bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of traffic noise from additional tolling lanes at Portage toll plaza
Authors: Bensing Silas
Published: May 2008

Electronic toll collecting systems quickly and efficiently move traffic through toll facilities by automatically collecting tolls from individual vehicle transponders. An ongoing study investigates the addition of three electronic toll lanes to the existing twelve lanes at the Portage toll plaza on the Indiana Toll Road (Portage, Indiana, USA), scheduled to be completed by December 2008. The study aims to predict noise levels of the plaza after the addition of the lanes, the hypothesis being that the additional lanes will have little or no effect on the toll plaza noise levels. Noise measurements are being made at locations in the vicinity of the existing plaza with consideration for a nearby residential area. An outdoor noise propagation software (SoundPlan) is used to create a comprehensive traffic noise model for the area under investigation. Test data from the existing site will be compared to the model and used to predict future noise levels.
Traffic noise in shielded urban areas: comparison of experimental data with model results
Authors: Randrianoelina Ando , Salomons Erik
Published: May 2008

Noise maps of cities are commonly produced with rather simple engineering models for sound propagation. These models may be inaccurate in complex urban situations, in particular in situations with street canyons. Street canyons are urban areas that are partly or completely enclosed by buildings, for example a street between two buildings or a backyard surrounded by buildings. In this paper we study sound propagation from a city bus in a street canyon to a receiver in a nearby street canyon. Multiple reflections of sound waves in both the source canyon and the receiver canyon play an important role in the sound propagation. Experimental data are compared with three types of model results: (i) results of a numerical boundary element model, (ii) results of a 1:30 scale model experiment in a semi-anechoic room, and (iii) results of the Dutch standard engineering model, which is similar to the international standard ISO 9613-2. The data are in reasonable agreement with model results (i) and (ii), while the engineering model yields sound levels that are about 10 dB too low.
Identification of noise sources in centrifugal blower with acoustic camera
Authors: Prezelj Jurij , Čudina Mirko
Published: May 2008

A centrifugal blower represents the main noise source in a vacuum cleaner. Noise emitted by the centrifugal blower working as a suction unit has aerodynamic, mechanical, and electromagnetic noise origins. Noise emitted by a suction unit consists of airborne and structure-borne noise. The contribution of the individual noise source to the total noise level depends on the geometry of the suction unit, rotational speed and on the operating conditions. Operating conditions of a suction unit depend on the amount of dust particles in the dust bag and are constantly changing during operation until a zero flow rate is reached. In order to reduce noise of suction unit at broad range of operating conditions, an identification of noise sources needs to be performed. Identification of most important noise sources on the centrifugal blower was performed with an acoustic camera at the design and off-design operation conditions. From the analyses we can conclude that the rotational noise usually prevails at the design point of operation, and that the nonrotational noise prevails at off-design operation. The main source of noise within a suction unit can be attributed to the aerodynamically generated noise, at the design as well as at off-design operation.
Inversion of infrasound signals for atmospheric remote sensing
Authors: Drob Douglas , Garces Milton , Meier Robert , Picone Michael
Published: May 2008

This paper investigates the utilization of observed long-range infrasound signals to improve our knowledge of upper atmospheric winds and temperatures. A series of numerical experiments designed to provide a mathematical framework for implementation of this idea is presented. The statistical performance of a realistic infrasonic upper atmospheric remote sensing network over a range of different environmental and propagation modeling assumptions, source types, and geophysical variables (season, local-time, latitude, etc) is quantified. For a series of fictitious events, infrasonic observables are calculated with 3D Cartesian ray tracer and a series of atmospheric profiles spanning the range of geophysical parameters. These synthetic measurements are then inverted to estimate the original atmospheric background fields.
A low power and low noise infrasound sensor for temporary measurements
Authors: Ponceau Damien
Published: May 2008

Temporary infrasound measurements require low power consumption, reliable, and compact equipments. As a consequence, these equipments are not always as accurate as equipments operating on long term stations. Measurements quality can be affected. DASE has developed a portable infrasound sensor from MB2005 microbarometer. This new microbarometer consists in improved mechanics from MB2005 and in a movement transducer providing a voltage directly proportional to pressure derivate all over infrasound bandwidth and even more: sensor response phase is purely independent from environment (temperature, condensationœ) all over the same bandwidth. Moreover, thanks to its very simple design this sensor needs very low power and is lighter, smaller and cheaper than previous generation sensors. It reaches Infrasound Low Noise Model (IS LNM) down to 0.02 Hz and is very portable as it weights less than 3 kg with less than 1 L. A batch of prototypes has been manufactured and evaluated in lab thanks to an infrasound generator used for routine calibration of microbarometers installed by DASE on some International Monitoring System stations (IMS). Sensors field evaluation is running. First results are promising.
Separation of multiple scatterers in NEWS-TR experiments
Authors: Vanaverbeke Sigfried , De Lathauwer Lieven , De Gersem Herbert , Van Den Abeele Koen
Published: May 2008

Nonlinear elastic wave spectroscopy combined with acoustic time reversal (NEWS-TR) is a promising new methodology for detecting microdamage at an early stage. When dealing with structures which could potentially contain many pointlike nonlinear scatterers, there is a need to develop techniques for separately imaging the defects using a distributed sensor network which acts as a time-reversal mirror. In this contribution, we present numerical simulations of a newly developed version of the DORT method for nonlinear imaging and also discuss the possibility of applying PARAFAC (parallel factor analysis) and ICA (independent component analysis) methods to solve the problem of separating multiple nonlinear scatterers in the time-frequency domain.
Lamb waves filtering by waveguides with linear varying section
Authors: Hamitouche Zahia , Ech-Cherif El-Kettani Mounsif , Djelouah Hakim , Izbicki Jean-Louis
Published: May 2008

This experimental and numerical work deals with the study of Lamb modes propagating in a plate with a linear variation of thickness. The varying section area exhibits a filtering phenomenon for Lamb modes having a frequency-thickness cutoff. If the incident Lamb wave, excited at a given frequency and propagating downslope, reaches its thickness cutoff in the varying section area, it is reflected and propagates upslope. Otherwise, it is transmitted outside the varying section domain with modes conversion. The S2 incident mode is a particular case: when it reaches its cutoff, it is converted into the S1 mode with negative groupe velocity and a downslope propagation; then the S1 Lamb wave is reflected at its cutoff. The experimental and numerical studies are in good agreements.
Viscosimetry using a new electromagnetic-acoustic microbalance
Authors: Caplain Emmanuel , Serfaty Stéphane , Griesmar Pascal , Le Huerou Jean-Yves , Wilkie-Chancellier Nicolas
Published: May 2008

The nanostructure evolution of gels, biomaterials or porous media can be characterized by its mechanical properties. Few nondestructive techniques are developed to investigate the viscosity evolution. This paper present a new electromagnetic-acoustic technique using a wireless thickness shear mode transducer. A suitable model of the measurement is also presented to characterize the viscosity of the nanostructure in contact with the transducer. This transducer is a double copper-clad PVDF substrate resonator, designed to operate over a wide radiofrequency range without lumped tuning capacitors. This architecture constitutes an alternative solution to design a high-Q ultrasonic microbalance. To characterize the material at the surface of the transducer, the evolution of the induced complex impedance is measured. From this evolution, the mechanical energy storage and dissipation in the material can be extracted. In order to validate the lumped element model used, a series of glycerol/water mixtures is studied. We show that the resonant frequency shift and damping follow an accurate linear shape (<5%) according to the square root of the liquid viscosity and density product. This result is in good agreement with the classical prediction of Martin and Kanazawa obtained with a quartz crystal microbalance.
Nondestructive evaluation of heterogeneous materials using acoustic emission and ultrasound
Authors: Faiz Adil , El Guerjouma Rachid , Bentahar Mouras
Published: May 2008

Heterogeneous materials as composites and concrete are advantageous as structural components in many applications. However, damage detection in such materials is difficult due to their heterogeneity and anisotropy. Furthermore, conventional non destructive technique as x-radiographic is mostly not very sensitive to early damage and very time consuming and expensive. The purpose of this contribution is to study the capabilities of several methods, nondestructive and very sensitive for damage characterisation, as acoustic emission (AE) and ultrasonic for the structural health monitoring of heterogeneous materials as polymer based composite materials and concrete. These materials are instrumented by piezoelectric sensors in order to detect acoustic emission and to measure the ultrasonic velocity. The mechanisms of the damage events and their space-time localizations are identified from AE. Simultaneously, the longitudinal ultrasonic velocity is measured in situ by transmission through the composite thickness. The AE is very well correlated with the loss of stiffness determined from ultrasonic velocity measurements showing the potentiality of this combined approach for in situ structural monitoring.
Close listening of a permanently degassing volcano: Yasur (Vanuatu)
Authors: Zielinski Christelle , Vergniolle Sylvie , Lardy Michel , Le Pichon Alexis , Frogneux Michel
Published: May 2008

Acoustic measurement is a very powerful technique to monitor gas volume and pressure at a safe distance of a volcano. Since eruptions are driven by a gas phase, acoustic recordings of eruptions can provide insights into the degassing processes. The permanent activity of Yasur volcano (Vanuatu) has been acoustically monitored continously to detect and understand the sudden increases in the volcanic degassing. In the absence of appropriate modeling of the sound source, we have used a dimensionless analysis of our infrasonic records close to the source to relate acoustic power and the velocity of the gas - ejecta mixture. Our one-year dataset at the source shows several sudden increases in gas flux over one week as well as more progressive evolution, over several months. Explosions are also detected using a method based on wavelet decomposition. This shows that most of the changes in gas flux are related to strong changes in the number of explosions. Understanding the origin of these variations has strong implications for hazards assessments.
Experimental study of the convergence of two-point cross-correlation toward the Green's Function
Authors: Gouedard Pierre , Roux Philippe , Campillo Michel , Verdel Arie , Campman Xander
Published: May 2008

Cross-correlation of seismic noise recorded at two points yields the Green's Function (GF) between the two points when seismic noise is spatially and temporally diffuse. Seismic events yield the same result (1) when direct waves are cross-correlated from sources that are azimuthally distributed or (2) when coda waves are cross-correlated whatever the source distribution. In this work, the question of convergence toward the GF is investigated with real data. From a high-resolution survey with dense arrays of geophones and sources, we select different sets of sources and time windows to compute the cross-correlation between two receivers. We compare correlations derivative with the actual GF, and show the influence of source locations and scattering on the GF reconstruction. For direct waves, sources located in the endfire lobes of the receiver pair have an essential contribution. With sources located outside the endfire lobes, the GF can nevertheless be retrieved using coda waves.
Role of peripheral nonlinearities in across-frequency processing of envelope fluctuations in normal hearing and hearing impaired listeners
Authors: Verhey Jesko , Rennies Jesko , Ernst Stephan M.
Published: May 2008

A psychoacoustical phenomenon related to the ability of the auditory system to compare information across frequency is comodulation masking release (CMR). CMR describes the effect that signal detectability of a sinusoidal signal embedded in a masker at the signal frequency can be improved by simultaneously presenting additional maskers in off-frequency regions if the additional maskers and the on-frequency masker (OFM) component have the same temporal envelope. Recently it was proposed that peripheral nonlinear processes such as suppression may account for large proportions of the CMR in conditions with a large spectral distance between the masker components. The aim of the present study was to test this hypothesis by measuring suppression and CMR within the same subjects for various frequency-level combinations of the off-frequency masker component. Average data for normal hearing listeners show a large overlap between the existence regions for suppression and CMR. The hearing impaired subjects with a sensorineural hearing loss show a negligible suppression and CMR. The data support the hypothesis that peripheral nonlinearities play an important role in CMR experiments with large spectral distances and large level differences between the masker components.
Cross-spectral integration of speech patterns by normal and impaired listeners
Authors: Healy Eric W.
Published: May 2008

According to the current session description, “Recent evidence suggests that speech recognition depends importantly on the ability to integrate information across the frequency spectrum, which is not accounted for by the sensitivity (information content) of the respective spectral regions.” Indeed, temporal speech patterns that yield near zero intelligibility when presented individually can provide intelligibility in excess of 80% when presented in pairs. These and other recent data involving the integration of speech patterns across the spectrum by the normal auditory system will be described. In addition, “speech-recognition data supporting the existence of a cross-spectral integration deficit in hearing-impaired patients” will be discussed and contrasted against similar experiments involving non-speech stimuli.
Several properties of distortion product otoacoustic emissions can be modeled by simple input/output functions
Authors: Fahey Paul , Martin Glen K.
Published: May 2008

Distortion product otoacoustic emissions (DPOAEs) often exhibit regular patterns in both amplitude and phase as functions of both the levels and frequencies of the generating primary tones. Many of these patterns can be approximated when modeled by simple input/output functions. In particular, nulling patterns in rabbit DPOAEs and their modifications upon noise damage or fatiguing tonal exposures can be modeled at the level of input/output functions. Also, input/output functions can be used to propose the possible physics that underlies some complicated DPOAE patterns in level/frequency space that occur in the presence of a third tone. Both data and models will be reviewed.
Temporal suppression and augmentation of click-evoked otoacoustic emissions
Authors: Verhulst Sarah , Harte James M. , Dau Torsten
Published: May 2008

This study investigates and models temporal suppression of click-evoked otoacoustic emissions (CEOAEs). This suppression-effect is created when a suppressor-click is presented close in time to a test-click. The analysis was carried out for short time-frames of short- and long-latency CEOAEs. The latter is defined as a CEOAE with duration greater than 20 ms, typically observed for test subjects with spontaneous otoacoustic emissions (SOAEs). Previous studies have tended to exclude these test subjects but they are incorporated here. The results from six exemplary subjects demonstrate that temporal suppression is present in all CEOAEs for inter-click intervals (ICIs) less than 8 ms. The long-latency CEOAEs showed augmentation (i.e., negative suppression) for ICIs of 6-7 ms which was not reported for the short-latency CEOAE at these ICIs. A phenomenological approach is adopted here to explain both temporal suppression and augmentation of CEOAEs. Recently, a feedback automatic gain control (AGC) system has been used to model CEOAE suppression. However, this system cannot account for augmentation and therefore another, dynamic nonlinear model was developed. Suppression and augmentation were modeled phenomenologically using compression or expansion of the system output. This was obtained by shifting the operating-point on the input/output-characteristic in relation to the ICI.
Deploying successfully Laser Doppler Vibrometry techniques within the automotive NVH process
Authors: Batel Mehdi
Published: May 2008

Laser Doppler Vibrometry is becoming today an established technique and the gold-standard for noncontact measurements in the automotive industry. These methodologies are widely used to characterize the mechanical behaviour of structures in vibration or strain, with always zero mass loading. They provide high precision results with very low operating costs as well as optimized setup times. The applications of laser vibrometry in the automotive industry are extremely various, and are helping today automotive professionals to improve dramatically the NVH performance of components and full vehicles. This paper explains how these methodologies are fitting today in the everyday challenge of automotive NVH Test & CAE engineers: providing best in class noise and vibration quality with mass reductions constraints. A new laser scanning technique including the use of a 3D robot is also presented, providing an innovative way to characterize the dynamics of body structures with very high precision and rapidity. The paper will present a measurement performed on a full vehicle (43 robot positions done in 1h30 hour), with 1094 points of vibration data at 1 Hz resolution.
Application of digital speckle interferometry for vibration analysis of a statically loaded vehicle tyre
Authors: Borza Dan , Nistea Ioana
Published: May 2008

Vehicle noise has, as one of its main sources, tyres and their interaction with the road. Experimental analysis of tyre vibroacoustic behaviour may provide useful information on the contributions of various regions of the tyre to the resultant noise. Digital speckle interferometry represents a reliable and efficient choice for vibration analysis, providing full field and real time information on surface displacement. The optical configuration used for this study is a standard out-of-plane sensitive setup, based on a continuous wave YAG laser. A 4 bucket phase stepping algorithm is applied, with the use of a piezo actuator, in order to eliminate the random phase difference between the object and the reference wave. The measurement results are images of the tested tyre, covered with interference fringes, representing contour maps of out of plane vibration amplitudes. This paper presents measurements for the case of a tyre subjected to a point excitation at the limit of the contact surface with the road, under statical load of 4 kN. The principal resonant modes and frequencies are presented, then difficulties related to sensibility vector variation over the test surface and coupled mode resonances are discussed.
Adaptive threshold estimation for speaker verification systems
Authors: Castilllo-Guerra Eduardo , Díaz-Amador Roberto , Julian Cárdenas-Barreras L.
Published: May 2008

This paper describes an adaptive threshold estimation mechanism for speaker authentication systems. The mechanism estimates speaker-dependent thresholds based on successful verifications considering the minimization of a relation-based cost function. Speaker authentication systems commonly use a threshold to decide whether a claimed identity matches a voice-print previously enrolled. Speaker independent threshold is a common option but it does not consider specific speaker characteristics that are relevant to achieve better system performance. Speaker dependent threshold on the contrary, uses speaker-specific data to estimate individual thresholds but the system performance can also suffer from suboptimal threshold conditioned by limited number of true scores. The algorithm reported in this paper starts with the speaker dependent threshold and use an adaptive algorithm to perform online re-estimation of the initial threshold based on speaker-dependent data. The threshold is re-estimated in each successful authentication transaction according to a custom-made confidence score. The reported technique keep the voice print up-to-date while is less sensitive to score outliers than traditional speaker dependent threshold. The algorithm provided a performance enhancement of up to 36.2% when compared to traditional speaker independent or dependent threshold using an ad-hoc database involving cell and land-line utterances from male and female speakers.
Proposition of new acoustical parameters to analyze the 3D spatial composition of sound in music spaces
Authors: Bassuet Alban A.
Published: May 2008

From acoustic measurements conducted in more than 100 renowned historical music spaces, for the Constellation Project, this paper proposes new acoustical parameters created to better describe the 3D spatial composition of sound in music spaces. Using B-format recordings, the author is proposing a visualization algorithm to plot the acoustic intensity at specific time frames and ranges. The acoustic energy is decomposed into relevant space segments and energy ratio parameters LH (lateral frontal high versus lateral frontal low), and FR (lateral rear high versus lateral rear low) are deduced and proposed for analyzing the distribution of sound and the envelopment characteristics of the room. Examples of intensity plots and of the proposed 3D acoustical parameters are given for various room types ranging from small to large concert halls, small to large opera houses, famous organ churches and Roman basilicas.
Adjustable acoustics --- Coupled volumes in Artec concert halls: an extravagance or necessity
Authors: Nakajima Tateo , Doria Damian J. , Arenius Edward , Morgan Andrew
Published: May 2008

Led by its founder, Russell Johnson, Artec has developed an unequalled body of experience in the practical application of coupled volumes in the design and construction of concert halls. This paper will present a survey of selected past and future Artec projects from the point of view of the artists and venue managers that perform and work in these halls on a daily basis. Are adjustable acoustics an extravagance or a necessity? What practical problems have been encountered and are they inherent in the concept of adjustability or can they be avoided? How have the musicians reacted? And what is the future of adjustable acoustics?
Coherence of tracked arrivals in SPICEX
Authors: Dzieciuch Matthew , Cornuelle Bruce , Worcester Peter
Published: May 2008

In the fall of 2004, 250 Hz broadband signals were received at 500 km and 1000 km ranges on a near full water-column vertical array in the North Pacific ocean. Individual ray arrivals of very high SNR could easily be identified and tracked using a turning-point filter (time-delay beamforming accounting for channel structure), thus providing accurate vertical coherence estimates. The observations can be compared to standard Monte Carlo estimates of coherence made using accurate parabolic-equation acoustic propagation in an ensemble of ocean states consistent with the standard Garrett-Munk ocean internal-wave spectrum. Acoustic coherence can also be expressed as a depth- dependent structure function. This is naturally estimated by the full-wave travel-time sensitivity kernel (TSK) which provides a linearized transformation from the internal wave spectrum to the structure function. Environmental measurements were conducted almost concurrently with the acoustic trials, constraining the acceptable ocean variability. Allowances must be made for scattering by sound-speed variability along isopycnals (spiciness) in the upper mixed layer. The most important conclusion to date is that the vertical coherence is depth-dependent but this statement must be qualified by the ability of the beamformer to separate arrivals.
High-frequency broadband acoustic current tomography in shallow water
Authors: Luo Jing , Karjadi Entin A. , Badiey Mohsen
Published: May 2008

To study current tomography in very shallow water regions a simultaneous oceanographic and broadband (1-25 kHz) acoustic experiment was conducted in the Delaware Bay. The mean water depth was 15 m and the source-receiver range was 760 m. In this paper, we discuss the feasibility of using reciprocal acoustic transmission for current tomography applications. A beamforming technique is used to resolve the arrival time of direct and surface-bounced rays since in shallow water the received acoustic signals are more complicated due to multiple interactions with bottom and sea surface. Using the experimental data, the accuracy of travel time measurements for variable environmental conditions is examined for different center frequencies and bandwidths. The current velocity prediction results are compared with ADCP measurements to determine the feasibility of current tomography in shallow water.
Deconvolution of freehand 3D ultrasound data using improved reconstruction techniques in consideration of ultrasound point spread functions
Authors: Hewener Holger J. , Lemor Robert M.
Published: May 2008

Medical ultrasound data suffers from blur caused by the volume expansion of the pressure field of the mechanical wave. This blur is dependent on the used excitation pulse and focusing of the ultrasonic wave and can therefore be examined. In order to improve the overall system resolution for 3D ultrasound reconstructions we have to know this signal degeneration to compensate it using deconvolution techniques or multicode compounding during the volume reconstruction step. Looking at the ultrasound transfer function we can focus on the simulation and measurement of the “point spread function” especially in the lateral and elevational direction. To understand its effects on a 3D reconstruction we compute a simulation of freehand-ultrasound slices based on synthetic phantom structures and given US parameters. Computing a 3D reconstruction of these simulated slices we are able to optimize the reconstruction algorithm itself to archive better resolution in the volume data sets considering ultrasound parameters like beamforming and the excitation pulses.
Vocal symptoms in preschool teachers and the working environment
Authors: Jonsdottir Valdis Inigbjörg
Published: May 2008

Research has shown that teachers experience a high risk of developing voice problems. Noise levels in classrooms with young children are higher than in classrooms with older students, indicating preschool teachers' voices may be at greater risk. Questionnaires were sent to 88 preschool teachers in five preschools in Akureyri, and the parents of the 424 children in daycare. The study was aimed to obtain information about (1) teachers: experienced vocal symptoms, occurrence of vocal symptoms, opinions on working environment; air quality, noise, heat, acoustics. (2) parents: children's hearing problems. The study also aimed to ascertain noise levels and reverberation time in pre-school classrooms, and to compare teachers' reported ages, teaching experience, vocal symptoms and frequency with findings in other studies. Sound and reverberation-time measurements were taken by the Icelandic Department of Occupational Health and Safety. Reported vocal symptoms were more common among preschool teachers than other teachers, even though their youth and lack of teaching experience was marked. They appeared to be workrelated. 40% of the children had a history of hearing problems. Noise levels measured were very high. Correlation was found between voice fatigue and high temperature, bad indoor air, and poor acoustics.
Acoustical evaluation of nonclassroom university learning spaces
Authors: Hodgson Murray , Garcia Moreno Jorge
Published: May 2008

This paper reports the results of an acoustical evaluation of non-classroom learning spaces at UBC. In twelve buildings, 25 indoor spaces -- a restaurant, a cafeteria, libraries, dedicated study spaces, building atria, etc. -- used for learning activities by at least 50 people were studied. The evaluation involved physical and acoustical (reverberation time, sound propagation, Speech Intelligibility Index) measurements, and occupant activity and satisfaction questionnaires. Questionnaires were administered three times (morning, lunchtime, and afternoon) on one day. The questionnaires asked about satisfaction with, and the effects of, the acoustical and nonacoustical environments. The acoustical measurement results were compared with established acceptability criteria. Questionnaires were analyzed for differences between times of day, test space, etc. The questionnaire responses and acoustical-measurement results were correlated. Using both as possible predictors, multivariable-regression models for predicting and explaining occupant satisfaction with, and the effects of, the acoustical environment were developed.
Soundfield amplification is a poor substitute for good classroom acoustics
Authors: Lubman David , Sutherland Louis C.
Published: May 2008

Soundfield (amplification) systems are widely and often aggressively marketed for small classrooms. In June 2006, the Acoustical Society of America (ASA) issued a public position statement on the use of sound amplification in typical small classrooms http://asa.aip.org/amplification.pdf. This paper attempts to explain why the ASA found that soundfield systems are poor substitutes for good acoustics. Good acoustics for learning requires unoccupied classroom noise levels of 35 dBA or less and midfrequency reverberation times of 0.6 s or less. At the same time, it is recognized that centralized amplifiers and sound distribution systems can provide valuable educational benefits in small classrooms with good acoustics. Such systems are useful for multimedia presentations and voice reinforcement. The authors urge that this message be brought to the attention of educators and educational facility decision makers.
Validating upper-wind models using infrasound from active volcanoes
Authors: Le Pichon Alexis , Antier Karl , Vergniolle Sylvie , Lardy Michel , Drob Douglas
Published: May 2008

Known and quasipermanent infrasonic sources are needed to evaluate and improve upper-wind models. Infrasounds generated by active volcanoes offer a unique opportunity for atmospheric studies. The Yasur volcano in the Vanuatu archipelago is an outstanding source of infrasonic waves due to its regular activity. This volcano is permanently monitored by the IS22 infrasound station located in New Caledonia and by one microbarometer installed close to its crater. A five-year monitoring period of Yasur at short and large propagation range provides new insights on quantitative relationships between infrasonic observables and atmospheric specifications. This experimental setting is proposed to validate consistently the Naval Research Laboratory Ground to Space (NRL-G2S) semi-empirical atmospheric model up to the stratosphere. The propagation modeling results accurately explain seasonal changes as well as small short-timescale variations of the infrasonic observables. This study demonstrates that the use of appropriate propagation tools along with the NRL-G2S specifications provides accurate enough results for most of the long-range observations for the purpose of operational infrasound monitoring.
Semianalytical modeling of plate flexural waves generated by laser-initiated air shock waves
Authors: Georgiev Vasil B. , Krylov Victor V. , Qin Qin , Attenborough Keith
Published: May 2008

The paper describes the results of the semianalytical modeling of the interaction of laser-initiated air shock waves with an infinite elastic plate. The impact of the incident shock wave on the plate has been approximated by an equivalent cylindrically diverging surface force resulting from the combined surface pressure of the incident and reflected shock waves. This force has been then represented in the wave number-frequency domain by means of Hankel and Fourier transforms which have been carried out numerically - and the problem has been solved using the Green's function method applied to an infinite plate. The resulting frequency spectra and time histories of the generated flexural wave pulses have been calculated for different values of laser pulse energy and for different heights of the laser beam focusing above the plate surface. The obtained theoretical results have been compared with the results of the reduced-scale model experiments on shock wave interaction with the ground in which large plastic and wooden plates have been used to represent the ground surface. The comparison shows that the obtained semi-analytical results are in good agreement with the experimental ones.
Nonlinear parabolic equation model for finite-amplitude sound propagation in an inhomogeneous medium over a nonflat, finite-impedance ground surface
Authors: Leissing Thomas , Jean Philippe A. , Defrance Jérôme , Soize Christian
Published: May 2008

A nonlinear parabolic equation (NPE) model for weakly nonlinear sound propagation in an inhomogeneous medium is described. The model being formulated in the time domain, complex impedances cannot be used to simulate ground surfaces. A second NPE model is thus derived to include the medium in the computational system. Based on a nonlinear extension of the Zwikker-Kosten model for rigidly-framed porous media, it allows to include Forchheimer's nonlinearities. Both models are then adapted to terrain-following coordinates, and used together with an interface condition, allow to simulate finite-amplitude sound propagation over a nonflat, finite-impedance ground surface. Numerical examples show that the NPE model is in good agreement with the solutions of the frequency domain boundary element method. Applications of this model to the simulation of sound propagation from explosions in air are then discussed.
A higher order parabolic equation for predicting in-duct propagation in high frequencies
Authors: Malbéqui Patrice
Published: May 2008

Complementary methods are required to predict the in-duct propagation in a large frequency range including the linear absorption and the flow effects. Numerical methods solving the Euler's equations are pertinent for rotational flow but limited to the low frequencies. The Boundary Element Method is applicable in a large frequency range assuming a homogeneous flow. The ray-model is valid in high frequencies but scattering effects are difficult to implement. This paper presents the capabilities of a Higher-Order Parabolic Equation (HOPE) to handle duct propagation in the high frequency range. In contrast with the so-called standard PE and the wide-angle PE, the HOPE improves the accuracy of the solution due to its wider propagation aperture angle, especially close to the cutoff frequency. Several duct propagation configurations including flow and liner are considered. Using a marching algorithm, the HOPE computes in a very short CPU time the sound propagation and represents an attractive alternative to the ray-model in the high frequency range. [Work supported by Airbus-France.]
Trapped wave in plan waveguides including gaussian varying section domain
Authors: Marical Patrick , Ech-Cherif El-Kettani Mounsif , Hamitouche Zahia , Predoi Mihai Valentin M.
Published: May 2008

In previous works on plan waveguides including an area of varying section of Gaussian shape, we have observed experimentally and numerically the existence of a trapped wave in the Gaussian varying section domain in the case of the A1 incident Lamb mode. The purpose of this work is to highlight the existence of this trapped wave, depending on the equation of the Gaussian profile of the varying section domain. This study is carried out numerically using FEM, as our numerical model has been previously validated. The results obtained show that the phenomenon of trapped wave is strongly linked to the Lamb wave conversion phenomenon: when the incident Lamb wave gives rise to a trapped wave, it is systematically converted into other Lamb waves transmitted outside the area of varying section. Otherwise, it is totally transmitted without any conversion and in this case, any trapped wave exists. The conversion phenomenon is quantified and we show that it is important and depend on the breaking symmetry of the incident Lamb mode by the varying section area.
Laser optoacoustic study of near-critical states and phase transitions in metals
Authors: Ivochkin Alexander Y. , Kaptilniy Alexander G. , Karabutov Alexander
Published: May 2008

Pulsed laser optoacoustic technique is used for generation and study of near-critical states and phase transitions in metals. Metal surface is confined by a layer of transparent dielectric. In this case the efficiency of pressure generation is much greater than in case of the free surface so it is possible to achieve states of metals with relatively high thermodynamic parameters: P ∼104 atm and T ̃ 104 K with a table-top laser system. The experimental setup for simultaneous measurements of pressure, temperature, and reflectivity of metal surface with nanosecond temporal resolution was assembled. Q-switched Nd:YAG laser with pulse duration ̃ ∼10 ns and pulse energy ∼1 J was used. Pressure was measured using LiNbO3 piezotransducer. Temperature was obtained with optical pyrometer. Lead and mercury were chosen as test metals. Pressure pulses up to 1 kbar in lead and up to 7 kbar in mercury (with T ∼2400 K - super-critical area of the phase diagram for Hg) were obtained. The curve of laser heating process in P-T coordinates was plotted. The measurements of optical properties showed considerable decrease of surface reflectivity both for lead and mercury at high laser fluences due to increase of temperature and density decrease.
Towards a theory for arbitrarily shaped sound field reproduction systems
Authors: Spors Sascha , Ahrens Jens
Published: May 2008

The simple source approach predicts that a distribution of appropriately driven loudspeakers (secondary sources) enclosing a given listening area is suitable for the physical recreation of any desired exterior virtual sound field within that listening area. A specific class of sound reproduction approaches (e.g., higher-order Ambisonics) is based upon the explicit solution of the simple source formulation with respect to the secondary source driving function. To the knowledge of the authors, such an explicit solution is currently only available for specific geometries of the sound reproduction system. This contribution presents a theoretical framework for the derivation of the explicit solution for the driving function of arbitrarily shaped secondary source arrangements. It is based upon the expansion of the reproduced wave field into a series of orthogonal basis functions. These basis functions emerge from the respective underlying geometry. It is shown that most of the sound reproduction systems that are based upon the simple source formulation can be seen as specialization of the presented approach to a particular geometry and basis function.
Numerical computation of reflected and transmitted waves at a fluid/solid interface
Authors: Bossy Laure , Cugnet Marie-Françoise , Bossy Emmanuel , Cassereau Didier
Published: May 2008

In this paper, we propose a numerical computation of the different waves generated when a spherical incident pulse is reflected and transmitted by a fluid/solid interface. In addition to the standard reflected and transmitted waves that propagate inside the volume, various surface waves can also be found in both propagation media. In the fluid, we can observe the longitudinal and transverse head waves, and the so-called leaky Rayleigh wave that generalizes the Rayleigh wave in a semi-infinite free solid medium to the case of an immersed interface. Similar effects can also be observed on the transmitted displacement field inside the solid material. We compare different numerical approaches, including semianalytic methods (high-frequency approximation coupled to ray modeling approach) and implicit methods (finite elements and/or finite differences scheme), each method having its own advantages and inconvenients, and domains of validity. These different methods are used to evaluate the field reflected by the interface ; the transmitted displacement field is also analyzed from the same point of view. The plane and curved geometries will be analyzed and the influence of the curvature of the interface will be pointed out.
The perceptual flow of phonetic feature processing
Authors: Greenberg Steven , Christiansen Thomas Ulrich
Published: May 2008

How does the brain process spoken language? It is our thesis that word intelligibility and consonant identification are insufficient by themselves to model how the speech signal is decoded - a finer-grained approach is required. In this study, listeners identified 11 different Danish consonants spoken in a Consonant + Vowel + [l] environment. Each syllable was processed so that only a portion of the original audio spectrum was present. Three-quarter-octave bands of speech, centered at 750, 1500, and 3000 Hz, were presented individually and in combination with each other. The conditional, posterior probabilities associated with phonetic-feature decoding were computed from confusion matrices in order to deduce the temporal flow of phonetic processing. Decoding the feature, Manner-of-Articulation, depends on accurate decoding of the feature Voicing (but not vice-versa), and decoding Place-of-Articulation requires precise decoding of Manner (but not the converse). From these data, we conclude that Voicing is processed prior to Manner-of-Articulation, and that Manner is decoded prior to Place-of-Articulation. Voicing and Manner cues are often correctly decoded in conditions where Place is not. This asymmetric pattern of feature decoding may provide extra-segmental information of utility for speech processing, particularly in adverse listening conditions.
Can CV intelligibility predict speech intelligibility
Authors: Hawkins Sarah
Published: May 2008

This paper begins by reviewing the speech perception literature to predict cues that would and would not be expected to survive energetic masking of various types. The focus is especially (but not exclusively) on spectrotemporal cues to stops in the vicinity of the segment boundary in CV syllables. The second part of the paper discusses influences that can restrict the generality of research findings from isolated CV syllables. This includes ways in which CV syllables change in different phonetic contexts and styles of speech, contributions of the visual modality, and other uses of top-down information, such as phonotactic, lexical, semantic and syntactic probability. The paper concludes by asking whether-and how-simple measures such as CV intelligibility can be used to reflect intelligibility of speech in real-life communicative situations.
Hydroacoustic blockage prediction and measurement at Diego Garcia using the Adiabatic Mode Parabolic Equation Model
Authors: Upton Zachary , Collins Michael D. , Pulli Jay
Published: May 2008

Underwater explosion monitoring with sparse sensors at long ranges relies on the efficient propagation of acoustic energy in the sound fixing and ranging (SOFAR) channel. When sound traveling in this channel encounters an island or seamount, it will either diffract, scatter, or be converted into seismic energy. Signals observed on the opposite side of these obstructions have been affected by some combination of these processes, and models of global detection and localization depend on knowing these effects. We present a study using the Adiabatic Mode Parabolic Equation (AMPE) model to predict these processes in three dimensions at the Chagos Archipelago. Predictions at 5, 10, and 20 Hz are compared with measurements of approximately 300 T-wave signals from six years of earthquakes on either side of the Chagos Archipelago. These have been recorded at the hydrophone arrays around Diego Garcia. The result of this 360-degree analysis, and the agreement with observed data, demonstrate the utility of the model in understanding the physical effects of these obstructions.
An in Vivo Map of the Yeast Protein Interactome
Authors: Tarassov Kirill , Messier Vincent , Landry Christian R. , Radinovic Stevo , Molina Mercedes M. Serna , Shames Igor , Malitskaya Yelena , Vogel Jackie , Bussey Howard , Michnick Stephen W.
Published: May 2008

Protein interactions regulate the systems-level behavior of cells; thus, deciphering the structure and dynamics of protein interaction networks in their cellular context is a central goal in biology. We have performed a genome-wide in vivo screen for protein-protein interactions in
Saccharomyces cerevisiae
by means of a protein-fragment complementation assay (PCA). We identified 2770 interactions among 1124 endogenously expressed proteins. Comparison with previous studies confirmed known interactions, but most were not known, revealing a previously unexplored subspace of the yeast protein interactome. The PCA detected structural and topological relationships between proteins, providing an 8-nanometer–resolution map of dynamically interacting complexes in vivo and extended networks that provide insights into fundamental cellular processes, including cell polarization and autophagy, pathways that are evolutionarily conserved and central to both development and human health.
Predictive Behavior Within Microbial Genetic Networks
Authors: Tagkopoulos Ilias , Liu Yir-Chung , Tavazoie Saeed
Published: May 2008

The homeostatic framework has dominated our understanding of cellular physiology. We question whether homeostasis alone adequately explains microbial responses to environmental stimuli, and explore the capacity of intracellular networks for predictive behavior in a fashion similar to metazoan nervous systems. We show that in silico biochemical networks, evolving randomly under precisely defined complex habitats, capture the dynamical, multidimensional structure of diverse environments by forming internal representations that allow prediction of environmental change. We provide evidence for such anticipatory behavior by revealing striking correlations of
Escherichia coli
transcriptional responses to temperature and oxygen perturbations—precisely mirroring the covariation of these parameters upon transitions between the outside world and the mammalian gastrointestinal tract. We further show that these internal correlations reflect a true associative learning paradigm, because they show rapid decoupling upon exposure to novel environments.