllables were determined. Overall, there was good agreement among labelers about what constituted a beat chain, with the average inter-beat-interval equal to approximately 550 ms. In experiment 2, naive listeners rated the rhythmicity of each sentence on a 6-point scale, ranging from 1 (very nonrhythmical) to 6 (very rhythmical). Sentences were judged as more rhythmic when the longest identified beat chain in experiment 1 for that sentence contained more beats and had an average IBI closer to 550 ms. IBI variability was not a significant predictor of perceived rhythmicity. The results of both experiments will be discussed in terms of preferred tempi in perceived rhythm and entrainment models of auditory event timing (McAuley and Jones, 2003).
Field experiments on the velocity dispersion and attenuation of acoustic waves through sandy sediments in shallow waters
Authors: Yamamoto Tokuo , Yamaoka Haruhiko , Sakakibara Junichi
Published: September 2013

The velocity dispersion and attenuation of acoustic waves though a sandy bottom in a shallow ocean were measured for a broad frequency band of 1–500 kHz using a buried horizontal hydrophone array and several broadband piezoelectric sources. The sands have a fairly uniform grain size of 0.22 mm and a porosity of 0.44. The experimental data were compared with the Biot theory, the BISQ theory, the squirt flow theory and the patchy-saturated theory. The data–theory comparisons indicate that the Biot theory best predicts the acoustic propagation though the sand bottom in shallow water in the medium to high frequency band of 1–500 kHz. The data–theory comparisons also confirm that the permeability, porosity, and added mass coefficient of shallow water sediments can be extracted from acoustic data. [Work supported by ONR Code 321 OA.]
Inversion of sediment parameters in Biot parameter space
Authors: Potty Gopu R. , Miller James H.
Published: September 2013

Long range sediment tomography technique [Potty et al., J. Acoust. Soc. Am. 108, 973–986 (2000)] using explosive sources has been developed and applied to data from the Primer and ASIAEX experiments. This inversion scheme estimates the compressional wave speed and attenuation matching the individual modal arrival times, i.e., inversion is carried out in the geoacoustic parameter space. This inversion scheme is now modified to invert for parameters in the sediment physical property space. Using the Biot–Stoll model as the interface between sediment physical and geoacoustic spaces, few of the most sensitive Biot parameters are inverted for. A sensitivity analysis will be carried out to identify the most sensitive Biot parameters and they will be considered as unknowns. Broad band acoustic data from wide band sources (WBS) collected on a vertical line array in frequency range 10–400 Hz will be used for the inversion. The goal of this study is to identify the sediment type (sand, silt, sandy-silt, clay, etc.) along with some physical attributes qualifying its nature (soft, hard, etc.) and the thickness of layers. This will enable us to describe the sediment characteristics over a large area with minimum number of parameters. [Work supported by ONR.]
Frequency dependence of modal attenuation coefficients from a simplified Biot sediment model
Authors: Saintval Wendy , Carey William M. , Pierce Allan D. , Lynch James F. , Siegmann William L.
Published: September 2013

Determination of the frequency behavior of modal attenuation coefficients is essential for estimation of propagation influences of poro-elastic sediments. A recent simplification of the Biot model [Pierce et al., J. Acoust. Soc. Am. 114, 2345 (2003)] provides an approach for this determination. For plane compressional waves in a homogeneous medium, the simplified theory reproduces the frequency-squared behavior of the full Biot model. However, data from a variety of shallow water locations suggests power-law exponents that are less than two. Inhomogeneities, particularly in the upper sediment layer, influence the frequency behavior. For a normally consolidated sediment (one never subjected to pressures higher than the current overburden pressure), depth profiles of porosity and sound speed can be estimated [Cederberg et al., J. Acoust. Soc. Am. 97, 2754–2766 (1995)]. We use these profiles to investigate the frequency behavior of the modal attenuations. Comparisons are provided with observations as well as previous numerical studies. [Work supported by ONR.]
Structure of acoustic reflection coefficient at the fluid-poroelastic interface and the medium propagating the slow wave
Authors: Ohkawa Keiichi
Published: September 2013

The closed-form expressions of the acoustic reflection coefficient at the fluid-poroelastic interface exist. Due to the complexity, it is, however, rather difficult to acquire good physical insight into dependencies of the coefficient on many measurable quantities defining the fluid/porous-medium interface. Introducing effective densities allows us to obtain fine physical insight into the structure of the reflection coefficient. In the absence of the shear wave, the fundamental structure of the reflection coefficient is of the form R=(1/Z0−1/Z1−1/Z2)/(1/Z0+1/Z1+1/Z2) where Z0, Z1, and Z2 are impedances of sound, fast, and slow waves, respectively. At the normal incidence this gives the exact solution. The phase velocities of fast and slow waves, c1 and c2, are approximated as c1≂√C/ρ1, c2≂√Kf/φρ2, where C is the Biot’s coupling constant, Kf is the fluid bulk modulus, φ is the porosity, and ρ1 and ρ2 are effective densities of fast and slow waves. In air-saturated medium, ρ2 approaches the dynamic added mass density. For the super fluid 4He, c2 becomes the same result derived by Dutta. This supports that the medium propagating the slow wave is without doubt the pore fluid in any porous media.
Resolution cell size effects on the statistics of seafloor backscatter
Authors: Johnson Shawn F. , Lyons Anthony P. , Abraham Doug , Pouliquen Eric
Published: September 2013

An understanding of high-frequency scattering is essential for the design and implementation of successful object detection algorithms. Due to their highly heterogeneous nature, seafloors in shallow water pose a particularly difficult problem for target detection with scattered envelope probability density function (PDF) often having heavier tails than the Rayleigh distribution. One aspect of high-frequency scatter that has not been resolved to date, and that should also shed light on the causes of non-Rayleigh distributions, is the relation between the size of the resolution cell of the sonar system and the envelope distributions. Seafloor scattering data from transmitted CW pulses (50 and 100 kHz) and FM signals (37–65 kHz) were collected by the NATO Undersea Research Centre off of Elba Island, Italy in May 2003. Water depths were less than 100 m and bottom structures of the test sites included Posidonia Oceanica sea grass, rippled sand, and rocks. Varying the length of the CW pulses and the bandwidth of the FM signals allowed the effective resolution cell size of the sonar to be varied. The impact of changing resolution cell size on the seafloor scattering statistics will be discussed as well as implications. [Research performed under ONR Grant No. N00014-03-1-0245.]
Backscattering of acoustic pulses from rough surfaces: Statistical properties of first arrivals
Authors: Fuks Iosif M. , Godin Oleg A.
Published: September 2013

In a number of applications, including echo sounding of the ocean bottom, nondestructive evaluation of materials, and satellite altimetry, measurements of travel time and/or shape of a backscattered pulse are employed to retrieve information about position and properties of scatterers. When the scatterer is an extensive rough surface with sufficiently large slopes, the backscattered wave consists of numerous pulses, of which the earliest arrivals are often of primary interest. In this paper, the geometrical acoustics approximation is applied to study signal intensities and the difference between the travel times of waves scattered by a random rough surface and those reflected from the mean, plane boundary. For a Gaussian statistical distribution of roughness, probability density functions (PDFs) of the travel-time differences are found for the first and second arrivals in terms of variances of the surface roughness elevation and slope. The joint PDFs of the travel times and intensities are derived. It allows one to obtain the travel-time PDF for signals exceeding a given intensity threshold. It is shown that the travel time and the intensity are strongly correlated; on average, the earlier a signal arrives, the smaller is its intensity.
Bat’s auditory system: Corticofugal feedback and plasticity
Authors: Suga Nobuo
Published: September 2013

The auditory system of the mustached bat consists of physiologically distinct subdivisions for processing different types of biosonar information. It was found that the corticofugal (descending) auditory system plays an important role in improving and adjusting auditory signal processing. Repetitive acoustic stimulation, cortical electrical stimulation or auditory fear conditioning evokes plastic changes of the central auditory system. The changes are based upon egocentric selection evoked by focused positive feedback associated with lateral inhibition. Focal electric stimulation of the auditory cortex evokes short-term changes in the auditory cortex and subcortical auditory nuclei. An increase in a cortical acetylcholine level during the electric stimulation changes the cortical changes from short-term to long-term. There are two types of plastic changes (reorganizations): centripetal best frequency shifts for expanded reorganization of a neural frequency map and centrifugal best frequency shifts for compressed reorganization of the map. Which changes occur depends on the balance between inhibition and facilitation. Expanded reorganization has been found in different sensory systems and different species of mammals, whereas compressed reorganization has been thus far found only in the auditory subsystems highly specialized for echolocation. The two types of reorganizations occur in both the frequency and time domains. [Work supported by NIDCO DC00175.]
Geoacoustic inversion of M-sequence data from experiments in the South Florida Straits
Authors: Chapman Ross , Jiang Yongmin
Published: September 2013

Matched field inversion is applied to low frequency data from experiments in the South Florida Straits to estimate a sediment velocity profile. The acoustic data consist of signal envelopes derived from M-sequences that were transmitted to a vertical hydrophone array over a range of 10 km. The sound speed profile supported a strong waveguide in the deeper parts of the water column. Signal propagation for a source in the waveguide was dominated by waveguide refracted paths, and surface-reflected bottom-reflected paths that interacted eight to ten times with the bottom. The very long range, shallow water geometry presents a significant challenge for an inversion based on matched field processing. However, examination of the spatial coherence of the received signal indicated useful spatial phase information for spectral components with high signal-to-noise ratios. A Gibbs sampling approach was used to test two different geoacoustic models for the site: (a) a constant gradient sediment and (b) a constant velocity sediment over a half space. The inversion showed a preference for slower speeds of around 1550 m/s at the sea floor, increasing to higher values up to 1700 m/s within about 100 m deeper. These values are consistent with ground truth at the site.
Recent advances in elastography
Authors: Ophir Jonathan
Published: September 2013

No known modality is capable of imaging the elastic properties of tissue directly. It is therefore necessary to apply an external or internal mechanical stimulus to the tissue system, and to observe the tissue response in terms of local internal deformations. The use of ultrasound for this purpose has several important advantages that include real-time imaging, high resolution in motion estimation (1 micron), simplicity, noninvasiveness, and low cost. Elastography is performed by obtaining a set of ultrasonic echo signals from a target, subjecting the target to a small axial deformation and obtaining a second set of echo signals. Time-delay estimations along the direction of the applied load are computed. Using the gradient operator, the time-shift estimates are then converted to strain information, which is displayed in the form of a two-dimensional image named elastograms. We demonstrate that the strain distributions in tissues are well correlated with the distribution of tissue elastic moduli under certain conditions. It is also possible to obtain lateral strain elastograms and Poissons ratio elastograms, which convey additional tissue mechanical information. In this presentation we will give an overview of elastography and describe some of the newer capabilities and clinical applications. [Work supported by NIH Grant P01CA64597.]
Doppler ultrasonic detection of targets buried in grass-covered soil
Authors: Sabatier James M. , Petculescu Andi G.
Published: September 2013

An ultrasonic Doppler vibrometer (UDV) is used outdoors to detect vibrating targets buried in grass-covered soil. The sensor head uses two solid-dielectric transducers, in a pitch–catch configuration. A first set of measurements is done using calibrated vibrational sources (shakers), whose vibrational characteristics are known and/or easily predictable. Then, the system is put to the test of detecting a landmine buried in a realistic environment. The target (landmine) is excited either by a mechanical shaker or by a loudspeaker, through acoustic-to-seismic coupling. The wind speed was monitored continuously. Since it is known that wind degrades the UDV signal, efforts were made to perform the experiments in a still environment. The UDV results are compared with those obtained with a laser Doppler vibrometer.
Vowel acquisition by prelingually deaf children with cochlear implants
Authors: Bouchard Marie-Eve , Le Normand Marie-Thérèse , Ménard Lucie , Goud Marilyne , Cohen Henri
Published: September 2013

Phonetic transcriptions (study 1) and acoustic analysis (study 2) were used to clarify the nature and rhythm of vowel acquisition following the cochlear implantation of prelingually deaf children. In the first study, seven children were divided according to their degree of hearing loss (DHL): DHL I: 90–100 dB of hearing loss, 1 children; DHL II: 100–110 dB, 3 children; and DHL III: over 110 dB, 3 children. Spontaneous speech productions were recorded and videotaped 6 and 12 months postsurgery and vowel inventories were obtained by listing all vowels that occurred at least twice in the child’s repertoire at the time of recording. Results showed that degree of hearing loss and age at implantation have a significant impact on vowel acquisition. Indeed, DHL I and II children demonstrated more diversified as well as more typical pattern of acquisition. In the second study, the values of the first and second formants were extracted. The results suggest evolving use of the acoustic space, reflecting the use of auditory feedback to produce the three phonological features exploited to contrast French vowels (height, place of articulation, and rounding). The possible influence of visual feedback before cochlear implant is discussed.
An across-frequency deficit in hearing-impaired listeners is supported by acoustic correlation
Authors: Healy Eric W. , Kannabiran Anand , Bacon Sid P.
Published: September 2013

It has been recently suggested that listeners having a sensorineural hearing impairment (HI) may possess a deficit in their ability to integrate speech information across different frequencies. When presented with a task that required across-frequency integration of speech patterns and controlled for other known deficits, HI listeners performed more poorly than their normal-hearing (NH) counterparts [C. W. Turner et al., J. Speech Lang. Hear. Res. 42, 773–784 (1999); E. W. Healy and S. P. Bacon, J. Speech Lang. Hear. Res. 45, 1262–1275 (2002)]. The latter study also showed that HI performance fell more steeply when increasing amounts of temporal asynchrony were introduced to the pair of widely separated patterns. In the current study, the correlations between the fluctuating envelopes of the acoustic stimuli were calculated, both when the patterns were aligned and also at various between-band asynchronies. It was found that the rate at which acoustic correlation fell as a function of asynchrony closely matched the rate at which intelligibility fell for the NH listeners. However, the intelligibility scores produced by the HI listeners fell more steeply than the acoustic analysis would suggest. Thus, these data provide additional support for the existence of an across-frequency deficit in HI listeners. [Work supported by NIH.]
Motor learning of volitional nonspeech oral movements: Intraoral pressure and articulatory kinematics
Authors: Shaiman Susan , McNeil Malcolm R. , Szuminsky Neil J.
Published: September 2013

This study provides initial validation of a complex nonspeech task that will be used in future research for examining and comparing the neurophysiologic mechanisms of speech and volitional nonspeech oral movements. Motor learning of a complex sequence of lip, jaw, and tongue movements was explored as speakers produced one of three intraoral air-pressure targets during each bilabial closing gesture in the sequence. Motor learning was demonstrated by retention of pressure targets subsequent to acquisition. Transfer to other nonspeech tasks was also explored, as were changes in articulatory kinematics with learning. The current nonspeech task was constructed to parallel speech production, by controlling several commonly observed physiologic characteristics of speech (i.e., complex sequence of potentially overlapping articulatory segments; goal of intraoral pressure during bilabial closure). This construction of the nonspeech task, along with its demonstrated motor learning, greatly extends the ability to make valid comparisons between speech and nonspeech productions. [Work supported by CMRF-University of Pittsburgh.]