bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of shock waves on growth of endothelial cells in vitro
Authors: Tamagawa Masaaki , Kitayama Masanobu , Iwakura Seiya
Published: October 2013

Recently shock wave phenomena in living tissues are being widely applied in the fields of medical and chemical engineering, such as extracorporeal shock wave lithotripsy, bioprocess for environmental protection and tissue engineering. In the field of tissue engineering, the bone therapy to regenerate the bone by extracorporeal shock waves shows the possibility for new therapy. In this paper, to investigate the effects of shock waves on the endothelial cells in vitro, the cells by plane shock waves are observed by microscope and the growth rate and others are measured by image processing. The peak pressure works on the endothelial cells in water at the test case is 0.4 MPa. After working shock waves on suspended cells and fixed cells, the disintegration, shape and growth are investigated. It is found that the younger generation cells have small differences of shape index, and the growth rate of the shock-worked cells from 0 to 4 h are clearly high compared with control ones. It is concluded that once shock waves worked, some of them are disintegrated, but the other has capacity to increase growth rate of cell culture in vitro.
A mechanistic analysis of stone comminution in lithotripsy
Authors: Maxwell Adam D. , Sapozhnikov Oleg A. , Bailey Michael R. , MacConaghy Brian , Crum Lawrence A.
Published: October 2013

In vitro experiments and an elastic wave model were employed to isolate and assess the importance of individual mechanisms in stone comminution in lithotripsy. Cylindrical U-30 cement stones were treated in an HM-3-style research lithotripter. Baffles were used to block specific waves responsible for spallation, squeezing, or shear. Surface cracks were added to stones to simulate the effect of cavitation, then tested in water and glycerol (a cavitation suppressive medium). Each case was simulated using the elasticity equations for an isotropic medium. The calculated location of maximum stress compared well with the experimental observations of where cracks naturally formed. Shear waves from the shock wave in the fluid traveling along the stone surface (a kind of dynamic squeezing) led to the largest stresses in the cylindrical stones and the fewest SWs to fracture. Reflection of the longitudinal wave from the back of the stone—spallation—and bubble-jet impact on the proximal and distal faces of the stone produced lower stresses and required more SWs to break stones. Surface cracks accelerated fragmentation when created near the location where the maximum stress was predicted. [Work supported by NIH DK43881, NIH-Fogarty, NSBRI SMS00203, RFBR, and ONRIFO.]
Mass loading effect of shock accelerometers
Authors: Wu Lixue , Wong George S. K. , Hanes Peter , Ohm Won-Suk
Published: October 2013

Mass loading affects the sensitivity of an accelerometer. The mass loading effect can be corrected using mass loading correction curves published by manufacturers. These curves, however, are only applicable to the sinusoidal acceleration below 500 m/s2. The mass loading effect on the sensitivity of an Endevco 2270 accelerometer in shock calibration, from 500 m/s2 and up, was investigated using a laser vibrometer. A new method for conversion of a velocity signal to an acceleration signal was developed. With this method, the sensitivities of the above accelerometer for different mass loads at different shock levels were measured. The mass loading effect in shock calibration for this accelerometer was then obtained. The limitations of the sensitivity measurements were also studied. The variance of the measured sensitivity was mainly due to the resolution limitation (8-bit) of the A/D converter in the digital oscilloscope. A correlation matching algorithm was then developed that utilizes the similarity between the measured acceleration signal and that converted from the velocity signal to further improve the resolution of the digital oscilloscope.
Characterization of a small moving-magnet electrodynamic linear motor for use in a thermoacoustic refrigerator
Authors: Liu Jin , Garrett Steven L.
Published: October 2013

The mechanical and electrodynamic parameters of a small, potentially inexpensive, moving-magnet electrodynamic linear motor are determined experimentally. Employing the formalism introduced by Wakeland [J. Acoust. Soc. Am. 107, 827–832 (2000)], these parameters are used to predict the electromechanical efficiency of the motor. The transduction coefficient Bl was observed to be a function of position. As will be shown analytically, the variation in Bl with position has a reduced effect on the drivers output power because Bl is largest around the equilibrium position where the piston velocity is also largest. By mechanical co-linear joining of the armatures of two such motors, an electrodynamic load (dynamometer) is created. Motor efficiency is then measured as a function of electrical energy dissipated in resistors placed in series with the motor which acts as the alternator in the pair. The measured efficiencies are shown to be in good agreement with the predictions if a position-averaged effective transduction coefficient is introduced. Based on these results, this linear motor is judged to be an attractive power source in small electrically driven thermoacoustic refrigerator applications. [Work supported by the Applied Research Laboratory Exploratory and Foundational Research Fund and Ben and Jerrys with motors donated by Bose Corporation.]
Medical ultrasound education for bioengineers
Authors: Vaezy Shahram
Published: October 2013

The widespread adoption of ultrasound technologies in medicine has necessitated the development of educational programs to address the growing demand for trained expertise in both academia and industry. The demand has been especially great in the field of therapeutic ultrasound that has experienced a significant level of research and development activities in the past decade. The applications cover a wide range including cancer treatment, hemorrhage control, cardiac ablation, gene therapy, and cosmetic surgery. A comprehensive educational program in ultrasound is well suited for bioengineering departments at colleges and universities. Our educational program for students in Bioengineering at the University of Washington includes a year-long coursework covering theory and practice of ultrasound, conducting research projects, attending and presenting at weekly seminars on literature survey, presentations at scientific meetings, and attending specialized workshops offered by various institutions for specific topics. An important aspect of this training is its multi-disciplinary approach, encompassing science, engineering, and medicine. The students are required to build teams with expertise in these disciplines. Our experience shows that these students are well prepared for careers in academia, conducting cutting edge research, as well as industry, being involved in the transformation of research end-products to commercially viable technology.
Meeting the textbook needs of modern acoustic courses
Authors: Raichel Daniel R.
Published: October 2013

A truly modern textbook constitutes an essential tool for both the instructor and students of acoustics or, for that matter, of almost any other technological subject. Thus, a newer edition of an acoustics text for upper science/engineering undergraduates and graduate students should not only thoroughly cover the fundamentals (including the derivations of the wave equation for both solids and fluids—a feature, unfortunately, still lacking in many fundamental texts) but also include a coverage of the latest applications such as medical and industrial uses of ultrasound, computer programs for mapping noise contours and solving architectural acoustics problems, introduction to nonlinear acoustics, acousto-optics, sonoluminescence, voice recognition devices, surround-sound systems and newer means of sound reproduction such as iPod, advances in sound measurement equipment and prosthetic hearing devices, and so forth. While the metric system prevails throughout the world, the use of the British system of units in the example problems in a text still may be essential to U.S. students who are likely to work with architects or deal with non-SI units in U.S. industry and the military.
Subjective comparison of single channel versus two channel subwoofer reproduction
Authors: Welti Todd S.
Published: October 2013

Bass management has many advantages for surround sound listening, however there is still a question regarding audibility of two channel versus single channel bass reproduction. Many previous investigations have lacked rigor or been preliminary in nature. The study presented here includes strict control of nuisance variables and significance testing of results. A test is described wherein trained listeners compared four different subwoofer configurations in controlled listening tests, using a very sensitive triangle test, in a typical listening room. Methods of controlling nuisance variables are discussed. These include double blind testing, equalizing all responses flat below 120 Hz, and allowing pre-training for the listening test. Critical selection of audio test loops using low frequency decorrelation is discussed. Results are presented.
Physiological and content considerations for a second low frequency channel for bass management, subwoofers, and low frequency enhancement (LFE)
Authors: Miller Robert E. (Robin)
Published: October 2013

Perception of very low frequencies (VLF) below 125 Hz reproduced by large woofers and subwoofers (SW), encompassing 3 octaves of the 10 regarded as audible, has physiological and content aspects. Large room acoustics and vibrato add VLF fluctuations, modulating audible carrier frequencies to >1 Hz. By convention, sounds below 90 Hz produce no interaural cues useful for spatial perception or localization, therefore bass management redirects the VLF range from main channels to a single (monaural) subwoofer channel, even if to more than one subwoofer. Yet subjects claim they hear a difference between a single subwoofer channel and two (stereo bass). If recordings contain spatial VLF content, is it possible physiologically to perceive interaural time/phase difference (ITD/IPD) between 16 and 125 Hz? To what extent does this perception have a lifelike quality; to what extent is it localization? If a first approximation of localization, would binaural SWs allow a higher crossover frequency (smaller satellite speakers)? Reported research supports the Jeffress model of ITD determination in brain structures, and extending the accepted lower frequency limit of IPD. Meanwhile, uncorrelated very low frequencies exist in all tested multi-channel music and movie content. The audibility, recording, and reproduction of uncorrelated VLF are explored in theory and experiments.
The transition to equipartitioning and its relation to scattering strength
Authors: Malcolm Alison E. , Scales John A. , van Tiggelen Bart A.
Published: October 2013

In a coarse-grained rock scattering plays a dominant role in determining the characteristics of the ultrasonic wavefield. Immediately after a pulse excites waves in such a sample energy propagates away from the source as a packet. As this packet travels, the individual grains scatter its energy in all directions. This scattering process continues until there are equal amounts of energy propagating in all directions. If the scattering is strong enough, this transition is completed before the signal strength has relaxed to the ambient level. By collecting a dense data set on several rock samples we are able to watch this transition and see the influence of grain size on the wavefield. More quantitatively we show, with noncontacting laboratory data, how this transition can be tracked using the symmetry of the advanced and retarded Green functions. These Green functions are estimated by cross-correlating the signal recorded at two detectors; the two Green functions have equal amplitude only when equal amounts of energy are propagating in all directions. [Work supported by the NSF (EAR-0111804), the US Army Research Office (DAAG55-98-1-0070), the Center for Wave Phenomena, and ACI 2066 of the French Department for Research.]
Spatial release from masking for amplitude modulated and non-modulated noise stimuli
Authors: Kopčo Norbert , Shinn-Cunningham Barbara G.
Published: October 2013

The ability to hear a target sound (T) masked by another sound (M) improves when the T and M are spatially separated, a phenomenon known as spatial release from masking (SRM). Target detectability is also influenced by temporal characteristics of T and M (e.g., by the presence or absence of amplitude modulation). The current study examines how SRM is influenced by amplitude modulation. Detection thresholds were measured for a broadband noise target (T) temporally and spectrally centered within a broadband noise masker (M). Thresholds were measured for all combinations of five spatial configurations of T and M and five modulation conditions (all combinations of T and M modulated and unmodulated; when both T and M were modulated, the modulation could either be equal or pi out of phase). In all cases, the amplitude modulation, if present, had a rate of 40 Hz and depth of 0.5. Modulation had a complex effect on detection threshold. Thresholds improved by as much as 6 dB (relative to the no-modulation control) in some spatial configurations, but were nearly unaffected in others. These results have important implications for understanding the processes involved in the perception of simultaneous complex signals. [Work supported by NSF and NAS.]
Searching for sources of variance in speech recognition: Young adults with normal hearing
Authors: Watson Charles S. , Kidd Gary R.
Published: October 2013

In the present investigation, sensory-perceptual abilities of one thousand young adults with normal hearing are being evaluated with a range of auditory, visual, and cognitive measures. Four auditory measures were derived from factor-analytic analyses of previous studies with 18–20 speech and non-speech variables [G. R. Kidd et al., J. Acoust. Soc. Am. 108, 2641 (2000)]. Two measures of visual acuity are obtained to determine whether variation in sensory skills tends to exist primarily within or across sensory modalities. A working memory test, grade point average, and Scholastic Aptitude Test scores (Verbal and Quantitative) are also included. Preliminary multivariate analyses support previous studies of individual differences in auditory abilities (e.g., A. M. Surprenant and C. S. Watson, J. Acoust. Soc. Am. 110, 2085–2095 (2001)] which found that spectral and temporal resolving power obtained with pure tones and more complex unfamiliar stimuli have little or no correlation with measures of speech recognition under difficult listening conditions. The current findings show that visual acuity, working memory, and intellectual measures are also very poor predictors of speech recognition ability, supporting the independence of this processing skill. Remarkable performance by some exceptional listeners will be described. [Work supported by the Office of Naval Research, Award No. N000140310644.]
Simulated phase-locking stimulation: An improved signal processing strategy for cochlear implant
Authors: Wu Xihong , Qu Hongwei , Chen Jing , Qu Tianshu , Li Liang
Published: October 2013

Electrical stimulation of the auditory pathway produces different patterns of neural activity than those acoustically elicited. Traditional signal-processing strategies for cochlear implant usually do not utilize phase information contained in sound waves. Here, to evaluate potential advantages of introducing phase information to cochlear implant devices, a new signal processing method, so called simulated phase-locking stimulation (SPLS), was developed. To convey phase information of sound signals to the auditory nerve, electrical stimulation pulses were delivered at the zero-crossing time of sine waves of frequency bands after band-pass filtering and envelope extraction. The advantages of the SPLS method over the method of Continuous Interleaved Sampling (CIS+) were demonstrated by both objective evaluations, such as the spectro-temporal modulation index (STMI), and subjective evaluations, such as recognition of processed Chinese speech by normal hearing listeners under either noise (energetic) masking or speech (informational) masking conditions. The results suggest that the SPLS method is able to improve the function of cochlear devices by extracting and transferring fine-structure signals, which are important for cochlear-implant listeners to perceive tonal speech and music.
Diversity of vowel systems
Authors: Maddieson Ian
Published: October 2013

Systems of vowels vary greatly across the world’s languages while nonetheless conforming to certain general structural patterns. All languages have at least two qualitative distinctions between vowels based on the major parameters of height, backness and rounding, but probably none has more than 15 or so, and the modal number is 5. Generally these basic vowel qualities respect dispersion principles, but deviations can be considerable. When additional parameters, such as nasalization, length, phonation type and pharyngealization are included, the total number of vowel distinctions may easily exceed 40. These ‘‘additive’’ features never occur with a larger number of vowel qualities than those occurring in a ‘‘plain’’ series. Languages may differ markedly in the distributional patterns of their vowels as well as in their inventory. Some languages have different (usually reduced) vowel inventories in unstressed or other non-prominent positions; others constrain vowel sequences in (phonological) words through vowel harmony limitations. Co-occurrence patterns between vowels and consonants also vary greatly, as does the degree of coarticulation between vowels and neighboring segments. Learners must master all of these factors to speak an individual language fluently. Constraints that are universal or shared may be expected to facilitate this task.
Perceptual assimilation and categorial discrimination of American vowels by Japanese listeners
Authors: Hisagi Miwako , Strange Winifred , Akahane-Yamada Reiko , Kubo Rieko
Published: October 2013

Best’s Perception Assimilation Model predicts that relative difficulty discriminating non-native (L2) contrasts is predictable from perceived similarity of L2 segments and native (L1) segments. Japanese listeners performed a categorial discrimination task in which 9 vowel pairs (6 adjacent height pairs, 3 front-back pairs) involving 6 tokens (2 speakers/3 repetitions) of each of 8 American vowels / i, I, ε, æ, a, ■, U, u/ were tested in the context of hVba disyllables. In a second task, listeners were asked to categorize all stimuli with respect to which Japanese vowel they were most similar, and to rate their goodness on a 9-point Likert scale. Overall error rates on height pairs ranged from 1 percent to 29 percent, and on front/back pairs, from 1 percent to 18 percent. The most difficult height contrasts were /U-u/ and /a-■/; perceptual assimilation patterns showed that these pairs were assimilated to the same Japanese vowels (Single Category or Category Goodness pattern) although /a-■/ were assimilated to 2-mora versus 1-mora Japanese /a/, respectively. The most difficult front/back contrast was /æ-■/. Surprisingly, American /i-I/ was discriminated very well and were assimilated to different Japanese vowels /i, e/, respectively. In general, perceptual assimilation patterns predicted discrimination accuracy quite well. [Work supported by NIDCD.]
Acoustic properties of vowels in clear and conversational speech by female non-native English speakers
Authors: Li Chi-Nin , So Connie K.
Published: October 2013

Studies have shown that talkers can improve the intelligibility of their speech when instructed to speak as if talking to a hearing-impaired person. The improvement of speech intelligibility is associated with specific acoustic-phonetic changes: increases in vowel duration and fundamental frequency (F0), a wider pitch range, and a shift in formant frequencies for F1 and F2. Most previous studies of clear speech production have been conducted with native speakers; research with second language speakers is much less common. The present study examined the acoustic properties of non-native English vowels produced in a clear speaking style. Five female Cantonese speakers and a comparison group of English speakers were recorded producing four vowels (/i u ae a/) in /bVt/ context in conversational and clear speech. Vowel durations, F0, pitch range, and the first two formants for each of the four vowels were measured. Analyses revealed that for both groups of speakers, vowel durations, F0, pitch range, and F1 spoken clearly were greater than those produced conversationally. However, F2 was higher in conversational speech than in clear speech. The findings suggest that female non-native English speakers exhibit acoustic-phonetic patterns similar to those of native speakers when asked to produce English vowels clearly.
Diphthongs in the repopulated vowel space
Authors: Bogacka Anna
Published: October 2013

The study examined 8 British English diphthongs produced by Polish learners of English, testing the diphthongs’ quality, duration, nasalization, and occurrence of glottal stops before the diphthongs. There were twelve conditions in which the diphthongs were tested: word-initial, word-final, before a voiced obstruent, before a voiceless obstruent, before a nasal consonant, and before a nasal consonant followed by a fricative, and each of these conditions was tested in a stressed and unstressed position. The diphthongs were tested in real words, embedded in sentences, controlled for the stress position, rhythmic units, and length. The sentences were read by 8 female and 8 male Polish learners of English and control subjects. The aim of the phonetic analysis done with Praat, and employing the methodologies used by Flege (1995) for SLA and Peeters (1991) and Jacewicz, Fujimara, and Fox (2003) for diphthongs, is to examine the shape of the restructured vowel space (Liljencrants and Lindblom 1972; Stevens 1989). The approach taken here is termed Vowel Space Repopulation to emphasize that the vowel space of Polish speakers of English is re-structured by new categories in complex ways which are not adequately captured by traditional notions such as ‘‘transfer,’’ ‘‘interference,’’ or ‘‘interlanguage.’’
Auralization studies to develop a classroom questionnaire
Authors: Nocke Christian , Hilge Catja , Meis Markus
Published: October 2013

Modern, computer-based room acoustic modeling software allows apart from the calculation and visualization of sound fields also the auralization of room acoustic conditions. By these means the listening conditions in (virtual) class rooms can easily be modeled and modified. Furthermore, for each listening position a full set of room acoustical parameters is available. Corresponding measurements in real class rooms would require much effort; well-defined changes could only be reached by interior works in the building. So, computer modeling offers a larger variety of well-defined acoustic conditions. This contribution reports on the auralizations carried out for the development of a questionnaire for subjective evaluations in real class rooms. For this purpose six different virtual class rooms have been modeled. In each of the six situations auralizations at two different listening positions for male and female speakers have been deduced. The auralizations have been presented to 80 test persons. The objective room acoustic parameters have been correlated with the subjective judgements. The questionnaire has been used by Meis et al. in real life experiments on the subjective evaluation of listening conditions. Results of these experiments will be presented in another contribution to this session by M. Meis (2pAAa1).
Acoustical conditions for speech communication in active elementary school classrooms
Authors: Sato Hiroshi , Bradley John
Published: October 2013

Detailed acoustical measurements were made in 34 active elementary school classrooms with typical rectangular room shape in schools near Ottawa, Canada. There was an average of 21 students in classrooms. The measurements were made to obtain accurate indications of the acoustical quality of conditions for speech communication during actual teaching activities. Mean speech and noise levels were determined from the distribution of recorded sound levels and the average speech-to-noise ratio was 11 dBA. Measured mid-frequency reverberation times (RT) during the same occupied conditions varied from 0.3 to 0.6 s, and were a little less than for the unoccupied rooms. RT values were not related to noise levels. Octave band speech and noise levels, useful-to-detrimental ratios, and Speech Transmission Index values were also determined. Key results included: (1) The average vocal effort of teachers corresponded to louder than Pearsons Raised voice level; (2) teachers increase their voice level to overcome ambient noise; (3) effective speech levels can be enhanced by up to 5 dB by early reflection energy; and (4) student activity is seen to be the dominant noise source, increasing average noise levels by up to 10 dBA during teaching activities. [Work supported by CLLRnet.]
Acoustical conditions of typical classrooms in Hong Kong
Authors: Li Kai Ming , Lam Coriolanus C. L.
Published: October 2013

This paper presents measurement results of the acoustical environments of local schools in Hong Kong. In the measurements, several acoustical aspects that affect verbal communication in classrooms have been studied. These conditions include outdoor and indoor ambient noise levels, signal-to-noise ratios, reverberation time and the speech transmission index. Typical classrooms in many different schools and other higher-education institutions have been selected in the present study. Experimental results are compared with such national standards as USA (ANSI S 12.60 V 2002), Australian/New Zealand (AS/NZS 2107:2000), China (GB/T 15508 V 1995) and other national and industrial standards. This study will form the basis of devising acceptable standards for use in Hong Kong. [Work supported by the Research Grants Council of the SAR Government, the Research Committee of the Hong Kong Polytechnic University and Architectural Services Department of the Hong Kong SAR Government.]
New schools design: Acoustics as main target
Authors: Maffei Luigi , Lembo Paola
Published: October 2013

The effects of poor intelligibility and high background noise levels on the cognitive development of school children and on the dissatisfaction of teachers has been largely investigated. National standards have been implemented and attempts to harmonize these standards in international guidelines are ongoing. All these activities have led to the awareness that design of new schools must be centered on the achievement of a good acoustic environment. At this point a strong research effort to study and implement best solutions must be conducted, in collaboration, by architects, acousticians, pedagogues, psychologists, builders and acoustic materials producers. Recently an international competition for the planning of new primary schools in Rome, Italy has been announced. The aim of the competition is to study new architectural and running features of primary schools to obtain, among other parameters such as lighting, low cost energy solutions and air quality, the control of reverberation time, sound insulation and mechanical equipments noise. In these school buildings, as innovative requirement, children must be also able to elaborate interpretative hypothesis of physical phenomena such as sound emission and perception and be aware of their influence on these phenomena. Different possible solutions are presented.
The effect of 40 kHz ultrasound on tissue plasminogen activator-induced clot lysis in three in vitro models
Authors: Pieters Marlien , Hekkenberg Rob T. , Barrett-Bergshoeff Marrie , Rijken Dingeman C.
Published: October 2013

In previous work from the same laboratory, high-frequency ultrasound (US) (3 MHz) was shown to promote in vitro fibrinolysis through enhanced supply of plasminogen to the clot surface. The application of high-frequency US is limited in vivo due to tissue heating. Low-frequency US, however, has less tissue heating and improved penetration. Internal plasma clot lysis and external lysis with compacted and non-compacted plasma clots were used to determine the magnitude of the effect of low-frequency US (40 kHz; 0.5 W/cm2) on tissue plasminogen activator-induced lysis and to elucidate the mechanisms behind the effect. Ultrasound enhanced lysis in all three models, with the largest effects (4-fold) in the external lysis model with compacted plasminogen-poor clots. The acceleration effect of ultrasound in this model decreased with increasing t-PA—and decreasing plasminogen concentrations. Ultrasound had a much smaller effect in this model when compacted plasminogen-rich clots were used. In the external lysis, non-compacted clot model, ultrasound resulted in consistently higher lysis rates. The acceleration effect of lysis, increased slightly (1.3 to 1.8-fold) with increasing t-PA—and decreasing plasminogen concentrations. Plasminogen supply to the clot surface was again shown to be an important contributor to ultrasound-enhanced lysis. [M. Pieters, R. T. Hekkenberg, M. Barrett-Bergshoeff, and D. C. Rijken. Ultrasound in Med & Biol 30, 1545–1552 (2004).]
Complete geometric computer simulation of a classical guitar
Authors: Bader Rolf
Published: October 2013

The aim of formulating a complete model of a classical guitar body as a transient-time geometry is to get detailed insight into the vibrating and coupling behavior of the time-dependent guitar system. Here, especially the evolution of the guitars initial transient can be looked at with great detail and the produced sounds from this computer implementation can be listened to. Therefore, a stand-alone software was developed to build, calculate, and visualize the guitar. The model splits the guitar body into top plate, back plate, ribs, neck, inclosed air, and strings and couples these parts together including the coupling of bending waves and in-plane waves of these plates to serve for a better understanding of the coupling between the guitar parts and between these two kinds of waves. The resulting waveforms are integrated over the geometry and the resulting sounds show up the different roles and contributions of the different guitar body parts to the guitar sound. Here cooperation with guitar makers is established, as changes on the guitars geometry on the resulting sound can be considered as computer simulation and promising new sound qualities can then be used again in real instrument production.
A scale model study of parallel urban street canyons
Authors: Hornikx Maarten , Forssen Jens , Kropp Wolfgang
Published: October 2013

The access to quiet areas in cities is of increasing importance. Recently, the equivalent sources method for a two dimensional situation of parallel urban street canyons has been developed. One canyon represents a busy road, whereas the other is one without traffic; the quiet side. With the model, the transfer function between the two canyons can be calculated, as well as the influence of diffusion, absorption, and atmospheric turbulence on the transfer function. A scale model study of two parallel canyons has now been executed. A scale of 1:40 has been chosen and the maximum length sequence technique has been applied using the MLSSA system. Results of the scale model study have been compared to calculations with the equivalent sources method. The difference between a two-dimensional and a three-dimensional quiet side, between a coherent and an incoherent line source and the influence of absorption and diffusion has been investigated. The scale model study also gives insight in the evolution of the sound field in the time domain. [Work supported by the Swedish Foundation for Strategic Environmental Research (MISTRA).]
Acoustic pulse propagation in an urban environment
Authors: Albert Donald G. , Liu Lanbo
Published: October 2013

Experimental measurements conducted in a full-scale artificial village show that complex signatures are formed by multiple reflections and diffractions from buildings along the propagation path. A two-dimensional finite difference time domain (FDTD) simulation running on a personal computer allows this wave interaction to be studied in detail. Time reversal processing to locate a sound source in an urban area is investigated using this simulation method. The results demonstrate that as few as three non-line-of-sight sensors are sufficient to determine the source location, and that errors on the order of a meter in the building or sensor locations still allow the correct source location to be determined. [Work supported by U.S. Army.]
Detecting and characterizing infrasound signals with optical fiber infrasound sensors
Authors: Walker Kristoffer , Zumberge Mark , Berger Jonathan , Hedlin Michael , Arrowsmith Stephen
Published: October 2013

Optical Fiber Infrasound Sensors (OFIS) are long compliant tubes wrapped with two optical fibers that interferometrically measure the differential pressure variation along the length of the tube. Because each sensor averages spatially along the length of the tube, the frequency response of the recorded pressure variation is a function of the orientation of the OFIS sensor relative to the back azimuth and incidence angle of the incoming wave. We have exploited this property to investigate the ability of various OFIS geometries to determine the back azimuth of infrasound signals. We have found that an OFIS comprised of two orthogonal 89-m-long arms having their centers separated by 63 m can resolve the back azimuth of most infrasound signals with a good signal-to-noise ratio. We find a good match between the back azimuths determined with our technique and those determined for the same signals recorded on the co-located pipe array I57US with the Progressive Multichannel Cross-Correlation technique. Based on these results and additional synthetic tests, we have built and are testing a larger OFIS with several arms that will be able to resolve signals from all directions and with small signal-to-noise ratios.
Use of improved propagation models to investigate novel infrasound signals
Authors: Bhattacharyya Joydeep , Gibson Robert
Published: October 2013

The recent availability of improved infrasound propagation modeling tools and the installation of infrasound arrays in regions of sparse cover- age provide new opportunities for analysis of rare signals. Analyses are presented resulting from recent natural and manmade events, and insights are discussed. Events of interest include the train explosion in Iran of February 18, 2004 and the South Asian tsunami event of December 26, 2004. Using near-real-time environmental profiles and infrasound propagation models, it is shown that the predicted travel times, azimuth deviation and signal duration closely match the observed values. As the dataset of such events is small, predictive modeling can be a valuable tool in developing detection strategies for such events and may ultimately lead to a decreased incidence of false alarms in global monitoring.
Spectral integration in speech and non-speech sounds
Authors: Jacewicz Ewa
Published: October 2013

Spectral integration (or formant averaging) was proposed in vowel perception research to account for the observation that a reduction of the intensity of one of two closely spaced formants (as in /u/) produced a predictable shift in vowel quality [Delattre et al., Word 8, 195–210 (1952)]. A related observation was reported in psychoacoustics, indicating that when the components of a two-tone periodic complex differ in amplitude and frequency, its perceived pitch is shifted toward that of the more intense tone [Helmholtz, App. XIV (1875/1948)]. Subsequent research in both fields focused on the frequency interval that separates these two spectral components, in an attempt to determine the size of the bandwidth for spectral integration to occur. This talk will review the accumulated evidence for and against spectral integration within the hypothesized limit of 3.5 Bark for static and dynamic signals in speech perception and psychoacoustics. Based on similarities in the processing of speech and non-speech sounds, it is suggested that spectral integration may reflect a general property of the auditory system. A larger frequency bandwidth, possibly close to 3.5 Bark, may be utilized in integrating acoustic information, including speech, complex signals, or sound quality of a violin.
Similarities and differences in the perception of formant frequency transitions and center-of-gravity glides
Authors: Lublinskaja Valentina
Published: October 2013

In Lublinskaja (1996) the spectral ‘‘center-of-gravity’’ (COG) effect was observed in the identification of synthetic vowels in which the amplitude ratio of F2 and F3 was gradually changed in time, formant frequencies being constant. The stimuli with such virtual formant transitions (VT) were perceived as diphthong-like Russian vowels when F3−F2<4.5 Bark. Within this F3−F2 frequency separation, the stimuli with the dynamic perceptual formant (F2*) were identified as their equivalent vowels with real F2 and F3 transitions (FT). But the perception of both types of transitions was not identical. Generally, the VT signals were less salient than FT. Within smaller F2−F3 separations (F2*=1.68 Bark), the VT signals were first identified with 100%-accuracy as diphthong-like vowels and with larger F2* the glide transitions were gradually less perceptible. With separations F3−F2>4.5 Bark the VT stimuli were identified as stationary vowels, and listeners’ decisions were based on terminal values of F2*. Reduced salience of VT glides relative to FM tones was also reported for non-speech signals [Dawson and Feth, ARLO 5, 95–99 (2004)]. The talk will discuss possible mechanisms for why VT signals are less perceptually prominent than FT sounds.
Lexical representation of novel L2 contrasts
Authors: Hayes-Harb Rachel , Masuda Kyoko
Published: October 2013

There is much interest among psychologists and linguists in the influence of the native language sound system on the acquisition of second languages (Best, 1995; Flege, 1995). Most studies of second language (L2) speech focus on how learners perceive and produce L2 sounds, but we know of only two that have considered how novel sound contrasts are encoded in learners’ lexical representations of L2 words (Pallier et al., 2001; Ota et al., 2002). In this study we investigated how native speakers of English encode Japanese consonant quantity contrasts in their developing Japanese lexicons at different stages of acquisition (Japanese contrasts singleton versus geminate consonants but English does not). Monolingual English speakers, native English speakers learning Japanese for one year, and native speakers of Japanese were taught a set of Japanese nonwords containing singleton and geminate consonants. Subjects then performed memory tasks eliciting perception and production data to determine whether they encoded the Japanese consonant quantity contrast lexically. Overall accuracy in these tasks was a function of Japanese language experience, and acoustic analysis of the production data revealed non-native-like patterns of differentiation of singleton and geminate consonants among the L2 learners of Japanese. Implications for theories of L2 speech are discussed.
Perception of coarticulated tones by non-native listeners
Authors: Bent Tessa
Published: October 2013

Mandarin lexical tones vary in their acoustic realization depending on the surrounding context. Native listeners compensate for this tonal coarticulation when identifying tones in context. This study investigated how native English listeners handle tonal coarticulation by testing native English and Mandarin listeners discrimination of the four Mandarin lexical tones in tri-syllabic sequences in which the middle tone varied while the first and last tones were held constant. Three different such frames were tested. As expected, Mandarin listeners discriminated all pairs in all contexts with a high degree of accuracy. English listeners exhibited poorer discrimination than Mandarin listeners and their discrimination accuracy showed a high degree of context dependency. In addition to assessing accuracy, reactions times to correctly discriminated different trials were entered into a multidimensional scaling analysis. For both listener groups, the arrangement of tones in perceptual space varied depending on the surrounding context suggesting that listeners attend to different acoustic attributes of the target tone depending on the surrounding tones. These results demonstrate the importance for models of cross-language speech perception of including contextual variation when characterizing the perception of non-native prosodic categories. [Work supported by NIH/NIDCD]
Plasticity in speech production and perception: A study of accent change in young adults
Authors: Evans Bronwen G. , Iverson Paul
Published: October 2013

This study investigated plasticity in speech production and perception among university students, as individuals change their accent from regional to educated norms. Subjects were tested before beginning university, 3 months later and on completion of their first year of study. At each stage they were recorded reading a set of test words and a short passage. They also completed two perceptual tasks; they found best exemplar locations for vowels embedded in carrier sentences and identified words in noise. The results demonstrated that subjects changed their spoken accent after attending university. The changes were linked to sociolinguistic factors; subjects who were highly motivated to fit in with their university community changed their accent more. There was some evidence for a link between production and perception; between-subject differences in production and perception were correlated. However, this relationship was weaker for within-subject changes in accent over time. The results suggest that there were limitations in the ability of these subjects to acquire new phonological rules.
Paired variability indices in assessing speech rhythm in Spanish/English bilingual language acquisition
Authors: Work Richard , Andruski Jean , Casielles Eugenia , Kim Sahyang , Nathan Geoff
Published: October 2013

Traditionally, English is classified as a stress-timed language while Spanish is classified as syllable-timed. Examining the contrasting development of rhythmic patterns in bilingual first language acquisition should provide information on how this differentiation takes place. As part of a longitudinal study, speech samples were taken of a Spanish/English bilingual child of Argentinean parents living in the Midwestern United States between the ages of 1;8 and 3;2. Spanish is spoken at home and English input comes primarily from an English day care the child attends 5 days a week. The parents act as interlocutors for Spanish recordings with a native speaker interacting with the child for the English recordings. Following the work of Grabe, Post and Watson (1999) and Grabe and Low (2002) a normalized Pairwise Variability Index (PVI) is used which compares, in utterances of minimally four syllables, the durations of vocalic intervals in successive syllables. Comparisons are then made between the rhythmic patterns of the child’s productions within each language over time and between languages at comparable MLUs. Comparisons are also made with the rhythmic patterns of the adult productions of each language. Results will be analyzed for signs of native speaker-like rhythmic production in the child.
Reconciling data using Markov chain Monte Carlo: An application to the Yellow Sea–Korean Peninsula region
Authors: Pasyanos Michael
Published: October 2013

We present a technique for developing seismic models using multiple data sets using a probabilistic inverse technique. A Markov Chain Monte Carlo (MCMC) algorithm is used to sample models from a prior distribution and test them against multiple data types to generate a posterior distribution. This approach has several advantages over deterministic models, notably the reconciliation of different data types that constrain the model, the proper handling of uncertainties, and the ability to include prior information. We also benefit from the advantage of forward modeling rather than inverting the data. We demonstrate this method by using it to determine the 3-D crust and upper mantle structure for the Yellow Sea and Korean Peninsula (YSKP) region. The model is parameterized as a series of layers in a regular lat-lon grid. We start with an a priori model and use surface wave dispersion measurements, body wave travel times, teleseismic receiver functions, and gravity data to drive the model. The end result is a robust model distribution for the region that is best able to fit multiple data sets, and is consistent with our understanding of the tectonics of the region.
Direct-path rough surface scattering experiments with milled surfaces in acoustic tank facilities
Authors: Soukup Raymond J. , Gragg Robert F. , Summers Jason E. , Kunz Edward L.
Published: October 2013

To investigate specific issues relating to rough surface scattering theoretical predictions, the Naval Research Laboratory has been conducting scaled-down versions of its direct-path ocean bottom scattering experiments. These experiments utilize milled elastic rough surfaces in acoustic tank facilities. Investigations into the dependence of scattering on roughness and geoacoustic parameters lend themselves to a systematic treatment with milled surfaces that are fabricated to match specific roughness spectral parameters. The characterization and fabrication of such rough surfaces, and the methodology for creating experimental geometries that are analogous to previous measurements with elastic ocean bottoms, are described. A set of scattering strength measurements in the 100–300 kHz band with a quasi-monostatic geometry is compared with the theoretical predictions given by perturbation theory and the NRL small slope model. The results show that these experiments are a viable means of verifying the predictions of the scattering models, given a sufficiently large statistical sample. [Work supported by ONR.]
Laboratory study of high frequency scattering from water-saturated sandy sediments
Authors: Ivakin Anatoliy , Sessarego Jean-Pierre , Sanchez Patric
Published: October 2013

Backscattering from a water-saturated well-sorted fine sand and from this sand with various inclusions was studied in a laboratory tank at frequencies from 200 kHz to 3 MHz and grazing angles from 20 to 90 degrees. Acoustic and granulometric properties of the sand are presented and discussed in a companion paper. First, the measurements of the frequency-angular dependencies of the backscattering strength were made for a thick sediment layer with a smoothed surface and without any inclusions in the volume. Then glass beads and coarse sand particles were used as additional scatterers or inclusions placed on the sediment surface or covered by sediment layers of various thickness. The data were compared with a previously reported model of scattering from discrete inclusions in the sediment [A. N. Ivakin, J. Acoust. Soc. Am. 116, 2575 (2004)]. The model inputs are material parameters of the sediment and inclusions and the size-depth distribution of inclusions. The results of model/data comparison are discussed and possibilities for inversion of various sediment parameters from backscattering data are shown.