bluuebunny/crossref_metadata_2025 huggingface dataset:
Multibeam sonar and echosounder to study schooling behaviour and predator-prey interactions of marine animals
Authors: No/ttestad Leif
Published: May 2008

In the past the technological developments and improved spatial and temporal resolution in hydro-acoustics, have made it possible to study schooling and aggregation behaviour of fish and predator-prey interactions in considerable detail. Hydro-acoustic methodology have thus revealed new and interesting scientific findings on animal behaviour and ecology previously difficult to observe and document from the marine environment. A fundamental challenge is still to be able to track individual fish within a school or animal aggregation at the same time as we observe the collective movements. The spatial resolution of hydro-acoustics is usually not sufficient enough to track individual fish within dense aggregations. Underlying mechanisms and motivations of individual animals swimming in aggregations are needed, in order to improve our understanding and predictability of collective behaviour. Improved post-processing programs for quantitative analysis of multi-beam sonar data are also needed. High-resolution underwater cameras, Crittercam-technology and individual tagging will offer complementary data sources to our understanding of detailed behaviour of marine animals. I will present synoptic ecological studies using multi-beam sonar and echosounder on schooling behaviour and predator-prey interactions including fish, seabirds and marine mammals.
Clinical experiences with extracorporeal Ultrasound-guided high-intensity focused ultrasound treatment for cancer patients
Authors: Wu Feng
Published: May 2008

Noninvasive, image-guided tumour thermal ablation with extracorporeal high-intensity focused ultrasound (HIFU) has received increasing interest in the treatment of patients with solid tumours. Since December 1997, an extracorporeal ultrasound-guided HIFU system (Mode-JC, Haifu Technology Co. Ltd., Chongqing, China) has been used to treat approximately 10,000 patients with solid tumours in China, including those of liver, breast, bone, kidney, pancreas, soft tissue, and uterus. The same device has been recently introduced into the UK, Italy, Japan, and South Korea, and so far, more than 1,000 patients have received HIFU treatment outside China. The purpose of this article is to introduce our clinical experiences using extracorporeal, ultrasound-guided HIFU ablation for solid tumours. Five-year follow-up data are observed in patients with primary liver cancer, breast cancer, and osteosarcoma. Among patients treated with HIFU, an extremely low major complication rate is observed. In conclusion, our clinical studies indicate that HIFU treatment is a safe, effective, and feasible modality in the treatment of cancer patients.
Localization and enhancement of cavitation and heating during HIFU exposure using microparticles of high surface roughness
Authors: Arora Manish , Arvanitis Costas , Cox Emma , Coussios Constantin C.
Published: May 2008

The occurrence of cavitation during HIFU exposure is associated with higher heating rates than in the absence of bubble activity. However, the peak rarefaction pressures required to initiate cavitation in vivo are high (7-10 MPa), making it difficult to localize, sustain, and confine cavitation activity and its associated bioeffects. In this work, we explore the use of rough microparticles to promote and localize cavitation nucleation during HIFU exposures. Polystyrene microparticles of mean diameter ∼2 μm are embedded in a polyacrylamide tissue mimicking phantom, which has a high cavitation threshold similar to tissue. The temperature rise during HIFU exposure is measured using an embedded needle thermocouple, whilst cavitation activity is simultaneously monitored using a passive cavitation detector (PCD). The presence of particles is shown to lower the cavitation threshold significantly and, above this threshold, to result in higher heating rates than in the absence of particles for the same focal intensity. Furthermore, it is found that particles make it possible to repeatedly initiate cavitation at the same location and lead to increased broadband noise emissions. Finally, a strong correlation is found between enhanced heating and the broadband emissions arising from inertial cavitation.
Spherical harmonic analysis applied to the reconstruction of the sound field radiated by a loudspeaker
Authors: Fazi Filippo M. , Brunel Vincent , Nelson Philip A.
Published: May 2008

The three dimensional acoustic radiation patterns generated by different models of loudspeaker have been measured in an anechoic environment using an array of 40 omnidirectional microphones, arranged on a hemispherical surface. The acquired data have been numerically processed in order to obtain the complete three dimensional reconstruction of the analysed sound field. The theory of the applied method is based on the spherical harmonic decomposition of the sound field defined over the surface of a sphere containing the sound source and sampled at a finite number of positions. The reconstruction of the sound field in the region of the space inside and outside the measurement surface has been obtained by multiplying each coefficient of the spherical harmonic series by the corresponding spherical propagator, defined as the ratio of two spherical Hankel functions. The conditioning of the inverse problem related to the reconstruction of the sound field in the interior of the measurement surface has been analysed and put in relation to the behaviour of the spherical propagators of different orders.
Action plans (PPBE) : experience of municipal noise fighting plans
Authors: Gaucher Eric
Published: May 2008

The European Noise Directive (END) relating to the assessment and management of environmental noise requires the elaboration of action plans (Plans de Prévention du Bruit dans l'Environnement PPBE). However, these plans are limited to their concerned sources: trains, roads, planes and industrial plants. Municipal noise fighting plans (Plans Municipaux de Lutte contre le Bruit PMLB) taking equally into account any annoying sound situation, regardless of its nature, have been developed and implemented in around forty towns in France, with increasing success before the END was published. Acoustique & Conseil have already implemented thirty PLMBs. This experience has lead us to think that the strict application of PPBEs will in most cases not answer all the expectations of the concerned populations, in terms of solutions to their daily noise problems. It therefore seemed relevant for us to present a synthesis of the situations encountered during our works in order to enrich the approach of towns willing to enlarge their actions beyond those of the END. Now that it is time to elaborate the PPBE, it seems relevant and appropriate to implement PLMBs equally for the towns concerned.
Lions Bay noise mitigation program
Authors: Marriner Duane E.
Published: May 2008

The Ministry of Transportation (MoT) of the Province of B.C. noise abatement policy requires that environmental community noise impacts of highways projects involving new or substantially upgraded highways be assessed and mitigation implemented where warranted. This paper presents an extraordinary noise model developed to mitigate residential areas of the Village of Lions Bay on the rugged B.C. coastline from the Sea-to-Sky Highway connecting Vancouver, B.C. to Whistler, B.C. home of the Winter Olympic and Para-Olympic Games in 2010. The Cadna/A Version 3.9.15 software was used to develop a new 4 lane split grade alignment model incorporating two mini-interchanges. With the objective of achieving a 10 dBA noise reduction benefit, mitigation in the form of quiet pavement (OGA), traffic calming and 5 meter high absorptive sound walls or noise barriers were introduced into the model which included 150 mountain side residential receptors along the 2 km long corridor at elevations up to 35 meters above the project. Noise reduction benefits for dwellings were further analyzed to determine contributions during each stage of project development by creating a super user, modular, multi-layer noise model of Lions Bay. This work was carried out under the sponsorship of BCMoT.
Evaluation models for the noise diminution due to the phonique barrier walls
Authors: Arghir Mariana , Borza Dan , Blaga Florin , Vesseleny Tiberiu , Solea Geamilia , Runcan Mariana
Published: May 2008

The present paper contains our study regarding the diminution of the urban noise using the phonique barrier walls conformed to the EMPARA procedure, which is based on the simplified of the standard method for the measurements and computes of the surface traffic inside the urban agglomeration, as they are given in SRM2 laws (Netherlands standards). There are made the studies taking into account all the parameters that characterize the the noise and they are graphical representations having the “n-1” constant parameters and only one having the time variation law. In this way we are obtained the influence of each parameter in the diminution of the urban noise using the phonique barrier walls. In addition we realized a measurement for a real barrier wall inside the Oradea town. The comparison between them was enough good, that means our theoretical study is correct and characterizes the noise pollution and its diminution on the urban agglomeration. The measurement device was a CENTER 322 Sound Lever Meter. This study contains the two steps for the “noise map” asked for the Romania integration in the European Union, and was made by the researchers of the Oradea University under the direction of the Prof. Dr. Ing. Mariana ARGHIR from the Technical University of Cluj-Napoca.
Definition of traffic scennaries, application on a practise case of the criteria followed by the guide of good practises for elaboration of strategic traffic noise maps in urban routes
Authors: García Pérez Igone , Aspuru Soloaga Itziar
Published: May 2008

Configuration of noisy environment in towns mostly depends upon the characterization of traffic noise in urban routes. Frequently there is a lack of information when it is a question of having data from the whole urban area. To solve this lack of information the above-mentioned guide (WG-AEN 002.2006) proposes some suppositions for this characterization which can turn out to be very general in practical applications. Through the presentation of these criteria applied to a practical case it can be seen the tools necessary to adjust real traffic characterization to the elaboration of noise maps and definition of an Action Plan. The analyzed variables are: AVT, % of heavy vehicles, time distribution and speed considering, for this last factor, the lacks shown by the interim method and the applicable supposes based upon the state of the art.
Semi-empirical time domain model of sound attenuation in porous materials
Authors: Umnova Olga , Turo Diego
Published: May 2008

A semi-empirical model for complex tortuosity function, which satisfies physically correct low and high frequency limits and allows analytical transformation into the time domain has been developed. It is based on the assumption, that a network of pores with two characteristic sizes can approximate the internal structure of the material, and thus requires the knowledge of two relaxation times. It is proven, however, that the model can predict sufficiently well the acoustical properties of rigid porous materials with various microstructures when is complete with the tortuosity as an additional parameter. It is shown that relaxation times can be easily related to the “equivalent fluid” model parameters. Numerical time domain calculations confirm that the contribution of both viscous and inertial effects on the evolution of acoustical pulses as they propagate through a porous material can be accounted for simultaneously within the framework of the model. It is shown that the extended version of the model, which accounts for the thermal effects can also be explicitely used for time-domain computations.
Acoustic waves propagation along mechanically free surface of unconsolidated granular porous media
Authors: Jacob Xavier , Aleshin Vladislav , Tournat Vincent , Leclaire Philippe , Lauriks Walter , Gusev Vitali
Published: May 2008

Unconsolidated granular materials exhibit strong dependence of elastic properties on pressure due to high sensitivity of the intergrain contacts to magnitude of loading. As a consequence the gravity field makes these granular assemblages highly elastically inhomogeneous particularly near mechanically free surface. Theoretical and experimental investigations conducted recently have demonstrated that multiple waveguide surface acoustic modes propagate along the free surface of the solid-state skeleton in the disordered air-saturated granular packings. These modes are localized near the surface. In ordered granular packing the acoustic waves can travel along the surface inside the horizontal channels, which are localized beneath the surface. The waves of different frequencies are travelling at different depths. The anisotropy of these inhomogeneous granular phononic crystals has an important influence of the existence of the waveguide modes. The experiments with acoustic waves traveling in the vicinity of a free surface provide fundamental information on the mechanical behaviour of unconsolidated granular media at very low pressures in the vicinity of the jamming transition. The perspectives of this research could be related to the analysis of the role which could be played in the considered phenomena by the acoustic waves predominantly travelling in these granular porous assemblages through the fluid-saturated pores.
Acoustic defect mode in a finite 1-dimension lattice
Authors: Chu Kanghyun , Kim Yang-Hann
Published: May 2008

If there is a defect in a periodic lattice, then the defect modes are expected. The wave localization can be one of representative examples of defect modes applications. However, it is not likely possible to deal with an infinite-periods lattice in practice, and this implies that it is impossible to obtain a perfect wave localization. This motivates us to study a lattice with a finite period which allows the wave tunneling through it. Therefore, the behavior of the acoustic wave in a 1-dimension periodic lattice containing a defect with a finite period has been studied. For simplicity, we considered the lattice composed of two kinds of media with different characteristic impedance in the repeating order with finite periods and the defect with arbitrary size and characteristic impedance Finally, the limitation of wave localization in the real world application is discussed.
Floquet Lamb modes in periodic plates
Authors: Pagneux Vincent , Maurel Agnes
Published: May 2008

An elastic waveguide with periodic perturbation of its thickness or of its elastic properties can support Floquet modes that are the extension of the classical Lamb modes. In this work, we obtain the spectra of the Floquet modes by using a new numerical coupled mode method which is based on a pseudospectral discretization in the transverse direction and a Magnus exponential integration in the longitudinal direction. The Floquet mode spectra are analyzed and compared to the Lamb mode spectra for different configuration of the periodic perturbation of the plate. A particular emphasis is given to the existence of backward wave propagation and to the number of propagating modes as the frequency is increased.
Acoustic transparency by switching of phononic band gaps
Authors: Sanchez-Dehesa José , Sanchis-Alepez Helios , Torrent Daniel , Cai Liang-Wu
Published: May 2008

Acoustic transparency is here studied in two-dimensional phononic crystals made of hexagonal arrangements of layered cylinders. These layered cylinders, which have their acoustical properties radially dependent, can be achieved by using the recently proposed acoustical metamaterials [D. Torrent and J. Sanchez-Dehesa, New J. Phys., 9, 323 (2007)]. The transparency condition is here achieved by switching of the phononic band gaps, which is governed by the scattering form factor of the acoustic parameters (bulk modulus and sound speed). Various dependence have been studied. The feasibility of this proposal is demonstrated by multiple scattering simulations of the proposed metamaterials [Work supported by NSF of USA and MEC of Spain.]
Information-based sensor management for landmine detection using electromagnetic induction, ground-penetrating radar, and seismic sensors
Authors: Kolba Mark P. , Torrione Peter A. , Scott Waymond R. , Collins Leslie M.
Published: May 2008

An information-based sensor management framework is presented that enables the automated tasking of a suite of sensors when detecting static targets. The sensor manager chooses the sensors to use and the grid-based locations to observe in order to maximize the expected information gain that will be obtained with each new sensor observation. Initially, sensor probabilities of detection and false alarm, Pd and Pf, are assumed to be known by the sensor manager. In a field setting, however, Pd and Pf cannot be known exactly, and so uncertainty modeling for Pd and Pf is also presented. The sensor manager is tested on real landmine data using electromagnetic induction (EMI), ground-penetrating radar (GPR), and seismic sensors. A matched subspace detector is used to process the EMI data, an adaptive pre-screening algorithm based on the least mean squares (LMS) adaptive filter is used to process the GPR data, and whitening followed by an energy detector is used to process the seismic data. The sensor manager is able to detect the landmines more quickly and more effectively than an unmanaged, blind-search approach. Using all three sensor modalities also results in superior detection performance to that achieved by only a single modality.
Mechanical resonances in the low-frequency vibration spectrum of a cylindrically symmetric, anti-tank landmine
Authors: Alberts William C. , Sabatier James M. , Waxler Roger
Published: May 2008

Acoustic-based landmine detection methods have enjoyed success, in part, because of structural resonances in many landmines. The unburied VS 1.6, a member of a family of plastic, cylindrically symmetric anti-tank landmines, exhibits seven modes below 1.6 kHz and a large frequency shift of the first symmetric mode such that its frequency is greater than that of the first asymmetric mode, a phenomenon observed in timpani of reduced kettle volume [Christian et al., J. Acoust. Soc. Am., 76(5), 1336-1345 (1984)]. An elastically supported, thin, elastic plate acceptably models the unperturbed modes of the pressure plate. Coupling of the acoustic analog of the first symmetric mode to the cavities beneath the plate shows those cavities to be the cause of the perturbation. Shallow burial in sand effectively removes the frequency shift of the first symmetric mode. Comparisons to burial simulation experiments in water will be made, thus allowing a qualitative explanation of the effect sand has on the first symmetric mode of the plate. [This work was sponsored by US Army Research, Development, and Engineering Command, Night Vision and Electronic Sensors Directorate under Contract DAAB15-02-C-0024.]
On frequency scaling of ultrasonic cavitation and cleaning
Authors: Mettin Robert
Published: May 2008

In virtually all applications of acoustic cavitation, variations of the effects with sound frequency are observed. However, a simple comparison of analogical setups at different frequencies can be misleading, as other parameters, like wavelength or emitted transducer power, change jointly with the driving frequency. Indeed, the similarity of acoustically cavitating systems under scaling of frequency is not well defined yet, in particular because it is not clear what observable should stay the same. A possible way of characterization of “similar” systems could be the observation of similar cavitation bubble structures, “such as” for hydrodynamic flow patterns or hydrodynamic cavitation structures. This idea is debated on experimental and theoretical basis, and the consequences for cleaning applications in the higher frequency range are discussed.
Surface cavitation on micro- and nanometer scales
Authors: Lohse Detlef , Bremond Nicolas , Borkent Bram , Ohl Claus-Dieter , Arora Manish , Vancso Julius , Schoenherr Holger
Published: May 2008

Heterogeneous bubble nucleation at surfaces has been notorious because of its irreproducibility. Here controlled multibubble surface cavitation is achieved by heterogenous nucleation of bubbles on a hydrophobic surface patterned with microcavities. The expansion of the nuclei in the microcavities is triggered by an impulsive lowering of the liquid pressure. The procedure allows to control and fix the bubble-distance within the bubble cluster. We observe a perfect quantitative reproducibility of the cavitation events where the inner bubbles in the two-dimensional cluster are shielded by the outer ones, reflected by their later expansion and their delayed collapse. Apart from the final bubble collapse phase (when jetting flows directed towards the cluster's center develop), the bubble dynamics can be quantitatively described by an extended Rayleigh-Plesset equation, taking pressure modification through the surrounding bubbles into account. When repeating the same experiments with flat polyamide and hydrophobized silicon surfaces populated with surface nanobubbles (as can be seen through atomic force microscopy), these nanobubbles do not act as nucleation sites for cavitation bubbles, in contrast to the expectation. This implies that surface nanobubbles are not just stable under ambient conditions but also under enormous reduction of the liquid pressure down to -6 MPa. We denote this feature as superstability.
Pressure fields and their effects in membrane cleaning applications
Authors: Reuter Fabian , Mettin Robert , Lauterborn Werner
Published: May 2008

It is known that the use of ultrasonic cavitation can support the cleaning of filtration membranes. We study the final purification step in drinking water production by ultrafiltration through a submerged filter module. The module consists of parallel polymer membrane sheets. Its filtration efficiency is rapidly decreased by fouling. Here, the removal of membrane attached fouling layers by backflushing can successfully be enhanced using ultrasound without membrane damage. To better understand the cleaning mechanism and cavitation properties for further optimization of efficiency, the sound pressure field is measured and the bubble distribution is characterized. Different sound field arrangements are investigated with respect to cleaning performance, while membrane integrity is controlled by turbidity and particle monitoring of the permeate. Results show that a strong influence due to the geometrical configuration can be present, for instance due to impedance effects of the membrane layers.
The peculiarities of energy characteristics of acoustic waves
Authors: Zaitsev Boris D. , Teplykh Andrey A. , Kuznetsova Iren E.
Published: May 2008

Acoustic waves propagating in piezocrystals transport kinetic and potential energies. Potential energy consists of mechanical, electrical, and mutual contributions. At that the change in potential energy of the voluentary unit of medium is identified with the work of mechanical stress for infinitesimal displacement. Versus method of integrating this equation there are two different expressions for density of potential energy. In case 1 (traditional approach) the density of energy is equal to the half-product of mechanical stress and strain. At that for any type of plane acoustic wave the instantaneous density of total energy in given point of medium depends on time and there is no mutual transformation of potential and kinetic energies. For this case there exists well-known traditional expression for power flow. In case 2 suggested by authors the density of potential energy is equal to half-product of mechanical stress gradient and displacement. At that the density of total energy does not depend on time. It means the mutual transformation of potential and kinetic energies according to motion equation. The new expression for power flow is derived for this case. The peculiarities of energy characteristics for piezoactive waves are discussed. The work is supported by RFBR grant N°08-08-00793.
Audio acoustic modeling using full-wave methods
Authors: Lahivaara Timo , Huttunen Tomi , Simonaho Simo-Pekka
Published: May 2008

The numerical simulation of wave propagation poses a significant challenge in scientific computation. Historically, several approaches are explored in order to get a stable method that can be efficiently used for approximating wave propagation without excessive numerical dissipation or dispersion. Unfortunately, the traditional approaches, such as the finite element and the finite difference, require many discretization points per wavelength to obtain reliable solutions. In this study, two alternative full-wave methods for reducing the computational complexity are consider. The methods are the time-domain discontinuous Galerkin method and the ultraweak variational formulation in the frequency domain. Using these techniques, the directivity and the frequency response of a loudspeaker are studied. Moreover, the simulated results are compared to experimental measurements.
Multistability in audiovisual speech scene analysis: behavioral and neurophysiological data on multimodal verbal transformations
Authors: Schwartz Jean-Luc , Basirat Anahita , Sato Marc
Published: May 2008

The multistable perception of speech refers to the perceptual changes experienced while listening to a speech form cycled in rapid and continuous repetition, the so-called Verbal Transformation Effect. Because distinct interpretations of the same repeated stimulus alternate spontaneously, this effect provides an invaluable tool to examine how speech percepts are formed in the listener's mind. In a series of behavioural studies, we demonstrated that (1) articulatory-based representations play a key part in the endogenously driven emergence of auditory speech percepts; (2) vision penetrates into the transformation process, intervening both in the stability of a given pattern, and in the temporal dynamics of perceptual switches. Furthermore, we determined the cortical circuit in charge for the emergence of a shift of percept associated to a given audio input. This circuit involves a cortical “dorsal route” for speech perception, linking temporal, parietal, and frontal regions. Current experiments involve further tests about the nature of both perceptuo-motor and audio-visual interactions in verbal transformations. Altogether, these results shed some new lights on the cognitive and neurobiological bases of speech perception, in which multimodal interactions between sensory and motor representations play a crucial role.
Why is sensitivity to interaural time differences (ITD) poorer than normal with bilateral cochlear implants? Neurophysiological considerations
Authors: Delgutte Bertrand , Hancock Kenneth E.
Published: May 2008

Bilateral cochlear implantation improves sound localization and speech reception in noise. Yet ITD sensitivity is clearly poorer than normal with bilateral implants, even when the stimulation bypasses the processors (which discard the temporal fine structure of the stimulus). This poor behavioral ITD sensitivity is surprising from a physiological perspective because (1) electric stimulation produces precise temporal patterns of activity in the auditory nerve, and (2) most neurons in the inferior colliculus of acutely-deafened, bilaterally-implanted cats show precise tuning to ITD of pulse trains at the appropriate intensity (Smith and Delgutte, J. Neurosci. 27:6740). We will present physiological and modeling results bearing upon two hypotheses for reconciling neural and psychophysical observations. One hypothesis is that plastic changes to the neural circuitry resulting from binaural deprivation may impair the binaural processing in long-term deafened animals (and humans), particularly if deafening occurs during the neonatal period. Alternatively, the abnormal spatio-temporal pattern of activity across the population of binaural neurons (due in part to limited dynamic range with electric stimulation) may impair the ability of the central decoding stages to extract the ITD information available in individual binaural neurons.
3D-localization of virtual sound sources in normal-hearing and cochlear-implant listeners
Authors: Majdak Piotr , Laback Bernhard , Goupell Matthew J.
Published: May 2008

The ability to localize sound sources in 3D-space was tested in humans. Five normal-hearing (NH) subjects listened via headphones to noises filtered with subject-specific head-related transfer functions. Four bilateral cochlear implant (CI) subjects listened via their clinical speech processors to noises filtered with subject-specific behind-the-ear head-related transfer functions. A virtual structured environment was presented via head mounted display. Two conditions were used: a condition where the subjects were naive and had no response feedback and a learning condition where the subjects were trained by providing extensive feedback during the test. Response feedback was provided via the visual virtual environment. The results show that the CI listeners performed generally worse than NH listeners, both in the horizontal and vertical dimensions. Both subject groups were able to learn to better localize sound sources, which is supported by lower localization errors in the learning condition. However, in the learning condition, the CI listeners showed a front/back confusion rate comparable to naive NH listeners, which was two times higher than for the trained NH listeners. These results indicate the necessity of new CI processing strategies which include spectral localization cues. Funding by FWF (P18401-B15).
Emergence of sound localization acuity in children who are fitted with bilateral cochlear implants
Authors: Litovsky Ruth , Grieco-Calub Tina , Godar Shelly
Published: May 2008

Sound localization was investigated in children who are born deaf and hear with either monaural or bilateral cochlear implants (CIs). Using a 2AFC discrimination task with stimuli to the right/left, in a sound proof booth, loudspeaker locations varied along the horizontal plane between +/-70 deg. Minimum audible angle (MAA) thresholds were estimated adaptively. In study 1, 4-14 year-old children who received two CIs in sequential procedures participated. They were first tested while functioning monaurally, then at 3- and 12-months following activation of bilateral hearing. Following bilateral activation, MAA thresholds were significantly lower, especially after 12 months. In study 2 children were 2.5 years old, with 6-20 months of bilateral experience. MAAs were typically better when children had ⩾12 months of exposure to bilateral stimulation. Overall, these findings suggest that binaural hearing abilities can be established in an auditory system that is strictly stimulated with electrically pulsed signals, but that unlike a normal auditory system, here a year of exposure may be required before localization acuity is better under bilateral than monaural conditions. These findings are especially relevant to considerations of localization in absence of fine-structure, a cue that is discarded by the speech processors utilized in CIs.
Theory and application of pseudo-damping in structures
Authors: Akay Adnan , Carcaterra Antonio
Published: May 2008

This presentation describes the underlying physics and theory of pseudo damping to reduce vibration of conservative structures. The theoretical approach is based on particular properties of harmonic functions that lead to construction of a complex system that exhibits nearly irreversible energy transfer. This approach also provides the ability to tailor energy absorption from a particular structure in the absence of damping. The authors will also discuss extension of the concept to continuous systems and its application to waveguides. The presentation will illustrate test results including application to reduce vibrations in a satellite. [Research carried out while AA served at NSF.]
Vibration of a submarine hull under harmonic propeller-shaft excitation
Authors: Caresta Mauro , Kessissoglou Nicole J.
Published: May 2008

A model to describe the dynamic response of submarine hull to a harmonic propeller shaft excitation is presented. The submarine is modeled as a ring stiffened cylindrical shell, with bulkheads and end caps. The stiffeners are introduced using a smeared approach. The bulkheads are modeled as circular plates with in plane and bending motion, and the end closures are modeled as truncated conical shells. External fluid loading is introduced to take into account the interaction of the structure with the acoustic medium. The propeller introduces a harmonic varying force in both the axial and transverse directions. The force is transmitted to the structure through the shaft that is connected to the end plate of the cylindrical hull and supported by the conical end cap. The axial component excites the axisymmetric modes of the structure. The transverse force component excites the hull through the conical shell and excites the higher circumferential modes. Since these modes are mainly flexure in nature, they can result in a high noise signature level. Results are presented in terms of FRFs calculated analytically and compare the axisymmetric vibration caused by the axial excitation and the asymmetric response due to the transverse component of the force.
Identification of noise sources by means of inverse finite element method using measured data
Authors: Weber Matthias , Kletschkowski Thomas , Sachau Delf
Published: May 2008

Identification of noise sources in airplane cabins proves to be difficult particularly at low frequencies. A new approach reconstructs the spatial distribution of sound pressure and particle velocity based on the inverse finite element (FE) method. This procedure requires measurements in the cavity of the cabin. If all sound sources are located on the boundary of the cabin, the equation system resulting from a matching FE model can be resorted in such way that computation of the unknown boundary data is possible, even with distorted measurement data. The method is explained using a simplified 2D laboratory experiment consisting of a flat sound-hard bounded rectangle with a loudspeaker included in the boundary. A corresponding FE model with given boundary conditions is verified by mapping the sound pressure in the test bed. The inner part of the measurement data is used to compute the boundary values. Regularization methods are applied to find an optimal solution. To prepare a verification of this technique in real world conditions, the sound field in the cavity of an airplane mock-up (Airbus A340) exited by both an interior and exterior noise source is mapped with a custom-built microphone array. Taking advantage of the results of the 2D examination, the current status of this verification process is shown.
Speech perception in noise with binary gains
Authors: Wang Deliang , Kjems Ulrik , Pedersen Michael S. , Boldt Jesper B. , Lunner Thomas
Published: May 2008

For a given mixture of speech and noise, an ideal binary time-frequency mask is constructed by whether SNR within individual time-frequency units exceeds a local SNR criterion (LC). With linear filters, co-reducing mixture SNR and LC does not alter the ideal binary mask. Taking this manipulation to the limit by setting both mixture SNR and LC to minus infinity produces an output that contains only noise with no target speech at all. This particular output corresponds to turning on or off the filtered noise according to a pattern prescribed by the ideal binary mask. Our study was designed to test on speech intelligibility of noise gated by the ideal binary mask obtained this way. It is observed that listeners achieve nearly perfect speech recognition from gated noise. Only sixteen filter channels and a frame rate of one hundred Hertz are sufficient for high intelligibility. The results show that, despite a dramatic reduction of speech information, a pattern of binary gains provides an adequate basis for speech perception in noise.
Regional variation in vowels and vowel systems: normalization and optimization
Authors: Van Hout Roeland
Published: May 2008

We made an acoustical description of regional variation patterns in the vowel system of Dutch spoken in the Netherlands and Flanders. The speech material consisted of read monosyllabic utterances in a neutral consonantal context, representing the vowels of Dutch. A discriminant analysis applied on the raw measurements to classify each speaker into one of the eight regions involved (socio-geographic variation) gave a correct regional classification for 72.0% of the 160 speakers. When normalization procedures were applied, the percentages of proper classification increase to 82.5%. Several questions have to be answered though. Which normalization procedure is the best one and why, and how can we be sure that specific parts of sociophonetic variation are not distorted by the normalization procedure? We will present additional materials collected on the same set of speakers in reading aloud a strictly controlled list of words containing all Dutch vowels in different consonantal contexts. Another question is how to reduce the amount of information used in a normalization procedure. The z transformation (Lobanov) performs well, but is rather expensive in the amount of information needed. Can we minimize the information needed and yet uncover the patterns of sociophonetic variation?
Differences in the time-course of accent adaptation: a comparison of adaptation to foreign-accented and unfamiliar regionally-accented speech
Authors: Evans Bronwen G. , Adank Patti
Published: May 2008

Recent work in speech perception has demonstrated that listeners are able to rapidly adapt to foreign- accented speech (Clarke and Garrett, 2004). However, it is not clear whether adaptation to an unfamiliar regional accent operates in the same way. Although some studies have shown that listeners are able to adapt to different accents within the same language after only a short amount of exposure (e.g., Maye et al., in press), others have shown that listeners do not always alter their perceptual representations when listening to a non-native regional accent even if they are highly familiar with that accent (Evans and Iverson, 2004, 2007). In this study, we further explored perceptual adaptation to different accents by comparing the time course of adaptation to an unfamiliar regional accent with adaptation to foreign- accented speech. Listeners identified sentences in noise produced in either an unfamiliar regional accent (Glaswegian) or foreign-accented speech (Spanish-accented English). Preliminary results suggest a different pattern of adaptation for each accent: although listeners show greater adaptation to foreign- accented speech, they perform more poorly with foreign-accented speech overall and the rate of adaptation is slower.
Articulatory perturbation due to ultrasound imaging: an acoustic analysis
Authors: Knight Rachael-Anne , Villafana Dalcher Christina , Jones Mark J.
Published: May 2008

A safe, non-invasive imaging technique which captures articulatory movements in real time is the Holy Grail of articulatory analysis. Ultrasound imaging of the tongue seems suitable, albeit for a single articulator. However, ultrasound requires positioning a probe under the chin which may inhibit jaw movement. It is well known that speakers compensate rapidly for similar articulatory perturbations such as bite-blocks. Consequently, the images obtained by ultrasound may show compensatory articulations due to jaw inhibition, rather than natural articulations. This study assesses the effects of articulatory compensation during ultrasound imaging using acoustic analysis. The experiment compares acoustic data from three speech conditions: probe-free, probe held manually, probe fixed non-manually. It is hypothesised that sounds requiring a low jaw position, such as low vowels, velars, and velarised laterals, will be worst affected. High jaw sounds such as /s/ and /i/ are also assessed. Any differences between conditions are assumed to be due to compensation for jaw immobility rather than learned segment-specific register effects and are therefore unlikely to diminish as the subjects relax. Variability may diminish, however, as compensatory strategies become more practised. We expect to find some effects on certain segments, but that manual probe holding allows for more natural speech.
The influence of the feature (sonorant) in lexical access in Spanish
Authors: Moates Danny R. , Marks Emilia A. , Barrera Dario
Published: May 2008

Does the feature (sonorant) influence access to lexical entries? In current feature geometry, the feature (sonorant) is a root node feature, distinguishing resonants from obstruents. Marks, et al. (2002) demonstrated its influence in lexical access using the word reconstruction task in Spanish. Participants heard a nonword, e.g., dirmar, and were asked to change it into a real word (firmar) by changing just one consonant. Errors in recovering the correct word (firmar) were much higher when the word contained an obstruent that had been replaced with a resonant (nirmar) than when the word contained an obstruent that had been replaced by another obstruent (dirmar). Obstruent target words were easier to recover when the target segment and the replacing segment matched on the feature [sonorant]. Why do obstruents show this matching effect? The present study subdivided obstruents into stops and fricatives. Two experiments compared them separately to resonants in the word reconstruction task. Are fricatives alone or stops alone responsible for the observed obstruent effect? Results showed greater errors in the mismatch condition for both fricatives and stops, but significantly greater for fricatives than for stops, suggesting that the mismatch effect observed for obstruents is largely based on fricatives.
HRTF modeling in due consideration variable torso reflections
Authors: Guldenschuh Markus , Sontacchi Alois , Zotter Franz , Höldrich Robert
Published: May 2008

Head related transfer functions (HRTFs) describe the physical path from an acoustical source to the ears. It can be gained within the relation of two measurements. The first will give the reference sound pressure in the virtual middle of the head the second has to be done in both ears. In literature exhaustive investigations concerning the idealized location of the second position can be found. Beyond that measurements with various artificial heads and human-beings considering various source directions (azimuth and elevation) with different angular resolutions have been undertaken. The obtained HRTFs exhibit, with subject to the examined source position, frequency dependent magnitude and phase. These complex transfer functions are caused by various reflections, diffractions, pressure superelevation, and shadowing, respectively. Reflections are caused form pinna, head and torso, too. Heretofore during determination of the transfer functions the influence of various head-torso arrangements have not be considered. Within this paper the differences which will be caused due to different head-torso angles will be highlighted. Beyond that a numerical model based on interpolation using spherical harmonics will be presented. By the aid of that model the integration within an existing binaural resynthesis model can be realized and perceptual differences within a dynamic system can be investigated.
Does a depth variable sound-speed profile matter for SW06 geoacoustic inversion
Authors: Tolstoy Alexandra
Published: May 2008

This work will discuss the effects of depth variability for a sound-speed profile with regard to goeacoustic inversion on some simulated SW06 "data". First, broadband (400-800 Hz) simulated "data" are generated using RAM_PE (by Collins) in the time domain for some short range (less than 1 km) SW06 scenarios. Next, the first 4 boundary reflection arrivals (from surface, bottom, surface-bottom, bottom-surface) are studied as a function of source range and depth, phone depth, and sound-speed variability. Finally, we examine the effects of sound-speed depth variability on geoacoustic inversion via MFP. We note that knowledge of array phone locations has a large impact on inversion capabilities.
Nonlinear pulsing schemes for the detection of ultrasound contrast agents
Authors: Averkiou Michalakis A. , Mannaris Christophoros , Bruce Matthew , Powers Jeffry
Published: May 2008

Ultrasound contrast agents are used in cardiology for the assessment of myocardial perfusion and in radiology for the detection and characterization of tumors. One widely used approach of imaging contrast agents is to use a low Mechanical Index (MI) nonlinear imaging technique to avoid bubble destruction and image both the macro- and micro-circulation in real-time. Various pulsing schemes are employed for the detection of nonlinear echoes from contrast microbubbles. The objective of this paper is to evaluate the various pulsing schemes for low MI imaging of contrast microbubbles and better understand their similarities and differences. The pulsing schemes considered are pulse inversion, power modulation, and their combination. Emphasis is placed on identifying whether nonlinearity due to propagation in tissue may be discriminated from nonlinearity due to scattering from bubbles. Bubble destruction (use of high MI) and tissue motion were not considered in this work. The evaluation of the different pulsing schemes was performed with numerical simulations from well established theoretical models and experimental data from microbubbles in tissue phantoms and human tissues.
Noise emissions at intersections: comparing microscopic and macroscopic traffic simulation approaches
Authors: De Coensel Bert , Botteldooren Dick , Dekoninck Luc , Gillis Dominique , Lauwers Dirk
Published: May 2008

Environmental noise mapping often involves the use of traffic simulation software. In most cases, traffic flows are simulated in a macroscopic way, considering only traffic flow parameters averaged over road segments. This approach does not allow to correctly account for the typical deceleration and acceleration patterns of traffic at intersections, which influence local noise emissions. Microscopic traffic simulation models, which model each vehicle individually, incorporate these dynamic effects. However, they require much larger amounts of input data for calibration, and are therefore less suited to map large areas. In this paper, we investigate the possible influence of the choice of simulation detail on simulated traffic flow parameters and, as a consequence, on noise emissions near intersections. As a case study, several types of road intersections under various traffic demand and traffic composition conditions are considered. Simulation results are obtained using a microscopic (Paramics) as well as a mesoscopic (MaDAM) and a macroscopic (OmniTRANS) traffic simulation model, and predicted traffic flow parameters and noise emission values are compared between these approaches.