bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of porous plate/water layered structures by means of the transition terms method
Authors: Belhocine Ferroudja , Derible Serge , Franklin Cole
Published: May 2008

This paper is devoted to the study of water-saturated porous plate/water layered structures by means of the transition terms defined from the reflection and transmission coefficients R and T as follows: TTsym=(1-(R+T))/(2i) , TTasym=(1-(R-T))/(2i). They are the eigenvalues of the scattering matrix of the water-immersed structure and are directly connected with its symmetric or antisymmetric vibrations. The N porous plates associated in our structures obey Biot's theory which is first used to calculate the reflection and transmission coefficients of a unique water-saturated plate. An induction on N process allows to find the reflection and transmission coefficients of a given N plate/water-layer structure. The plates used in the experiments at normal incidence are 5mm thick. The reflection and transmission coefficients of sets of 1, 2, 3, and 4 water immersed plates, separated from each other by a 1cm water gap, are measured thanks to two wideband transducers with central frequency 0.5MHz. There are good agreements between the calculated and experimental transition terms which exhibit the symmetric and antisymmetric resonances of the structures. They obey the Breit-Wigner resonant form which characteristics can be obtained
Acoustic pulse attenuation and transmission in rigid porous media: Experimental investigation and numerical simulations
Authors: Turo Diego , Umnova Olga
Published: May 2008

This paper presents an investigation on acoustic pulse attenuation and transmission in rigid porous media. Transmission measurements of acoustic pulses through porous material with a rigid frame were performed using an appropriate standing wave tube. A vertical tube was built to make measurements on granular materials. The influence of pulse duration, layer thickness and material microstructure on the transmission has been investigated. Numerical time domain simulations based on two different semi-empirical models with one and two viscous relaxation times, respectively, were performed to compare with existing data. First, material microstructure and pulse durations were adapted to investigate the influence of viscous and inertial effects on pulse propagation separately. The simultaneous contribution of both viscous and thermal effects was then investigated. In the finite difference time domain (FDTD) model, different approaches are used to correctly simulate the pulse transmission through a porous layer. Accuracy and computational time required for the numerical methodologies have been compared and their advantages and drawbacks applied to this particular case shown.
On heterogeneous blankets: Analytical solution for the interaction between masses and poro-elastic layers
Authors: Idrisi Kamal , Wagner Andreas , Johnson Marty , Bartylla David
Published: May 2008

There has been substantial research over the last five decades on control of aircraft cabin noise. One new passive approach is the heterogeneous (HG) blanket where a traditional acoustic blanket treatment is altered by adding mass inhomogeneities into the poro-elastic/viscoelastic layers. These masses act like distributed vibration absorbers and can be used to reduce vibration and sound transmission by targeting modes of the fuselage. The natural frequency of a mass inhomogeneity is determined by the mass itself and by the effective stiffness of the porous layer due to the mass/poro interaction. An experimental 1st order approach to predict the effective stiffness based on the shape of the mass inhomogeneities is reviewed. An analytical model for poro-elastic media proposed by Allard et al. was simplified for low frequencies and is used to validate and extend the 1st order approach. It is shown that the effective stiffness depends on mass shape, the foam thickness and material constants such as the modulus of elasticity and Poisson's ratio. Furthermore the model can be used to calculate the stress and displacements fields in the blanket in order to give further insight into the behaviour of the HG blankets.
Surface profile investigations by means of acousto-optic technique
Authors: Gurevich Boris S. , Shapovalov Valentine V. , Andreyev Sergey V. , Belyaev Andrey V. , Kolesov Ilya A.
Published: May 2008

Acousto-optic tunable filters (AOTF) represent a very strong tool in different kinds of investigations where high rate light wavelength variations are required. The rough surfaces profile investigation is among the problems which can be solved partially by this way. Our investigations have been connected with use of AOTF and lens components with strong chromatic aberration. One of the problems was to choose the z-distance resolving power criterion. The proposed criterion is defined by the admissible probability to miss information unit regarding the object characterization in z-distance. In our experiments we used the specially elaborated AOTF based on tellurium dioxide crystal with transmission bandwidth of several nm, depending on the central wavelength position. Also we have used the lenses fabricated with tellurium dioxide because this material provides high chromatic aberrations. The results of experiments are discussed from the point of view of the AOTF possibilities to increase the z-distance resolving power in comparison with existing systems. The 90%-probability distinguishing of defocusing while electric frequency variation of 200 kHz, can be considered as serious advantage. The device improvement can be attained by means of the noise level decreasing to the level taking place for electric frequency of 94 MHz.
Critical cone channelling in directly bonded wafers
Authors: Twerdowski Evgeny , Von Buttlar Moritz , Wannemacher Reinhold , Grill Wolfgang
Published: May 2008

Directly bonded semiconductor wafers have been investigated using ultrasonic transmission tomography and imaging of the phonon focusing patterns at ultrasonic frequencies. Beside of total disbonds, several bonded wafers contained defects that are fully transparent to normally incident waves of longitudinal polarization, and are fully opaque to those of transverse polarization. These defects, which are due to slip boundary conditions at the wafer-wafer interface, generate an additional acoustic mode by mode conversion at the interface. The additional mode is clearly observable in the experimental phonon focusing patterns and is indicative of the critical cone channelling phenomenon, which is caused by the generation of pseudo-surface and head waves at weakly bonded solid-solid interfaces. The effect is also expected to be present in the case of weakly-bonded isotropic materials. Since the strong pseudo-surface wave resonance exists only in the case of boundary conditions that allow for the relative displacement of the two adjoining media along the interface, the critical cone channelling effect can serve as a measure of the type and quality of the bond.
Theoretical and experimental ultrasonic investigation of a thin plate with regions of different periodic double-corrugations
Authors: Herbison Sarah W. , Declercq Nico F.
Published: May 2008

In order to provide a qualitative measurement of the depth of periodic double-corrugations existing on both sides of a thin plate, theoretical and experimental ultrasonic techniques have been applied. The aesthetic galvanized steel sheets under investigation contain many regions of periodic double-corrugations, each region with a different corrugation depth. An ultrasonic technique is investigated as a means to improve existing optical testing techniques in quality and speed. Theoretical simulations using the theory of diffraction from periodically corrugated surfaces have been employed to obtain reflection spectra to facilitate qualitative observations regarding the depth of the corrugation in the different regions. Experiments to obtain reflection spectra correlate well with the theoretical simulations, and show the application of ultrasound to the qualitative measurement of the corrugation depth. Because the wavelengths necessary to make the investigations produce Lamb waves, some difficulty lies in the generation of diffracted bulk waves and Lamb waves. The research shows that correlations between theory and experiments exist, but they can only be obtained after thorough simulations that do not produce easy to apply rules of thumb.
Frequency-domain diffraction for edges of arbitrary length with efficient numerical integration
Authors: Svensson Peter , Calamia Paul
Published: May 2008

Frequency-domain edge diffraction from an infinite wedge insonified by a point source has been widely studied, with various analytical solutions dating back nearly a century. In this talk we present an alternative frequency-domain solution which can be used for finite as well as infinite edges. The expression, given as a line integral along the diffracting edge, is derived from an analytical time-domain expression presented in [U. P. Svensson et al., J. Acoust. Soc. Am. 106, 2331-2344 (1999)]. The new formulation is shown to be equivalent to an exact, analytical, contour-integral formulation for the infinite wedge via a variable transformation. Results for various finite and infinite edge cases will be presented, and numerical integration using an efficient quadrature method for highly oscillatory integrals will also be discussed.
Methodological and metrological benchmarks for determining experimental values of meteorological parameters
Authors: Gauvreau Benoit
Published: May 2008

Outdoor sound propagation is largely influenced by meteorological conditions: mean refraction, intermittency and atmospheric turbulence. Thus, acoustic engineers and scientists have to rigorously characterize those propagation conditions through several parameters, both for numerical predictions (input data) and for operational reports (impact studies). One of these influent parameters is the well-known (and widely used) effective vertical sound speed gradient, which depends on spatial and temporal mean values of wind and temperature between source and receiver. However, the experimental characterization of wind and temperature (and next sound speed) vertical profiles remains delicate: it requires accurate meteorological devices and adapted measuring methods. At this purpose, an experimental campaign has been carried in 2007 on a perfectly flat and open ground, in order to quantify the confidence, uncertainty and spreading of such parameter values for different time scales. This campaign involved different meteorological devices: instrumented towers, classical sensors, 3D sonic anemometers, etc. The benchmark results will be presented and next analysed in terms of metrological and methodological requirements for acousticians in charge of environmental studies for standard organizations and/or scientific institutes.
Facing the challenge of calculating outdoor sound propagation using a 3D multi domain approach based on linear euler equations
Authors: Junker Fabrice , Crouzet Fabien , Lafon Philippe
Published: May 2008

Solving the Linear Euler Equations (LEE) is the reference method that allows to take into account all the phenomena involved in Outdoor Sound Propagation. However, the huge size of the problems to be treated is still a great limitation to the practical application of this method. The concept of multi domain computations associated with the use of massively parallel computers now pushes the limits away. The code SAFARI, recently developed by EDF, solves LEE with high order numerical schemes on structured grids. To deal with complex and large geometries, a multi domain approach is used. The computational domain is composed of several partially overlapping grids (overset grids). Computations are parallelized by domain decomposition to be runned on cluster facilities. The presentation means to show the capability of SAFARI to deal with propagation over realistic 3D domains. The strategy used to carry out the calculations is detailed. The new perspectives of this kind of method are finally given.
Computing the parameter sensitivities of outdoor sound propagation in a random environment
Authors: Pettit Chris L. , Wilson Keith
Published: May 2008

Computational forecasts of near-ground sound levels are compromised by uncertainty (e.g., randomness) and error (e.g., grid resolution) in the atmosphere and terrain representations, and by simplified or incorrect physics. For an incompletely known environment, a model's predictive power cannot be assessed without first quantifying the sensitivity of its forecasts to the full range of every parameter. Knowledge of these sensitivities throughout the spatial domain also is essential for effectively investing data-gathering resources to support sound propagation forecasts. Sensitivity analysis therefore is central to raising the relevance of computational acoustics in practical applications. These considerations should motivate practitioners of computational acoustics to adopt a consistent framework for sensitivity and uncertainty analyses. Topics to be discussed include: (1) standard uncertainty taxonomies in computational mechanics, (2) why uncertainty about a parameter should be distinguished from sensitivity of a model to that parameter, (3) sources of uncertainty in the near-ground acoustics, (4) a sampling-based sensitivity analysis framework that facilitates estimating typical and extreme values of sensitivities at each point in the spatial domain (i.e., full-field sensitivities), (5) factors to be aware of when applying sensitivity analysis to forecasts of near-ground sound propagation, and (6) ways of representing sensitivity estimates to facilitate insight.
Variation in measured sound level as a function of propagation environment and distance
Authors: Swearingen Michelle E. , Huseby Morten , White Michael J.
Published: May 2008

The propagation environment exerts a large influence on the range of received levels of impulsive events. This talk focuses on the variation in excess attenuation over durations of less than approximately 15 minutes. Data are presented for greatly different measurement distances (25 m to 7 km) and propagation environments (sparse vegetation to forested), illustrating the effects of distance and terrain cover on sounds from a propane cannon and an artillery source. Over sparse vegetation 7 km from an artillery source, the received CSEL varied 11 dB within a 12-minute duration. In measurements up to approximately 300 m from the source, variation in received level (both peak and SEL) was less than 1 dB within the forest, and much more in the open. The control of the forest canopy on the micrometeorology seems to explain the effect.
Sound propagation in areas with a complex meteorology: a meteorological-acoustical model
Authors: Van Der Eerden Frits , Van Den Berg Frank
Published: May 2008

Long range sound propagation is largely affected by the vertical wind and temperature gradients. These gradients are more complicated in areas where the meteorology can be complex, such as: coastal areas, islands, and lake districts. Furthermore, the gradients usually vary as a function of the horizontal distance, for instance at water-land crossings near a coast or a lake. As a result the sound propagation in these areas cannot be calculated with "standard" acoustic models, such as the ISO 9613 or Harmonoise engineering model. By using an advanced meso-scale meteorological model, which is using large-scale weather forecast data, and an acoustical model, that incorporates horizontal and vertical meteorological variations, long range sound propagation in such complex areas is calculated. In this paper we present two applications of this hybrid meteorological-acoustical calculation scheme: i) propagation of impulse noise in a coastal area, and ii) propagation of industrial noise in a rural area with a lake. For the coastal area sound level contours have been calculated as a function of the meteorology for a complete year. For the lake area the effect of the lake on the sound propagation is demonstrated.
Numerical modeling of sonic boom propagation from hypersonic aircraft
Authors: Loubeau Alexandra , Coulouvrat François
Published: May 2008

A numerical study of sonic boom propagation from hypersonic aircraft is performed including the effects of nonlinearity, atmospheric absorption and dispersion, and atmospheric stratification. A second-order split-step algorithm, which alternates application of nonlinearity in the time domain and complex absorption in the frequency domain, allows for a faster convergence of results with fewer range steps than with conventional first-order algorithms. Nonlinearity is calculated using the potential, the integral of the pressure, as proposed by Burgers and later applied to sonic booms by Hayes et al. This method, an alternative to Landau's law of equal areas, efficiently locates the shock position by selecting the maximum potential in multivalued regions. Definition of atmospheric absorption at high altitudes is important for modeling the propagation of sonic booms from hypersonic aircraft. Some aspects of an extended absorption model by Sutherland and Bass are adopted, therefore, which extend absorption predictions above the 20 km limit of the current ISO and ANSI standards. The study is completed using the meteorological conditions at two locations, Le Havre, France and Edwards Air Force Base, CA, USA, over the course of a year. [Work supported by European Union through ATLLAS AST5-CT-2006-030729, meteorological data provided by ECMWF.]
Experimental studies of generation and propagation of high frequency acoustic waves in various solid materials using ultraviolet picosecond laser pulses
Authors: Tzianaki Eirini , Tatarakis Michael , Bakarezos Makis , Elefteriou Maria , Papadogiannis Nektarios , Kazianis Spyros , Kosmidis Costas , Lyras Andreas
Published: May 2008

The generation of high frequency acoustic waves by picosecond laser pulses in the ultraviolet region and their detection by optical interferometric schemes, is presented. The two main acoustical modes, longitudinal and shear are clearly apparent in the time resolved spectra of solid materials, for various absorbing energies, extending from the thermoelastic to the ablative regime. The ultraviolet light is strongly absorbed by insulator materials like Pyrex and thus strong elastic waves are produced. From the time separation of the longitudinal waves we have deduced values for the speed of sound in various materials and of different thickness, that are in very good agreement with those reported in the literature. Also the time bandwidth of the sound waves is measured and significant differences, originating from different sample thickness, are apparent.
Thickness measurement of submicron metal coatings on transparent substrate by laser optoacoustic method
Authors: Pelivanov Ivan , Kopylova Daria , Podimova Nataliya , Karabutov Alexander
Published: May 2008

New nondestructive method for measurement of the thickness of submicron metal coatings on a transparent dielectric substrate is developed. Theoretical background includes the consecutive solution of the thermal and acoustic problems. The experimental part is based on the measurement of frequency dependence of the laser-ultrasound excitation efficiency on the metal coating thickness for the system where the coating is covered by a transparent liquid. Three chrome coatings of various thicknesses (0.2, 0.3 and 0.6 micrometers) deposited on a quartz substrate were tested experimentally. A rough estimate of their thickness was obtained from the sputtering time. Two different experimental modes were used: forward mode (laser pulses irradiate the metal film through the substrate, excited acoustical transients are detected in the liquid) and backward mode (both laser irradiation of the film and detection of excited acoustical transients are performed in the liquid). Spectral dependencies of the thermo-optical transformation efficiency were calculated analytically and obtained experimentally for both signal detection modes. The values of the film thicknesses were determined by the least squares fitting of the theoretical curves to experimental data. It is demonstrated, that the developed optoacoustic method can be used for metal coatings thickness measurement in the range of 50 nm - 5 microns with inaccuracy of 50 nm.
Mechanical contacts probed with picosecond ultrasonics
Authors: Dehoux Thomas , Tomoda Motonobu , Wright Oliver B.
Published: May 2008

We investigate the contact between a thin metal film and a ball bearing indented to nanometre depths using picosecond ultrasonics. The area of contact is acoustically imaged to micron spatial resolution using GHz acoustic pulses produced by ultrashort pulsed optical excitation of the film through a transparent substrate. In particular, acoustic echoes are detected through transient optical reflectance changes that are monitored by probe optical pulses. In this way we image the acoustic reflection coefficient at the interface between the film and the indenter. In addition, by imaging the arrival time of the acoustic echoes we determine the penetration profile of the indenter to nanometre precision. Furthermore, imaging the transient thermoreflectance gives a different means for measuring the contact area through spatial variations in thermal diffusion. We thus demonstrate that picosecond ultrasonics and thermoreflectance provide powerful tools for the non-contact evaluation of mechanical contacts. These techniques could be applied to the in situ characterization of contact interfaces between machine elements.
Acoustic waves generated by a laser point pulse in a micrometric fiber
Authors: Segur Damien , Shuvalov Alexander , Pan Yong Dong , Chigarev Nikolay , Rossignol Clément , Audoin Bertrand
Published: May 2008

Having emerged in the 1980s, the laser ultrasonics technique with its non-contact generation and detection process overpasses the difficulties of coupling piezoelectric transducers with curved surfaces. To date, the authors [1] have been interested in acoustic generation for cylinders opaque at a given laser wavelength and for the acoustic source located at the cylinder surface. In this presentation, assuming point focusing of the laser pulses, we propose a three-dimensional (3D) semi-analytical model for acoustic waves generation and propagation in a partly transparent isotropic cylinder. First, the radial displacement at any position on the free surface is derived, in a 3D Fourier domain, for an inner point source. The response to a volume-source distribution along a radius is obtained as a convolution of the above Green function with the corresponding source distribution caused by optical absorption. Three inverse transforms are then applied to obtain the radial displacement at the cylinder surface. Picosecond ultrasonics experiments are performed on different micrometric fibers and compared with calculated waveforms for different optical absorptive properties. References [1] Y.D. Pan, C. Rossignol and B. Audoin, Appl. Phys. Lett. 82, 4379 (2003).
Simulations of Thermally Induced Photoacoustic Wave Propagation Using a Pseudospectral Time-Domain Method
Authors: Sheu Yae-Lin , Li Pai-Chi
Published: May 2008

Physical models used to evaluate thermally induced photoacoustic waves in biomedical applications are mostly approximations based on certain hypotheses, such as the thermal and stress confinements, for the sake of obtaining analytical results. On the other hand, using numerical methods to solve the general photoacoustic wave equations gives detailed information of wave phenomena without making as many assumptions. The photoacoustic wave generated by thermal expansion involves the heat conduction theorem and the state, continuity, and Navier-Stokes equations. In this study a numerical approach was developed in 2.5D axis-symmetric cylindrical coordinates using a pseudospectral time-domain (PSTD) scheme. The method is efficient for large scale simulations in that only two grids for the smallest wavelength are required, where in conventional methods 10̃20 grids are typically needed. The numerical techniques include Berenger's perfectly matched layers (PMLs) for free wave simulations, and linear-perturbation analytical solutions are used to validate the simulation results. The numerical results using 2 grids for the minimum wavelength in simulation domain agree with theory to within an error of 7×10-3 in the absolute differences. On the other hand, conventional methods such as finite-difference time-domain method requiring 10 grids result in an error of 1.3×10-3.
Applications of psychoacoustics to information technology products
Authors: Beltman Willem M. , Doherty Rina A. , Salskov Eric , Corriveau Philip J. , Gabel Doug , Baugh Eric
Published: May 2008

Emerging usage models for computing devices require low acoustic noise, for example in home entertainment systems. Studies have shown that not only the overall level, but also the psychoacoustic aspects matter. This paper provides an overview of testing techniques that are used in the information technology industry and outlines two specific case studies. First, an extensive subjective psychoacoustic study was designed and conducted in multiple geographies to determine the aspects of sound that best describe the annoyance to sound from information technology products in a home type environment. Over 200 participants in four countries participated in this carefully controlled experiment and rated typical steady state sounds on a 5 point annoyance scale. The relevant sound quality metrics were extracted and geographical variations quantified. Second, in a paired comparison study the influence of modulation on annoyance was investigated by superimposing different frequency and amplitude modulated sounds onto a baseline sound. The results indicate that modulation can have a significant effect on subjective perception.
An algorithm modelling the Irrelevant Sound Effect (ISE)
Authors: Schlittmeier Sabine J. , Weissgerber Tobias , Kerber Stefan , Fastl Hugo , Hellbrueck Juergen
Published: May 2008

Verbal short-term memory capacity is reduced significantly during certain background sounds. Remembering a series of digits is significantly impaired by speech or music with prominent staccato passages whereas, for example, music with prominent legato passages does not disturb performance in comparison to silence. This so-called Irrelevant Sound Effect (ISE) occurs although the background sounds are irrelevant with respect to the digit sequences to be remembered. Until now, a multitude of cognitive psychological experiments explored the ISE and collected behavioral performance data during different sound conditions. The talk presents an algorithm which models performance data in ISE experiments, i.e. the detrimental impact of background sounds on memory performance. The data base of this algorithm is about 50 background sounds and corresponding performance data, which have been collected in cognitive psychological experiments at the KU Eichstaett-Ingolstadt. The algorithm is based on the instrumental measuring of the hearing sensation fluctuation strength and is able to reconstruct the performance results in about 90% of cases within the interquartile ranges. The algorithm will be discussed within the scope of cognitive short-term memory models, which claim to explain the ISE and with respect to practical implications.
A Structuralistic Approach to Acoustic-Auditory Functions of Meaning
Authors: Jekosch Ute , Altinsoy Ercan , Merchel Sebastian
Published: May 2008

In this paper we introduce a methodology of semio-acoustics to get information on how human listeners associate meaning to acoustic-auditory events. We concentrate on identifying cues in the auditory stream listeners base the association of meaning on as well on modelling major characteristics of the reference system of meaning. The methodology we use is closely related to structuralism, an approach that has its origins in semiotics. In principle, structuralism differentiates between creating functions, carrying functions and changing functions of systems of meaning. We concentrate on carrying and changing functions here using the following procedure: a sign-carrier (in our case an acoustic-auditory event the association of meaning is based on) is decomposed into sub-units. By a minimal pair analysis we investigate carrying and changing functions of acoustic-auditory features with regard to the associated meaning. We will introduce the methodology used and discuss first results of a pilot study.
Signal processing algorithms for speech in fluctuating noise
Authors: Nelson Peggy , Rutledge Janet , Tejero-Calado Juan Carlos
Published: May 2008

Fluctuating background noise is a significant problem for listeners with sensorineural hearing loss (SNHL). Data indicate that fluctuating noise significantly affects both speech understanding and satisfaction with hearing aids. Listeners with SNHL do not take advantage of momentary dips in the noise and thus to not experience release from masking in fluctuating noise, as normal-hearing listeners do. Our results have shown that listeners with SNHL obtain about half of the masking release of their normal-hearing counterparts, and that this masking release is generally related to the audibility of the speech in the noise dips. Current slow-acting amplitude compression is based on the level of the background noise and does not improve the audibility of speech in the dips of fluctuating noise. Fast-acting multiband compression can improve audibility but may produce unwanted artifacts. Fast-acting algorithms based on spectral peaks shows potential for maximizing the audibility of speech in fluctuating noise to improve speech intelligibility, with limited artifact. Portions of this work are supported by the University of Minnesota and Starkey Laboratories.
Numerical study of the transition to chaos in nonlinear forced vibrations of plates
Authors: Camier Cédric , Touze Cyril , Thomas Olivier , Bilbao Stefan
Published: May 2008

Geometrically nonlinear vibrations of free edge circular plates subjected to a harmonic excitation are discussed. Particularly, transition from periodic to chaotic motion is observed when increasing the amplitude of the forcing. The present work is devoted to reproduce numerically these highly nonlinear behaviours. The temporal integration of such dynamics, including instabilities and chaotic regimes, is not straight forward because a stiff problem with a very large number of dofs is at hand. Consequently, numerical instabilities are observed when typical Runge-Kutta schemes are applied. To settle the matter, two methods have been tested and compared. They both rely on a modal approach applied to the von Kármán's model for large amplitude vibrations of plate. For the first one, the energies of the plates are expressed at the continuous level. The Hamiltonian of the system is then derived and discretized using the eigenmodes. The Hamiltonian formulation ensures the conservation of energy. An implicit time discrete scheme is then chosen to approximate the equations of motion. For the second one, the Gear's BDF method, implemented in the IMSL Fortran library, is used to integrate the nonlinear oscillator equations.
Estimation of received acoustic levels in the near-field of a ship
Authors: Barber Christopher
Published: May 2008

Measured acoustic levels at the face of a receiver in close proximity to a ship in shallow water can differ substantially from the levels predicted by applying standard propagation models to a source level determined from a far-field radiated noise measurement. At distances typical of mine-ship engagements, the dimensions of the source (ship) can be large with respect to range, ocean depth and acoustic wavelength, and the ship cannot be approximated as a single point source, nor is the receiver necessarily located outside the acoustic near field. Direct free-field measurements of ship radiated noise at short range are problematic, so that the received acoustic level in the near-field of a ship must be estimated from other available information. Options for generating such estimates are presented, including a hybrid approach combining empirically-derived transfer functions, a virtual distributed-source representation of the ship, and in-situ hull vibration measurements. The potential for computational methods such as BEM - FEM and measurements such as Nearfield Acoustic Holography to provide an improved understanding of the vibration sources, structural responses, radiation mechanisms and propagation paths associated with the radiated noise field of realistic ship structures is also explored. (Work sponsored by ONR Code 331).
Some notes on the sound reduction index of pax cabins panels on cruise ships
Authors: Biot Marco , De Lorenzo Francesco
Published: May 2008

The issue of comfort of passenger ships has became in the last years of paramount importance; in this context the noise and vibration control plays a leading role. The concept of comfort on board is subjective and it is impossible to define it with simple formula. On the other hand, a few number of significant parameters is commonly used to characterize the level of comfort on board of ships, and the sound insulation index in one of the most important. As known, it has a paramount importance in defining the contractual comfort on board of ships. The report is related with the problem of setting up the sound insulation index for pax cabins, specifically in relation to the nature and characteristics of the panels between cabins.
General model of a structure-borne sound source and its application to shock vibration
Authors: Bobrovnitskii Yuri , Tomilina Tatiana
Published: May 2008

One of the well-known models of structure-borne sound sources is described by the quantities defined at the source-receiving structure interface: by the matrix of the source impedances or mobilities and by the vector of the blocked forces or free velocities. Together with the receiver impedances or mobilities it allows one to predict the vibration field in the receiver and to develop and examine candidates for source characterization. In this paper, it is shown analytically that this model is valid when the sound is generated inside the source by a kinematic excitation as well as by force excitation or their combination and, thus, it represents a rather general model with wide range of applications. Most attention is paid to its peculiarities and limitations when applied to shock sources. Results are illustrated by the data measured in the shock tests of some scientific space instruments.
A Statistical Prosodic Model for Voice Conversion
Authors: Schwarz Jan , Heute Ulrich
Published: May 2008

Nowadays Text-to-Speech (TTS) systems adapt the output voice to the user and the corresponding application. The aim is a personalisation. Thereby, the user is set into familiar surroundings, increasing the TTS acceptance. For example, an e-mail client that may read the incoming messages with the synthesised voice sounding like that of the sender. Such a personalised TTS system is costly; so, voice-conversion (VC) techniques are used to save resources. VC transforms the voice of a ''source speaker'' in such a way that the converted voice sounds like that of another ''target speaker''. This voice sounds only natural, if it includes all features relevant for the true target voice. Here, a main problem is the mapping of the prosody which is one of the essential features. This contribution introduces a statistical prosodic model for voice conversion. It is based on Gaussian-Mixture Models (GMM), trained for the pitch and the duration of diphones. To ensure sufficient data for the GMM training, seven diphone classes are separated as related to the international phonetic alphabet. The suitability for VC as well as limitations, necessary extensions (stress) and problems are pointed out.
Phonological specificity of vowels and consonants in 20-month-olds' word representations
Authors: Ho/jen Anders , Madsen Thomas O. , Vach Werner , Østerbye Torkil , Christensen Karina F. , Basbo/ll Hans , Caporali Sueli , Bleses Dorthe
Published: May 2008

At the onset of word learning around the age of 12 months, infants are highly capable of perceiving native phonological distinctions. However, required to make word-object associations, infants sometimes fail to perceive certain phonological distinctions. The present study used an inter-modal preferential looking technique to examine Danish 20-month-olds' sensitivity to mispronunciations involving either a vowel or a consonant in familiar words. Each mispronounced word could be "reconstructed" to either of two familiar Danish words. By way of example, the English nonword "bock" can be turned into either "rock" or "book" depending on whether the mispronunciation is perceived to be in the first consonant or in the vowel. The results so far indicate that the infants were not differentially sensitive to vowel vs. consonant mispronunciations. This result, in turn, suggests that vowels and consonants do not differ in constraining lexical access to familiar words in Danish 20-month-olds.
Nonnative listeners prefer perceptual cues they know from their L1: Dutch listeners use vowel duration less than English listeners for English final /v/-/f/
Authors: Broersma Mirjam
Published: May 2008

Two 2AFC experiments investigated Dutch and English listeners' use of preceding vowel duration for the English nonword-final /v/-/f/ contrast. Like English, Dutch has a /v/-/f/ contrast, but unlike English, Dutch has no final /v/. Dutch listeners therefore have no native language experience with the use of preceding vowel duration as a final voicing cue. Previous research showed that Dutch listeners used preceding vowel duration less than English listeners when it was invariable in the experiment (Broersma, 2005, JASA, 117, 3890-3901). The present results show that they also used it less when it was varied. An 11-step fricative voicing continuum from a natural /v/ to a natural /f/ and a 7-step vowel duration continuum from a long (originally /v/-preceding) to a short (originally /f/-preceding) vowel were created. In Experiment 1, all steps of the fricative voicing continuum were combined with one long and one short vowel. In Experiment 2, all steps of the vowel duration continuum were combined with the /v/ and /f/ endpoints and with one ambiguous fricative. In both experiments, Dutch listeners used fricative voicing more and vowel duration less than English listeners did. Thus, the nonnative listeners especially used the perceptual cues they knew from their native language.
2004 M6.0 Parkfield earthquake characterization using Time Reversal
Authors: Larmat Carene , Johnson Paul A. , Huang Lianjie
Published: May 2008

Time reversal has proved to be a robust source location method in acoustics and is now being developed for a number of seismic applications. One problem of particular interest is locating sources where the signal-to-noise ratio is small. These include small earthquakes (<M5.5) or atypical seismic sources with a small seismic energy radiation (e.g., tremor, slow earthquakes). Time reversal has been shown to be very robust and work in the presence of poor data, low signal to noise ratio, etc. We present a prototype study showing the power of time reversal, using seismic data from the 2004 M6.0 Parkfield earthquake, which is the world's best recorded event to date and thus one of the most studied. The back-propagation of recorded seismic data in a 3D Earth velocity model is numerically carried out. We show that the reconstructed reverse wave-field exhibits clear focusing at the source point but also displays a four-lobe radiation pattern for each type of rebroadcast waves (body, surface), which is consistent with the known source mechanism: a right-lateral strike slip along the almost-vertical San Andrea fault.
Green's function estimation in speckle using the FDORT method
Authors: Robert Jean-Luc , Fink Mathias
Published: May 2008

The FDORT method (French acronym for Decomposition Of the Time Reversal Operator using Focused beams) is a Time Reversal based method that can detect point-scatterers in a heterogeneous medium and extract their Green's function. It is particularly useful when focusing in a heterogeneous medium. In this presentation, the theory of the FDORT method is generalized to random media (speckle), and it is shown that it is possible to extract Green's functions from speckle signal using this method. Therefore it is possible to achieve a good focusing even if no point scatterers are present. Moreover, a link is made between FDORT and the Van Cittert Zernike theorem. We deduce from this interpretation that the normalized first eigenvalue of the Focused Time Reversal Operator is a well-known focusing criterion. The concept of an equivalent virtual object is introduced, that allows the random problem to be replaced by an equivalent deterministic problem and leads to an intuitive understanding of FDORT in speckle. Applications to aberration correction are presented. The reduction of the variance of the Green's function estimate is discussed.
Super-resolution imaging of active sound and vibrational sources using a time-reversal sink
Authors: Bavu Eric , Berry Alain , Polack Jean-Dominique , Gibiat Vincent , Besnainou Charles
Published: May 2008

Theory and experiments of super-resolution focusing using a time-reversal sink have been investigated in high-frequency regime [Rosny and Fink, Phys. Rev. Lett. 89] and in audible range [Bavu, Besnainou, Gibiat, Rosny and Fink, Act. Acoust., 93]. This technique, generalized to the case acoustic and vibrational imaging of active sources, allows super-resolution imaging and provides a new method of characterization of active sources in a known background medium. This imaging technique involves a measurement in the background medium using an array, and the simulation of the backpropagating-field in a fictive medium. An ideal numerical time-reversal sink (NumTRAS) is then used to refine results and obtain high-contrast, high-resolution imaging of initial sources. The algorithm has been validated in parallel supercomputer simulations, in both vibrational and acoustics fields and has been used to detect active vibrational sources in a clamped Mindlin plate and active sound sources in an anechoic room. All results show high-resolution imaging capabilities when compared with classical time-reversal backpropagation. NumTRAS provides an alternative to other imaging and source detection techniques, such as acoustic holography and beamforming. Beyond the applications of acoustic and vibrational non-destructive evaluation of industrial structures, NumTRAS has applications in evaluation of musical structures and is being tested to detect and characterize moving sources.
The Centre: It's Impact on Ocean Science---Past, Present and Future
Authors: Bradley David
Published: May 2008

The Centre (NATO Undersea Research Centre) was formed in 1959, in response to the (then) clear Soviet Union expansion of submarine operations and consequent threat to the NATO Alliance. It began as an experiment to provide a "water leveling" of ASW capability to the Nations of the Alliance. The combination of multi-national staff, on site for 3-5 years for the most part; together with the resident staff, has made this "experiment" an incredible success. The contributions to this success come in two parts: Specific work and scientific progress on site at the Centre and equally importantly, continued international collaboration upon return to one's Nation. The primary purpose of this presentation is to provide some "data" to illustrate both the impact of the Centre on Ocean Science and it's role within the Alliance. Given the rather specific circumstances that lead to the creation of the Centre, the question should be (and is) asked: "Should the experiment end?" The simple answer is: "NO!" The Centre is poised to have an even more critical international role in the future: The knowledge and stewardship of vital marine resources.
Analysis and comparison of acoustic insulation in dwellings and buildings, recently build
Authors: Meza Leonardo
Published: May 2008

At this work the acoustic quality of new dwellings is analyzed from acoustic insulating measurements taken in both single-family dwellings and buildings. Through this work is intended to conduct a case study in order to know the acoustic quality of dwellings built after the year 2001, which fulfill the in force regulations called Basic Standards for Building. Therefore, acoustic insulation tests where realized in-situ in sitting rooms and bedrooms of the dwellings. We performed a total of 30 trials according to the ISO standard measure 140-5. This work is part of an investigation that will continue with the implementation of the Basic Document HR Code Technical Construction in Spain, which recently entered into force, so that this future will be how to compare the real benefits obtained with the implementation of this new regulation, to make a new campaign measures in dwellings built fulfilling this new regulation.
Opera House Acoustics - Case Studies of Renovations
Authors: Holden Mark
Published: May 2008

In the Unites States, there has been a rapid increase in the number and type of perfomance halls built and renovated in the last 10 years. New Opera Houses are few, however three significant Opera Houses have been renovated by our firm, including the Seattle Opera House, The Houston Grand Opera House, and the Kennedy Center Opera House in Washington DC, home of the National Opera. This paper will discuss, compare and contrast approaches to pit design, wall shaping and ceiling shaping, materials for surfaces and orientation and distribution of acoustic volume. Design calculations and completed measurement data, where applicable, will be presented.
AIA/FGI interim acoustical guidelines for health care facilities
Authors: Tocci Gregory C. , Cavanaugh William J.
Published: May 2008

Currently, noise is one of, if not the most prominent complaint of hospital care by patients and staff. In response to a growing concern for sound in hospitals and other types of healthcare facilities, the Facility Guidelines Institute (FGI) of the American Institute of Architects (AIA) has asked for assistance in incorporating acoustical guidelines into their Guidelines for the Design and Construction of Health Care Facilities. A group of 40 acoustical consultants and persons from the architectural and medical professions were assembled to develop the resulting 32-page document entitled "Interim Sound and Vibration Design Guidelines for Hospital and Healthcare Facilities." The document divides the variety of health care facility acoustical design issues into 6 sections as follows 1) site exterior noise, 2) interior finishes, 3) room noise levels, 4) sound isolation and speech privacy, 5) electroacoustics and alarms, and 6) building vibration. The presentation will provide an overview of the Interim Guides as they are expected to be adopted into the 2010 issue of the AIA/FGI Guidelines for the Design and Construction of Health Care Facilities.