bluuebunny/crossref_metadata_2025 huggingface dataset:
Low intensity ultrasound—Diverse biomedical applications
Authors: Szabo Thomas L.
Published: May 2014

Low intensity ultrasound has been useful in a surprisingly wide range of biomedical applications. Ultrasound can affect both the central nervous system (CNS; brain and spinal cord) and the peripheral nervous system (PNS). Ultrasound methods offer the possibility of stimulating receptor structures and unmyelinated nerve fibers not just on the surface but also those otherwise inaccessible, deeper in the body or brain. Preliminary work indicates that information can be transferred via unmyelinated nerve fibers when normal avenues of sensing are damaged or inoperative. Tones and acoustic speech have been directly transferred through nerves without direct hearing. Radiation force effects can provide a variety of sensational effects and can be employed in ultrasound dynamic tactile arrays. Early prototype devices for diagnosis of diseases of hearing and audio prosthetics were developed in the early 1980s in the Soviet Union by Gavrilov and Tsirulnikov. Neuromodulation of the brain transcranially has demonstrated activation of motor responses. Low intensity ultrasound has also been applied to bone and wound healing. In a related application, it has been applied to the growth of artificial neovessels.
Localization of ultrasound induced in-vivo neurostimulation in the mouse model
Authors: King Randy L.
Published: May 2014

Developments in the use of ultrasound to stimulate and modulate neural activity have raised the possibility of using ultrasound as a new investigative and therapeutic tool in brain research. The phenomenon of ultrasound induced neurostimulation has a long history dating back many decades, but until now there has been little evidence demonstrating a clearly localized effect in the brain, a necessary requirement for the technique to become genuinely useful. Here, we report clearly distinguishable effects in sonicating rostral and caudal regions of the mouse motor cortex. Motor responses measured by normalized EMG in the neck and tail regions changed significantly when sonicating the two different areas of motor cortex. Response latencies varied significantly according to sonication location suggesting that different neural circuits are activated depending on the precise focus of the ultrasound beam. Taken together our findings present good evidence for being able to target selective parts of the motor cortex with ultrasound neurostimulation in the mouse, an advance that should help to set the stage for developing new applications in larger animal models including humans.
Enhanced fracture repair and mitigation of fracture-healing risk factors using low-intensity pulsed ultrasound
Authors: Brodie Christopher R. , Harrison Andrew
Published: May 2014

Low-intensity pulsed ultrasound (LIPUS) is used clinically to enhance fracture healing. Level-I clinical studies demonstrate that a specific signal (1.5 MHz ultrasound pulsed at 1 kHz, 20% duty cycle, 30 mW/cm2 SATA) can accelerate the healing of acute fractures. This result remains a unique benefit of LIPUS, and to date, no other drug or device has been approved by the FDA for accelerated fracture repair. The same signal has been shown in many studies to heal a high proportion of non-union fractures. LIPUS appears to be effective for all three types of non-unions—atrophic, oligotrophic and hypertrophic—even in the absence of revision surgery. The findings are broadly applicable to orthopedics, with similar results regardless of fracture type, fracture location and fracture-management technique. Given the varied causes of non-union, the ability of LIPUS to overcome a high proportion of obstacles to healing indicates that the signal is likely to have pleiotropic effects on multiple cell types within the healing process. Smoking, age, and diabetes are known risk factors for delayed union and nonunion. Clinical data, including randomized controlled trials and a registry of 1546 nonunion patients, suggest that LIPUS mitigates these risks and restores the course of normal bone healing.
Planar microphone based on piezoelectric electrospun poly(γ-benzyl-?,L-glutamate) nanofibers
Authors: West James E. , Ren Kailiang , Yu Michael
Published: May 2014

Velocity and pressure microphones comprised of piezoelectric poly(γ-benzyl, L-glutamate) (PBLG) nanofibers were produced by adhering a single layer of PBLG film to a Mylar diaphragm. The device exhibited a sensitivity of 65 dB/Pa in air, and both pressure and velocity response showed a broad frequency response, which was primarily controlled by the stiffness of the supporting diaphragm. The pressure microphone response was 3 dB between 200 Hz and 4 kHz when measured in a semi-anechoic chamber. Thermal stability, easy fabrication, and simple design make this single element transducer ideal for various applications including those for underwater and high temperature use.
Experimental results of motional current velocity control intended for broadband piezoelectric projectors
Authors: Randall Robert C. , Brown David A. , Bachand Corey
Published: May 2014

Velocity control with active feedback can be useful for flattening a projector's frequency response, reducing distortion, and mitigating array interaction effects. This has been demonstrated and commercialized for HiFi audio, but has seen little attention for underwater SONAR and communications applications. The benefits and tradeoffs of using velocity control to drive an underwater piezoelectric transducer or array of transducers is presented, comparing array beam patterns both with and without velocity control. The theoretical effectiveness of motional current velocity control is discussed for various piezoelectric loads with coupling coefficients ranging from 0.3 to 0.9. The utility of using a digital feedback amplifier and in situ calibration methods with this approach is discussed. A prototype Class D amplifier using motional current feedback driving an equivalent circuit load for a BTech Acoustics single crystal segmented cylinder is presented. Experimental results of frequency response, bandwidth, and feedback stability are also considered.
Model for the design of a pressure actuated self-sustained oscillator as an acoustic projector
Authors: Thompson Stephen C.
Published: May 2014

Wind musical instruments are examples of a pressure operated self-sustained oscillator that acts as an acoustic projector. Recent studies have shown that this device can also be implemented underwater. However the design parameters for such a device are necessarily different due to the large difference in medium density and acoustic impedance. This paper describes a model that is sufficient to predict the performance of the projector and to understand the effects of design changes on the performance.
What to expect when you're expecting media calls
Authors: Bardi Jason S.
Published: May 2014

A decade's worth of college, grad school, and post-doc work, countless sleepless nights toiling in your own laboratory, a long route to discovery, your ultimate breakthrough and it has come to this: the phone is ringing. A reporter is on the line. What does she/he want? What should you say? I'm here to tell you, “Don't panic!” You have been preparing for this interview your entire professional career. You are one of the world's leading experts in your area, and that's one of the reasons why the reporter is calling. You also have a story to tell, the reporter wants to hear it, and the interview should be more conversation than inquisition. This talk will help you realize that, helping you make the most of your time in the spotlight by putting the PR and press process into perspective, offering some tips of the trade, describing your rights and responsibilities as a source, and sharing best practices for handling media inquiries.
Simulated and laboratory models of aircraft sound transmission in residences
Authors: Thomas Ashwin , Ryherd Erica , Bowling Thomas , Irizarry Javier
Published: May 2014

Current aircraft noise guidelines are based primarily on outdoor sound levels. As people spend the majority of their time indoors, however, human perception is highly related to indoor sound levels. Investigations are being made to provide further insight into how typical residential constructions affect indoor sound levels. A pilot, single-room “test house” has been built using typical mixed-humid climate region construction techniques and the outdoor-to-indoor transmission of sound was directly measured—with specific focus on continuous commercial aircraft signatures. The measurements included a variety of construction iterations (e.g., window type, wall construction) and a variety of instrumentation iterations (e.g., source and sensor locations). The results of this study are being used to validate and improve modelling software that simulates a wide range of construction types and configurations for other US climate regions. Overall, the project intends to improve the ability to predict acoustic performance for typical US construction types as well as for possible design alterations for sound insulation.
The spectral effect of masking of intruding noise by environmental background-noise
Authors: Rosenhouse Giora -.
Published: May 2014

Annoyance by noise depends strongly on its informative, spectral contents and individual effect on people. Yet, standards dictate certain formal limitations, ignoring such details. In practice, it happens in many cases of recreational areas, industrial premises and other kinds of activities, that even when results of measurements satisfy the standards limits, complaints do not stop, yielding threats of legal acts. Case studies of the effect, based on actual acoustic measurements are analyzed here, showing factors that cause extreme sensitivity to certain noise patterns, even if the total amount of noise remains unchanged. The effect of color difference is enhanced if the added noise has a certain periodicity, located where the background noise has lower masking effect. Since in many cases the background noise has less effect or resembles white or pink noise, certain noise sources can be clearly heard, if they include higher local amplitudes in the frequency spectra domain of the background noise. Acoustic solutions include means for undesired noise reduction to levels much below the background noise¸ by as much as by 9 dB, to allow background noise masking of disturbing sources. Such reduction alters its status from being strongly heard to the privacy zone.
A sonic levitation system for the study of Faraday waves on bubbles
Authors: Escobedo Jorge , Holt R. Glynn
Published: May 2014

Acoustic levitation is a method by which the gravitational force on a sample can be balanced by the time-averaged acoustic radiation force in a standing wave. Levitation has in the past been utilized as an ideal system to study phenomena at fluid interfaces, since boundary influences are small. Previous work on Faraday waves on bubbles has been carried out at ultrasonic frequencies, where the disadvantages are the need for fast diagnostics at small spatial scales. In this talk we describe efforts to develop a sonic frequency levitation system, employing hardware elements from previous NASA investigations in drop physics. Proof-of-concept styrofoam levitation in air will be demonstrated, and injection and deployment schemes for large (1-in. diameter) bubbles will be discussed. [Work supported by the Robert W. Young Undergraduate Award of the ASA.]
Acoustic streaming from a resonant elastic surface vibration
Authors: Sunny Megha , Aho Katherine , Miniter John C. , Thompson Charles
Published: May 2014

Acoustic streaming induced by the vibration of an elastic membrane is examined. Adjustment of the impedance along the membrane allows one to control the spatial characteristics of the time-averaged fluid motion. It is shown that under resonant conditions spatial localization of the time-averaged Reynolds stress occurs. As a result, the fluid motion outside of the viscous boundary layer is driven into motion by a wall-jet at locations of maximal vibration. The velocity field is evaluated in terms of elemental Stokeslets where streaming motion is expressed in terms of a surface force distribution. At high oscillatory Reynolds numbers, regularization procedures to deal with singularities that occur in the formulation are addressed. Streaming motion is expressed in terms of the surface force distribution. Results for oscillatory and time-averaged fluid motion are presented.
Interaction acoustic radiation force and torque on a cluster of spheres suspended in an inviscid fluid
Authors: Andrade Jose Henrique A. , Azarpeyvand Mahdi , Silva Glauber T.
Published: May 2014

The acoustic radiation force and torque exerted by a time-harmonic beam of arbitrary wavefront on a cluster of suspended spheres in an inviscid fluid is theoretically analyzed. In the proposed method, the effective incident wave is modelled as a coherent sum of an external beam and the contributions from the re-scattering events by other spheres present in the medium. Using the translational addition theorem for spherical functions the effective beam-shape and scattering coefficients are numerically computed [J. Acoust. Soc. Am. 98, 495 (1995)] for different external incident fields. The radiation force and torque exerted on the probe sphere can then be calculated using the farfield partial-wave expansion method [J. Acoust. Soc. Am. 130, 3541 (2011); Europhys. Phys. Lett. 97, 54003 (2012)]. The method was employed to obtain the radiation force due to an external plane and spherical waves on a cluster of three solid elastic or fluid spheres suspended in water. The results show that the radiation force deviates considerably from that exerted solely by the external incident wave and that the radiation torque arises on the spheres when a asymmetric spatial distribution of the effective incident acoustic field takes place in the medium. In addition, the proposed method may help on the study of acoustic tweezers devices and acoustofluidic systems, which involve several suspended particles.
The auditory image model and me
Authors: Akeroyd Michael
Published: May 2014

As a Ph.D. student in Roy Patterson's group at the MRC Applied Psychology Unit in Cambridge, UK, in the early 1990s, I was introduced to computer models of hearing. Much of my Ph.D. was devoted to exploring Roy’s Auditory Image Model, a time-domain model for representing regularities in hearing sensations that we hear. It was built on a gammatone filterbank, a hair-cell model, and strobed temporal integration, and was programmed with a speed that was remarkable for the age. The pictures and movies that it made—and the insights into hearing that it gave—were exciting and inspiring; my resulting enthusiasm for what good models can do has remained with me throughout my scientific career. This talk will describe some of Roy’s contributions to modelling and his influence on the field, as ever-improving computational models are crucial to making progress in understanding how hearing works. [Work supported by the Medical Research Council and the Chief Scientist Office, Scotland.]
Acoustic surface structure, across-formant integration, and speech intelligibility
Authors: Roberts Brian , Summers Robert J. , Bailey Peter J.
Published: May 2014

An important aspect of speech perception is the ability to group or select formants using cues in the acoustic surface structure—for example, fundamental frequency (F0) differences between formants promote their segregation. This study explored the role of more radical surface-structure differences. Three-formant (F1 + F2 + F3) synthetic speech analogues were derived from natural sentences. In one experiment, F1 + F3 were generated using second-order resonators (R1 + R3) and a monotonous glottal source (F0 = 140 Hz); in the other, F1 + F3 were tonal analogues (T1 + T3). F2 could take either form (R2 or T2). In some conditions, the target formants were presented alone, either monaurally or dichotically (left ear = F1 + F3; right ear = F2). In others, they were accompanied by a competitor for F2 (F1 + F2C + F3; F2), which listeners must reject to optimize recognition. Competitors (R2C or T2C) were created using the time-reversed frequency and amplitude contours of F2. In the absence of F2C, the effect of surface-structure mismatch between F1 + F3 and F2 was typically modest. When F2C was present, intelligibility was lowest where F2 was tonal and F2C was a buzz-excited resonance, irrespective of which type matched F1 + F3. This finding suggests that surface structure type, rather than similarity, governs the phonetic contribution of a formant. [Work supported by ESRC.]
Loudness summation across ears for hearing-impaired listeners
Authors: Moore Brian C. , Glasberg Brian R.
Published: May 2014

The summation of loudness across ears is often studied indirectly by measuring the level difference required for equal loudness (LDEL) of monaurally and diotically presented sounds. Typically, the LDEL is 5–6 dB, consistent with the idea that a diotic sound is about 1.5 times as loud as the same sound presented monaurally at the same level, as predicted by the loudness model of Moore and Glasberg [J. Acoust. Soc. Am. 121, 1604–1612 (2007)]. One might expect that the LDEL would be smaller than 5–6 dB for hearing-impaired listeners, because loudness recruitment leads to a greater change of loudness for a given change in level. However, previous data from several laboratories showed similar LDEL values for normal- and hearing-impaired listeners. Here, the LDEL was measured for normal-hearing and hearing-impaired listeners using narrowband and broadband noises centered on a frequency where the latter had near-normal audiometric thresholds (500 Hz) and at a frequency where audiometric thresholds were elevated (3000 or 4000 Hz). The LDEL was similar for the two center frequencies for the normal-hearing listeners, but was smaller at the higher center frequency for the hearing-impaired listeners. The results were predicted reasonably well by the loudness model of Moore and Glasberg.
Acoustic radiation from fluid-loaded cylindrical shells—A review
Authors: Cuschieri Joe M.
Published: May 2014

The acoustic radiation from fluid-loaded cylindrical shells received significant attention in the past. Reviewing the literature, the number of papers published in this area is significant. The body of work covers thin walled small diameter shells applicable to the sound transmission in pipes, to large diameter shells with internal stiffeners and bulkheads. Also, considered is the influence of full and partial compliant coatings. A significant portion of work was based on analytical techniques useful to understand the phenomena and some of the critical parameters. More recent, with the availability of more capable computers and modeling codes, the focus has been on application of these computational tools to solving field problems. This paper reviews some of the past computational work and how some applications evolved from this work. However when presented with actual submerged cylindrical structures with complex internals, while modeling is useful, when dealing with the acoustic radiation from shell like structures at medium to high frequencies modeling tools still cannot handle the full extent of the problem and the prevalent approach still relies on implementation of good engineering practice.
Response of a cylindrical shell with finite length ring stiffeners
Authors: Hull Andrew J.
Published: May 2014

This talk derives an analytical model of a thin shell of infinite extent that contains periodically spaced ring stiffeners that have finite length. The governing model of the system is the Donnell shell formulation affixed to ring stiffeners that are modeled as translational springs in the radial direction. The shell is excited by an external load that is harmonic in time and space. An orthogonalization procedure is developed and the resulting system equations are an infinite set of algebraic equations containing a diagonal matrix that represents the shell dynamics and a sparse matrix that contains permutations of the Fourier coefficients of the Heaviside step function that represent the stiffener forces. This matrix equation is truncated and inverted and yields a solution of the shell displacements. An example problem is formulated and the effects of the stiffeners on the system dispersion curves are illustrated.
Acoustic directional response of distributed fiber optic sensor cables
Authors: Boisvert Jeffrey E.
Published: May 2014

Distributed fiber sensor systems based on Rayleigh backscatter interferometry have demonstrated the capability for highly sensitive strain measurements over tens of kilometers using low cost fiber-optic cable for terrestrial and maritime applications. These cables are typically multilayered in construction and contain a fiber optic (glass) core. A generalized multi-layered infinite-length cable is modeled using the exact theory of three-dimensional elasticity in cylindrical coordinates. The cable is excited by an acoustic plane wave with an arbitrary angle of incidence. At each angle of incidence the radial and axial strains within the cable are integrated over a desired sensor zone length to determine the optical phase sensitivity using an equation that relates the strain distribution in an optical fiber to changes in the phase of an optical signal. Results for the cable in a free-field water environment are presented for two different cable geometries. The analytical model was used to identify the root cause of a marked increase in cable sensitivity that exists at certain angles of incidence for plane wave excitation. Specifically, the enhancement occurs when the trace wavelength of the incident wave matches the propagation wavelength of a natural frequency of the cable. [Work supported by NAVSEA Division Newport ILIR Program.]
Contrastive apical post-alveolar and laminal alveolar click types in Ekoka !Xung
Authors: Miller Amanda L. , Holliday Jeffrey J.
Published: May 2014

Ekoka !Xung has four contrastive click types—dental, alveolar, lateral, and “retroflex.” We provide acoustic and ultrasound results of five speakers’ productions of the typical alveolar click and the contrastive “retroflex” click. Ultrasound results show that the “alveolar” click is apical post-alveolar and the “retroflex” click is laminal alveolar. The burst duration of the post-alveolar click averages 12 ms which is “abrupt,” while the burst duration of the alveolar click averages 30 ms, which is “noisy.” Mixed effects logistic regression models tested the effects of rise time and burst duration. Burst duration differed significantly among the two clicks (p < 0.001), while the effect of rise time was not significant. The ratio of energy in the click noisebursts below 20 ERB to the energy above 20 ERB is between 1.0 and 1.5 for the post-alveolar click, but between 0.5 and 1.0 for the alveolar click. The ratio was a significant predictor of click type (p = 0.014). The highest concentration of energy for the post-alveolar click is between 12 and 18 ERB, while the highest concentration of energy in the alveolar click is between 25 and 30 ERB. We attribute the frequency difference to a larger lingual cavity volume in the post-alveolar click, and a smaller volume in the alveolar click.
Native language interference on the overnight consolidation of a learned nonnative contrast
Authors: Earle Sayako , Myers Emily B.
Published: May 2014

In a prior investigation, discrimination of a trained nonnative (dental/retroflex, Hindi) contrast was mediated by different effects of overnight consolidation depending on the time of day of training. For individuals trained in the evening, sleep appeared to promote continued improvement in discrimination for ~24 h without further training. For participants who were trained in the morning, performance returned to baseline following the overnight session interval. A possible explanation for the lack of improvement in the morning training group is that incidental exposure to the alveolar /d/, the category in which dental/retroflex are considered allophones in English, throughout the daytime interval interfered with overnight consolidation of the nonnative variants. We tested this interpretation directly, by training all participants (n = 44) in the evening and assigning them to one of two conditions of interference: passive exposure to a stream of either 1500 /bV/ or /dV/ tokens immediately after training. We observed continuous improvement in discrimination for ~24 h in those who were exposed to /bV/ tokens, while those who were exposed to the /dV/ tokens did not improve. Our results support the interpretation that incidental exposure to English prior to overnight memory consolidation interferes with sleep-mediated improvement in discrimination of an L2 contrast.
Can adjustment to accented speech affect native language perception?
Authors: Lewandowski Eva M. , Liburd Teljer , Nygaard Lynne C.
Published: May 2014

The human auditory system can quickly accommodate foreign-accented speech. However, the cognitive mechanisms underlying perceptual adjustment to non-native speech are not fully understood. The current study examined the perceptual consequences of adaptation toward foreign-accented speech on native language perception. Native English speakers performed an auditory shadowing task on word-length utterances in English. There were four blocks of trials. The words in the critical block (Block 3) were spoken by either a native American English speaker or a native Spanish speaker. The speaker in flanking blocks (Blocks 1–2, 4) was the same speaker, a different speaker with the same accent, or a different speaker with a different accent. Shadowing response times in the critical block were used to assess rapid perceptual adjustment and readjustment. Results showed that the nature of the preceding context influenced response times. Response times for items in the first quartile of the critical block were reliably slower when accent and talker changed than when accent and talker remained constant. These findings suggest that listeners develop perceptual expectations about ongoing speech, which when violated incur a short-term processing cost even for spoken words in the listeners’ native language.
The production of non-modal phonation types in English vowels by Brazilian speakers
Authors: Engelbert Ana Paula
Published: May 2014

Esling (2000) claims that each language has its own pattern of physiological behavior in which articulators are trained to operate in different ways based on the language’s phonetic structure. To test this claim, this study compares phonation types in speech production when Brazilians speak Portuguese and English. More specifically, we investigate coarticulation effects of consonants on vowels in English with regards of non-modal phonation. According to Garellek (2012), non-contrastive non-modal phonation happens in English vowels due to adjacent glottalized and aspirated consonants. However, this coarticulation effect does not happen in Brazilian Portuguese because voiceless stops have short lag VOT and neither voiced nor voiceless stops are allowed as codas. Thus, our hypothesis is that bilingual Brazilians do not produce non-modal phonation due to coarticulation when producing English vowels. To test this hypothesis, native speakers of English and Brazilians who are proficient speakers of English were recorded performing reading tasks in a soundproofed room. The target words containing the vowels to be measured were placed in a carrier-sentence. The acoustic analysis was based on H1*-H2*, H1*-A2*, and HNR measures. [Research funding by CAPES (Brazil) and Fulbright.]
Acquisition of the complex three-way Korean plosive contrast by native English speakers
Authors: Perrachione Tyler , Finn Amy S. , Minas Jennifer , Tan Caitlin , Chan Brian , Gabrieli John D.
Published: May 2014

Learning to perceive foreign language speech sounds is a core challenge in adult second language acquisition. Previous research has considered how listeners learn novel foreign language categories for a known phonetic continuum [e.g., voice onset time (VOT)], or how listeners learn to use a previously unattended phonetic feature (e.g., F3). We investigated perceptual learning of the Korean three-way plosive contrast (lenis, aspirated, and fortis) by native English speakers. Unlike VOT continua in other languages, this contrast is distinguished by complex trading relations between VOT and pitch, with place of articulation differences in VOT adding further complexity. In this study, participants (N = 38) learned a vocabulary of 18 Korean pseudowords comprised of six minimal triplets (e.g., pan, ban, and ppan) by undergoing four days of high-variability (multi-talker) training on a lexical identification task. Mixture model analysis suggested two learner groups: (1) two-thirds of the participants were partially successful at learning words beginning with the fortis stops, but did not differentiate the lenis and aspirated stops; and (2) one-third of the participants successfully learned words beginning with the fortis stops, and exhibited progress distinguishing the lenis and aspirated stops. (Fortis stops most closely resembled listeners' existing English voiced stop categories.) Both groups acquired these contrasts best for bilabial stops and least accurately for alveolar stops.
Prosodic realization of focus in American English by Beijing Mandarin learners
Authors: Chen Ying
Published: May 2014

In addition to an increase of duration, F0 and intensity in phonetically realizing focus, post-focus compression (PFC) of F0 and intensity has been found in many languages, including American English and Beijing Mandarin. Recent studies found that PFC did not easily transfer from language to language (Wu and Chung, 2011); however, language experience impacted the realization of PFC (Chen et al., 2012). The effect of length of residence (LOR) in an L2-speaking environment on L2 pronunciation accuracy remains controversial (Piske, 2007). The current study examined English focus production of Beijing Mandarin learners, who were college freshmen, residing in the United States for 3 to 6 months, and college seniors for 3.5 to 4 years. Compared to the control group, both learner groups produced comparable patterns of duration change; the freshman group did not present significant PFC of F0 and intensity in either initial-focus or medial-focus condition; the senior group presented a native-like PFC in the initial-focus condition and an intermediate pattern of PFC among the three groups in the medial-focus condition. The preliminary results indicate that Beijing Mandarin learners with long LOR in the US produced more native-like prosodic focus in English than those with short LOR in the United States.
Steady as /∫i/ goes: The spectral kinematics of sibilant fricatives in English and Japanese
Authors: Reidy Patrick F. , Beckman Mary E.
Published: May 2014

Sibilant fricatives are often treated as having steady-state articulatory targets, which fix their spectra throughout their duration; however, Iskarous et al. (2011) reported that the centroid frequency of English /s/ varies considerably across the fricative's time course. This study replicates their spectral analysis using a psychoacoustic measure (peak ERB) and then extends it to English /∫/ and Japanese /s, ɕ/. The time-varying spectral pattern of each fricative was approximated with a nine-point peak ERB trajectory, computed from 20-ms windows spaced evenly throughout each token. There were three notable results. First, adults did not produce the same spectral kinematic pattern for all sibilants in a given language: the spectral peak of English /s/ followed a concave trajectory, while /∫/ remained relatively flat. Second, phonetically similar fricatives from different languages did not necessarily show similar dynamical spectral patterns: the peak trajectory of /s/ was curved in both languages, but reached its maximum much earlier in Japanese. Finally, three- to five-year-old children exhibited a developmental path toward language- and consonant-specific spectral patterns: as age increased, English-acquiring children produced /∫/ with decreasing curvature to its spectral peak trajectory, approaching that produced by the adults.
Nasals resonances in diphthongization: A preliminary study by nasal and oral acoustic output recording separately
Authors: Demasi Rita , Demolin Didier
Published: May 2014

Our goal is to find new acoustical evidences that characterize the nasality correlation by recording the month and nostril signal separately. This allows visualize the nasal and vocalic resonances individually. Few studies cover the nasal diphthongization and this phenomenon combines a partial nasalized vowel and a nasal glide. In Brazilian Portuguese (BP) the diphthong /aw/ and /ã / are distinctive. All data were recorded by Handle Separator from Glottal Enterprises. This records two acoustics output in different channels using two microphones. The plate is supported between the mouth and the nose. Six speakers from Paulistano dialect were recorded. The corpus covered back diphthongs in offset: [paw]; [saw]; [maw]; [taw]; [kaw]; [pã ]; [sã ]; [mã ]; [kã ] and [tã ]. In this task, each subject had to read the carry-sentence three times: [dʒigʊ_todʊ dʒigɐ]. Because the acoustic outputs are mixed, this method simplifies the separation between the both signal. The partial results show that the waveform and the spectrogram in this signals have a different configuration. In /ã /, the nasal waveform starts and finishes with a very-low energy. The higher energy is concentrated between the boundary of the both vocalic segments. In the spectrogram, the formants configuration are plates and they used to lose energy gradually (average: Fn1 374Hz, Fn2 2333 Hz, and Fn3 3049 Hz). This is different in oral format configuration where F2 has a descent movement and F3 has a ascend movement.
Prevention of learning of a non-native phonetic contrast by prior exposure to the contrasting stimuli while performing an irrelevant visual task
Authors: Wright Beverly A. , Conderman Jessica S. , Waggenspack Matthew K. , Marrone Nicole
Published: May 2014

Exposure to an acoustic stimulus can facilitate learning when encountered near in time to practice on a perceptual task. Here, we explored the possibility that this learning enhancement arises in part because the stimulus exposures encountered in the absence of practice amplify the internal representation of the stimulus and this amplification then remains during the subsequent practice period. If this is the case, learning should be disrupted if the stimulus representation is instead suppressed during stimulus exposure without practice, because that suppression should also spread to the practice period. To test this idea, we trained listeners on a non-native phonetic-contrast categorization task using regimens in which a period of practice followed a period of stimulus exposure without practice in each daily session. We manipulated the extent to which listeners presumably suppressed the auditory stimuli that were presented without accompanying practice by varying the attentional demands of a visual task performed during their presentation. Learning decreased markedly as the attentional demand during these periods increased. Thus, it appears that the magnitude of the internal stimulus representation affects learning and that changes in this magnitude can spread beyond the time in which they are induced to promote or interfere with learning. [Work supported by NIH.]
A virtual environment for modeling the acquisition of vowel normalization
Authors: Plummer Andrew R.
Published: May 2014

Vowel normalization is a computation that is meant to account for the differences in the absolute direct (physical or psychophysical) representations of qualitatively equivalent vowel productions that arise due to differences in speaker properties such as body size types, age, gender, and other socially interpreted categories that are based on natural variation in vocal tract size and shape. We present a virtual environment for vocal learning which provides the means to model the acquisition of vowel normalization, along with other aspects of vocal learning. The environment consists of models of caretaker agents representing five different language communities—American English, Cantonese, Greek, Japanese, and Korean—derived from vowel category perception experiments (Munson et al., 2010, Plummer et al., 2013) and models of infant agents (Plummer, 2012, 2013) that “vocally interact” with their caretakers. Moreover, we develop a model of caretaker social and vocal signaling in response to infant vowel productions, and of an infant's internalization of these signals and the internal computations over them. More broadly, we model the acquisition of vowel normalization within a developmental framework encompassing a suite of vocal learning phenomena, including language-specific caretaker vocal exchanges, perceptual warping, and multisensory matching and narrowing.
Deconvolution-based acoustic source localization and separation algorithms
Authors: Bai Mingsian R. , Kuo Chia-Hao
Published: May 2014

In this paper, localization and separation of acoustic sources are examined. Depending on the number of sources in relation to the array channels, the problem is investigated in terms of underdetermined and overdetermined configurations. In the underdetermined configuration, virtual monopole sources are assumed in uniformly spaced angles. The problem is then formulated into compressive sampling (CS) problem which can be solved by using the linearly constrained -norm convex (CVX) optimization. The solution yields the directions of real sources and the source signal spectrum, which enables localization and reconstruction of sources at one shot. In the underdetermined configuration, source localization and signal separation is carried out in two steps. First, the directions of arrival (DOA) are estimated with Minimum Variance Distortionless Response (MVDR) or Multiple Signal Classification (MUSIC). Next, Tikhonov regularization (TIKR) is utilized to recover the source spectrum. In the localization problem for both configurations, Neyman-Pearson detector is employed to determine thresholds for source detection. Numerical and experimental results show that the proposed methods produce improved speech quality in terms of mean opinion score (MOS) in perceptual evaluation of speech quality (PESQ) test.
A study of broadband sensor location selection using convex optimization in very large scale arrays
Authors: Lai Yenming , Balan Radu V.
Published: May 2014

Consider a sensing system using a large number of N microphones, placed in multiple dimensions to monitor a broadband acoustic field. Using all the microphones at once is impractical because of the amount of data generated. Instead, we choose a subset of D microphones to be active. Specifically, we wish to find the set of D microphones which minimizes the energy of the interference gains at multiple frequencies while monitoring a target of interest. A direct, combinatorial approach—testing all N choose D subsets of microphones is impractical because of problem size. Instead, we use a convex optimization technique that induces sparsity through a l1-penalty to determine which subset of microphones to use. We measure the energy of the interference gains in three ways: the maximum gain, the average gain, and the average squared gain and compare the results. Furthermore, we assume one reflection off of each wall in our problem setup and minimize the gains of the reflections. We test the robustness of the our solution through simulated annealing and compare its performance against a classical beamformer which maximizes SNR. We also do exhaustive searches to compare the performance of our algorithm against the global optimum.
Random matrix theory model for mean notch depth of the diagonally loaded minimum variance distortionless response beamformer for a single interferer case
Authors: Tuladhar Saurav R. , Buck John R. , Wage Kathleen E.
Published: May 2014

Adaptive beamformers (ABFs) suppress interferers by placing notches in the beampattern at interferer directions. This suppression improves the detection of weaker signals of interest even in the presence of strong interferers. The magnitude of the notch depth (ND) is an important parameter governing the adaptive gain obtained from using ABFs over conventional beamforming in the presence of interferers. This research derives models for the mean ND of a diagonally loaded minimum variance distortionless response (MVDR) beamformer for a single interferer case. The model describes the mean ND as a function of the number of snapshots, the number of sensors in the array, the interferer to noise ratio (INR) level, the interferer direction, and the diagonal loading level. The derivation exploits random matrix theory (RMT) results on the behavior of the eigenvectors of the spiked covariance matrix. The RMT based ND model predictions are in close agreement with simulation results over a range of INR values and number of snapshots.
A rigid-body model for diffraction imaging of solid objects: Theory and experimental results
Authors: Pees Edward H.
Published: May 2014

Acoustical imaging via the method of diffraction tomography is typically applied to weakly scattering, fluid objects, wherein the first Born approximation holds. Nonetheless, the technique can be applied to strong scatterers in a meaningful way if an appropriate object function is considered. In this talk, the theoretical form of the object function for a rigid body is developed along with an inversion formula for centripetal, broadband data collection. Applying the latter to experimental, underwater echo data from a variety of objects, reconstructions are presented and interpreted in terms of a Kirchhoff boundary condition. The approach can potentially reveal the relative importance of different scattering mechanisms in the overall pressure field reflected from a body by how closely the rigid body object function is reconstructed. Morphological characteristics may also be identified for objects that are, for example, hidden or buried.
Using hydrophones as vector sensors
Authors: Yildiz Selda , Dorman LeRoy M. , Kuperman W. A. , Sabra Karim , Roux Philippe , Green Dale , Fried Stephanie , Schmidt Henrik
Published: May 2014

Hydrophone arrays with spacing much less than an acoustic wavelength can be converted to vector sensors. Subsequent vector sensor signal processing can then be applied. Two particular applications are presented: The first is converting very low frequency acoustic data to seismic type data that contain polarization information and the second is getting directional information from sub wavelength acoustic arrays. We start with a review of the simple theory followed by some illustrative simulation examples. We then apply these signal processing methods to ocean acoustic data.
Combined effects of amplitude compression and reverberation on speech modulations
Authors: Srinivasan Nirmal Kumar , Gallun Frederick J. , Reinhart Paul N. , Souza Pamela E.
Published: May 2014

It is well documented that reverberation in listening environments is common, and that reverberation reduces speech intelligibility for hearing impaired listeners. it has been proposed that multichannel wide-dynamic range compression (mWDRC) in hearing aids can overcome this difficulty. However, the combined effect of reverberation and mWDRC on speech intelligibility has not been examined quantitatively. In this study, 16 nonsense syllables (/aCa/ format) recorded in a double-walled sound booth were distorted using virtual acoustic methods to simulate eight reverberant listening environments. Each signal was then run through a hearing-aid simulation which applied four-channel WDRC similar to that which might be applied in a wearable aid. Compression release time was varied between 12 and 1500 ms. Consonant confusion matrices were predicted analytically by comparing the similarity in the modulation spectra for clean speech and compressed reverberant speech. Results of this acoustical analysis suggest that the consonant error patterns would be strongly influenced by the combination of compression and reverberation times. If confirmed behaviorally and extended to wearable hearing aids, this outcome could be used to determine the optimum compression time for improved speech intelligibility in reverberant environments. [Work supported by NIH R01 DC60014 and R01 DC011828.]
On the use of a real-time convolution system to study perception of and response to self-generated speech and music in variable acoustical environments
Authors: Whiting Jennifer K. , Leishman Timothy W. , Hunter Eric J.
Published: May 2014

A real-time convolution system has been developed to quickly manipulate the auditory room-acoustical experiences of human subjects. This system is used to study the perception of self-generated speech and music and the responses of talkers and musicians to varying conditions. Simulated and measured oral-binaural room impulse responses are used within the convolution system. Subjects in an anechoic environment experience room responses excited by their own voices or instruments via the convolution system. Direct sound travels directly to the ear, but the convolved room response is heard specialized headphones spaced away from the head. The convolution system, a method for calibrating room level to be consistent across room impulse responses, and data from preliminary testing for vocal effort in various room environments are discussed.
Behavioral response of select reef fish and sea turtles to mid-frequency sonar
Authors: Watwood Stephanie L. , Iafrate Joseph D. , Reyier Eric A. , Redfoot William E.
Published: May 2014

There is growing concern over the potential effects of high-intensity sonar on wild marine species populations and commercial fisheries. Acoustic telemetry was employed to measure movements of free-ranging reef fish and sea turtles in Port Canaveral, Florida, in response to routine submarine sonar testing. Twenty-five sheepshead (Archosargus probatocephalus), 28 gray snapper (Lutjanus griseus), and 29 green sea turtles (Chelonia mydas) were tagged, with movements monitored for a period of up to four months using an array of passive acoustic receivers. Baseline residency was examined for fish and sea turtles before, during, and after the test event. No mortality of tagged fish or sea turtles was evident from the sonar test event. There was a significant increase in daily residency index for both sheepshead and gray snapper at the testing wharf subsequent to the event. No broad-scale movement from the study site was observed during or immediately after the test. One month after the sonar test, 56% of sheepshead, 71% of gray snappers, and 24% of green sea turtles were still detected on receivers located at the sonar testing wharf.
Machine learning an audio taxonomy: Quantifying biodiversity and habitat recovery through rainforest audio recordings
Authors: Treuer Tim , Altosaar Jaan , Hartnett Andrew , Twomey Colin , Dobson Andy , Wilcove David , Couzin Iain
Published: May 2014

We present a set of tools for semi-supervised classification of ecosystem health in Meso-American tropical dry forest, one of the most highly endangered habitats on Earth. Audio recordings were collected from 15-year-old, 30-year-old and old growth tropical dry forest plots in the Guanacaste Conservation Area, Costa Rica, on both nutrient rich and nutrient poor soils. The goals of this project were to classify the overall health of the regenerating forests using markers of biodiversity. Semi-supervised machine learning and digital signal processing techniques were explored and tested for their ability to detect species and events in the audio recordings. Furthermore, multi-recorder setups within the same vicinity were able to improve detection rates and accuracy by enabling localization of audio events. Variations in species' and rainforest ambient noise detection rates over time were hypothesized to correlate to biodiversity and hence the health of the rainforest. By comparing levels of biodiversity measured in this manner between old growth and young dry forest plots, we hope to determine the effectiveness of reforestation techniques and identify key environmental factors shaping the recovery of forest ecosystems.