bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical monitoring of ultrasound-induced damage in glass catfish after injection with contrast agents
Authors: Maruvada Subha , Hynynen Kullervo
Published: October 2013

This work is an investigation of the ultrasound interaction with contrast agent bubbles in the blood vessels of fish in vivo. Glass catfish were used for these experiments because they are optically transparent. Anesthetized fish were injected with the contrast agent, Optison, using microinjection techniques. Shortly after injection, the fish were insonified with one of two single-element focused transducers (1.091 and 0.747 MHz). An inverted microscope combined with a digital camera was used to optically monitor ultrasound interaction with the blood vessels in the tail of the fish at 200× magnification. The entire interaction was videotaped and digitized. The fish were insonified at power levels between 1–80 W, which translated to acoustic pressures from 0.45–3.55 MPa. Sonifications were pulsed with burst lengths of 1 ms, 10 ms, 100 ms, and 100 s, and a repetition frequency of 1 Hz. The entire length of one sonification at a specific power was 20 s. The effects of the sonification were analyzed at each power level. Ultrasound-induced damage to the fish included structural damage to the cartilage rods in the tail, formation of large gas bubbles within the blood vessels, and hemorrhaging.
Enhancement of the biocidal efficacy of a mild disinfectant through enhanced transient cavitation
Authors: Cunefare Kenneth A. , Carter Stephen D. , Ahern Don
Published: October 2013

Cavitation is known to have biocidal effect upon micro-organisms. The work presented here considered the impact of transient cavitation at elevated hydrostatic pressures as a means to improve the biocidal efficacy of otherwise mild disinfectant solutions. Cultures of Bacillus stearothermophilus and Bacillus subtilis were exposed to a mild isopropyl alcohol-based disinfectant for 15 to 18 minutes, which resulted in negligible cell reduction. Spores from the same cultures were exposed to the disinfectant for 15 to 18 minutes while being cavitated for one minute at a frequency of 24 kHz, and at ambient pressure, with an estimated energy density of 70 watts per liter. This achieved cell reduction of approximately 2%. Spores from the same cultures were exposed to the same cavitation field but at a hydrostatic pressure of approximately 210 kPa. The pressure was selected to exploit ‘‘the anomalous depth effect’’ for enhanced transient cavitation. These conditions achieved cell reduction of approximately 90% after 1 minute of cavitation exposure. The results are suggestive of more efficient means of sterilizing the burgeoning numbers of heat sensitive surgical instruments.
Characterization of the noise emitted by a washing-machine due to the pump
Authors: Sanchez Tabuenca Beatriz , Llado Paris Juan
Published: October 2013

The noise sources during the pump operation of a washing machine are: the electric motor, the water–air impulsion, and the structural radiation of the pump-housing, hose, and cabinet. The determination of the sound power level under different working conditions let us identify that the noise emitted by the cabinet vibration was the more noticeable, being irrelevant the noise emitted by the other elements. In order to know which part of the cabinet is the noisiest, the standard ISO-TR 7849 was applied to calculate the contribution of the noise emitted by the structural radiation of each part of the cabinet to the total sound power level. This experimental procedure relates the noise radiated by a structure with its vibration velocity, and it was found that the kick plate was the more relevant element. Once the noise transmission paths have been characterized, the proposals to reduce noise are focused on a new design of the kick plate to make it more flexible and the modification of the join zone of the pump to the kick plate to reduce the force transmitted between both elements. (To be presented in Spanish.)
A study of standing pressure waves within open and closed acoustic resonators
Authors: Daniels C. , Steinetz B. , Finkbeiner J. , Raman G. , Li X.
Published: October 2013

The first section of the results presented herein was conducted on an axisymmetric resonator configured with open ventilation ports on either end of the resonator, but otherwise closed and free from obstruction. In the remaining section we present the results of a similar resonator shape that was closed, but contained an axisymmetric blockage centrally located through the axis of the resonator. Ambient air was used as the working fluid. In each of the studies, the resonator was oscillated at the resonant frequency of the fluid contained within the cavity while the dynamic pressure, static pressure, and temperature of the fluid were recorded at both ends of the resonator. The baseline results showed a marked reduction in the amplitude of the dynamic pressure waveforms over previous studies due to the use of air instead of refrigerant as the working fluid. A sharp reduction in the amplitude of the acoustic pressure waves was expected and recorded when the configuration of the resonators was modified from closed to open. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic pressure amplitudes varied little from baseline measurements.
Interaction of a slot-tone with a pipe
Authors: Billon J. Alexis , Valeau Vincent , Sakout Anas
Published: October 2013

The self-sustained tone generated by a low Mach number free flow impinging on a slotted plate, usually referred to slot-tone, is experimentaly studied. In this work we focus on its coupling with the pipe from which the jet flows out. The jet nozzle and the beveled slot are aligned and have the same large aspect ratio. The tones generated have a single well defined frequency (around 1 kHz), a high amplitude (typically, 105 to 115 dB) and exhibit typical characteristics of self-sustained tones. Their frequencies are about the same order of magnitude than the natural frequency of the shear layer calculated from the linear stability theory. For some Reynolds numbers and some plate distances, a standing wave pattern is observed in the pipe. The outer and inner acoustic fields show high coherence and the slot-tone locks on a pipe eigenmode, which indicates an acoustic feedback. However, especially for lower Reynolds numbers, this coherence vanishes but the self-sustained tones are still present. It suggests that the hydrodynamic feedback becomes preponderant.
Turbulent airflow noise production and propagation patterns of a subsonic jet impinging on a flat plate
Authors: Martin Stephen , Meecham William
Published: October 2013

Turbulent airflow noise production is examined utilizing a four-inch diameter jet impinging on a flat plate. The analysis utilizes cross-correlation techniques to investigate the far field sound pressure relationship to turbulent sources produced near the plate surface. The variables examined include the effects of jet speed, the angle of the plate with respect to the jet axis, the location of the turbulent source from the plate center, the location of the far-field microphone, and the plate-jet distance. The cross-correlation techniques allow discrimination of the far-field sound pressure related to the turbulent noise source located near the surface of the plate. By rotating the far-field microphones, directivity patterns are obtained for a source located a particular distance from the plate center. The resulting cloverleaf shaped directivity patterns indicate a quadrupole source, verifying Powells developments on Lighthills theory on jet noise. The variations of the parameters of the experiment allow a comparison of the directivity patterns for each condition. [Work was performed through the UCLA School of Engineering with the experimental data collected at the NASA-Ames research facility.]
The development of polymer layers for vibration damping steel sheet
Authors: Oh T. S. , Ryou J. H.
Published: October 2013

The characterization of damping resins, and the forming characteristics of vibration damping steel sheets were carried out in order to evaluate polymer layers for vibration damping steel sheets. The bonding strength and damping properties depend on the chemical nature of individual polymers on the vibration damping steel sheets. Polyester-based thermoplastic polymer shows the best performance. Damping characteristics of vibration damping steel sheet can be well predicted from the dynamic loss factor of resins via the WLF equation. The vibration damping properties of polymers can be changed by a plasticizer. It was found that the service temperature of polymer generally decreased using an increasing amount of plasticizer. It is concluded that the vibration damping steel sheet made by the loss factor greater than 0.1 in the range of normal service temperature as well as the tensile shear strength greater than 80 kgf/cm2 at room temperature and the addition of Ni powder have been found to improve weldability the same an ordinary steel sheet. [Work supported by POSCO.]
Development of beam volume displacement sensors using genetic algorithm
Authors: Jangiti Saiprasad , Zahui Marcellin , Bibel George
Published: October 2013

Further development of total (local) volume displacement sensors is presented. This development supports the implementation of noise control techniques that are based on the minimization of local volume displacement of vibrating structures. In this work, a genetic algorithm is used for the design of volume displacement sensors for vibrating beams using PolyVinyliDene Fluoride (PVDF). First the sensor is assumed to cover the entire beam surface. Then, the covered area is discretized into small patches. The algorithm selects the required patches to yield the PVDF shape necessary to measure the beam volume displacement. The sensor is numerically verified for various beam boundary conditions. The results show close agreement between the calculated beam volume displacement of the beam and the simulated output charge of the sensor. The extension of the genetic algorithm methodology to volume displacement sensors for 2-D vibrating structures is briefly discussed.
Interior noise profile of buses in Curitiba
Authors: Zannin Paulo H. T. , Giovanini Clifton R. , Diniz Fabiano B. , Ferreira Jose C.
Published: October 2013

Evaluating the noise levels to which the bus drivers of Curitiba are exposed to during their working days is the main scope of this study. The city is served by an internationally known public transportation system featuring 1902 buses, which attend 1.9 million people per day. Two measurements have been taken inside each one of the 60 buses surveyed, one close to the driver and another one at the back of the bus. The results have showed that the dose levels the drivers are exposed to were below 50% in 92% out of the buses, but the normalized exposure levels were over 65 dB(A) in all cases. This level is considered as the threshold of comfort according to the Brazilian legislation on occupancy health NR-17—Ergonomics. The surveyed buses have been divided into three categories, according to their characteristics: feeder, rapid, and bi-articulated. A total of 20 buses within each category have been surveyed. Among the different categories, it has been found that the feeders have presented the highest noise levels. (To be presented in Portuguese.)
Analysis of the levels of ambient noise present in the Colonia Auditorium (October 2001)
Authors: Jalisco Zapopan , Palafox Lourdes , Orozco Martha , Rodriguez Erika
Published: October 2013

The study area is located in the city of Guadalajara, defined by: delimited in the north by the Gonzlez Gallo street; in the south by the Anillo Perifrico street; in the east by Avenida Mezquitan; and in the west by Avenida Alcalde. There were 38 measurement points outside the auditorium and 25 inside. A poll was conducted among the neighbors and visitors in both areas, getting 70 replies. Noise levels were between 41–101 dB(A) on the outside, average Leq on the outside was 64.5 dB(A), and inside was 80.15 dB(A). The conclusion is that the whole area is affected by traffic noise, as well by the huge number of visitors, the electric games, and the electric generators that supply energy to them. On the outside 21 points were above 65 dB(A), which means that 55% were above the average; on the inside, 100% were above 65 dB(A). Thus the neighbors are exposed to high noise levels due to the festivities during October. The biggest problem, however, is the noise exposure of the workers inside the auditorium, due to music, games, people, and electric generators.
Declaration and verification of noise emission values of machinery and equipment in Russia
Authors: Tsukernikov Ilya Evseevich , Nekrasov Igor Alekseevich
Published: October 2013

Original positions of the interstate standard GOST 30691-2001 are considered, in which the requirements are established to declaration and verification of noise emission values of machinery and equipment, being manufactured in Russia and imported there from different countries. The comparison of the standard with the International standard ISO 4871:1996 is conducted. The main differences are marked. The suggestions for standards revision are made.
Study on the correlation between field experiments and laboratory experiments for audible environmental noise
Authors: Tokashiki Takeshi , Yamashita Yasuhiro , Takagi Naoki
Published: October 2013

Our objective in this study is to clarify, by some experiments, that there would be a different response and that subjective appraisal differs when audible sound types change even under the same sound level. So far various methods that we, appraise sound environment by our subjectivity, have been proposed and utilized. But we have seen a few study cases about the correlation between sound types, subjective appraisal, and, moreover, sound level. In this research, we have surveyed environmental noise in terms of data obtained by physical quantity (LAeq), and subjective appraisal and audible noise types, then examined the correlation between them. Consequently we could confirm their audible sound types might influence noise level and subjective appraisal. Moreover, as a result of the surveillance of noise environment along boulevards, commercial, and residential areas, the sound heard in each area constitutes the same ratios. The data obtained by subjective appraisal on each area is almost the same. This fact indicates we might infer an annoying response through its noise types.
Analysis of Spanish adjectives to develop a Likert scale useful for studies of urban noise annoyance
Authors: Vílchez-Gómez Rosendo , Barrigón-Morillas Juan Miguel , Gómez-Escobar Valentín , Méndez-Sierra Juan Antonio , Vaquero-Martínez José Manuel
Published: October 2013

The present work describes the development and analysis of a Spanish annoyance scale for use in community noise assessments. The use of different descriptors and intervals for different authors prevents comparing studies of assessment of noise reactions. It is not clear how many semantic distinctions can be made to describe subjective reactions to noise. There is also great variability in language use reflecting educational, social class, regional, and subcultural differences. Finally, scaling annoyance responses, when the considered intervals are not equally distributed, may seriously distort results when analyzed with parametric statistics. Using three different questions, almost 400 subjects were asked to rate 25 different Spanish descriptors of annoyance. Our attempt to produce a Spanish standardized annoyance scale with descriptors marking clear semantic distinctions, roughly equidistant from each other, and having wide acceptability is presented here. Taking into account that Spanish is the official language in 21 countries and it is spoken by more than 300 million people, one of our goals in this meeting is to discuss our method and try to generalize it in order to obtain a real, universal Spanish annoyance scale.
Large meteoroid detection using the global International Monitoring System infrasound system
Authors: ReVelle Douglas O.
Published: October 2013

We will review the subject of infrasound from large bolides (large meteor-fireballs) entering the atmosphere at hypersonic speeds and their expected rate of detection by the 60 infrasonic arrays of the global IMS network (International Monitoring System). This will include the details of the generation of a quasiline source blast wave and its subsequent decay for near-continuum flow conditions. We will also discuss new highly refined models of bolide ablation and fragmentation and of known compositional types and their effect on sound and light production. In addition, we will consider the effects of refraction of the waves by the middle atmospheric and tropospheric thermodynamic sound speed and horizontal wind profiles in a range-independent atmosphere so that the characteristic velocity and wave normal directions radiated at the source are conserved during the propagation. Next, we will discuss the detection of the signals and their interpretation in terms of plane wave arrivals regarding the 3-D source location (latitude, longitude, height), the source energy level, etc. Finally, we will use the infrasound data from bolides to estimate the expected steady-state global influx rate, including formal errors, as a function of their observed source energy. Infrasound from recent large events will also be examined.
Observations of infrasonic signals from natural and manmade sources
Authors: Noble John M. , Tenney Stephen M. , Whitaker R. W. , Revelle D. O.
Published: October 2013

We report on data recorded from small aperture (20-m) infrasonic microphone arrays. These data will include the well-observed Pennsylvania bolide of 23 July 2001, space shuttle launches, sounding rocket launches, and local severe storm passages. Data were obtained from two infrasonic arrays in southern Maryland. Analysis results from two independent packages will be presented, including bearing estimates and detector performance. Bolide detection results will be correlated with eyewitness reports of the flight trajectory. Estimates will be made of the bolide source energy from the application of the historical explosion scaling law relating the period at maximum acoustic amplitude. Detection of sounding rockets from over 150 km will be discussed. Finally, data from the passage of several severe storms will be presented showing the detection and tracking of a low-frequency acoustic signature of the storm.
A stopping rule for the conjugate gradient regularization method for ill-posed problems
Authors: DeLillo Thomas , Hrycak Tomasz
Published: October 2013

We present a novel parameter choice strategy for the conjugate gradient regularization algorithm which does not assume a priori information about the magnitude of the measurement error. Our approach imitates the truncated singular value decomposition within the Krylov subspaces associated with the normal equations. Conjugate gradient is implemented using the Lanczos bidiagonalization process with reorthogonalization. We compare our method with one proposed by Hanke and Raus and illustrate its performance with numerical experiments, including an inverse problem of acoustic source detection.
Multipole error estimation of an acoustical boundary-element solver combined with a dual-layer CHIEF approach
Authors: Ochmann Martin , Osetrov Alexander
Published: October 2013

The sound radiation from vibrating structures is studied using an iterative boundary-element method. The starting point is a self-adjoint formulation of the Helmholtz integral equation. The generalized minimum residual method (GMRES) is used for solving the corresponding system of equations. Three aspects of the method are investigated. First, the accuracy of the iterative solver is checked by performing multipole error tests: The body is forced to vibrate with the corresponding surface normal velocity of a multipole. Hence, the radiated sound field is analytically known and can be used for determining the exact error caused by the boundary-element solver. Second, instabilities at irregular frequencies are suppressed by combining the iterative solver with a special variant of the CHIEF method, where the total boundary of the body is retracted to an auxiliary surface lying totally within the interior of the structure. CHIEF points can be placed on such an auxiliary surface. The effectiveness of this combined dual-layer GMRES–CHIEF approach and of the Burton–Miller method will be compared. Third, the radiation from a structure with mixed boundary conditions will be investigated. One part of the surface is coated with an absorbing impedance, another part is vibrating with a prescribed normal velocity.
Phase determination of reverberant structural-acoustic systems using pole and zero distribution
Authors: Betts Juan F. , Fuller Christopher
Published: October 2013

This study investigates the phase behavior of a simple coupled structural acoustic system with high modal overlap. It proposes that phase is simply accumulated across the components making up the structure. Classical dynamic solutions breakdown with high modal overlap and complex geometries, and standard Statistical Energy Analysis (SEA) solutions work well for high modal overlap but give no phase information. Many applications such as active control predictions and time-domain signal analysis require phase information. Results of the investigation show that the amount of damping in the system is very important in the estimation of reverberant phase. The amount of energy lost due to coupling with adjacent subsystems was also demonstrated to be important for both acoustic and structural subsystems. The reverberant phase of an acoustic subsystem was found to be affected more by the inclusion of coupling loss to an adjacent structure than the reverberant phase of a structure attached to an acoustic subsystem. The phase of the overall system is calculated by simply accumulating the phase of each of the subsystems.
Communications/Navigation Outage Forecasting System (C/NOFS) statistical energy analysis
Authors: Betts Juan F.
Published: October 2013

The objective of this study was the assessment of the dynamics response of the Communications/Navigation Outage Forecasting System (C/NOFS) spacecraft due to incident acoustic environments. C/NOFS is space vehicle (SV) launched using a Pegasus launch vehicle (LV). A statistical energy analysis (SEA) model of the SV was developed from a NASTRAN finite-element model (FEM). The study compared the dynamic response of the structural subsystems (panels and structural elements) due to incident acoustic Pegasuss protoflight environment [which is 3 dB above maximum expected flight environment (MEFL)] and compared it against the Mil-340 standard workmanship acoustic levels. A concern was raised as to whether the workmanship acoustics, required by Mil-340, imposed on C/NOFS may induce higher vibration responses than what C/NOFS was qualified for, and may result in unnecessary increases in component test levels. The two incident acoustic spectrums were introduced as reverberant loads on the model. The PSD results at the structural panels were compared to random vibration test levels performed on the components for C/NOFS.
Experimental investigation of sound transmission through thin-walled structures due to nonuniform pressure–fluctuation fields. Part 2: Supersonic flow
Authors: Efimtsov Boris M , Golubev Alexey Yu , Zverev Alexander Ya , Andersson Anders O. , Kravchenko Sergey V.
Published: October 2013

Theoretical models of the sound–energy transmission through thin-walled structures from nonuniform, convecting pressure–fluctuation fields were validated through experiments. The fields were created with separated flows at forward-facing and backward-facing steps and an airfoil as the shock generator. Thin plates and model fuselage panels were used and vibrations and acoustic radiation of the structures were investigated. The data permit a direct comparison with predicted results as well as an evaluation of the validity of the prediction-model assumptions. In particular, the elastic and inertial properties of the skin but not of the stiffeners need to be taken into account. The experiments support the validity of previously reported theoretical predictions.
Sensitivity to voiceless closure in the perception of Spanish and English stop consonants
Authors: Zampini Mary L. , Clarke Constance M. , Norrix Linda W.
Published: October 2013

The duration of voiceless closure that precedes the release of a stop consonant is a temporal cue that, like voice onset time (VOT), varies across languages. This talk will examine the interaction between VOT and voiceless closure in Spanish and English and will focus on monolingual and bilingual listeners sensitivity to changes in the duration of voiceless closure during perception. Experimental data will show that monolingual Spanish listeners mean VOT boundaries decrease as the duration of voiceless closure increases. This pattern is consistent with the finding that Spanish speakers produce voiceless stops with longer voiceless closure durations than voiced stops [K. P. Green, M. L. Zampini, and J. Magloire, J. Acoust. Soc. Am. 102, 3136 (1997)]. It will also be shown that monolingual Spanish listeners show greater sensitivity to voiceless closure than monolingual English listeners. Lastly, the impact that experience with both languages has on perception by late English–Spanish bilinguals will be discussed. It will be shown that the bilinguals under study are affected by their first language (English) while listening to tokens in isolation, but perform like monolingual Spanish listeners when listening to tokens in a Spanish sentence context.
Perception of word-final /t/, /d/, /s/, and /z/ by beginning Spanish-speaking learners of English
Authors: Pikser Roberta , Strange Winifred
Published: October 2013

Previous research has indicated that speakers of Spanish learning English have problems perceiving and producing the word-final /t/–/d/ contrast [Flege, 1992]. In this study we examined whether beginning learners of English from Latin America could distinguish word-final voicing and manner contrasts among /d/, /t/, /s/, and /z/ when produced in three different vowel contexts by two speakers. As expected, subjects had difficulty correctly discriminating the voicing distinction in both stops and fricatives. On average, performance was poorer on /t/–/d/ than /s/–/z/. Subjects had no difficulty distinguishing voiced or voiceless consonants differing in manner. There was a clear vowel effect; performance was poorer on average for voicing contrast in the high front vowel context than for low central and high back contexts, although there were individual differences. There was also a strong speaker effect; subjects more easily identified the /d/–/t/ contrast of the male speaker, who had longer closure durations and stronger release bursts than those of the female speaker.
Effect of age on perceptual learning of second-language phonetic contrasts
Authors: Akahane-Yamada Reiko , Takada Tomoko , Kubo Rieko
Published: October 2013

This paper is a mid-term report on an examination of the effect of age on learning new second language (L2) phonetic categories. Approximately 1000 Japanese speakers of various ages, from children (10 years old) to elderly (70 years old), were trained to identify English words produced by native speakers of American English. The words used minimally contrasted in /r/–/l/ for all age groups (10–70), and words contrasting in /b/–/v/ and /s/–/th/ were additionally used only for the younger age groups (10–22). A pretest–post-test design was administered in which the effect of the training was evaluated by the amount of improvement in accuracy from the pretest to the post-test. Results obtained at this point suggest that: (1) in general, the amount of improvement decreases with age; (2) during the early phases of training, the /r/–/l/ distinction is an extremely difficult one for Japanese children; and (3) elderly subjects, even in their 60s, can improve significantly. Implications for the theories of acquisition of speech perception will be discussed. [Work supported by TAO, Japan.]
Does semantic context help Japanese speakers identify English /r/ and /l/?
Authors: Rothwell Amanda , Akahane-Yamada Reiko
Published: October 2013

Second language learners experience difficulty distinguishing phonemic contrasts that do not occur in their native language. In this study we investigated the effect of providing Japanese speakers with a semantic context when identifying /r/s and /l/s in English words. Questions addressed were: (1) whether semantic context improves performance; and (2) if context helps, whether the written or spoken context is most helpful. Japanese speakers participated in a two alternative forced-choice identification task in which participants identified words they heard by choosing one of two words contrasting in /r/ and /l/. Words were presented either: (a) in isolation; or (b) within contextual sentences in a variety of written and spoken forms. Preliminary results show that Japanese speakers’ identification accuracy of the /r/–/l/ contrast was significantly better when words containing the contrast were presented in contextual sentences than when they were presented in isolation. The amount of improvement in performance was almost equal, whether the context was provided in written or spoken form, or a combination of thereof. These results suggest that a semantic context, both written and spoken, helps second language learners’ identification of difficult phonemic contrasts. Implications of this work on second language learning will be discussed. [Work supported by TAO, Japan.]
Examining developmental patterns of neural activation during the discrimination of native and non-native speech contrasts by American–English adults and children
Authors: Pruitt Jesica C. , Nelson Tobey L. , Pruitt John S. , Kuhl Patricia K.
Published: October 2013

To better understand the effects of language experience on speech perception, the present study examined developmental differences in the neural processes underlying the perception of native and non-native speech contrasts. Native American-English speaking adults and pre- and post-pubescent children participated in a functional magnetic resonance imaging (fMRI) study in which they discriminated non-native consonants from Hindi, Spanish, and Mandarin. The non-native contrasts differed in place of articulation, voicing, and manner. For comparison with the neural data, behavioral data were collected outside the scanner for the non-native and a native contrast (AE r/l) using a child-friendly computer-based testing method that presented the same contrasts to all subject groups. Results are discussed with regard to developmental differences in the location and extent of activation patterns for the native and non-native contrasts and the level of difficulty for the individual contrasts. [Work supported by NICHD grant HD37943 to Patricia K. Kuhl and Talaris Research Institute.]
Native and non-native perception of phonemic length contrasts in Japanese: A categorization study
Authors: Kato Hiroaki , Tajima Keiichi
Published: October 2013

Segment length is distinctive in Japanese, for example, /kaze/ (‘‘wind’’) versus /kaze:/ (‘‘taxation’’). Such length contrasts are not necessarily categorical for non-native speakers. To study this property precisely, a series of perception experiments were conducted. Stimuli were based on a pair of nonsense Japanese words, /erete/ and /ere:te/. A continuum gradually varying between these words was synthesized using STRAIGHT, a high-fidelity speech analysis, synthesis, and manipulation system [Kawahara et al., Speech Commun. 27, 187–207 (1999)]. Three subject groups were tested: (1) English speakers with no Japanese experience; (2) English speakers who had spent 1–6 months in Japan; and (3) native Japanese speakers. All subjects participated in a single-stimulus two-alternative forced-choice identification task. Subjects in the second group were tested a second time after five days of perceptual training on phonemic length contrasts during which they were exposed to 1800 pairs of real Japanese words that minimally differed with respect to vowel length. Results suggest that identification boundaries of English speakers are less sharp than those of native speakers, and that identification boundaries sharpen with both exposure to Japanese and with perceptual training. Implications of these findings for second-language learning will be discussed. [Work supported by TAO, Japan.]
Learning stop-consonant voicing in English: The effect of perceived cross-language similarity
Authors: Baker Wendy , Trofimovich Pavel
Published: October 2013

Previous research has demonstrated that perceived similarity between native- (L1) and second-language (L2) sounds overall influences how accurately L2 sounds are produced. No study, however, has examined whether certain phonetic cues to an accurate production of L2 sounds are susceptible to the influence of perceived similarity between L1 and L2 sounds more than others. In English, vowel duration is the primary cue to distinguishing word-final voiced and voiceless stops (e.g., bad versus bat). A secondary cue to stop-consonant voicing is the duration of the stop-gap closure of word-final voiced and voiceless stops. In this study we examined how perceived similarity between L1 and L2 sounds influences adult L2 learners’ production of these two cues to stop-consonant voicing. Thus specifically examined were vowel and stop-gap closure duration in beginning, intermediate, and advanced native Korean adult learners’ productions of six English vowels in 18 CVt and CVd words. The results of these acoustic analyses indicated that: (1) these two cues to stop-consonant voicing are differentially susceptible to the influence of perceived similarity between L1 and L2 sounds; and (2) perceived similarity between L1 and L2 sounds influences how accurately and quickly these cues are learned.
Earth imaging using seismic migration
Authors: Fehler Michael , Huang Lianjie , Alde Douglas , Sun Hongchaun
Published: October 2013

Most subsurface imaging of the Earth is accomplished using seismic migration, which uses the entire wave forms recorded at the surface. The traditional method for performing migration was to use the Kirchhoff integral using a ray-based Green function to backproject the recorded data to positions of reflectors within the subsurface. Recent developments in Kirchhoff migration include the use of multivalued traveltime tables calculated with methods like wave-front construction ray tracing. Additional advances include the use of ray amplitudes calculated using dynamic ray tracing. Recently, more attention has been given to the development of wave-equation-based methods in which the recorded wave field is backprojected using some approximation to the wave equation. Wave-equation-based methods have grown in acceptance because better implementation of the backprojection operators have been developed and computing capability has allowed the generally slower methods to become more feasible.
3-D tomographic imaging of the geologic structure in the Salton Sea Geothermal Field
Authors: Meyer Alan W. , Hutchings Lawrence J. , Kasameyer Paul W.
Published: October 2013

A three-dimensional tomographic reconstruction of the Salton Sea Geothermal Field is presented. This reconstruction is developed from data gathered in the course of one year between 15 September 1987 and 30 September 1988 using a microearthquake network. This geothermal field is important not only due to understanding potential energy sources but also because it is the result of a tectonic spreading zone bounded between two transverse fault systems: The San Andres system to the North and the Brawley fracture zone (BFZ) to the South. Here magma has penetrated into the crust to a depth of at least 8 km. This magmatic source is responsible for the microearthquakes generated along the BFZ as well as providing the thermal source for the geothermal activity. Using techniques for both blind source estimation as well as blind deconvolution, a travel time tomographic algorithm is applied to these data. The objective is to characterize the subterranean geological structure and estimate the fracturing that supports the geothermal field. These studies are a necessary foundation for future research into the energy capacity of this field. [Work performed under the auspices of the Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
Identification of a reversed-phase compressional in dipole borehole logging. Physical principle, theoretical modeling, and field examples
Authors: Tello Lucio N. , Kozak Marek
Published: October 2013

Dipole array sonic tools are particularly suited for estimating acoustic shear wave velocities in soft, unconsolidated, slow formations in boreholes. Dipole sources induce flexural waves, which are sustained in such formations. By contrast, monopole sources create pseudo-Rayleigh waves, related to shear wave velocity, which, in slow formations, refract away from the borehole and vanish before reaching the receivers. In addition, monopole sources create compressional and Stoneley waves. The typical order of these arrivals is compressional, shear (when present), and Stoneley. In an ideal situation dipole sources excite only borehole-flexural waves. The propagation velocity of the flexural wave is near that of the shear wave. Field experience backed by theoretical modeling indicates that in real situations dipole sources might also generate (reversed-phase) compressional and Stoneley waves. Theoretical simulations using well parameters taken from other logs render nearly identical wavetrains. Verification of the results with seismic measurements further validates the processing.
Transmission mode acoustic time-reversal imaging for nondestructive evaluation
Authors: Lehman Sean K. , Devaney Anthony J.
Published: October 2013

In previous ASA meetings and JASA papers, the extended and formalized theory of transmission mode time reversal in which the transceivers are noncoincident was presented. When combined with the subspace concepts of a generalized MUltiple SIgnal Classification (MUSIC) algorithm, this theory is used to form super-resolution images of scatterers buried in a medium. These techniques are now applied to ultrasonic nondestructive evaluation (NDE) of parts, and shallow subsurface seismic imaging. Results are presented of NDE experiments on metal and epoxy blocks using data collected from an adaptive ultrasonic array, that is, a ‘‘time-reversal machine,’’ at Lawrence Livermore National Laboratory. Also presented are the results of seismo-acoustic subsurface probing of buried hazardous waste pits at the Idaho National Engineering and Environmental Laboratory. [Work performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.] [Work supported in part by CenSSIS, the Center for Subsurface Sensing and Imaging Systems, under the Engineering Research Centers Program of the NSF (award number EEC-9986821) as well as from Air Force Contracts No. F41624-99-D6002 and No. F49620-99-C0013.]
Shallow subsurface applications of high-resolution seismic reflection
Authors: Steeples Don
Published: October 2013

Shallow seismic reflection surveys have been applied to a wide variety of problems. For example, in many geologic settings, variations and discontinuities on the surface of bedrock can influence the transport and eventual fate of contaminants introduced at or near the ground surface. Using seismic methods to determine the nature and location of anomalous bedrock can be an essential component of hydrologic characterization. Shallow seismic surveys can also be used to detect earthquake faults and to image underground voids. During the early 1980s, the advent of digital engineering seismographs designed for shallow, high-resolution surveying spurred significant improvements in engineering and environmental reflection seismology. Commonly, shallow seismic reflection methods are used in conjunction with other geophysical and geological methods, supported by a well-planned drilling-verification effort. To the extent that seismic reflection, refraction, and surface-wave methods can constrain shallow stratigraphy, geologic structure, engineering properties, and relative permeability, these methods are useful in civil-engineering applications and in characterizing environmental sites. Case histories from Kansas, California, and Texas illustrate how seismic reflection can be used to map bedrock beneath alluvium at hazardous waste sites, detect abandoned coal mines, follow the top of the saturated zone during an alluvial aquifer pumping test, and map shallow faults that serve as contaminant flowpaths.
Use of the Bayesian Cramér–Rao bound in seismic exploration and research planning
Authors: Deffenbaugh Max
Published: October 2013

Modern exploration for oil is heavily dependent on seismic data, which is used to detect and estimate properties of subsurface reservoirs. Seismic data is processed by applying a sequence of algorithms to filter, estimate velocity fields, beamform, and invert for reservoir properties. There are multiple algorithms to choose from at each processing step—ranging from simple and inexpensive to complex and costly. The Bayesian Cramér–Rao bound, combined with a statistical model of the signal and noise in seismic data, can be used to predict the information content of a specific data set at each stage in a proposed processing flow. This allows the exploration manager to identify the least-cost processing flow to achieve a certain information goal and to identify when the goal is unachievable at any cost. It can also guide research efforts to those processing steps where the greatest amount of information is being lost.
The feedback phenomenon applied to underwater acoustics
Authors: Roux Philippe , Jordan Jason E. , Kuperman W. A.
Published: October 2013

People are familiar with the feedback phenomenon that results in the loud sound heard when a musician plays an electric instrument directly into a speaker. Feedback occurs when a source and a receiver are connected both acoustically through the propagation medium and electrically through an amplifier in such way that the received signal is simultaneously and continuously added to the emitted signal. A resonance is then obtained when the emitter and the receiver are in phase. The resonant frequency appears to be highly sensitive to fluctuations of the propagation medium. The feedback phenomenon has been experimentally demonstrated as a means to monitor the temperature fluctuation of a shallow water environment [‘‘Acoustic monitoring of the sea medium variability: experimental testing of new methods,’’ by A. V. Furduev, Acoust. Phys. 47, No. 3, 361–368 (2001)]. The goal of our work is to reproduce the feedback experiment using an alternative method that decomposes the feedback phenomenon into an iterative process. Successful reproduction of the feedback is accomplished using a step-by-step algorithm which details the evolution of the system from the initial signal to its steady-state form. These experimental and numerical results illustrate the potential of the feedback process for use in narrow-band acoustical tomography.
The partial wave expansion for scattering in oceanic wave guides
Authors: Dacol Dalcio K.
Published: October 2013

The partial wave expansion for target scattering in oceanic wave guides is obtained via the pseudo-potential method and discussed in detail. The case of sound scattering by multiple objects in an oceanic waveguide will also be discussed. The Fermi pseudo-potential was introduced in quantum mechanics as a means of simplifying problems involving scattering by a multicentered potential including applications to many-body problems. As such, it has direct applications in acoustics. It can also be used to discuss scattering off targets in confining geometries such as the interior of cavities or in wave guides. [Work supported by ONR.]
The split-step Padé–Fourier solution
Authors: Küsel Elizabeth , Espinoza Flor A. , Siegmann William L. , Collins Michael D.
Published: October 2013

At lower frequencies, the split-step Padé solution is at least comparable in efficiency to the split-step Fourier solution [J. Acoust. Soc. Am. 100, 178–182 (1996)]. For deep-water problems in the kilohertz regime, the split-step Fourier solution provides greater efficiency but is not as accurate as the split-step Padé solution. The split-step Padé–Fourier solution combines the attributes of the two split-step solutions to achieve greater efficiency for some problems without sacrificing accuracy. This approach is based on factoring the exact exponential operator by multiplying and dividing by the approximate exponential that is used in the split-step Fourier solution. The multiplicative factor is implemented using the classical algorithm based on the fast Fourier transform. The other two factors are handled together with a rational approximation. Since the oscillation rate of these two factors is much lower than for the exact exponential, an efficient solution can be obtained using a very large range step and a relatively small number of terms in the rational approximation. [Work supported by ONR.]
Influence of shallow water currents on the performance of a broadband time-reversing array
Authors: Sabra Karim G. , Dowling David R.
Published: October 2013

In recent shallow water experiments, the temporal and spatial focusing properties of time-reversing arrays (TRAs) were shown to be robust in a reciprocal medium and useful for underwater applications. The presence of oceanic currents in coastal environments leads to nonreciprocal acoustic propagation. In this case, time-reversal invariance is modified because the propagation speed inhomogeneity depends on the direction of acoustic propagation. Therefore, similarly to phase coherent reciprocal transmissions, a TRA will be influenced by the current-induced effects but not by the scalar contributions due to temperature or salinity. TRA performance, in the presence of steady currents, is investigated both theoretically using a simple first order normal mode formulation and numerically using a parabolic equation code for moving media, GCPEM [D. Mikhin, J. Acoust. Soc. Am. 105, 1362 (1999)]. In a multipath shallow ocean environment, the retrofocus field is shifted relative to its location in a nonmoving medium. This shift depends on the current speed and the range-depth dependency of the ocean current profile because each acoustic mode is influenced differently. The possibility of using TRAs for monitoring coastal currents will be discussed.
A range-dependent propagation model based on a combination of ray theory and plane-wave reflection coefficients
Authors: Hovem Jens M. , Knobles D. P.
Published: October 2013

The paper describes a range-dependent propagation model based on a combination of range-dependent ray tracing and plane-wave bottom responses. The ray-tracing module of the model determines all the eigenrays between any source/receiver pairs and stores the ray histories. The received wave field is then synthesized by adding the contributions of all the eigenrays, taking into account the reflections from the bottom and the surface. The model can treat arbitrarily varying bottom topography and a layered elastic bottom as long as the layers are parallel. In the current version, the bottom is modeled with a sedimentary layer over an elastic half space, but more complicated structures are easily implemented. The new model has been tested against other models on several benchmark problems and also applied in the analysis and modeling of up-slope and down-slope propagation data recorded on a 52-element center-tapered array that was deployed at two locations about 70 miles east of Jacksonville, FL. The paper presents the results of these tests with an assessment of the potential use in connection with geo-acoustic inversion of range-dependent and elastic scenarios. [Work supported by Applied Research Laboratories, The University of Texas.]