bluuebunny/crossref_metadata_2025 huggingface dataset:
Significance of Psychoacoustic Aspects for the Evaluation of Vehicle Exterior Noise
Authors: Genuit Klaus
Published: May 2008

For 25 years acoustic engineers have been using specific measurement technologies and analyses to determine sound quality of vehicle interior noise. However, with regard to exterior vehicle noise only standard measurements, e.g. the A-weighted sound pressure level (ISO 362), have been used and interpreted so far. Extensive knowledge and experiences concerning the evaluation of interior noise are still unutilized for an advanced assessment of vehicle exterior noise. Within EU research projects, such as SVEN or QCity, exterior noise was investigated, methods established and psychoacoustic analyses carried out. The relevance of vehicle exterior noise with respect to perceived product quality was underestimated for a long time. Today, manufacturers recognize the importance of exterior noise beyond the annoyance perspective. Vehicle exterior noise conveys an impression of product quality. By optimizing the product sound quality manufacturers can compete against others and meet increased requirements. Customers prefer vehicle sounds which match their expectations, which also applies to the exterior sound of a vehicle. The acoustical fingerprint of a vehicle - inside and outside - provides enormous marketing opportunities. This paper shows how the knowledge of sound quality analyses with regard to interior noise can be transferred to the evaluation of exterior vehicle noise.
Rating the Dieselness of engine-sounds
Authors: Fastl Hugo , Priewasser Bernhard , Fruhmann Markus , Finsterhölzl Herbert
Published: May 2008

Sounds of idling Diesel engines were rated according to their Dieselness with two different psychoacoustic methods. On the one hand, a yes/no procedure was used. Subjects were presented sounds of two seconds duration and had to answer by yes or no to the following question: Does this sound stem from a Diesel engine? Histograms were calculated and a hypothesis was put forward as follows: The more positive answers are given to a specific sound, the larger is the Dieselness of this sound. On the other hand, the method of paired comparison was used, applying a kind of Bradley-Terry-Luce (BTL) procedure. Results are discussed with respect to the psychophysical method used and possible differences in ratings by expert versus naive listeners. Finally, psychoacoustic data are compared to predictions of Dieselness calculated by four different algorithms.
Synthesis of pass-by railway noise
Authors: Khan Shafiquzzaman , Ulhas Mohite , Goel Virendra
Published: May 2008

Pass-by railway noise is one of the main problems in the community. Typically pass-by railway noise is estimated using Leq or Lden in dB(A) and often these methods do not reflect the listener perceptual overview. It is therefore necessary to reduce the pass-by railway noise by synthesizing the noise characters into various segments. The segments could be based on the physical properties of rail vehicles like rolling, traction, pantograph, cooling system noise, etc. There are few other segments which are also based on the perceptual view of the pass-by railway noise like squeaking, rattling or beating (tadak, tadak). In this study only a few of the physical characteristics of the railway noises are examined. The idea of synthesization is to determine what segments in the noise characters are annoying. And thereby make a virtual pleasant pass-by railway sound. Several pass-by noises from Swedish rail vehicles were recorded using binaural technology according to ISO 3095. Recorded noise signals were then analyzed with the help of spectrogram analysis using Matlab. The results of the studies indicate that the rolling noise and broadband noise are most annoying for the long distance passenger rail vehicles.
Noise mapping of public roads in Norway: New calculation tool based on the Nord2000 Road Engineering Method
Authors: Milford Ingunn
Published: May 2008

To comply with requirements in the Directive 2002/49/EC on environmental noise (END) and to national guidelines on land use and transport noise, the Norwegian Public Roads Administration has developed the calculation tool called NorStoy, which is composed of two main modules: 1. A calculation module with the Nord2000 Road Engineering Method algorithms. 2. An ArcGIS module to arrange the input data, delimit the calculation area, locate the calculation points and report the results. Nord2000 Road Engineering Model was completed in 2006, in cooperation with the Nordic countries. The model has very much in common with the coming joint European Harmonoise model. The challenge in using these models is to obtain an acceptable calculation time. To prevent NorStoy from stopping every time insufficient data occurs, we use default values based on either a typical mean value or the nearest registered value. At this time preparing input data is quite time consuming. We are able to produce the noise maps for the EC directive, but NorStoy is not yet an efficient tool for noise mapping in general. The development of NorStoy is still in progress.
The Port of Livorno noise mapping experience
Authors: Morretta Mario , Iacoponi Andrea , Dolinich Fabrizio
Published: May 2008

Livorno Municipality and its seaport are requested to produce the strategic noise map according to the European Directive only in 2012. However Livorno Port Authority, following the principle of environmental sustainability and in coherence with its EMAS status, started the investigation about the interaction between the noise generated by port activities and the nearby city. This analysis has been carried out within the Life funded project NoMEPorts, whose goal is to develop and provide tools and expertise to European ports for implementing their strategic noise maps, by means of a collaborative mapping of 8 Port Authority technical representatives from all around Europe. The work presented outlines in detail the process followed in performing the noise mapping of the Livorno port area and the port-city interface area, focusing in the problems encountered in the data collection, in port noise model building steps and in the consequent solutions adopted. The paper also talks about the result obtained by showing the noise maps in six detail levels and reports about the action plan proposed. As a result this experience emphasises the importance of noise maps as a powerful tool for decision-makers in port planning.
Mixed Industry and Traffic Noise Mapping
Authors: Boutin Céline , Bigot Alexis
Published: May 2008

The authors have a large experience on Noise Mapping of both transportation sources and industrial plants. This paper provides examples of Noise Maps for Communities of different sizes with road, railway and industrial sources. The difficulties to estimate Noise Emission from industrial sites are discussed. Recommandations are provided. A Methodology to create the Industry data base for a Noise Map with a large number of industrial sites in the territory is presented. It is shown how Noise Maps can be an attractive tool to be used in the Environmental Management System of the Plant Manager to communicate on the Plant environmental integration and Noise Abatement Plan.
Comparison of International Standards for Measuring Sound Power in Tool-Machines
Authors: Ballesteros Jose A. , Fernandez Marcos D. , Quintana Samuel , Suarez Ivan , Rodriguez Laura
Published: May 2008

Industrial noise is one of the most important contaminant agents in the industrialised countries due to its effects on health. Sound power is used in order to characterize the noise emitted by the machines because it does not depend on aspects like place or distance of the measurement. These measurements are handled by international standards like UNE-EN ISO 374x and UNE-EN ISO 9614-x. The advantages and disadvantages of each one of these standards have been evaluated after making a representative number of measurements in several types of tool-machines and then, a set of recommendations have been derived to choose the best standard depending on the machine that is going to be measured.
Phase spectral processing for improved time-domain soft microphone based noise estimation
Authors: Paraskevas Ioannis , Rangoussi Maria , Potirakis Stylianos M. , Savvaidis Stylianos
Published: May 2008

'Soft Microphones' (SM) constitute a cost-effective, yet quality alternative to the multiple microphones measurement, in applications related to noise mapping. SM offer a solution of great interest to real field applications, e.g., industrial plants. The SM approach, proposed in previous work of the authors, is based on the estimation of the noise signal and the calculation of noise levels over a set of points within the space of interest. To this end, a novel, frequency domain method was introduced and verified in a real field, textile plant experiment, with satisfactory results. However, in order to expand the use of SM from accurate noise mapping to a full Active Noise Control application, it is necessary to obtain accurate noise signal estimates in the time rather than the frequency domain. Further research into the deconvolution step of the proposed method reveals that discontinuities, appearing across the phase spectrum of the estimated signals, cause ambiguities that affect the deconvolution process. We propose here the use of the Hartley transform phase spectrum, which conveys fewer discontinuities as compared to its Fourier Transform counterpart, while it allows for a discontinuities compensation scheme. Experimental results verify that phase spectrum preprocessing provides accurate time domain signal estimates.
Sensitivity analysis and non linear parameters estimation of porous materials from normal sound coefficient absorption measurements
Authors: Garoum Mohammed , Idchabani Rachida , Tajayouti Mohammed , Rhachi Mohammed , Moreno Antonio
Published: May 2008

In literature, various models have been proposed in order to predict characteristic impedance Zc and wave number kc of porous materials. To use these models their involved nonacoustical parameters (i. e. flow resistivity, tortuosity porosityœ) are usually measured. Unfortunately measurements require specialised equipments and are often difficult on loose porous materials leading most often to erroneous values. Moreover, the inverse estimation of theses parameters from experimental data is not an easy task as believed. This is due to the non linearity of models and the presence of some parameters with weak and/or linearly dependent influences. In this work an approach based on the tradeoff between magnitude and linear independence of the sensitivity matrix components is presented in order to achieve an efficient ranking of parameters according to their inherent ease of estimation. Next this approach is associated to Genetic Algorithms to minimize the least squares norm between measured and modelled normal sound absorption coefficient. For five widely used models in literatures, the application of the proposed inverse estimation procedure on loose granular cork and vegetable fibres, shows that, unlike classical gradient approaches methods, better estimation has been obtained.
The effect of mechanical elasticity on the surface impedance of a organic/inorganic composite aerogel
Authors: Dong Winny , Dong Wayland , Faltens Tanya , Scott Elizabeth , Thompson Travis
Published: May 2008

Previous reports on the acoustical properties of monolithic silica aerogels have indicated that although the material's high porosity, pore tortuosity, and surface area contribute to a low sound velocity in the material, the rigid matrix of the aerogel exhibit a high reflection coefficient. Work by Forest et al. and others have shown that using granules instead of silica aerogel monoliths, the acoustical properties can be significantly enhanced. We report the acoustic properties of a polydimethylsilicate (PDMS)/silica composite aerogel that has both high surface area and a mechanically elastic matrix. Both monoliths and granules are studied. The surface impedance (at normal incidence) as a function of open porosity, pore size distribution, surface area, elasticity, and granule size will be reported.
On the adsorption-desorption relaxation time of carbon in very narrow ducts
Authors: Mellow Timothy J. , Umnova Olga , Drossos Konstantinos , Holland Keith , Flewitt Andrew , Kärkkäinen Leo
Published: May 2008

Loudspeakers generally have boxes to prevent rear wave cancellation at low frequencies. However, the stiffness of the air in a small box reduces the diaphragm's excursion at low frequencies. Hence the size of the box is generally a compromise between low frequency performance and practicality. Activated carbon has been found to increase the apparent size of a given box through adsorption of the air molecules when the pressure increases and likewise desorption when it decreases. However, the exact viscous effects in the granular structure are difficult to model. Thus it is impossible determine the high frequency limit due to the natural adsorption/desorption relaxation time in the absence of viscous losses. In this study, a tube model is presented which takes into viscous and thermal losses with boundary slip together with adsorption. Impedance measurements are performed on an array of 12 million holes, each 2 micrometers in diameter, etched in a 0.5 mm thick silicon wafer so that the viscous and thermal losses can be verified against the model without adsorption. Impedance measurements are then performed on an array of holes coated with graphite in order to create an activated carbon-like structure, thus enabling the adsorption/desorption relaxation time to be evaluated.
Acoustic emission before avalanches in granular media
Authors: Gibiat Vincent , Plazza Eric , De Guibert Pierre
Published: May 2008

Avalanches of granular media are mainly characterized by the observation and the measurement of the main angles of avalanche corresponding first to the movement of isolated beads and to the whole movement of a great part of the grains. These characterisations do not give any information about the rearrangements of the grains inside the layer of granular beads. As any movement of a grain produces a deformation of the structure it is quite normal to expect for a sound that will propagate inside the granular medium. We present an experimental study of the precursors of avalanches on spherical granular glass beads and silica aerogels in powder (size of grains less than 80 micrometers). Acoustic emission has been recorded with two piezoelectric transducers placed on the lower part of the material layer. Our results show clearly that before any movement on the upper part of the beads layer, so for an angle less than the first angle of avalanche, movements inside the material produce pulsed sounds that can be recorded. Theses vibrating events are occurring more and more when the angle is increasing until the first angle of avalanche where acoustic emission becomes intense.
Time-Resolved Spectroscopy of Water confined in Vycor
Authors: Cucini Riccardo , Taschin Andrea , Bartolini Paolo , Torre Renato
Published: May 2008

We present measurements on water confined in Vycor 7930 by heterodyne-detected transient grating experiments (HD-TG) [1]. We studied the acoustic wave propagation, the thermal diffusion and the liquid viscous flow through the pores as a function of temperature (-15 - 90 °C) and of the exchanged q-vector (0.63 - 2.5 μm-1). The data show interesting aspects due partly to the confinement effects and partly to the peculiarities of bulk water. Acoustic results are compared with the predictions of the Biot theory finding a good agreement only for the sound velocity data, while the predictions for the acoustic wave attenuation is poor as just reported in [2]. Our technique is able to induce a thermal grating inside the sample. The analysis of the data requires an extension of the Biot theory, that takes into account the temperature variations. Surprisingly, our data show that the acoustic oscillation are not affected by the temperature. The induced thermal grating is also used to analyze the viscous flow of water inside the pores and the thermal diffusion. [1] Time-resolved spectroscopy of complex liquids, edited by Torre R. (Springer, New York) 2008 [2] A. Taschin, R. Cucini, P. Bartolini, R. Torre, Europhys. Lett., in press.
Spectral instruments based on acousto-optical tunable filters: advantages and prospects
Authors: Pustovoit Vladislav , Pozhar Vitold
Published: May 2008

A review of modern spectral techniques and instruments using acousto-optical tunable filters (AOTF) is presented. New approaches for spectrometers and spectral systems development are considered. The following instruments are described: a series of compact spectrometers and spectrophotometers of ultra-violet, visible, and infra-red ranges for Raman, fluorescence, and absorption spectroscopy for various applications, including out-of-door measurements; spectroradiometers for environment monitoring (open air, Earth surface, subsurface and depth seawater), specialised spectral equipment for industrial monitoring (microelectronics, alcoholometry), imaging spectral devices, time-resolve fluorescent spectrometers, and instruments for differential spectroscopy. Also some fundamental problems of AOTF-based spectroscopy are considered: spectrogram correction of instrument function distortions, ultimate spectral resolution of different methods, modulation techniques for instrument function synthesizing, optimization of measurement procedures, including adaptive algorithms. Basic trends of the past 30 years of AOTF-based spectroscopy development are formulated. The most promising ideas are discussed.
Advances in acousto-optic devices based on frequency intermodulations suppression
Authors: Proklov Valeriy V. , Antonov Sergey , Rezvov Yury , Vainer Alexander
Published: May 2008

The limitative influence of the frequency intermodulation effect on the most important parameters in a big family of acousto-optic (AO) devices is well known. The proposed presentation deals with new principles and related technical tools to perform significant suppression of the inherent intermodulation effects within broadband AO devices. The different AO interaction mechanisms in solids offering the intermodulations decrease have been considered. On this basis there were theoretically established and experimentally verified facilities to design a few types of advanced AO devices for a wideband signal processing with the extended spurious free dynamic range, as well as for a flexible laser beam forming with extremely high efficiency and etc.
Acousto-optic collinear diffraction of arbitrary polarized light
Authors: Mantsevich Sergey , Balakshy Vladimir I.
Published: May 2008

Acousto-optic collinear diffraction of light is a type of light scattering interesting as a physical phenomenon and important from practical point of view. This type of diffraction is used in tunable acousto-optic filters. In this case, the incident light has to be linearly polarized along one of the acousto-optic crystal anisotropy axes. If the incident light is not primordially polarized, a polarizer should be disposed at the input of the acousto-optic cell. Unfortunately, this leads to loss of half the light power. The present work is devoted to theoretical and experimental investigation of collinear acousto-optic interaction peculiarities that arise when the incident optical beam is not polarized. It is shown that the output diffraction spectrum in the general case contains four components which have different polarization and frequency. Beating of these components leads to modulation of light intensity passed through the output analyzer. In this work, dependences of modulation components amplitudes on frequency and power of the acoustic wave are examined for different polarizer and analyzer orientations.
Ultrasonic diffraction grating spectroscopy: particle size measurements and investigation of the inertial model for attenuation
Authors: Greenwood Margaret
Published: May 2008

The experimental setup consists of a unit with a grating machined on the surface of the unit. Send and receive transducers are placed at equal angles to the grating surface that is in contact with a slurry. The transmitted beam of spectral order m = 1 reaches an angle of 90° at the so-called critical frequency, where it becomes an evanescent wave that interacts with particles in the slurry. As a result of this interaction, the signal in the receive transducer exhibits a dependence upon particle size of the slurry. Data will be presented for slurries of polystyrene spheres, ranging in size from 45 μm to 467 μm, as a function of the volume fraction. The velocity of sound is also determined from the critical frequency. The distributions will be compared with the viscous and inertial models. The results show that larger particle sizes can be understood in terms of the inertial model, while the smaller sizes can be explained as a result of scattering. Also, arguments will be presented to show that this technique can probe the inertial model, without the simultaneous observation of scattering effects. Such studies can improve the theoretical interpretation of standard attenuation measurements.
Non-reciprocity of acousto-optic interaction at high acoustic frequencies
Authors: Dobrolenskiy Yury , Voloshinov Vitaly , Zyuryukin Yury
Published: May 2008

Modern acousto-optic (AO) tunable filters have reached the values of spectral resolution exceeding 104 and operate with acoustic frequencies up to a few gigahertzes. At such high frequencies and such narrow bandwidths, there appear effects so far neglected. Among them there is non-reciprocity of AO interaction. It consists in the fact that acoustic frequency of light diffraction by ultrasound is different when optic beams propagate in directions opposite to each other. In the present research, the new effect has been studied theoretically and experimentally for the example of collinear AO diffraction. Theoretical analysis and calculations related to particular AO materials have shown that the effect is essential at acoustic frequencies about 1 GHz and higher. The value of the non-reciprocal shift of acoustic frequency can be as high as the frequency bandwidth of the filter. The effect has also been registered and investigated experimentally in a sample of lithium niobate crystal. The experimental data has totally confirmed the theoretical analysis. Therefore, it has been proved that the non-reciprocal effect influences the parameters of AO diffraction and, consequently, operation of AO filters at high frequencies. On the other hand, one can design devices, e.g. directional couples, exactly based on the non-reciprocity.
Theory of resonant acoustic transmission through subwavelength apertures
Authors: Christensen Johan , Martín-Moreno Luis , García-Vidal Francisco Jose
Published: May 2008

The discovery of the phenomenon of extraordinary optical transmission through a two-dimensional array of subwavelength holes in a metallic film has opened a new line of research within optics. The key role played by surface plasmons in transferring light efficiently from the input side of the metal film to the output region was soon realized. This fundamental knowledge enabled extension of this surface-plasmon ability to achieve extraordinary optical transmission and strong collimation of light in a single hole surrounded by a finite periodic array of indentations. Here, we show how these ideas developed for electromagnetic radiation can be transferred to other classical waves such as acoustic waves.
Phononic crystals in the diffraction regime
Authors: Laude Vincent , Benchabane Sarah , Khelif Abdelkrim
Published: May 2008

Phononic crystals are periodic composite materials exhibiting amazing wave propagation properties. In many works, complete band gaps are being looked for, i.e. the materials constituting the phononic crystal and its lattice arrangement are chosen such that propagation for all waves within a prescribed frequency range is forbidden. In other studies, the phononic crystal is considered a metamaterial, the anisotropic spatial dispersion of which can be tuned, and in which negative refraction can even be observed under certain circumstances. Such effects are usually considered in the sub-diffraction regime, i.e. below some critical onset frequency. In this work, we specifically examine phononic crystals in the diffraction regime. Indeed, the boundaries of a finite size phononic crystal embedded in a host propagation medium can be viewed as diffraction gratings, as we show. We will specifically consider two cases: two-dimensional phononic crystals composed of steel rods in water, and two-dimensional phononic crystals for surface acoustic waves achieved by etching cylindrical holes in a solid substrate.
Methods to investigate the possibilities of using a three element periodic structure to suppress the transmission of energy in an elastic tube
Authors: Holst-Jensen Ole , Sorokin Sergey
Published: May 2008

In industrial applications, such as pump and compressor systems, pipe vibrations can exceed an acceptable level. Periodically spaced masses added to the piping are an appropriate method of attenuation, and investigations to develop valid prediction models and measurement techniques has been initiated in the Danish Makunet network. The present investigation concern the effect of three masses attached periodically to a pipe of small diameter. The pipe is small enough that it can be treated as a beam. The masses are eccentric to the center of the beam, to achieve a large change in the moment of inertia by the added elements. The theoretical model is formulated as a system of boundary equations, which describe propagation of flexural, axial and torsion waves within each segment of a tube between periodic elements. An exact solution of this system is obtained and the power transfer is dramatically reduced in some frequency 'stop bands' regardless the excitation conditions. Transfer impedance measurements between the force input and the acceleration on selected positions are used to find the insertion loss due to the application of the periodic elements, showing good agreement with theory.
Acoustic cloaking by two-dimensional sonic crystals
Authors: Torrent Daniel , Sanchez-Dehesa José
Published: May 2008

It has been previously shown that a two dimensional sonic crystal made of a periodic arrangement of solid cylinders in air behaves in the low frequency limit (homogenization) like an acoustic metamaterials with anisotropic effective density and isotropic effective bulk modulus [D. Torrent and J. Sanchez-Dehesa, New J. Phys. February 2008]. Here, the homogenization method is extended to the case of sonic crystals with two types of cylinders in the unit cell, and analytical expressions for the anisotropic effective density are then obtained. Moreover, it will be shown how these new acoustic metamaterials can be used to physically realize the solution for the acoustic cloaking proposed by Cummer and Schurig [New. J. Phys., vol. 9, 45, 2007] [Work supported by MEC of Spain.]
Expected mean in an environmental noise measurement and its related uncertainty
Authors: Paviotti Marco , Kephalopoulos Stylianos
Published: May 2008

In the context of the implementation of the Environmental Noise Directive 2002/49/EC a study on noise measurement uncertainty was developed. In performing any noise measurement average, there might be assumptions over the distribution and independency of the samples. In a concrete example dealing with environmental noise, this might be the case of a series of measurements of a constant noise source like an industrial plant or a fluctuating noise source like road traffic. Using a series of 1 day Leq in the first case, or a series of 15 minutes samples in the second case, the average of these values is usually considered as the expected mean, however, the error caused by the specific selection of the samples is not evaluated. Statistically speaking, before establishing an average value, at least the lognormal distribution of the samples and the effect of adding-up several uncertainties should be evaluated. This article will focus on the formulas to be used and will discuss differences in assessing the expected mean for normally distributed values, or for lognormally distributed, and will suggest an approach to properly add-up all uncertainties related to an environmental noise measurement campaign.
The revision of the French method for road traffic noise prediction
Authors: Dutilleux Guillaume , Defrance Jérôme , Gauvreau Benoit , Besnard Francis
Published: May 2008

A revision of the French method for road traffic noise prediction (NMPB-Routes-2008) has been released. The major principles of NMPB-Routes-2008 are outlined. The most important modifications regarding the source are the reduction of its height and the introduction of two different spectra. In this complete revision, the main change is the replacement of the ISO 9613-2 - based ground attenuation formula in downward conditions by the formula for ground attenuation in homogeneous conditions of NMPB-Routes-1996 with corrected heights in order to take into account the mean curvature of rays (refraction) and its spreading (turbulence). The revised NMPB adds an attenuation term for an occasional cutting embankment. Regarding diffraction the Δdif formula is now suitable for low height barriers. The validation of the revised NMPB with respect to experiment is presented. It is based on measurement campaigns on 6 sites with complex geometries and shows that the predicted noise levels obtained from the revised NMPB are significantly closer to experimental results than in the case of the original method.
A numerical study of sound propagation over urban canyons
Authors: Schiff Martin , Hornikx Maarten , Forssén Jens
Published: May 2008

Because quiet areas in dense urban environments are important, there is high interest in propagation to areas shielded from direct road traffic noise. Sound levels in shielded areas are strongly influenced by distant sources, so intermediate propagation factors such as metrology, screening, and intermediate canyons must therefore be addressed in a realistic propagation model. A numerical investigation of sound propagation across the open tops of intermediate urban canyons has been performed, using the Parabolic Equation and Equivalent Sources methods. Results have been collected for various canyon geometries, and the influence of multiple canyons, canyon/rooftop absorption, variable rooftop height, and correlated versus uncorrelated source models has been investigated. By characterizing the "insertion loss" of canyons intermediate to the source and receiver, the influence of these intermediate canyons could be addressed simply, without the overhead of a detailed numerical calculation.
A validation test for the Acoustic Footprint Mission Planning System
Authors: Velea Doru , Schultz Troy D. , Plotkin Kenneth J. , Rogers Andy
Published: May 2008

QinetiQ North America, Technology Solutions Group (QNA) and Wyle Laboratories have integrated two mature, proprietary technologies into a prototype Acoustic Footprint Mission Planning System. Wyle's Noise Model Simulation (NMSim) uses validated linear noise propagation routines in combination with ray-tracing algorithms based on weather data provided by QNA's Precision Airdrop System (WindPADS) to predict the time history of spectral noise levels from a flying aircraft at any number of user-defined receptor locations. Through interpolation over a ground-based receptor grid, the impact of noise propagated through a stratified atmosphere may be quantified in terms of audibility at any point inside the acoustic footprint. Weather data for the NMSim ray-tracing routines is extracted from the WindPADS three-dimensional forecast of wind, pressure, temperature and humidity in the atmosphere as a function of time. The three-dimensional field is the result of physical and dynamic assimilation of forecast and measured atmospheric data, with wind-forcing by the underlying terrain. This paper describes the results of a validation test performed at Yuma Proving Ground, AZ. It is shown that the noise propagation model predictions agree satisfactorily with the measurements of a C-130 cargo plane. [Work supported by Natick Soldier Center.]
Modal probabilistic analysis
Authors: Heinkele Christophe , Lamarque Claude-Henri
Published: May 2008

In this paper, we first recall a method for estimating the numerical Probability Density Function (PDF) with Parzen-Rosenblatt estimators of experimental data (like the sound absorption coefficient with the Kundt's tube). Then we focus on the model of Mikki which is used as a predictive tool. We are interested then in inversing the model and in identifying the 3 parameters (q,σ,φ) of Mikki's model. But we want to go further and to identify from the estimated PDF directly the PDF of the 3 parameters. We explain first when it is possible, then we give some examples to illustrate the method. This work allows for evaluating the robustness of a model from experimental data.
Sound propagation in a street canyon: A study by modal decomposition
Authors: Pelat Adrien , Félix Simon , Pagneux Vincent , Ayrault Christophe , Richoux Olivier
Published: May 2008

An urban, U-shaped, street canyon being considered as an open waveguide in which the sound may propagate, one is interested in a multimodal approach to describe the sound propagation within. The key point in such a multimodal formulation is the choice of the basis of local transversal modes on which the acoustic field is projected. For a classical waveguide, with a simple and bounded cross-section, a complete orthogonal basis can be analytically obtained. The case of an open waveguide is more difficult, since no such a basis can be exhibited. However, an open resonator, as displays for example the U-shaped cross-section of a street, presents resonant modes with complex eigen frequencies, owing to radiative losses. This work first presents how to numerically obtain these modes and, then, how they can be used as a basis for the modal decomposition of the sound field in a street canyon. Results are compared with experimental measurements on a scale model.
A high-density infrasound array of particle velocity sensors in the Netherlands
Authors: Van Zon Arnout Tim , Evers Laeslo G.
Published: May 2008

A small aperture, High-Density Infrasound Array (HDIA) is being operated by the Royal Netherlands Meteorological Institute (KNMI). This 80 sensor array is part of the geophysical application within LOFAR, i.e. an astronomical low-frequency array in the Netherlands. HDIA occupies an area of 100 by 100 meter, so about the size of a noise reducer used in infrasound arrays for verification purposes. HDIA will be able to estimate the wind-noise correlation length, which has implications for noise reducer design. Of the 80 instruments, 74 are Microflowns. These measure particle velocity and have a directional sensitivity. If two of them are closely spaced, then the azimuth of the incoming sound wave can be calculated from the amplitude ratio. The field setup has 37 elements, each containing a pair of Microflowns. Six elements also have a pressure microphone. We will present the first results of using the vector properties of the particle velocity to estimate the direction of arrival (DOA) of events. These will be compared with DOA-estimates from beamforming of 1) the pressure data, 2) the particle velocity data and 3) pressure data of a nearby 6-element microbarometer array. Furthermore, the observed correlation length of wind will be discussed.
Effect of photoacoustic generation mechanisms on transient grating measurements of thin films on silicon
Authors: Maznev Alexei A.
Published: May 2008

Laser induced transient gratings technique is widely used for non-contact measurements of surface acoustic waves (SAWs). One major application of such measurements is characterization of thin films used in microelectronics. A peculiar phenomenon has been observed in transient gratings measurements of thin films on a silicon substrate: if the film is transparent, there is a systematic discrepancy between the measured and expected SAW velocity values that cannot be accounted for by instrumental errors. However, as soon as the sample is coated by an opaque metal film, the discrepancy disappears. In this presentation, we will show that the origin of the effect is in the competition of thermal and electronic mechanisms of the optical generation of sound in silicon. We will also describe another effect of the same origin observed on very thin semi-transparent metal films: at a certain film thickness, the SAW signal vanishes as the thermal expansion of the film and the contraction of silicon caused by photoexcited carriers cancel each other.
Photoacoustic imaging and laser-ultrasonics using Fourier domain reconstruction methods
Authors: Burgholzer Peter , Berer Thomas , Reitinger Bernhard , Nuster Robert , Paltauf Günther
Published: May 2008

Laser-ultrasonics as well as photoacoustic imaging use optically generated acoustic waves detected at the sample surface to image its interior. In laser-ultrasonics a laser pulse is absorbed at the sample surface generating an ultrasound pulse that propagates into the sample, is subsequently reflected at internal structures, and finally detected at the surface by an interferometer. In photoacoustic imaging ultrasound is generated by heating of light-absorbing structures inside of an optical semitransparent sample. The goal in photoacoustic imaging is to recover the spatial distribution of the absorbed energy density inside the sample from the acoustic pressure signals measured outside the sample (photoacoustic inverse problem). Fourier reconstruction is based on the decomposition into plane waves and is a fast and efficient method used in photoacoustic imaging. Interpolation is needed when signal Fourier components are mapped to source Fourier components. We have shown that the synthetic aperture focusing technique (SAFT) in frequency domain, which needs no interpolation, and the Fourier reconstruction method are mathematically equivalent if the step size of the spatial discretization goes to zero. Both imaging methods are compared using simulated data and measurement data acquired with our interferometer set-up. This work has been supported by the Austrian Science Fund (FWF), project P18172-N02 and project L418-N20.
Stroboscopic interferometric full-field imaging of laser-induced surface acoustic waves
Authors: Sarens Bart , Matsuda Osamu , Xu Xiaodong , Kalogiannakis Georgios , Salenbien Robbe , Côte Renaud , Glorieux Christ
Published: May 2008

Surface acoustic waves (SAW) have the interesting property that they specifically interact with surface and sub-surface regions, rendering them suitable for non-contact investigation of sub-surface properties and heterogeneities. Transmission, reflection and diffraction effects of SAW propagation are analysed in order to reveal information on the region over which they propagate. Laser excitation allows to efficiently excite SAW with short wavelengths, enhancing both the lateral and the depth resolution. Typically information on the waves is collected by scanning a part of the surface of interest with a fast laser probe, using the surface displacement or slope as a real time witness of the wave field. Here we present results obtained by a full field imaging technique [1], in which the sample is repetitively excited by a pulsed pump laser, and the wave displacement field is stroboscopically gathered by illuminating the sample surface with an electronically delayed pulsed probe laser, whose displacement induced optical path variations are visualized by interferometrically analyzing it. In this work, the technique is applied on different samples, varying the geometry of the pump laser beam pattern, the interferometric configuration, and the heterogeneities of the sample. [1] "Phase mask-based interferometer: operation principle, performance, and application to thermo-elastic phenomena", C. Glorieux, J.D. Beers, E.H. Bentefour, K. Van de Rostyne and K.A. Nelson, Rev. Sci. Instrum. 75(9), 2906-2920 (2004).
Laser-ultrasonic defectoscope with focused transducer
Authors: Karabutov Alexander , Podimova Nataliya
Published: May 2008

The novel focused laser-ultrasonic transducer for ultrasonic microscopy of constructive materials is presented. Short and sharp ultrasonic pulse is produced by optoacoustic effect - excitation of ultrasound by absorption of nanosecond laser pulse in special layer. Absorbing layer is integrated with the wide-band ultrasonic receiving system into common unit - laser-ultrasonic transducer. Ultrasound beam is focused by acoustical lens with relatively low numerical aperture (convergence angle - 15°, focal distance - 20 mm). An acoustic impedance of the lens matches that of the laser-ultrasonic transducer. The duration of the irradiated ultrasonic pulse was ̃0.1 μs. The focused laser-ultrasonic transducer was mounted on 3-D linear translation system. The object under control and the transducer was placed in a tank with distilled water. The transducer was moved across the object with 2.5 μm step. The caustic of the probe ultrasonic beam was analyses by sliding the transducer across sharp beard of a knife. The reflected ultrasonic signal was recorded by 12-bit ADC. The diameter of the focal area was 0.53 mm. The length of caustic of ultrasonic was 28 mm. The amplitude of the probe ultrasonic pulse was ̃20 kPa at laser energy 0.1 mJ. The dynamic range of ultrasonic trace measurement exceeded 90 dB.
Determination of filtering parameters for dichotic-listening binaural hearing aids
Authors: Suzuki Yôiti , Murase Atsunobu , Itoh Motokuni , Sakamoto Shuichi
Published: May 2008

Sensorineural hearing-impaired people have difficulty in hearing sounds not only because of the increased hearing threshold, but also because of their reduced dynamic range of hearing (loudness recruitment), as well as the large and extensive masking resulting from the reduced frequency selectivity, especially masking by which middle-frequency and high-frequency components are masked by the intense low-frequency component, the so-called upward spread of masking. Dichotic listening, listening to complementary filtered speech signals given to the two ears, has been proposed to cope with these problems. We introduce a dichotic listening technique for binaural hearing aids and the relationship between the effect of this technique and auditory characteristics of hearing-impaired people. The results of listening tests imply that some relationship exists between the width of the auditory filter and the effect of this technique. Moreover, intelligibility test results obtained using the low-frequency-boosted sounds suggest that this dichotic listening reduced the upward spread of masking. We are applying this technique to hearing aid systems and have begun evaluating the performance of this hearing aid.
The next generation of artificial heads
Authors: Fels Janina , Vorlaender Michael
Published: May 2008

Standardised artificial heads are vital means when it comes to describing the binaural transmission from the sound field into the ear canal or rather the eardrum. In recent years numerous fields of application were created ranging from room acoustics, to product sound design or telecommunications, all based on the well-known KEMAR standard IEC TR 959. In the meantime, however, it has become a well-known fact, that a) specific artificial heads with natural heads or replicas in hearing experiments are superior to standard artificial heads as far as the quality of spatial hearing is concerned and that b) the standardised heads do not comply with the dimensions of an average population (the standard heads are too small). In this contribution first of all today's situation will be assessed and then a possible way will be outlined that could lead to a new future artificial head standard. This includes an adequate match with adult population for various continents, and also new approaches such as children-size artificial heads to measure and fit hearing aids or for new measurement techniques for classroom acoustics.
Acoustical aspects of travel comfort in the aircraft cabin
Authors: Baumann Ingo , Buss Sandra , Freese Nils , Mellert Volker , Weber Reinhard
Published: May 2008

In several European projects tests were conducted during real flights and in aircraft simulators in order to identify important parameters of travel comfort. Physical environmental, physiological and questionnaire data were measured and investigated with respect to human perception. Besides numerous intrinsic quantities affecting health, well-being and awareness of ambience defined measurable environmental parameters influence flight and cabin crews' as well as passengers' perception, psychology and physiology. Sound and vibration are relevant environmental parameters with impact on passenger and crew. Other important influence is caused by e.g. air quality, pressure, local climate. Statistical analysis of the collected data reveals significant correlations between environment and human response for selected groups of test persons. A specific acoustic comfort is not well defined but part of common well-being and comfort. The demand for a general human response model is discussed, which relates ambience and perception.
The Adequate Sound Levels for Acoustic Signs for Visually Impaired in the Sound Environment with Ambient Musics from shops
Authors: Yamauchi Katsuya , Nagahata Koji , Ueda Mari , Iwamiya Shin-Ichiro
Published: May 2008

Providing auditory signs for the visually impaired is one of the most effective ways to support their orientation and mobility. Although the use of such sounds by the visually impaired has been revealed qualitatively, the acoustical properties of ideal sound-designs for them have not known sufficiently, even a basic property such as the sound level of these sounds. On the other hand, the advertising sounds from shops such as ambient musics are the one of the typical sounds in the Japanese downtown. These sounds also disturb their sound information listening and make their mobility difficult. Our previous studies revealed the adequate sound levels of acoustic signs under the road traffic noise environment. This study discusses the the effect of the ambient musics from shops on the adequate sound levels of acoustic signs through the psychoacoustical experiment. The results showed that the difference between the adequate sound level of acoustic signs and the environmental noise levels are larger than that under the road traffic noise environment. This trend is thought to be attributed to the frequency characteristics of the acoustical signs and the environmental noise.
Electronic pass-through hearing protection and directional hearing restoration integrated in a helmet
Authors: Vos Wouter K. , Bronkhorst Adelbert W. , Verhave Jan A.
Published: May 2008

Compared to standard earplugs, electronic pass-through earplugs provide better sound localisation. Provided that the bandwidth is sufficiently wide and the earplugs do not change the shape of the pinnae. However, when a helmet is worn that partially or completely covers the ears, the directional hearing capability is diminished. We attempt to restore directional hearing when wearing a helmet by attaching a microphone array to the helmet. The signals from the microphone array are filtered with Finite Impulse Response (FIR) filters to recreate an individual or generic open-ear Head Related Transfer Function (HRTF). The filters are designed by minimisation of an error measure in the frequency domain. The error measure incorporates both the log magnitude and the phase differences between the original and the recreated HRTF. The global minimum is found using modern optimisation techniques like Particle Swarm Optimisation (PSO) or Differential Evolution (DE). The total system is evaluated with subject experiments. Participants have to localise sounds and rate the quality of sounds. Independent variables are the number of microphones that should be used and their positions on the helmet.