bluuebunny/crossref_metadata_2025 huggingface dataset:
Perception of phonological variants by non-native listeners
Authors: Abrahamyan Hayk
Published: May 2016

Recent research has demonstrated that listeners process carefully pronounced words (canonical forms) more quickly and accurately than casually produced words (non-canonical, reduced forms), despite the fact that casually produced word forms are more frequent in everyday language use. To date, research on the perception of phonological variants that are typical of casually produced speech has focused, with a few exceptions, on monolingual listeners. The current research examined non-native English speakers' processing of canonical and non-canonical word-forms in an attempt to more fully understand how non-native speakers of English cope with phonological variants in American English. Monolingual American English speakers and non-native American English speakers completed a cross-modal identity priming task with canonical, non-canonical, and unrelated auditory primes and visual targets. Overall, the non-native speakers were significantly slower than native speakers at recognizing both canonical and non-canonical forms, although our data suggest that non-native speakers may encounter more specific difficulties than native speakers when processing phonological variants. Our results constitute an initial attempt at understanding how non-native speakers cope with phonological variation in their second languages.
Children’s perception of native dialects and nonnative accents
Authors: Bent Tessa , Holt Rachael F. , Wilcox Tiarah , Mabie Sarah , Neczypor Leah
Published: May 2016

In quiet listening conditions, school-aged children can have difficulty understanding nonnative-accented speech whereas adults tend to be highly accurate. The addition of noise substantially depresses word recognition accuracy for both groups. Here, these findings are extended to the perception of an unfamiliar native dialect. Children between the ages of 5 and 7 years (n = 90) were presented with HINT-C sentences produced by three female talkers with different accents—American English (midland dialect), British English, and Japanese-accented English—in quiet or in 8-talker babble with a + 4 dB SNR. Results showed highly significant main effects of accent, listening condition (noise, quiet), and age in the expected directions, as well as an interaction between talker accent and listening condition. In quiet, children showed very accurate word recognition for the American and British talkers (97% and 95% correct, respectively) with lower accuracy for the nonnative talker (73% correct). Compared to the quiet condition, performance declined more in the noise-added condition for the British (20% decline) and nonnative talkers (21%) than for the American talker (7%). These results suggest that although school-aged children can understand unfamiliar native dialects, their representations of these dialects may be fragile and highly susceptible to environmental degradation.
Production of English vowels preceding voiced and voiceless consonants by Korean learners of English
Authors: Chung Juyeon
Published: May 2016

In English, consonant voicing has large effects on both the quality and duration of the previous vowel, as does the status of the vowel as tense or lax. Our aim is to examine whether there is L1 interference on L2 English vowel productions and whether temporal acquisition is easier than vowel quality acquisition. Korean L2 speakers were chosen as participants; Korean has no contrasts in tense vs. lax vowels, and no coda consonant voicing contrast in a monosyllabic structure, but does exhibit post-vocalic voicing contrasts in disyllabic structures, and in these cases, voiced consonants exhibit lengthening of the preceding vowel. The participants were asked to read the list of English nonce words consisting of the English high vowels and sets of plosives contrasting in voicing as a coda in the two different structures. None of the speakers exhibited different patterns in monosyllabic and disyllabic structures. All speakers did exhibit durational correlates to the voicing contrast, and to the tense-lax distinction. Formant frequency differences were found for both voicing and the tense-lax distinction, however, not as consistently. Specifically, back vowels were not distinguished by a number of subjects. In sum, temporal properties were more easily acquired than vowel quality properties.
The language-familiarity effect in talker identification by highly proficient bilinguals depends on second-language immersion
Authors: Dougherty Sara C. , Perrachione Tyler K.
Published: May 2016

Listeners identify voices more accurately in their native language than an unfamiliar, foreign language in a phenomenon called thelanguage-familiarity effect (LFE). Talker identification studies consistently find that even highly proficient speakers of a foreign language persist in identifying voices more accurately in their native language than their second language. It remains unclear why some bilinguals continue to exhibit the LFE despite fluent receptive and expressive second-language skills. In the present study, native Mandarin speakers who were fluent in English and living in the United States learned to identify Mandarin- and English-speaking talkers by the sound of their voice. We assessed hypotheses proposing that either depth of second-language immersion or age of second-language acquisition account for the magnitude of the LFE among highly proficient second-language speakers. Only the extent to which bilinguals were currently immersed in second-language use affected the magnitude of the LFE; native Mandarin speakers who currently used predominately English in their daily lives exhibited no LFE, whereas those who currently used predominately Mandarin continued to have superior native-language talker identification abilities. These results suggest that the magnitude of the LFE in talker identification by bilinguals is a function of real-world immersion in foreign language use.
Intelligibility, fluency, and variability in non-native speech
Authors: Baese-Berk Melissa M. , Morrill Tuuli H. , Bradlow Ann R.
Published: May 2016

Native and non-native speech differ in many ways, including overall speech rate, which tends to be substantially slower for non-native speakers (Guion et al., 2000). Recent work has suggested that non-native speech may be not only slower, but also more variable when non-natives are reading aloud (Baese-Berk and Morrill, 2015). Speaking rate also influences how listeners perceive non-native speech—slower readers are perceived as more accented and less comprehensible (Munro and Derwing, 1998). In the present study, we ask whether variability in speaking rate also has this effect on listeners. Specifically, we ask whether speaking rate variability is correlated with non-native speaker intelligibility and/or with judgments of fluency. In the present study, we ask listeners to transcribe sentences from speakers who show more or less variability in speaking rate across sentences in a paragraph-length reading passage. We also ask them to rate the fluency of the read sentences. Speech samples were taken from native Mandarin, Korean and English speakers’ recordings of the English “North Wind and the Sun” passage in the ALLSSTAR collection of digital speech recordings (Bradlow et al., 2010). These results provide insight into the relationships between variability, intelligibility, and fluency in both native and non-native speech.
Variability and stability in native and non-native Japanese speech
Authors: Vaughn Charlotte , Baese-Berk Melissa , Idemaru Kaori
Published: May 2016

The speech of second language learners is often characterized as more variable than the speech of native speakers (e.g., Baese-Berk and Morrill, 2015; Jongman and Wade, 2007; Jongman et al., 2007; Rogerset al., 2012). However, among the relatively few studies which have examined this question directly, the majority have focused on: learners of English, learners from one L1 background, and have examined one linguistic feature per study, leaving open the possibility that non-native speech may not be more variable than native speech in all cases. The present work examines the production of Japanese sentences by native Japanese speakers, and learners of Japanese from two language backgrounds (English and Chinese). Counter to previous results, we find several cases where non-native speakers are less variable than native speakers, including on various measures of vowel spectrum variability, and voiced stop realization. Thus, the relationship between variability and language background appears to be more complex than previously thought. Accurately characterizing variability across native and non-native speech has implications for models of second language acquisition, and speech perception. We suggest that future work on variability in non-native speech should examine factors such as speakers’ L1 and L2, and multiple linguistic features.
Categorization training for non-native accented word recognition
Authors: Tessmer Rachel , Atagi Eriko , Bent Tessa , Chandrasekaran Bharath
Published: May 2016

Non-native accented speech is considered an adverse listening condition for native speakers (Mattys et al., 2012). Previously, accurate categorization of non-native accents was found to relate to accented speech-in-noise recognition (Atagi and Bent, 2015). The goal of the current study is to examine (1) the extent to which native speakers can be trained to categorize the language backgrounds of non-native talkers using feedback, and (2) the extent to which accent categorization training, relative to word and sex identification tasks, improves non-native accented word recognition. Participants were randomly assigned to one of three training tasks: an accent categorization task with trial-by-trial feedback (n = 10), a transcription task (n = 10), and a speaker sex categorization task (n = 10). Critically, all participants were exposed to the same set of training stimuli. Participants completed a transcription task with speech-shaped noise prior to and following training. We assessed keyword accuracy for non-native accented speech and native accented speech. Our results demonstrate that single-session training can improve accent categorization. Accent identification training, word identification, and sex identification all yielded more accurate non-native speech perception (post>pre). We find that irrespective of training task, exposure to non-native accents enhances intelligibility of non-native accented speech.
The bilingual advantage in phonetic/phonological learning: A study of bilingual and monolingual patterns in the reproduction of word-final stops in three novel accents of English
Authors: Spinu Laura , Hwang Jiwon , Lohmann Renata
Published: May 2016

As part of a larger study investigating the acoustic correlates of accentedness in the reproduction of various accents of English by English monolinguals and French-English bilinguals, we explored speakers' ability to imitate and spontaneously reproduce patterns of realization of word-final coronal stops in three different accents: SE England (Sussex) in which these stops are 100% glottalized, and Russian English and South African English, in which these stops exhibit canonical release about 50% of the time. We have so far fully analyzed the Sussex results and partially analyzed the Russian results. The two groups were characterized by different behaviors: while the bilinguals successfully reproduced the Sussex English accent, the monolinguals did not. By contrast, neither of the groups was successful in reproducing the Russian English accent. After considering the characteristics of each group of speakers and each accent, we conclude tentatively that it is the bilinguals, as a group, who were more successful in the phonetic/phonological learning of a new pattern, perhaps as a result of some type of “bilingual advantage.” Based on work by Calabrese (2011) and Krizman et al. (2012), we propose that this advantage stems from longer availability of acoustic information in echoic memory.
The effect of speaking style adaptations on speech perception in noise by native and non-native listeners
Authors: Meemann Kirsten , Smiljanic Rajka
Published: May 2016

It is well established that non-native listeners perform worse on speech perception in noise tasks compared to native listeners. However, few studies have directly compared the effect of speaking style adaptations on speech perception in energetic and informational maskers for these two listener groups. The present study examined intelligibility of conversational (CO), clear (CS) and noise-adapted (NAS) meaningful sentences mixed with speech shaped noise (SSN) and 2-talker (2T) babble. Sentences were presented at −5 dB signal to noise ratio (SNR) to native and −3 dB SNR to non-native listeners. The results revealed that CS and NAS significantly improved word recognition in noise for both listener groups. However, the gains in intelligibility were substantially greater for native compared to non-native listeners. Word recognition was overall better in 2T babble than in SSN. Our findings confirm that both native and non-native listeners benefited from speaking style adjustments, but native listeners were better able to utilize the intelligibility-enhancing modifications. The results also suggest that informational masking in 2T babble is less disruptive than energetic masking in SSN. This may in part be due to the “glimpsing” windows through which the target speech could become more easily accessible.
Information-theoretic analysis of Bayesian localization of a narrowband source in an uncertain environment
Authors: Hayward Thomas J.
Published: May 2016

Previous work has explored the application of fundamental information-theoretic constructs, including posterior entropy of source location and per-iteration information gain (relative entropy) and their large-ensemble limits, to quantify the performance of iterated (sequential) Bayesian localization of an acoustic source. These information-theoretic quantities are closely tied to Bayesian inference and provide global measures of the uncertainty of source location that is represented by the Bayesian posterior probability density. The present work extends this analysis to the localization of a narrowband acoustic source in an acoustic environment having uncertain sound speed and attenuation represented by a joint pdf of the two quantities. The fundamental principle relating the environmental and acoustic field uncertainties is the change-of-variables theorem of probability theory. The degradation of localization performance due to the environmental uncertainty is quantified by the increase in posterior entropy of source location, interpreted as an information loss. Examples are presented, and extensions to stochastic environments are discussed. [Work supported by ONR.]
Removing multiple scattering in underwater target detection
Authors: Woolfe Katherine F. , Photiadis Douglas , Calvo David
Published: May 2016

Recent advances have been made in the field of optics to image through multiple-scattering media in a regime where classical imaging techniques, which rely on the single-scattering approximation, fail. Using results generated by random matrix theory, it is possible to filter the response matrix generated by a source/receiver array to remove the multiple scattering components of the received signals. After removing the multiple scattering components, classical imaging techniques can be used to image with the single-scattering components. We show how this single-scattering filter can be adapted for underwater acoustical imaging in cases where multiple scattering effects are large compared to the reflection from the target. A full-wave 3-dimensional time-domain scaled model is used to characterize filter performance as a function of target strength and environmental coherence length for a shallow-water case. Preliminary results indicate that the filter can be used to detect a target located at least 2 mean free paths away from the source/receiver array.
Additional studies of the acoustics of coffee roasting
Authors: Johnson Jay R. , Wilson Preston S.
Published: May 2016

Cracking sounds emitted by coffee beans during the roasting process can be recorded by a microphone and used as the basis for automated acoustic roast profiling and monitoring, mimicking what expert artisanal coffee roasters do by ear. Three parameters are used for this purpose. Near the end of the roasting process, sounds known as “first crack” exhibit a higher acoustic amplitude than sounds emitted later, known as “second crack.” First crack emits more low frequency energy than second crack. Finally, the rate of cracks appearing in the second crack chorus is higher than the rate in the first crack chorus. This presentation is a companion to the previously published work on the same topic [J. Acoust. Soc. 185, EL265–EL269 (2014)], but expanded to include a discussion of automated crack detection signal processing, the acoustic characteristics of different coffee beans, and initial results of a study on how individual beans crack and emit their sounds.
A new time-domain model for bottom backscatter
Authors: Tang Dajun , Jackson Darrell R.
Published: May 2016

Bottom backscatter is important for a number of underwater applications: it is a source of noise in target detection and a source of information for sediment classification and geoacoustic inversion. Bottom backscatter measures sound scattered from roughness and volume heterogeneity in different sediment layers. While current models can successfully handle scattering from such sediment layers, they cannot correctly predict the scattered intensity as a function of time. A new model for bottom backscatter is introduced which provides an exact solution for scattered intensity as a function of time under first order perturbation theory. Examples of backscatter from various sediment layers will be shown in contrast to previous models. Issues such as the “spherical wave effect” will be addressed, and applications to model shallow water reverberation will also be discussed.
Looking to history for a modern paradigm in opera house design
Authors: Glosemeyer Petrone Robin , Pfeiffer Scott D.
Published: May 2016

The design of a 600-seat opera house is a rare opportunity. The cost of modern opera production leads to much larger facilities and small venues are more frequently multi-purpose venues by nature, leading to the use of concert hall or lyric theatre forms that can be pressed into service for opera. The United States has many small theatres, mostly on college campuses, but few see frequent use for Opera and as a result design choices tilt away from optimal for Opera performance. Historic opera houses of Europe present more opportunities for exploration. Many follow the Italianate form which is intimate and evokes our sense of what an opera house “should” be, though closer investigation exposes the weakness in these designs both theatrically and acoustically. The experience for many patrons is removed and lonely with severely challenged sightlines and an acoustic experience that is frontal, dry, and unengaging. Our exploration took us to the Royal Opera in the Palace of Versailles whose form varies in key ways from the typical. While the construction techniques of Versailles hinder its acoustic response, as inspiration, a new form for intimate opera is created.
Navigating the design of a 600-seat opera house
Authors: Pfeiffer Scott D. , Glosemeyer Petrone Robin
Published: May 2016

Negotiation of a design for a 600-seat opera and chamber music hall presents challenges of dimension. Can the main floor audience enter under the parterre? What is the relationship of the singer to the closest audience members, leaving room for a full-size orchestra? Two full concept designs were carried to fully plausible outcomes to test these questions as well as the question of the resulting acoustic environment in order to arrive at decisions amongst the design team and user groups. The power of auralization and visualization tools was brought to bear on the decision making process, supplementing comprehensive benchmarking studies. While each constituent went into the process with moderately to significant biases, all entered the final discussions having arrived with an open mind about the optimal outcome for the unique circumstances of the project. Communication among the team using the medium of greatest familiarity for multiple constituents led to an outcome that has broad support from the entirety of the design team.
The golden throat—Effect of proscenium zone shaping in opera houses on balance between stage and pit
Authors: Myers Joseph W.
Published: May 2016

This paper investigates the importance of the walls and ceiling in the “throat” of an opera house—the zone surrounding the proscenium—for encouraging a balance that favors onstage singers over musicians in the orchestra pit. By looking at a variety of opera houses, the author tests the idea that surfaces in this zone that are solid and not strongly angled are especially beneficial for encouraging balance.
Opera acoustics in multi-use performing arts centers
Authors: Holden Mark
Published: May 2016

There is very little information available on practical solutions for designing acoustics for an orchestra pit. This paper guides the reader through a brief history of orchestra pits and how to design them for the modern multi-use halls used by opera companies. Musicians generally abhor playing in a pit. They feel it is crowded, hot, loud, and a horrible environment in which to hear themselves and other musicians. The acoustician’s goal is to improve the acoustic environment within the pit and find the optimal projection of music to the audience and stage. Drawings and details along with photos from pits designed for halls around the world will be presented from Mark Holden’s new book Acoustic of Multi-Use Performing Arts Centers published by CRC Press in January.
Improving listening conditions in partially covered opera pits or “The strings are working so hard…why can’t I hear them?"
Authors: Blair Christopher N. , Scarbrough Paul H.
Published: May 2016

Since the introduction of the gargantuan orchestra to the world of opera by Wagner, opera house designers have been faced with the question of whether to place the orchestra in an open pit, a covered pit, or a partially covered pit. The open pit has long been favored by musicians but has it operational and economical drawbacks, including often large distances from conductor to singer, challenging pit/stage balance conditions, and reduced audience seating close to the stage. A fully covered pit works well for the special works that the Bayreuth master intended for this condition, but is inappropriate for the rest of the core operatic repertoire. The partially covered pit where some upstage musicians play under the stage is conceptually advantageous for a number of reasons, but can present challenges in uneven listening conditions within the orchestra (excessive loudness, ensemble difficulties) and in the house. In some instances, musician complaints have resulted in regulatory action. This paper explores the root causes of ensemble issues commonly found in partially-covered orchestra pits and presents specific solutions drawn from the consulting (and conducting) experience of the authors.
Improving orchestra and singer communication at the Brazilian Opera
Authors: Barbar Steve
Published: May 2016

Large opera stages present a challenge in maintaining optimum synchronization for principals or a chorus that are far upstage of the orchestra. Further complications arise when the orchestra located in a deep orchestra pit (typical) and only the conductor is visible. This condition induces disparity between the visual timing from the conductor and the arrival of sound from the orchestra. This paper describes how the implementation of electronic architecture solved the problem and improved acoustical conditions on the stage. In addition, the system was extended to the house to provide optimum conditions for symphony performances.
Applying double-difference methods for fine-scale acoustic tracking of controlled sources and sperm whales using a small aperture vertical array
Authors: Tenorio-Hallé Ludovic , Thode Aaron M. , Sarkar Jit , Verlinden Chris , Tippmann Jeffrey D. , Hodgkiss William S. , Kuperman William A.
Published: May 2016

Ray propagation modeling can estimate a source’s depth and range in a waveguide by exploiting multipath arrival information on a vertical array. However, environmental mismatch of the model, array tilt, and limited angular resolution of an array can yield highly scattered dive trajectories when ray tracing individual events. “Double-difference” methods have been used to localize earthquakes (Waldhauser and Ellsworth, 2000) and fin whales (Wilcock, 2012) by determining the location of multiple events relative to each other, rather than their absolute position. These same concepts can be reformulated into a “triple-difference” approach to track successive acoustic events on a single multi-hydrophone array. This method examines relative changes in the multipath arrival times and elevation angles over the course of a dive in order to establish a more robust track in terms of relative positions along the trajectory. Presented here are results of applying this new technique on both a towed source and sperm whales, using acoustic data recorded on a short aperture vertical array off the coast of Southern California in 4 km deep water. [Work supported by Office of Naval Research—Marine Mammals and Biology and Ocean Acoustics Program.]
Underwater acoustic vector sensor recording apparatus for soundscape measurements
Authors: Lenhart Richard D. , Sagers Jason D.
Published: May 2016

An Autonomous Underwater Multi-Dimensional Acoustic Recorder (AUMDAR) for making directional soundscape measurements has been designed, constructed, and tested at The Applied Research Laboratories. The AUMDAR includes several three-dimensional transducers (acoustic vector sensor, gravitometer, accelerometer, and gyroscope), a multichannel recording unit (six channels, up to 96 kHz sampling rate and 24 bit resolution), and a battery power supply housed in a 90 m depth-rated pressure vessel. The apparatus can be deployed on the seafloor via an oceanographic tripod, suspended within the water column on a vertical mooring line, or tethered below a surface float. Laboratory-based acoustical performance characterization measurements including vector sensor on-axis receive sensitivity, directivity, and electrical noise floor are discussed. Field measurements recorded by the AUMDAR in Lake Travis, TX, and Haro Strait, WA, are also presented.
Modelling the performance of fish tag monitoring stations on the Scotian Shelf
Authors: Moore Danielle , Barclay David R.
Published: May 2016

The Ocean Tracking Network operates and maintains a continental shelf scale array of 256 bottom mounted fish-tag monitoring stations, spanning from the entrance of Halifax harbour to the Scotian Shelf break. These stations detect tagged keystone, commercially important, and endangered species as they migrate across this acoustic curtain, known as the Halifax line. The detection performance of each station is dependent on the local bathymetry, oceanography (sound speed profile variability), ambient noise level, and source depth distribution. At each station, local sound speed profiles from archived glider data were collected and sorted into representative groups. An Nx2D ray-trace model was used to calculate the transmission loss and relative strength of the noise field at fish tag frequencies (69 kHz) for each of the representative sound speed profiles at a number of stations across the array. The performance variability at each station and between stations is presented and compared to real detection data.
The effects of bottom sediments on the measured spectrum of seismic airgun pulses as a function of range
Authors: Martin Bruce , MacDonnell Jeff , Bailey Loren
Published: May 2016

Sound from seismic airgun pulses is well known to be a measurable component of the marine soundscape even hundreds of kilometers from the source vessel. The peak frequency of the pulses is normally below 100 Hz, and hence the concern is often raised that the airguns may mask the communications of large baleen whales. Recently, there have been reports of significant energy from seismic airguns in the range of 1–10 kHz which could mask calls from a wider range of marine life. Measurements and modeling of a variety of deep water environments are compared to show that environments with very hard bottom types support the long-range propagation of frequencies above 500 Hz from seismic airgun arrays.
Application of acoustic technologies to study the temporal and spatial distributions of the Pacific hake (Merluccius productus) in the California Current System
Authors: Chu Dezhang , Thomas Rebecca , Clemons Julia , Parker-Stetter Sandy , Pohl John , Clemons Julia , Gauthier Stephane
Published: May 2016

Advances in acoustics technologies offer a remote and non-invasive sensing means to conduct fisheries acoustic surveys. Over the past two decades, joint US and Canada acoustic and trawl surveys on Pacific hake (Merluccius productus), one of the most important commercial fisheries off the West Coasts of the United States and Canada, have been conducted at the intervals of one to three years within the California Current System (CCS). In this presentation, the temporal and spatial distributions of Pacific hake resulting from these surveys spanning a period of nearly two decades will be presented. Challenges in converting the measured acoustic quantities to biological quantities, such as abundance and biomass, will be addressed, including uncertainties associated with mixed species, environmental parameters, and properties in fish morphology and anatomy. Issues related to transitions from single-species to ecosystem-based acoustic surveys will also be discussed.
An evaluation of the frequency response of hydrocarbon droplets
Authors: Loranger Scott , Weber Thomas C.
Published: May 2016

Development of instrumentation to detect and quantify submerged oil droplets would provide researchers and oil spill responders with crucial information about the fate and movement of oil in the environment. By detecting oil droplets in the watercolumn it should be possible to trace surface sheens to their source and to determine the location and extent of plumes of oil at depth. Methods of detecting oil currently exist, for example, mass spectrometers and fluorometers; however, they are limited to detecting oil that is submeter range from the instrument. Using broadband high frequency (30–300 kHz) acoustic echosounders, it is possible to not only detect oil droplets from a greater distance (10s of meters for individual droplets, depending on the background noise) but to quantify the physical properties of the oil, including the size of droplets. Droplet size is an important factor in determining the likely location of submerged plumes and surface sheens, the rate of biodegradation and rise rate of oil. Laboratory measurements of the broadband response along with the sound speed, density and droplet size of crude oil, diesel, gasoline, and kerosene have been made. The frequency response of the droplets have been compared to models for the target strength of fluid filled spheres to verify the models, and to empirically derive adjustments if necessary. The data are also used to empirically estimate a detection range limit for different densities of droplets determined.
Simulation and Implication of a two-dimensional phased array flexible ultrasound system for tissue characterization
Authors: Gan Zhihua , Guo Brian , Cheng Jiqi , Qin Yi-Xian
Published: May 2016

It has been demonstrated that phased-array ultrasound can be used for configuring spatial focal zone and perform noninvasive characterization of trabecular bone quality. Such a sensor configuration can also be integrated into existing ultrasound triggering, data analysis, mux, and imaging system in a flexible ultrasound platform. The primary goal of this study is focused on the unique dual 2-D array transducer kit design with 1MHz center frequency and simulation to a flexible ultrasound system for trabecular bone assessment. Transmission (Tx) and receiving (Rx) transducers are designed as two identical 2-D array sensors, with elements arrayed in 27*27 as a square. Element width is 1.05 mm and kerf is 0.2 mm. Tx elements are divided into sub-blocks to excite ultrasound signal in sequence to decrease the system complexity while maintaining beam pattern properties by the signal processing procedure at Rx side. Appropriate delay modules are inserted into the process of exciting signal. The working procedure is simulated by FIELD II program. The gray-scale simulation of acoustic resolution and side lobes are analyzed. The theoretical lateral resolution (LR) is 2.436 mm, with 2.8 mm in simulation. Hann window based apodization process shows the reduced side lobes. The results suggested that the reduced array size (27*27) simplifies the design and manufacturing, but maintains the image/signal resolution.
A stable numerical method for wide-angle parabolic models of focused ultrasound
Authors: Soneson Joshua
Published: May 2016

Wide-angle parabolic equations offer an attractive balance of utility, speed, and ease of implementation in the computation of sound beams in the frequency domain. These models are characterized by representing the pseudodifferential operator of the one-way Helmholtz equation with a Padé approximation, which is a quotient of polynomial operators, to which Crank-Nicolson-type numerical methods are easily applied. However, standard methods for determining the coefficients of these polynomials yield numerical schemes whose solutions exhibit oscillatory artifacts when source discontinuities are present, as is often the case for ultrasound transducers. In this work, two of three polynomial coefficients in a Padé approximation are used to obtain second order accuracy while the third coefficient is used to optimize stability. This results in a numerical method which effectively damps the spurious oscillations but retains the wide-angle capability, bringing to medical ultrasound a simple way to rapidly compute shallowly focused or steered beams.
A stethoscope for the knee: Investigating joint acoustical emissions as novel biomarkers for wearable joint health assessment
Authors: Inan Omer T. , Hersek Sinan , Teague Caitlin N. , Toreyin Hakan , Jeong Hyeon K. , Jones Michael L. , Millard-Stafford Melinda L. , Kogler Geza F. , Sawka Michael N.
Published: May 2016

Each year, millions of Americans endure knee injuries, ranging from simple sprains to ligament tears requiring surgical intervention. Our team is investigating wearable rehabilitation assessment technologies for patients recovering from knee injuries based on the measurement and analysis of the acoustical emissions from the knees. Using miniature electret microphones combined with piezoelectric sensors placed on the surface of the skin at the knee, we measure the sounds from the joint as subjects perform basic flexion/extension exercises and standardized sit-to-stand protocols. We then analyze the consistency of the knee acoustical emissions in the context of the activity, and the angle of the joint, to quantify the health of the joint. We have found, in early pilot studies, promising results differentiating the healthy versus injured knee, and longitudinal changes progressing from acute injury and recovery following rehabilitation. We have also determined that, in healthy subjects, the pattern of acoustic emissions is consistent within several repetitions of a movement, and for multiple recordings throughout the day (r > 0.88). Knee acoustic emissions combined with angle measurements provide promising in-depth information regarding joint health and exciting new opportunities for personalized rehabilitation protocols following injury.
Clinical results of ultrasound bladder vibrometry for assessment of bladder compliance
Authors: Bayat Mahdi , Cheong Mathew , Denis Max , Kumar Viksit , Mehrmohammadi Mohammad , Gregory Adriana , Nenadic Ivan , Husmann Douglas , Mynderse Lance , Alizad Azra , Fatemi Mostafa
Published: May 2016

Healthy human bladder is a viscoelastic shell capable of expanding to allow storage of urine at low pressures. The ability to maintain low pressures as the urine volume increases is called bladder compliance. Compliance is a key in proper functioning of urinary system. Spinal cord injuries and other neurogenic diseases can cause deterioration in bladder expansion capability (e.g., through excessive growth of fibrotic tissue), which in turn can increase the rigidity of the wall and reduce bladder compliance. Urodynamic study (UDS) is the clinical standard for evaluation of the bladder compliance through observation of bladder pressure-volume behavior. However, this method is costly and invasive. Ultrasound bladder vibrometry (UBV) has been introduced as noninvasive technique for evaluation of bladder viscoelasticity through excitation of the bladder using ultrasound radiation force and tracking the resulting Lamb waves. Here, we present the results of UBV from 44 patients undergoing concurrent UDS and UBV studies. Our results show that elasticity parameters obtained from the UBV closely correlate with the UDS pressure-volume data with a median Pearson’s correlation value of more than 0.8. These results prove the potential utility of UBV as an alternative noninvasive method for bladder compliance assessment. [Work supported by NIH grant DK99231.]
How well can a human mimic the sound of a trumpet?
Authors: Titze Ingo R.
Published: May 2016

The length of an uncoiled trumpet horn is more than 2 m, whereas the length of a human supraglottal airway is about 17 cm. The vibrating lips and the vibrating vocal folds can produce similar pitch ranges, but the resonators have vastly different natural frequencies due to the more than 10:1 ratio in airway length. Humans rarely attempt to tune more than one resonance to a harmonic because of the disparity between harmonic spacing and airway resonances spacing, but the brass-like timbre of a human “call” or “belt” can mimic that of a trumpet. A one-dimensional Navier-Stokes solution of non-steady compressible flow in soft-walled airways is used to show the similarities and differences in time-domain wave propagation and resulting flow and pressure frequency spectra along the airways. One striking structural similarity between the human instrument and the brass instrument is the shape of the airway directly above the sound source, known as the mouthpiece for brass and the epilarynx tube for the human airway. It plays a major role in shaping the source spectrum.
A broadband sound absorber based on lossy acoustic rainbow trapping metamaterials
Authors: Liu Tuo , Zhu Jie , Cheng Li
Published: May 2016

Acoustic rainbow trapping (ART) metamaterials offer spatial-spectral modulation and intensive trapping of broadband sound, with strong acoustic dispersion that is absent in naturally occurring materials. However, thermal and viscous losses stemming from the acoustic boundary layers within narrow resonance regions of ART metamaterials has not been thoroughly studied and effectively utilized. Here, we would like to propose a lossy model of ART metamaterials. By taking advantage of the thermal and viscous losses, such lossy metamaterials can effectively work as a broadband sound absorber. A rigid surface perforated with very narrow subwavelength holes that can provide boundary-layer losses and have gradient depth along the propagation direction is constructed to mimic the lossy ART model. Full wave numerical simulation results indicate that the system's thermal and viscous losses are governed by the geometry of the resonance unit cells. Together with the intrinsic trapping effect, this lossy ART metamaterials function as a high performance broadband sound absorber. It may contribute to the optimization of sound absorption materials and wedge design of anechoic chambers.
Iterative approaches to extend dilute homogenization predictions of Willis materials to higher volume fractions
Authors: Muhlestein Michael B. , Haberman Michael R.
Published: May 2016

Dynamic homogenization of generally heterogeneous elastic materials leads to three different effective material properties: stiffness, density, and parameters that couple momentum to strain and stress to velocity. This formulation was first proposed by Willis [Wave Mot. 3, 1–11, (1981)] and is thus commonly referred to as Willis coupling. While there are some homogenization methods which account for Willis coupling, those models rely on either the assumption of periodic media or on dilute concentrations of coupled inhomogeneities in an otherwise homogeneous matrix. This work presents the use of dilute models with iterative micromechanical methods to predict general material properties in materials with no long-range order and elevated volume fractions of inhomogeneity. Two such methods, self-consistent and differential effective medium models, will be presented for the homogenization of composites of arbitrary anisotropy and Willis coupling resulting from the presence of Willis coupled inclusions in an elastic matrix material. Predictions from both models are presented and compared with similar predictions using homogenization schemes which do not account for Willis coupling. It is found that incorporating Willis coupling in these iterative approaches does not significantly affect the prediction of the tensors describing the effective stiffness and density of the mixture.
On the use of the Willis Constitutive Laws of Elastodynamics of Stratified Media in reflection/transmission problems
Authors: Poncelet Olivier , SHUVALOV Alexander L.
Published: May 2016

The generalized constitutive relationships derived by Willis1,2 for elastodynamics of composites have incited an increasing interest in the community of effective media, and particularly in that of metamaterials. The structures for which homogeneous and dispersive equivalent media are sought include laminates,3,4 phononic crystals,5 as well as locally resonant materials.6 Those constitutive laws propose an extended vision of the notion of an effective medium since they fully generalize the linear relationship between the couple momentum/stress and the kinematic one particle velocity/strain through the tensors of anisotropic mass density (order 2), of elasticity (order 4) and of inertial coupling (order 3). Following general results obtained in [3] that provide the complete set of dispersive effective parameters describing exactly the “macroscopic” propagation in stratified media, this communication aims at exemplifying the use of the Willis model in different types of problems with interfaces coupling several media, at least one of which is actually inhomogeneous and described as a Willis effective medium. 1G. W. Milton, J. R. Willis, Proc. R. Soc. A 463, 855 (2007) 2J. R. Willis, Mech. Materials 41, 385 (2009) 3A. L. Shuvalov et al., Proc. R. Soc. A 467, 1749 (2011) 4S. Nemat-Nasser and A. Srivastava, J. Mech. Phys. Solids 59, 1953 (2011) 5A. N. Norris et al., Proc. R. Soc. A 468, 1629 (2012) 6D. Torrent et al., Phys. Rev. B 92, 174110 (2015).
Experimental validation of shear-mediated contributions to multiple scattering in concentrated random dispersions of spherical particles
Authors: Pinfield Valerie J. , Forrester Derek M. , Huang Jinrui
Published: May 2016

Multiple scattering models for ultrasound propagation in dispersions of spherical particles have conventionally included only multiple scattering of the compressional wave mode. Recent developments to these models by Luppé et al. [J. Acoust. Soc. Am. 131, 1113 (2012)] have incorporated the effects of mode conversions into the multiple scattering model; these arise from shear and thermal wave modes produced by scattering at each particle. In our recent work, we have reported the identification of the dominant contributions to effective attenuation in such dispersed systems for either solid or liquid particles, and have reported both analytical and numerical solutions for them. Here, we present the key results for shear-mediated multiple scattering effects which are dominant in concentrated systems of small solid particles (sub-micrometer) in the mega-Hertz frequency range. We show experimental validation of the model predictions for silica particles in the size range 100 nm to 1 micrometer and 1 to 20 MHz using two different spectroscopy techniques, first, a pseudo-continuous wave spectrometer (the Malvern Ultrasizer), and secondly a pseudo-random binary sequence cross-correlation spectrometer (Digusonic DSX) suitable for in-line process monitoring.
Controlling the exceptional points of parity-time symmetric acoustics
Authors: Shi Chengzhi , Dubois Marc , Chen Yun , Cheng Lei , Ramezani Hamidreza , Wang Yuan , Zhang Xiang
Published: May 2016

Parity-time (PT) symmetric systems experience phase transition between PT “exact” and “broken” phases at exceptional point. These PT phase transitions contribute significantly to the design of single mode lasers, coherent perfect absorbers, isolators, diodes, etc. However, such exceptional points are extremely difficult to access in practice because of the dispersive behavior of most loss and gain materials required in PT symmetric systems. Here, we introduce a method to systematically tame these exceptional points and control PT phases. Our experimental demonstration hinges on an active acoustic element that realizes a complex-valued potential and simultaneously controls the multiple interference in the structure. The manipulation of exceptional points offers new routes to broaden applications for PT symmetric physics in acoustics, optics, microwaves, and electronics, which are essential for sensing, communication, and imaging.
Multi-layered elastic shell metamaterial elements for improved transmission in sonic crystals
Authors: Titovich Alexey S. , Norris Andrew N. , O'Regan Stephen D.
Published: May 2016

A metamaterial-based sonic crystal, comprised of a lattice arrangement of cylindrical elastic shells, can be tuned to provide wave steering or phononic band filtering. The effective acoustic properties of such sonic crystals are determined by the geometric and material properties of each individual shell and the lattice spacing between shells. By matching the effective acoustic properties to those of the surrounding fluid, the sonic crystal can be made acoustically transparent at low frequencies, leading to improved transmission over that of non-matched shells. Bi-layered shells provide additional design parameters to broaden the region of acoustic transparency provided by a simple shell. In this effort, three-layered shells are employed to improve transmission further. Transformation acoustics analysis is applied to determine theoretical density and bulk modulus distributions, and then real-world materials are selected which best match these theoretical distributions. Finally, shell geometry is optimized to minimize scattering while constraining the effective acoustic properties to match those of the external fluid.
Reducing the pour point of crude oil by using of ultrasonic wave
Authors: Xu Delong , Lin Weijun , Deng Jingjun , Li Chao , Bai Lixin , Yang Yan
Published: May 2016

With the global economical development, high pour point crude oil (HPPCO) is getting more and more attentions. Due to its higher pour point and worse fluidity when it is cold, more difficulties are faced for its extraction. Ultrasonic wave technology is investigated to reduce the pour point of Sudan HPPCO in this paper. First, an ultrasonic horn is proposed and made. Then, after processing for 3 min by the horn, a decrease of more than 3 of the pour point of Sudan HPPCO is obtained. Furthermore, compared with that without ultrasonic processing, the percentage of higher molecular weight constituents becomes more, while that of heavier molecular weight component is less. The mechanism that the pour point of HPPCO can be changed through ultrasonic processing is analyzed and investigated by an experiment that three types of paraffin wax whose molecular weights are different are processed by ultrasonic wave. The main advantage of the ultrasonic processing for HPPCO is economical and environmental and the decrease of pour point after ultrasonic processing is irreversible.