bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient elastography: changing clinical practice in hepatology
Authors: Sandrin Laurent , Yon Sylvain , Fournier Céline , Miette Veronique
Published: May 2008

Transient elastography is one of several new approaches that have recently been proposed to manage liver diseases. This quantitative method is used in clinical practice to assess liver fibrosis noninvasively and rapidly. The technique consists in generating low-frequency elastic shear waves through the liver and measuring their velocity using ultrafast pulse-echo ultrasound acquisition. Liver stiffness is directly related to shear waves velocity. Nowadays more than 400 devices (Fibroscan®, Echosens, Paris, France) are being used worldwide in clinical practice. Studies reported a strong correlation between liver stiffness and the fibrosis stage obtained by liver biopsy in patients with chronic liver diseases: hepatitis B and/or C, HCV co-infection, HIV, alcoholism, etc. Stiffness measurements obtained using transient elastography are in good agreement with measurements performed using other elastography techniques (magnetic resonance elastography and radiation force). Main limitations of transient elastography are related to the morphology of the patients. Examinations may be difficult or impossible in overweighted to obese patients and in children. New probes have been developed for children and obese patients. Using these probes and dedicated measurement procedures the performance of transient elastography is significantly improved. The development of transient elastography currently focuses on heterogeneous stiffness measurement.
Towards the modeling of high-frequency ultrasound scattering from cells
Authors: Falou Omar , Kumaradas J. Carl , Kolios Michael C.
Published: May 2008

High-frequency ultrasound is a novel method to detect cell death based on changes in cell morphology that cause alterations in the acoustic properties of cell ensembles in tissues. In previous work, our group has suggested that for cells with a nucleus to cell volume ratio of 0.33, the backscatter response from single cells was best modeled as a fluid sphere. However, for cells with a larger nucleus, neither the fluid nor the elastic sphere models showed a good agreement. We hypothesize that cells with a large nucleus ratio (> 0.33) may be modeled as an elastic sphere surrounded by a fluid shell. In this work, the backscatter response from non-nucleated cells (Strongylocentrotus purpuratus oocytes) was measured Experimental RF lines were acquired using the VisualSonics VS40B ultrasound biomicroscope using 20 and 40 MHz transducers. A finite-element model of wave propagation was developed to solve high-frequency ultrasound scattering from spheres. A very good agreement was found suggesting that the cytoplasm of the oocytes is of fluid nature. Finally, a finite-element model treating the cells as having an elastic nucleus surrounded by a fluid shell is compared to experimental measurements. The implications of these findings on the prediction of ultrasound backscatter from cells are discussed.
Ultrasonic vibrometer for tissue characterization
Authors: Martin James S. , Rogers Peter H. , Gray Michael D.
Published: May 2008

Ultrasonic vibrometers are well suited to a variety of tissue-characterization tasks because they exploit the lateral resolution and depth of field available with diagnostic ultrasound systems for measurements at lower frequencies. In the past, ultrasonic vibrometers have been used to measure the motion of surfaces with high impedance contrast to their surroundings (otoliths, swim bladders, and lung tissue). New ultrasonic vibrometry techniques have been developed and tested that permit calibrated real-time (amplitude and phase) transduction of sub-nanometer-amplitude vibrations at audio frequencies. These can be configured using either analog or digital demodulation for carrier signals up to 10 MHz. In the fully digital configuration, the vibrometer offers better displacement resolution than has been previously reported for analog systems. It also has the capability to simultaneously distinguish between the displacements of multiple discrete vibrating scatterers or regions within a continuum of scatterers by exploiting a multi-sine carrier signal. Individual vibrating targets are separated by pulse compression and windowing. This reduces the problem of carrier drop-out or speckle noise that occurs when multiple reflections destructively interfere at the receiver of a narrow-band signal. The technique should permit the vibrometer a depth resolution comparable a typical pulse-echo ultrasound system. [Work supported by ONR.]
ANAIS: An ultrasound mammograph
Authors: Mensah Serge , Lasaygues Philippe , Debieu Eric , Franceschini Emilie
Published: May 2008

It is well established that ultrasonography is a cost-effective, patient-friendly imaging modality available for breast imaging. The main aim of this paper is concerned with a tomographic ultrasound mammograph allowing 3D-reconstruction of the uncompressed breast immersed in a water tank. The scanner, based on a 1024 semi-circular motorized antenna, provides more efficient way to view anatomical ductal structures of the breast. Quantitative volume parameter cartography is the unique means to make objective, reproducible, and operator-independent diagnoses (Computer Aided Diagnosis). The recovery of quantitative acoustical parameters requires solving a nonlinear inverse scattering problem from large amount of measurements. This is achieved using advanced computing resources; a front-end acquisition system based on 32*1024 multiplexed channels and specific reconstruction procedures. The objective is not only to offer a multiparameter tissue characterization using reflection and transmission measurements but also to provide a systemic inspection of the ductal tree.
Hydroflown: MEMS-based Underwater Acoustical Particle Velocity Sensor
Authors: Akal Tuncay , De Bree Hans-Elias , Guerrini Piero , Maguer Alain
Published: May 2008

The increasing problems related to homeland security and harbour/infrastructure protection have increased the level of interest on vector sensors. Market surveys carried out during the last three years gave the conclusion that there is a need for a new generation, small size, and low-cost underwater sensors capable of measuring particle velocity in three dimensional plain within a broad frequency band (2 Hz - 50 kHz) and with high angular resolution. The small size MEMS-based sensors developed by Microflown Technologies BV Inc are the world's only commercially available transducers that are capable of measuring the particle velocity, instead of pressure, in air. The development of a new generation, innovative and low-cost underwater sensors and technologies based on that in-air nano technology is therefore considered. This technology has a great potential to become a revolutionary underwater acoustic sensor using nano-technology, capable of finding many applications like sensors for Autonomous Underwater Vehicles, sensors for directional receivers for underwater acoustic systems, Floating autonomous systems, Sensors for seismic towed arrays for underwater oil and mineral prospecting and harbour and water-side infrastructure protection. This paper describes how Microflown technology can be adapted to underwater applications.
Computational fluid dynamic analysis of optimized windscreens for UAV based acoustic arrays
Authors: Prather Wayne E. , Bridges David H. , Edwards Tom , Thompson David S.
Published: May 2008

As part of an overall effort to place acoustic sensors on airborne platforms for surveillance applications, analysis studies were performed of acoustic probe windscreens that could minimize wind noise and be made relatively insensitive to small angle of attack and sideslip excursions. Through a collaborative effort between Miltec Research & Technology, Mississippi State University Department of Aerospace Engineering, Raspet Flight Research Laboratory, and the Engineering Research Center several probe designs were developed and analyzed using inviscid and viscous simulations with the objective of characterizing their flow fields and identifying potential modifications that could improve suitability for use as acoustic measurement probes. Several of the recommended probe shapes were fabricated and tested under real world conditions on an acoustically optimized 1/3 scale Schleicher ASH26 glider test bed.
Artificial characteristic landmarks for SLAM navigation
Authors: Pailhas Yan , Capus Chris , Brown Keith E.
Published: May 2008

The use of autonomous underwater vehicles (AUVs) for a variety of purposes is set to increase in the future. A key issue in the navigation processing, especially for survey applications, is the lack of accuracy or cumulative error introduced by the various position sensors: accelerometer; DVL; compass. Algorithms such as SLAM (simultaneous localisation and mapping) rely on accurate landmark recognition in order to correct the vehicle position. This paper proposes a solution based on broadband sonar and artificial coded landmarks to improve the navigation. Through resolution of the wave equation for acoustic propagation in a multilayer concentric sphere, we will show that there is a great diversity in the echo spectrum with small changes in internal structure. This enables the design of a set of passive landmarks which can be identified unambiguously, since each has a characteristic signature or 'spectral code' when insonified with a broadband sonar.
Surround sound echo cancellation in the spherical harmonic domain
Authors: Atkins Joshua , West James
Published: May 2008

The problem of creating a multiuser hands-free immersive telecommunications environment poses many challenges for acoustic signal processing. The most pressing is the creation of a fast multichannel acoustic echo canceller (MCAEC) to eliminate acoustic feedback created in the speaker-microphone loop. Traditional multichannel adaptive algorithms for echo cancellation are not fast enough to work in systems with highly correlated multichannel signals like those found in the traditional telecommunications setup. This work presents analysis of a proposed acoustic echo cancellation system that operates in the spherical harmonic domain. Transforming the microphone and speaker signals into the spherical harmonic domain reduces both the number of channels and the correlation between channels for faster convergence of the adaptive MCAEC filters. This method also has the added benefit of being independent of the microphone and speaker array configuration, resulting in a hybrid mono/stereo/multichannel acoustic echo canceller. This work is funded by NSF Grant IIS-0534221.
Improving the directivity of a Soundfield microphone using least-squares estimation
Authors: Jin Craig , Kan Alan , Van Schaik Andre
Published: May 2008

Faller [1] has recently shown that highly directive microphone systems can be obtained using coincident microphones and appropriate signal processing to separate direct and ambient sound. We apply this approach to a Soundfield microphone in which coincident virtual first-order microphone patterns pointing in any direction are available. The variation with our approach is that we apply a specific gain pattern across a set of coincident cardiod or hypercardiod microphones to determine the pick-up direction. A least-squares estimate is made of the spectrum of the on-axis sound. We empirically investigate the performance of this directive microphone technique. [1] C. Faller, "A highly directive 2-capsule based microphone system," in Proc. of 123rd Audio Engineering Convention, New York, U.S.A., October 5-8, 2007.
Towards 'not so spherical' microphone arrays
Authors: Epain Nicolas , Daniel Jérôme
Published: May 2008

An increasing number of applications require that the sound field spatial properties are accurately described. Using arrays consisting of omnidirectional microphones distributed at the surface of a rigid sphere has been proven to be an efficient yet practical strategy to obtain such three dimensional sound field descriptions. However these sensor arrays are known to suffer from frequency limitations, mainly due to the sphere directivity properties. In this paper, it is proposed to optimize the shape of the object upon which the microphones are located, in order to make them more directive. Results of measurements and simulations show that such "not so spherical" shapes could help at widening the microphone array frequency range.
Study of a concert harp's radiation using acoustic imaging methods
Authors: Leclere Quentin , Le Carrou Jean-Loic , Gautier François
Published: May 2008

Recent studies have been conducted to understand the low frequency radiation of a concert harp. Experiments have been carried out in a semi-anechoic room: the harp's soundboard is excited with a shaker and the pressure is measured at more than 600 positions on a nearly hemispherical surface at a distance of about 2 m from the instrument. Simple source models with a set of monopoles have been optimized to fit the measured acoustic radiation. These models are very satisfactory in the low frequency domain but cannot properly reproduce the measured field above 350 Hz. The aim of this paper is to present the application of acoustic imaging tools to this academic case: volumetric velocity and acoustic power maps in the harp plane are computed with an optimized beamforming and with a regularized inverse FRF method up to 1 kHz. The optimization of the beamforming is realized using a variable windowing factor, and the regularization of the inverse FRF method with a Tikhonov approach. The presented results permit the evaluation of the importance of the bass reflex effect in the harp, of the contribution of the first bending modes and of the contribution of the soundbox vibrations in the radiated sound field.
Prediction of perceived sound quality of hearing aids (algorithms) using perceptual models
Authors: Huber Rainer
Published: May 2008

This contribution presents an overview of basic approaches for predicting the perceived sound quality of hearing aids and hearing aid algorithms using auditory processing models for hearing impaired. Comparison-based concepts will be considered in particular. The main characteristic of these concepts is the comparison of internal representations (the outputs of the auditory models) of a test and a reference signal. While this approach is straight-forward and has proven to be successful for the prediction of sound quality of lossy speech and audio processing systems perceived by normal-hearing listeners, the requirement of a reference representing the optimal quality can pose a problem in the case of hearing aids and hearing-impaired listeners. The potential and limitations of comparison-based approaches will be illustrated by example results from different studies obtained with an extended version of the perceptual audio quality model PEMO-Q.
Whispering in your ear: a recent history of subminiature transducers
Authors: Warren Daniel M.
Published: May 2008

For 50 years, the history of hearing aid transducer development could be read in a simple photograph and timeline, where the size of the transducer was inversely correlated to the year it was developed. This size curve corresponds to hearing aid development over the same time period, progressing from body-worn aids in the 1940s to large behind-the-ear (BTE), smaller BTE's, in-the-ear (ITE), and successively deeper in- the-canal (ITC) devices through the 1990s. Although size still matters, in the last decade there has been less effort in reducing the size of hearing aids and more on increasing features, usability, and comfort. Development of hearing aid transducers has become similarly multidimensional. This paper charts the progress from the linear smaller-is-better design model to lower vibration, higher acoustic output, lower current draw, reduced radio frequency interference, wider bandwidth, and other multifaceted challenges of modern hearing aid transducer design.
Leveraged motion underwater sound piston transducers
Authors: Butler John , Butler Alexander L.
Published: May 2008

Flextensional transducers use leveraged shell motion to produce enhanced acoustic radiation from compact sources, which are often used in low frequency underwater sound applications. The most commonly used flextensional is the Class IV where an oval shell is driven along its major axis by a stack of piezoelectric ceramic elements. We present here a review of a new class of leveraged transducers in which the shell motion drives pistons attached to the shell at the location of maximum magnified motion. Because of the uniform motion of the pistons, greater source strength and radiation load is attained compared to the tapered motion of flextensional shells. The leveraged motion typically yields a motion magnification of approximately three and an impedance load magnification of approximately nine, resulting in reasonably low Q for a compact low frequency transducer. Various designs are presented and illustrated including one in which the piezoelectric drive simultaneously acts as a tail mass and one which operates in a high impedance velocity control mode under array conditions. Lumped models as well as FEA models and measured results are presented to illustrate the concept and performance of PZT and PMN-PT driven designs. [Work supported in part by ONR.]
Electro-active polymer transduction for distributed netted sensing
Authors: Jones Dennis F. , Blottman John B. , Richards Roger T.
Published: May 2008

The Naval Undersea Warfare Center in Newport, RI is developing an electro-active polymer-based sensing node for use in a persistent distributed underwater surveillance system. Persistence demands extreme energy conservation measures. The node will resemble a jellyfish in form, complete with tentacles housing a volumetric array of light-weight piezoelectric polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) copolymer cylindrical hydrophones designed for an ultra-low power acoustic receiver. Each cylinder has conductive silver electrodes on the inside and outside surfaces, a length of 2.5 cm, an outside diameter of 11 mm, a 1 mm wall thickness, and a mass less than 2 g. Operating in the hydrostatic mode, the hydrophone sensitivity is typically -195 dB//1 V/μPa and is stable with both hydrostatic pressure (50 to 1000 psi) and temperature (-1 to 35°C). [Work supported by the Office of Naval Research.]
Input impedance measurements of conical acoustic systems using the two-microphone technique
Authors: Lefebvre Antoine , Scavone Gary
Published: May 2008

The two-microphone technique with a broadband excitation has been used for the measurement of various objects including straight conical waveguides and alto saxophones. An improved procedure has been developed whereby the noise excitation signal is pre-filtered by the inverse frequency response of the system under consideration. This approach helps reduce distortion and improves the SNR of the measurement. Results with and without pre-filtering are compared for different fingerings of an alto saxophone. The input impedance of a straight conical waveguide is compared with theory and discrepancies are analyzed. The input impedance of saxophones are evaluated with the transmission matrix approach and compared with measurements. A software environment for efficient comparison and analysis of measurement data with theoretical calculations is presented. We also propose a framework for sharing raw measurement data among researchers to allow comparison of results obtained with different apparatus on similar objects to better quantify their accuracy.
A practical way to measure intonation quality of woodwind instruments using standard equipment without custom made adapters
Authors: Kausel Wilfried , Kuehnelt Helmut
Published: May 2008

Woodwinds are not much different from brass instruments in how intonation is determined by air column resonances. Nevertheless, it is easier to measure input impedance of brasses because the input cross-section at the mouthpiece rim is circular, plane and big enough to be easily coupled to standard measuring heads. In reed instruments the input cross-section is neither flat nor circular nor well defined. Flute instruments not even have any definable input cross-section as this is controlled by the player's lower lip. On top of that, flutes are played at an open end where some coupled impedance considerably influenced by the nearby environment like lips, mouth, and face of the player has to be taken into account. Existing approaches to measure input impedance of woodwind instruments usually require custom made adaptors optimised to yield nearly accurate intonation results for a specific instrument and playing range only. The proposed new approach is to separate instrument head or mouthpiece from the body and measure both parts from their cylindrical ends. During the measurement a natural playing condition can be simulated at the now available end. Both measurements can be assembled computationally yielding useful intonation results as will be demonstrated for flutes and saxophones.
Measured and calculated sounding frequencies of pipes coupled with free reeds
Authors: Cottingham James , Dieckman Eric A.
Published: May 2008

The Asian free-reed mouth organs incorporate approximately symmetric free reeds coupled to pipe resonators. Previous research has shown that the reeds in these instruments behave as “blown-open” reeds in which the playing frequency is above both the natural frequency of the reed and the first peak of the measured impedance curve. Measurements of the input impedance have been made for a variety of these instruments. Detailed calculations of input impedance have also been made using transmission matrices, taking into account the position of the reed along the pipe, tuning slots, finger holes, and nonuniform cross sections. These calculations are in good agreement with the measured impedances of the same instruments. If the reed is treated as a damped, driven harmonic oscillator, the sounding frequencies of these reed-pipes can be predicted using a phase relation between the reed vibration and the phase of the complex impedance. [Research supported by National Science Foundation REU Grant PHY-0649007.]
Mode transition of a flue organ pipe
Authors: Adachi Seiji , Angster Judit , Miklos Andras
Published: May 2008

A flue organ pipe can be excited in various acoustic modes by changing the air pressure supplied to it. This research aims to reconstruct this behavior from the result of numerical flow simulation of a jet deflected by sound and from physical modeling simulation of the total sound production system. In the numerical flow simulation, motion of the jet in the pipe mouth was replicated: The jet emerges from a flue and travels in a space where the air oscillates laterally to the jet direction. As a result, the jet oscillates with the same frequency as the oscillation of the air i.e., sound. From the flow simulation, a model of the jet deflection was developed. This model was then used as a model of the sound source in the physical modeling simulation where not only the sound source but the resonance of the pipe is also modeled in a set of differential equations with delayed feedback. The mode transition observed in the physical modeling simulation was discussed by comparing with that experimentally observed.
Development of an adjustable pipe-foot model of a labial organ pipe
Authors: Außerlechner Hubert , Angster Judit , Miklos Andras
Published: May 2008

In order to understand the physical processes involved in the build-up of the sound signal in a pipe (in our case a labial organ pipe) a pipe-foot model has been developed, with which the main important parameters, such as positions of the lower- and upper-labium, the wind pressure in the foot and the width of the flue can be adjusted. Moreover, different types of languids and pipe bodies (resonators) can be attached to the model. For the reason of corresponding to a real metal organ pipe these parts of the model are made of “organ metal.” The reproducibility of measurements is provided by the micrometer screws applied for the adjustments. Flow and edge-tone measurements were carried out with the help of this model. A comparison with real organ pipes gives some indications for the range of the parameters. Because of the flexible adjustments and the large range of values of every parameter, it is possible to find different ranges with varying parameter settings for the occurrence of the edge-tone. The analysis of these measurement results shows the dependency of the edge-tone of the adjusted parameters.
Very-low frequency range influence for free reed instruments physical modeling
Authors: Millot Laurent P.
Published: May 2008

Measurements of the inner and outer over-pressure for a diatonic harmonica were performed during blown, drawn, and bend notes notably. Using an energy analysis based on a nonregular spectral decomposition of the energy with only 10 frequency subbands, the IDS analysis, we have compared the relative weights of each subbands for both inner and outer pressure signals. This comparison underlines the key role played by the very low frequency range (0-50 Hz) and justifies a physical modeling without any waves occurrences but taking into account only acoustical flows descriptions. Within the presentation the audience will listen these phenomena and will access an explanation of the details of the physical modeling which has been used and which permits to refind chromatical playing on a diatonic harmonica, including the vocal tract player. We will also propose some clues to include a pipe in the modeling in order to study instruments like the sheng or the harmonium for instance.
Jet noise from large-scale turbulent structures
Authors: Morris Philip J.
Published: May 2008

The generation sound by large-scale turbulent structures in jets, where the structures are convecting supersonically with respect to the ambient speed of sound, is well understood. The pressure pattern generated by the large-scale structures couples directly with the radiated sound field. An instability wave model for the development of the large-scale structures gives excellent predictions of both the near and far acoustic fields. However, when the structures are convecting subsonically, there is no general agreement as to how or even whether they generate any noise directly. Recent experimental evidence has shown a remarkable similarity between the jet noise spectra in the vicinity of the peak noise radiation direction for both subsonic and supersonic jets. This suggests that the large-scale structures do contribute directly to jet noise radiation at all jet operating conditions. In the present paper a model is developed for the noise generation mechanism. Using experimental measurements of the far field noise, the near field pressure pattern required to generate the noise can then be calculated. The question of whether this pattern is consistent with a reasonable physical model for the evolution of the large-scale turbulent structures is then discussed.
Effect of jet temperature on jet noise: data and requirements for modeling
Authors: Viswanathan Krishnamurthy
Published: May 2008

The modifications to the jet spectra caused by the heating of the jet have been the subject of experimental and theoretical research since the early 1970s. Early experimental data produced ambiguous and contradictory trends, which complicated the modeling efforts. Disparate theories have been proposed; however, no fundamental explanation or theory exists to date. First of all, a comprehensive experimental program has been carried out to establish the effect of temperature on jet noise. Detailed analyses indicate that in addition to the jet velocity (Vj/a), the jet temperature ratio, either stagnation or static, is an independent controlling parameter. The spectral shape at the lower radiation angles (measured from the jet inlet) is universal and independent of the jet Mach number and temperature. In the aft directions, the spectral shape is controlled by the jet temperature ratio, regardless of the jet velocity. These recently established trends have not been incorporated in any existing theory. The modeling of the effects of jet temperature and the suitability of the proposed formulations in existing theories are examined; the need for fresh thinking and the requirements for a good model are highlighted.
Simulation of jets exhausting from chevron nozzles and their noise
Authors: Uzun Ali
Published: May 2008

Environmental concerns and strict noise regulations around major airports have made jet noise a crucial problem in present day aeroacoustics research, as it is the jet engine exhaust that is responsible for much of the noise generation during aircraft takeoff. Chevron nozzles have drawn a lot of attention recently due to their noise reduction benefits. Chevrons typically reduce low frequency noise at aft angles while providing an increase in high frequency noise at broadside angles relative to the jet. The streamwise vorticity generated by the chevrons affects the jet shear layer mixing and thus is responsible for the decrease or increase in noise over certain frequency ranges. The ultimate goal in chevron design is to decrease low frequency noise as much as possible while preventing the increase in high frequency noise. In our research, we are performing high-fidelity numerical simulations of jets exhausting from chevron nozzles to gain a better understanding of chevron jet shear layer mixing. These simulations employ a large eddy simulation tool utilizing state-of-the-art numerical techniques. In this talk, representative results from our research will be presented and an assessment of our current prediction capability of chevron jet noise will be provided.
On the separation of hydrodynamic and acoustic waves in linear free-shear flows
Authors: Agarwal Anurag , Gabard Gwenael
Published: May 2008

The governing equations for sound propagation through free-shear flows, like jets and mixing layers, are the linearized Euler equations. These equations support both hydrodynamic and acoustic waves. For an aeroacoustician wishing to study the refraction effects of a sound source by shear flows, it is important to distinguish the acoustic solution from the hydrodynamic waves. Agarwal et al. (AIAA J., Vol. 42, No. 1, 2004) presented a technique to achieve this in the frequency domain. In this talk, we present a time-domain technique to separate the hydrodynamic and acoustic waves. The idea is to implement a filter that filters out only the acoustic wave solution from the linearized Euler equations. Some sample solutions are presented for two-dimensional free-shear flows and comparisons are made against known analytical solution for parallel flows and from solution obtained by approximate methods, which have a limited range of applicability. The advantage for the present technique is that it is applicable to arbitrary frequencies and flow profiles.
Experimental analysis of the wall aerodynamics and acoustic radiation of the trailing edge of an airfoil in subsonic flow
Authors: Bonamy Cyrille , Gervais Yves
Published: May 2008

This experimental study treats of the trailing edge noise mechanisms, especially broadband noise, resulting from the hydrodynamic wave diffraction on the sharp edge of a foil in flow, with the aim of improving its modeling. A detailed review of the dynamic behaviour of the phenomenon characteristic aerodynamic quantities (wall pressure and velocity fluctuations) has been made on a Naca 0012 airfoil and particular statistical data analysis have been performed (POD, temporal and spectral visualizations, spatial filtering by transducer array). Some models from the literature related to the wall pressure statistics (Corcos, Chase) have been adjusted and validated, and finally used for the modeling of the noise from the trailing edge of the airfoil. To conclude, measurements of the radiated acoustic pressure have been made in an anechoic wind tunnel, showing as a result the validity and limits of the implemented aeroacoustic model. The approach proposed by Chase in terms of wall pressure statistic modeling appears to be able to correctly represent the influence of the problem main parameters (Reynolds number, airfoil incidence).
From strategic noise maps to action plan: Perspective of Spanish main roads
Authors: Jimenez Maria Dolores , Rubio Jesus , Segues Fernando , Fernandez Pilar
Published: May 2008

The Direccion General de Carreteras of the Spanish Ministry of Transport is finishing the process of Strategic Noise Mapping of Spanish major roads (EGRA). The whole National road network that has been noise mapped for the first END has a length of 6.400 km round. The present paper contains - Some conclusions from the process of noise mapping; - A general view of the process of making decisions about Action Plans; - Definition of the first steps to decide the scope of Action Plans: design of a pilot study to establish the elements needed technical studies, coordination with other administration bodies and public involvement.
Decision support system for Action Planning in the framework of the European Noise Directive
Authors: Borst Jeroen , Lohman Walter J. , Eisses Arno R. , Miedema Henk M.
Published: May 2008

The European Noise Directive (END) requires assessment of noise exposures as well as the formulation of Action Plans for the reduction of the number of people harmfully affected by environmental noise. TNO is developing a decision support system for noise mitigating measures. The proof of concept of such a system for road noise is presented here. On the basis of a detailed noise map, for each road segment an indication is given for the amount of negative effect (e.g., number of people being highly annoyed) per meter it is causing. On the basis of the characteristics of the road segment, the system suggests possible noise mitigation measures. The effect of the measure chosen by the user, such as the application of silent road surface types or lowering speed limits, can be interactively explored with the system. It directly shows the updated detailed noise contour maps as well as indicators describing the impact after a measure has been applied though the interactive interface.
Noise Action Plan in the Ile-de-France region: a complex process
Authors: Mietlicki Fanny
Published: May 2008

The transposition of the European Noise Directive (END) into French law was achieved in April 2006. Noise maps have to be established before June 30, 2007 and action plans have to be set up before July 18, 2008 for agglomerations with more than 250,000 inhabitants and for major infrastructures. The State representatives at the departmental scale are in charge of the infrastructure maps, while the local authorities are in charge of the agglomeration maps. The Paris agglomeration which counts 11 million inhabitants is made of 396 towns. Since some of them are grouped into cooperation structures for noise issues, there are 238 entities in charge of the application of the END in the Paris agglomeration. To face this administrative complex situation, Bruitparif has developed a program to help local authorities in setting up the END. Different actions are lead: - providing information and technical assistance on how to establish noise maps and action plans, - conducting noise measurements in order to validate maps and to provide complementary information, - coordinating actions and initiatives, - consolidating the map of the Paris agglomeration from the local maps in order to estimate the noise exposure, - preparing guidelines for the action plans.
Tire/road noise reduction
Authors: Ossipov Alexander , Engel Marc
Published: May 2008

Traffic running on high speed roads is a considerable source of noise annoyance and is frequently a source of complaint by the general public. One of the components of this noise is generated by the interaction between motor vehicles tires and the road surface. The amplitude and frequency content of this noise is a function of many parameters, including the road surface texture, tire dimensions, tire materials, and construction and the tread pattern design. The paper provides detailed insight concerning the factors influencing exterior (environmental) and interior (vehicle) tire/road noise reduction and includes recommendations with regard to optimize tire design.
Evaluation of Directive 2000/14/EC on outdoor machinery noise
Authors: Dittrich Michael G.
Published: May 2008

The European Directive 2000/14/EC sets a requirement for noise labeling for the sound power level of 57 types of outdoor equipment, and sound power limits for 22 of these. In the NOMEVAL project the Directive and its amendment 2005/88/EC were evaluated, resulting in recommendations for an update of the equipment list, the noise limits and the test codes. A European database of noise emission data was assessed, and environmental bodies and industry were consulted. The recommendations were also based on environmental, technical and economic impact assessments. A new environmental indicator was applied to rank the impact of the different equipment types. It was found that many types currently without noise limits have a higher impact than those with noise limits. Some new types of equipment have been identified including snowmobiles, mobile waste breakers and screens, motorised brooms, handheld cut-off saws, and power pruners. The technical impact assessment was based on current technology and trends and the feasibility of new or stricter limits. The economic impact assessment was based on estimated societal benefits versus the estimated additional cost to the consumer or purchaser. Finally, a number of instruments for further reduction of outdoor equipment noise were proposed.
Procedures of large scale noise mapping - examples based on German projects
Authors: Petz Markus
Published: May 2008

Noise mapping projects for the German Federal States Baden-Wuerttemberg, Hesse, and Schleswig-Holstein and for the cities Munich, Frankfurt, and Wiesbaden are presented. These large projects have been performed using newest software technology like fully automated parallel computing applying the PCSP technique (Program Controlled Segmented Processing) and by using all CPU cores of the noise mapping computer cluster (multithreading). With the noise mapping for all main roads and railways in Austria the 64 Bit technology has been applied - this allows to handle even files of more than 10 GB without the need of manual intervention. The influence of these techniques on uncertainties is discussed using the strategy of DIN 45687 and it is shown that such complete 3D models are the optimal basis to develop noise reduction measures in the frame of Action Planning.
Urban noise mapping - an approach to the establishment of standard making procedure
Authors: Vukadin Predrag , Bublic Ivan , Tudor Ivan
Published: May 2008

The Directive 2002/49 relating to the assessment and management of environmental noise and the Croatian legislative derived from it defines the basic rules to carry out strategic noise mapping. However, in real life situations, each mapping project implies a different approach, depending on various case related distinctions e.g. availability and quality of input data, extent of noise annoyance, the form and the volume of output data to be presented, etc. Based on the experience from various urban noise mapping projects, this work is an approach to defining key steps in urban noise map production and establishing standard step-by step procedure, and an attempt to define the procedure for each step. Examples for each step are given based on the case studies from our previous urban noise mapping projects.
Differences among European noise mapping methods
Authors: Kephalopoulos Stylianos , Paviotti Marco
Published: May 2008

This article will present the differences among noise maps of Lden and Lnight levels produced following the EU Interim methods and those produced following other national methods used in the EU MS. Lden and Lnight are the two indicators required by the European Environmental Noise Directive (2002/49/EC) defined at the position of 4 m height and 2 m away from the facade of a building. Four different comparisons will be presented for road, railway, industrial, and aircraft noise. This article will also focus on the methodology used to assess the equivalence among the national methods against the interim ones as well as the statistical approach used to consider uncertainties. Finally, the input values used, the parameters and the lay-outs of the four protocols corresponding to the four environmental noise sources (i.e., road traffic, railway, industrial, and aircraft noise) adopted for the equivalence exercise will be also presented.
Presenting Noise Mapping Information to the Public
Authors: Hinton John F. , Rasmussen Soren
Published: May 2008

Directive 2002/49/EC of the European Parliament and of the Council of 25 June 2002 relating to the assessment and management of environmental noise requires Member States to undertake strategic noise mapping. It also refers to legislation regarding access to the information from strategic noise maps, since it requires “that the strategic noise maps ... are made available and disseminated to the public in accordance with relevant Community legislation ... and in conformity with Annex IV ... to this Directive.” Under its terms of reference for 2007 the European Environment Agency's (EEA) Working Group on the Assessment of Exposure (WG-AEN) was asked to produce a Position Paper containing the Group's ideas and suggestions on good practice and associated strategies for presenting noise mapping information to the public at local and national levels. Many of these ideas and suggestion were developed from the outcomes of a workshop held in London in October, 2006. The final draft of the Position Paper was completed in December, 2007. This conference paper and associated verbal presentation will provide an overview of the contents of the Position Paper and report on developments since December, 2007.
Acoustical and micro-structural properties of recycled grains and fibres
Authors: Horoshenkov Kirill V. , Khan Amir , Benkreira Hadj , Pispola Giulio
Published: May 2008

This paper presents a systematic study into the production, characterisation and modeling of the acoustic behaviour of highly heterogeneous, low density porous layers having a complex pore size distribution. A new cold extrusion production method was developed at the University of Bradford to process recycled polymeric fibres and grains so that accurate control of the pore size distribution and the porosity of the resultant porous product could be attained. In this way high values of the acoustic absorption coefficient could be obtained in a relatively thin porous layer throughout the design frequency range . Two approaches were used to model the acoustic performance of the manufactured porous media. The first approach requires the direct numerical integration of the Biot viscosity correction function which depends on the probability density function of the pore size. The other approach assumes a low permeability contrast between the two porous scales so that the acoustic properties could be estimated using the semi-phenomenological models of Johnson and Lafarge for the viscous and thermal dynamic permeabilities. Numerical results predicted by the two models were then compared with impedance tube experimental data showing good accuracy of the selected prediction methods.
On the diffusion of sound energy in porous materials
Authors: Prodi Nicola
Published: May 2008

The sound intensity was used in the past to describe the surface properties of porous materials. Actually no extensive study used the same concepts to describe the properties of the energy flow inside the material. As known, the sound intensity has a twofold nature, that is an active part transferring the energy out of a point and a reactive one localizing the energy. These features are crucial in the development of the new model for the propagation of the energy inside porous materials developed in this work. In fact, by means of the intensimetric approach, it is shown that the one-dimensional transfer of sound energy can be fully described as a diffusion process. The role of the active and reactive sound intensities is outlined and specific parameters are defined to account for the material behaviour with respect to the transfer of the sound energy. Moreover the sinks of energy and the sources of reactivity in the material are derived and discussed.
Adsorption in activated carbon and its effects on the low frequency performance of hearing defenders
Authors: Bechwati Fouad , Cox Trevor J. , Avis Mark R. , Umnova Olga
Published: May 2008

Activated carbon displays interesting behaviours at low frequencies due to its large internal surface area and complex network of pores of various sizes and shapes. The material can produce larger than expected absorption and change the compliance of acoustic enclosures. This paper investigates the performance of hearing defenders which utilize activated carbon as the lining material of the cup. Compared to a standard foam liner, the introduction of activated carbon increases the insertion loss by up to 15 to 20 dB at frequencies between 31.5 and 250 Hz. The enhanced insertion loss is due to the increase in stiffness and apparent volume of the cup cavity as the activated carbon is introduced. This is probably due to the substantial change in local density as air molecules adsorb onto, and desorb from, the activated carbon pores during sound propagation. There is a change in entropy and energy loss from the sound wave during the adsorption/ desorption process due to the existence of a hysteresis loop. This additional absorption enhances performance.
Proof of the existence of large complete band gaps in high frequency silicon phononic crystal plates
Authors: Mohammadi Saeed , Eftekhar Ali Asghar , Khelif Abdelkrim , Hunt William D. , Adibi Ali
Published: May 2008

We show, for the first time, the evidence of the existence of large phononic band gaps (PBGs) in two-dimensional phononic crystal (PC) plates formed by etching a hexagonal (honeycomb) array of air holes through a free standing plate of silicon (Si). A CMOS compatible fabrication process is used on a Si on insulator (SOI) substrate to realize the PC devices. More than 30 dB attenuation is observed for eight periods of the hexagonal lattice PC at high frequency region, i.e. 133 MHz with a band gap to mid gap ratio of 25%. We show that the experimental results agree very well with the theoretical predictions for the PBG. This result opens a new direction in the implementation of high frequency practical PC structures for a variety of applications especially wireless communication, and sensing.
Bubble phononic crystals
Authors: Bretagne Alice , Tourin Arnaud , Tabeling Patrick , Leroy Valentin , Pannacci Nicolas , Willaime Hervé , Fink Mathias
Published: May 2008

Our aim is to investigate phononic crystals consisting of periodic arrangements of micron size gas bubbles. Such crystals are of great potential interest. Because of the high compressibility and high acoustic impedance contrasts between gas and water, a gas filled bubble in water is indeed a strong acoustic scatterer with a large value of its resonant wavelength compared with its size and a scattering cross section several orders of magnitude larger than its geometrical cross section. In that sense a microbubble can be viewed as the equivalent of an acoustic atom and even a small size sample made with such bubbles is expected to have a dramatic impact on acoustic propagation. Using microfluidics techniques we were able to produce perfectly monodisperse gas bubbles in a liquid. When these bubbles (radius=50 μm) are then injected into a liquid with surfactant, they are found to organize themselves to form an hexagonal close packed crystal. Its stability has still to be optimised before testing it successfully with acoustic waves. The calculation of the band structure of that crystal with the plane wave expansion (PWE) method confirms its interest for controlling propagation of MHz-ultrasounds: a 800-kHz wide band gap around 1.85 MHz is predicted.