bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards a prediction of the sound transmission from lightweight stairs
Authors: Scheck Jochen , Gibbs Barry M. , Drechsler Andreas , Fischer Heinz-Martin
Published: May 2008

The sound transmission from lightweight stairs which are connected to separating walls often gives rise for complaints. One reason for this is that at present there is no prediction method available. Treating the stair as an active component in a similar manner like vibrating machines stairs can be characterised as structure-borne sound sources. The source data then can be used to predict the sound transmission in buildings using parts of EN 12354. Following this approach investigations on a timber stair have been carried out in a staircase test facility. Based on a full characterisation by contact free velocity and mobility and in-situ measurement using an indirect method, more practical methods like the reception plate method and a characterisation based on a reference power calibration are investigated. The source data obtained was used to predict the sound transmission in buildings.
Impedance of standard impact sources and their effect on impact sound pressure level of floors
Authors: Zeitler Berndt , Nightingale Trevor
Published: May 2008

This paper reports on a systematic study of the Impact Sound Pressure Level (ISPL) due to different standard sources (ISO hammer box, Ball, and "Bang Machine") when applied to a wood-joist floor-ceiling construction with and without various floor toppings. Mea-surement data show that for each floor, the ISPL was different for each source. Not surprising since the blocked force for each source is different. But, after applying corrections for the applied force the ISPL's remain different, suggesting problems since the sources simulate the same human walking activity. Perhaps more importantly, the rank of topping effectiveness (which is simply the difference in ISPL with and without the topping) was different for the three sources. Measurements of the drive point impedance of sources and floors are presented to explain this behaviour and to recognise that the power injected is not just related to the applied force, but also a function the impedance match (or miss-match) between the source and floor. The paper shows using a simple model, it is possible to predict ISPL's for any source if the forces and impedances are known, and using this model floor treatment effectiveness can be correctly ranked by each of the three standardised sources.
Conversion of floor impact sound levels in apartment buildings
Authors: Lee Pyoung Jik , Sato Shin-Ichi , Jeon Jin Yong
Published: May 2008

A procedure to convert the floor impact sound level of the bang machine as well as the tapping machine into that of the impact ball was suggested. Because the bang machine has been the only standard heavy-weight impact source for a long time in Japan and Korea, much of its data is available. The conversion factor of the sound pressure level between the impact ball and other standard impact sources was applied to the sound pressure level of a bang machine and a tapping machine. In addition, a conversion method using a correlation analysis between the sound pressure level of impact ball and that of other standard impact sources at each octave band was also investigated. Results indicate that bang machine and tapping machine data can be successfully converted into impact-ball data, in the case of box-framed type, reinforced concrete structures.
Innovative building systems to improve the acoustical quality in lightweight masonry constructions: Application of resilient joints at junctions - PART 1: Analysis of the experimental results
Authors: Crispin Charlotte , Ingelaere Bart , Vermeir Gerrit
Published: May 2008

The more severe acoustic requirements imposed by the new Belgian standard for dwellings are a real challenge for the building professionals (architects, contractors, building elements manufacturers and suppliers, œ) and more particularly for the market of lightweight materials. An important brick producer in partnership with the BBRI has succeeded to propose efficient acoustic solutions for these kinds of materials by treating in particular the flanking transmission. Indeed, to obtain high sound insulations, the structural transmission paths of noise through the flanking walls cannot be neglected any more. By the application of resilient rubber interlayers at the junctions, these transmission paths are nearly eliminated. A large number of measurements was carried out in order to study in detail the effect of these flexible joints on the sound transmission. These measurements were made in a specially designed laboratory where vibration reduction indexes can be measured for all types of connections and for different loads. We present, in this paper, the measurement campaign and the analysis of the results.
Exposure of building roofs to road traffic noise; consequences on the field performance of skylights
Authors: Villot Michel , Jean Philippe A.
Published: May 2008

In this paper, the exposure to road traffic noise of building roofs is studied both theoretically and experimentally. First, the incident field is estimated using a BEM approach, taking into account the sound diffraction on the roof edge. The theoretical results show significant differences in noise exposure between roofs and vertical façades, particularly with relatively tall buildings; these differences are then confirmed by field measurements. The grazing incidence of the sound fields on roofs raises the question of the acoustic performances of skylights in real situation, as opposed to their laboratory performances measured under diffuse sound field; this problem is experimentally investigated by laboratory measurements of glazing under different angles of incidence, using a big size plane wave generator.
Location of Targets and Scatterers with Ambient Noise
Authors: Harrison Christopher H.
Published: May 2008

By placing a vertical array in an ambient noise field and forming an upward and downward beam one obtains two time series which can be cross-correlated to reveal a sub-bottom profile of the seabed [Siderius, et al., J. Acoust. Soc. Am., 120, 1315-1323, (2006)]. Here the cross-correlation approach is extended to the location in range and bearing of a point target. An experiment was designed using floats and weights mounted (and dismounted) on the same cable as the vertical array. Careful measurements were made of the location of all likely floats, ballast weights, array terminations, and so on. After suitable coherent averaging, peaks were seen at delays (correlation offsets) agreeing with the reflector positions and were shown to be absent when reflectors were removed. An implication for geoacoustic inversion is that, in priciple, the technique can be used to explore scattering as well as reflection properties of layers. A simple extension of the theory developed in [Harrison and Siderius, J. Acoust. Soc. Am., (2007), accepted] is used to explain the amplitudes of the reflections. The approach differs from "acoustic daylight" principally in determining a target range.
Geoacoustic inversion with recreational boat noise
Authors: Van Leijen A. Vincent
Published: May 2008

During the MREA07 sea trials various experiments involved geoacoustic inversion with sound sources of opportunity. A particular experiment that focussed on exploiting the self noise of autonomous vehicles suffered from interfering noise due to increased boating activity in the weekend. In this work the same data is re-examined to study the potential of recreational boats as sound sources for geoacoustic inversion. Even though recreational boats are non cooperative sound sources, in the sense that weekend traffic does not sail predefined tracks and navigational logging is absent, various boats swarm out and cover large areas thus acting as a distributed set of sound sources. A typical small boat signature counts numerous harmonics of narrowband tones that cover the frequency spectre from 100 Hz up to 2 kHz. With these tones matched field inversion and traditional Doppler techniques are used to find an initial geometry of the experiments and these results are fine tuned during the final geoacoustic inversion of a locally range-independent model of a coastal environment. Results of inversions with recreational boating sounds are shown to match with previous analysis results with self noise of autonomous vehicles, bottom grab samples and seismic data.
Fundamental study of shock induced acceleration of cell growth by plane shock waves
Authors: Tamagawa Masaaki
Published: May 2008

This paper describes effects of shock waves on cells to certificate the angiogenesis by shock wave in the clinical application. Especially, the effects of plane shock waves without cavitation bubbles on the endothelial cells are investigated by experiments and computation. In the experiments, the plane shock waves using shock tube apparatus are applied to the endothelial cells. The peak pressure working on the cells in the test case is 0.4 MPa, which is under disintegration level for endothelial cells. After working shock waves on suspended cell, the disintegration and growth rate are measured. It is found that the initial growth rate of the shock-worked cells are clearly higher than that of control ones. As for the effect of rise time of working shock waves, to change the rise time of shock wave, Air and He gas are used as driver gas in the shock tube. As a result, the shorter rise time brings higher growth rate. In the computation, to check the effects of rise time on the pressure and stress distribution on the cells, fluid and structural interaction model are analyzed. The result shows that shorter rise time makes high stress level distribution on the cell membrane.
Photoacoustic cancer imaging
Authors: Steenbergen Wiendelt
Published: May 2008

Photoacoustics, or optoacoustics, involves ultrasound imaging based on ultrasound generated by absorption of light by tissue chromophores such as blood and melanin. Ultrasound is generated when pulsed or intensity modulated light is used which locally deposits a sufficient amount of energy in a sufficiently short time to cause an efficient generation of internal stress in the tissue. When this stress relaxes, an ultrasound wave is emitted which can be detected at the surface of the tissue. On the basis of these ultrasound waves, a threedimensional image the internal distribution of absorption can be constructed. We will discuss various technical implementations of the technique, and will illustrate various medical applications. A particularly important application field is oncology: in cancer, the presence of blood vessels is essential for the tumor to grow and spread. We will show results of photoacoustic imaging performed on small animals with implanted tumors. It appears, that measurement speed is a key issue in obtaining images with sufficient quality. Furthermore, we will show results obtained with our photoacoustic mammoscope on patients with breast cancer.
Detection of elastic and optical contrasts in tissue mimicking phantoms based on the interaction of coherent laser light and transient displacements caused by the acoustic radiation force
Authors: Daoudi Khalid , Bossy Emmanuel , Tanter Mickael , Fink Mathias , Boccara Albert-Claude
Published: May 2008

We recently demonstrated experimentally the possibility to optically detect transient perturbations generated by the acoustic radiation force, applied several centimetres deep in a tissue-mimicking phantom [Bossy et al., APL 90(17), 2007]. We proposed a detection scheme based on the transient decorrelation (millisecond time scale) of optical speckle patterns formed by coherent laser light that propagates through the phantom during the application of the radiation force. We demonstrated that this approach allows to detect optical contrasts embedded several centimetres deep in the phantom, based on the time-evolution of the correlation coefficient during the transient motion of the medium. In the present work, we demonstrate that this approach also allows the detection of shear mechanical contrast. Moreover, the shape of the observed decorrelation curve provides a way to discriminate between an optical contrast and a shear mechanical contrast. We are now currently investigating the feasibility of detecting with spatial resolution the propagation of a shear wave, based on its effect on localized acousto-optic interaction.
Sonic gas analyzer for hydrogen and methane
Authors: Garrett Steven
Published: May 2008

In the late-1800s, Germans used a "methane whistle", known as a Schlagwetterpfeife, to determine the presence of hydrogen or methane in the air that was circulated in mines. This paper describes a modern version of that concept that should be suitable for safety-related applications in mines, sewers, garages that shelter hydrogen or methane-powered vehicles, etc. A compact, self-resonant standing wave tube, 2 cm in diameter and 3 cm long, is capped at both ends by two small electrodynamic speakers. The cylindrical copper resonator has two slits at the mid-plane to allow a 25 mm fan to continuously sample the air which is brought to the resonator's temperature after being drawn along the outside of the resonator body. Variation in the resonator's temperature is compensated electronically by an integrated-circuit temperature sensor that produces one microampere per Kelvin. The sensor can measure the concentration of hydrogen to an accuracy of better than ±30 ppm or methane to ±0.02% in air using phase-locked loop frequency tracking electronics and a voltage-controlled oscillator. Concentration data will be presented for several different gas mixtures and will be compared to concentrations determined by other techniques (e.g., thermal conductivity gauges).
A finite element tool for the analysis and the design of capacitive micromachined ultrasonic transducer (cMUT) arrays for medical imaging
Authors: Caronti Alessandro , Caliano Giosue' , Gatta Philipp , Longo Cristina , Savoia Alessandro , Pappalardo Massimo
Published: May 2008

The fabrication technology of capacitive micromachined ultrasonic transducers (cMUTs) is now mature enough to exploit the potential of this new generation of electro-acoustic transducers in the field of diagnostic medical imaging and non-destructive evaluation. Converting a demonstrator into a commercial product often requires many design and process refinements, and sometimes significant modifications to the fabrication process. Because each design-fabrication-and-test cycle is time-consuming and costly, the development of a modeling tool for the computer simulation of cMUTs is an essential aid to reduce the time to market and costs. Much effort has been put by researchers to develop more and more accurate and smart simulation tools, that advanced from the standard equivalent circuit modeling with lumped parameters to more powerful techniques based on the finite element method (FEM). This paper aims to give an overview of the most ordinary modeling approaches used for the simulation of cMUTs. It is shown that the pulse-echo operation of cMUT arrays for medical imaging applications can be analysed by a set of FEM models developed using a commercial software. The important aspects of the cMUT operation, including electro-mechanical-acoustical coupling and nonlinear effects in transmission, are taken into account.
Ultraviolet detector based on a surface acoustic wave oscillator system with ZnO-nanostructure sensing material
Authors: Wu Tsung-Tsong , Wang Wei-Shan , Chou Tai-Hsu , Chen Yung-Yu
Published: May 2008

Recently, ultraviolet (UV) detectors based on surface acoustic wave (SAW) devices utilizing the acoustoelectric effect have been demonstrated. However, most of presented cases were based on semiconductor sensing films. Sensors with nanostructure sensing material not only possess high sensitivity but also accelerate response and recovery time due to their high surface-to-volume ratio and fast charge diffusion rate. In this paper, ZnO-nanostructure and a dual delay line SAW oscillator system are combined to develop a high precision UV detector. The UV detector is made of ZnO nanorod on a 128oYX-LiNbO3 based SAW device. The operating frequency is around 145MHz. The system is illuminated by a UV source consists of a Xe lamp and a monochromator, resulting in frequency shifts. The frequency shifts related to different light wavelengths and power are measured and discussed. Results show the ZnO-nanostructure based SAW oscillator is a promising candidate for a real-time and high precision UV detector.
Methods for singing voice control and synthesis
Authors: Rodet Xavier
Published: May 2008

There are various methods to synthesize the singing voice. Whatever the method, in order to obtain high quality voice output, it is essential to respect the precise parameter values for the first three to five formants of the vowels. These parameters depend on many factors including the singer, note, vowel, vocal effort, etc. Articulation of the notes is achieved by variations of fundamental frequency, vibrato, vocal effort and eventually formant characteristics of the vowels. Finally, the succession of consonants and vowels also has to be taken into account and implemented. With the expertise of J. Sundberg, a method called Formant Waveform Synthesis and a program for the control of all the above mentioned variations, except consonants, were developed at Ircam in the 1980s. This program permitted high quality singing voice synthesis but without consonants. Another synthesis method is to is to concatenate units of recorded singing voice. This provides good consonant-to-vowel articulations. But it necessitates to transpose and change the duration of these units which often degrades the output quality and precise control over the formant characteristics is rather difficult. These various methods will be discussed and examples given.
Hi-Fi voice: observations on the distribution of energy in the singing voice spectrum above 5 kHz
Authors: Ternström Sten O.
Published: May 2008

Current audio technology enables the weak spectrum of the voice above 4-5 kHz to be studied reliably. It is known that energy in the 5-20 kHz range can be perceived even when it is 50 dB or more below the main voice spectrum peak. Also, these upper frequencies are conventionally emphasized in the production of popular vocal music; yet very few studies of the acoustic content of this range have been made. High fidelity recordings were made of singers sustaining vowels at varying levels of vocal effort. A general characterization of the two highest octaves (5-20 kHz) was sought. The prevalence of high-frequency energy, the variation of harmonics to noise over frequency, and the covariation with overall SPL were all highly variable, but several landmark features were identified. In addition to the commonly observed zero at 4-5 kHz, zeroes were often seen also around 6 and 12 kHz, as were clusters of resonances in the regions 7-10 kHz and 13-16 kHz. Harmonic energy was observed to over 16 kHz in strong female voices. The audibility of these features was assessed by listening tests with selective filtering. A feature-based nomenclature for these uppermost frequency bands is suggested.
Advancing Interdisciplinary Research in Singing through a Shared Digital Repository
Authors: Cohen Annabel J.
Published: May 2008

The domain of research in singing encompasses numerous disciplines, countless styles, and many lifespan stages of skill development. A comprehensive understanding of this domain would benefit from a vast digital repository for storing, accessing, and annotating recordings of singing in all its manifestations. A cross-cultural strategy for acquiring and storing the essential audio, audiovisual, and symbolic data parallels the Child Language Data Exchange System (CHILDES) developed and maintained by Brian MacWhinney (http://childes.psy.cmu.edu/) and used by hundreds of psycholinguistics researchers worldwide. A prototype of a digital repository for singing (http://vre.upei.ca/chimes) is under development using infrastructure at UPEI associated with a Canada Foundation for Innovation project on the enhancement of education through media. The database will support and be supported by an international team aiming to Advance Interdisciplinary Research in Singing (AIRS) on the following themes: (1) acquisition of singing (2) comparison of singing and speech acquisition (3) singing pedagogy (4) singing and intercultural understanding (5) singing and intergenerational understanding (6) singing and well-being. The breadth of the work of Johan Sundberg, an honoured member of this team, encompasses these themes and exemplifies the international, interdisciplinary scope of the initiative. (Supported by Canada Foundation for Innovation CFI).
A vibrating sitar string: Modeling the 3D dynamics of a plucked string impacting a spatial obstacle with friction
Authors: Vyasarayani Chandrika P. , Birkett Stephen , McPhee John
Published: May 2008

In some musical instruments of Indian origin, such as sitar, veena, or tambura, the string termination is a shallow curved (parabolic) bridge. The string is usually plucked obliquely and interacts with the bridge, thus producing a buzzing or ringing tone which is significantly different from stringed instruments with knife edge supports like guitar. The string is also not restricted to planar motion and friction between bridge and string plays an important role in damping the non-planar motion. A mathematical model is presented for simulating a 3D vibrating string as it impacts a curved obstacle with friction. The bridge is represented as a foundation model with nonlinear visco-elastic springs; multiple distributed spatial impacts occur between the bridge and string, however the locations of these are not known in advance so must be determined during the simulation. Galerkin approximation is used to reduce the partial differential equations of motion to a set of nonlinear ordinary differential equations. These equations have been solved numerically for different contact and friction conditions. Parametric studies show the effect of bridge geometry, impact damping, and friction on the bidirectional vibration behavior of the string subject to an oblique plucking idealized as an initial condition.
Acoustical measurement of Indian musical instruments (vina-s): Towards greater understanding for better conservation
Authors: Le Conte Sandie , Vaiedelich Stéphane , Bruguiere Philippe
Published: May 2008

Among the Musée de la musique collection of non-Western musical instruments are some rare and delicate ones from India, which have been the subject of acoustical investigation for a greater understanding, and hence a better conservation. In the case of the vina-s, the vibration of the string (exciter) plucked by the musician is transmitted to the resonators made from gourd through a flat bridge thus giving the instrument a remarkably singular timber. Acoustical and vibrational measurements were applied in order to determine the acoustic properties of resonators. These techniques are based on gauging the radiated acoustical field triggered by a light impact or a frequency sweep. This analysis confirms the importance given by instrument makers to the painstaking choice of gourd resonators. Thanks to the estimation of resonant frequency - and from the vibrating length - it is possible to hypothesise on the type of strings used (the material, diameter and strain). In short, these analyses make it possible the diagnosis of the mechanical state of constituent elements. These descriptors could facilitate decisions to optimise the choice of gourds in the production of instruments (sitar, tampura) that have today taken on semi-industrial shades.
Acoustics of the French Baroque Lute
Authors: Makris Nicholas
Published: May 2008

Design innovations of the French baroque lute characterize the final plateau in the lutes' millennia long evolution in Europe before its eventual extinction at the end of the baroque period. They came with a dramatic increase in number of strings, a new tuning, the first physical description of string vibration, by Marin Mersenne, and led to the "style brisee" which became ubiquitous in baroque music. Compared to the violin, the lute experienced relatively large variations in design and construction material over its lifetime. The aesthetic effect of these variations on musical acoustics were and are often described in compelling but qualitative terms, even by players such as Aristotle and Constantjin Huygens. Here we will use fundamental theoretical principles to quantitatively analyze the acoustic effects of typical design and construction variations found in historic instruments, ranging from the material and thickness of sound boards, bracing and ribs, to rosette design and stringing. We will show how quantitative analysis can be reconciled with qualitative descriptions to help match lute design with desired sound quality.
Finite Volume Solvers and Moving Least Square Approximations for the Linearized Euler Equations on Unstructured Grids
Authors: Khelladi Sofiane , Nogueira Xesús , Bakir Farid , Cueto-Felgueroso Luis , Colominas Ignasi
Published: May 2008

This paper presents the application of a high-order finite volume scheme based on the Moving Least Squares approximations (FVMLS) to solve Linearized Euler Equations (EEL) on unstructured grids. The proposed method allows the direct reconstruction of the (convective) fluxes using compact stencils, and without introducing new degrees of freedom, which is a real advantage over the most popular existing high-order methods. This particularity confers to the proposed methodology a significant reduction in workload and memory storage capability. The proposed scheme is compared to a second-order accurate finite volume scheme with centered fluxes around a uniform flow, with absorbing and/or reflecting boundary conditions. Some test cases are used to illustrate the potential of the FVMLS approximations on acoustic wave propagation. The ultimate objective of our research action is to simulate acoustic wave propagation into confined geometries and complex flows provided by subsonic turbomachines.
Weak Compressibility Method for Prediction of Fluid Noise Generation by Cavity Flow at Low Mach Number
Authors: Zhu Ming , Herfjord Kjell , Megahed Mustafa , Kamoulakos Argiris
Published: May 2008

This paper presents the implementation and validation of a numerical simulation method that takes into account the air-borne acoustic wavepropagation within the turbulent flow solution at low Mach number, which is so-called weak compressibility, in order to cope with fully coupled aero-acoustics problems in a nonlinear system. An academic single 3D cavity case is used to validate the method in comparison with the experiment. The simulated results showed excellent agreement with the experimental data in regard to the acoustic pressure and frequency for the dominant peak of the sound pressure level (SPL) spectra over a wide speed range up to 55 meter per second. An industrial case of so-called singer riser in the system of ocean natural gas rig is studied using this method. There is fluid sound generation due to the interaction of the gas flow field with the pipe grooves. This sound causes strong resonance and vibration over the equipments on the gas rig platform therefore forces the gas producer to control the gas production rate. By using numerical simulation, the aero-acoustic behaviour of a gas flowing in a lab-scale corrugated pipe has been captured which provides deep insights of fluid sound generation mechanism of this singer riser. Experimental results are used to validate the numerical models.
Spherical near field acoustic holography with microphones on a rigid sphere
Authors: Jacobsen Finn , Hald Jo/rgen , Fernandez Efrén , Moreno Guillermo
Published: May 2008

Spherical near field acoustic holography (SNAH) is a recently developed technique that makes it possible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering. Because of the versatile geometry of a sphere SNAH is potentially extremely useful for source identification. On the other hand a rigid sphere is somewhat more practical than an open sphere, and it is possible to modify the SNAH theory so that a similar sound field reconstruction can be made with an array of microphones flush-mounted on a rigid sphere. However, this approach is only valid if it can be assumed that the sphere has a negligible influence on the incident sound field, in other words if multiple scattering can be ignored, and this is not necessarily a good assumption when the sphere is close to a radiating surface. This paper describes the modified SNAH theory and examines the matter through simulations and experimentally.
Array based measurement of radiated and absorbed sound intensity components
Authors: Hald Jo/rgen , Mo/rkholt Jakob , Hardy Pierre , Trentin Dominique , Bach-Andersen Martin , Keith Graeme
Published: May 2008

Calibration of energy flow models for cabin environments requires tools able to measure the energy flow between the sub-systems of the models. Here we shall specifically consider the energy flow between acoustic energy in the cabin and vibration energy in the panels. Sound intensity measurement, for example with a two-microphone intensity probe, can provide the total sound intensity at some distance from panels. It cannot resolve, how much of the intensity is due to radiation from the surface and how much is due to absorption of energy from the sound field. And it cannot provide the information right on the panel surface, leading to a degraded resolution. The ability to distinguish between radiated and absorbed intensity is important for energy flow modeling, and for identification of the areas where noise energy enters the cabin. The present paper describes some work done to measure the radiated and absorbed intensity components by the use of a double layer microphone array. Two measurements are performed: A measurement of surface absorption coefficient and an operational measurement. Non-locally reacting surfaces represent a particular challenge, the handling of which will be discussed. Results from both loudspeaker measurements and in-flight measurements will be presented.
Large array optimization using a genetic algorithm and application to wide band moving sources imaging
Authors: Debert Sébastien , Ollivier François
Published: May 2008

In order to design a microphone array able to follow moving wide band acoustic sources, and improve the quality of the images obtained with a classical beam forming technique, numerical simulations were carried out. The various steps of the study are presented here. Searching the best design for a large microphone array, a simple genetic algorithm was developed. Considering a constant outer dimension of the array and technological constraints in order to design an adaptive array of 60 microphones, the algorithm selects among a large set several combinations of their positions. The functional being optimized is the directivity pattern, in terms of side lobes level. The genetic algorithm always converges to solutions comparable to a randomized set of microphones. Besides, taking advantage of symmetry properties of the array, an improvement of the speed of beamforming calculation was introduced. The optimum array being chosen, wide band moving sources were simulated and images were processed. In order to provide beam formed images with a constant resolution over the band a homotetic-balanced array of 120 microphones was assembled. Finally the dynamic of the images was significantly improved by performing a non-coherent image synthesis technique.
Tyre/road noise prediction: A comparison between the SPERoN and HyRoNE models - Part 2
Authors: Klein Philippe , Beckenbauer Thomas , Hamet Jean-François , Kropp Wolfgang
Published: May 2008

The SPERoN and HyRoNE models predict the pass-by tyre/road noise of a passenger car from intrinsic characteristics of the road surface. Both models are hybrid: they combine statistical laws with physical models. With a computing time of a few minutes (very quick compared to full physical models), they provide operational tools for tyre/road noise prediction. Particular fields of interest are road surface optimisation with respect to noise at the laboratory scale, conformity of production of a new surface and acoustic monitoring of roads. They are now implemented as user-friendly stand-alone applications. The presentation will address the principles of the models, their performances and their respective main fields of application. Part 2 will address the performances of the models.
Austrian experience with the backing board method for statistical pass-by measurements
Authors: Conter Marco , Haider Manfred
Published: May 2008

Traffic noise is one of the major environmental concerns within the countries of the European Union. 80 to 90% of the traffic noise pollution is generated by road traffic. The major part of the noise emitted by vehicles on roads in the mid- to high-speed range is nowadays due to tyre/road noise. It is generated by the interaction between tyre and road surface, and therefore the measurement of the typical noise emission is essential for the classification of pavements with regard to noise. The SPB method (Statistical Pass-By, ISO 11819-1) is nowadays the most widely used method to characterise road surfaces, but it is difficult to apply especially in the presence of roadside noise barriers. The backing board method, further developed within the EU Project SILENCE in the past years, offers a possibility to measure and to characterise surfaces also close to reflective objects and in urban environments. This paper describes the first Austrian experimental experience with the application of this variant of the SPB method.
Acoustic characterization and noise reduction strategies for a general aviation aircraft
Authors: Rusciano Nicola , Viscardi Massimo
Published: May 2008

This work concerns with the vibro-acoustic characterization of a general aviation aircraft with the objective of designing solutions to reduce the inside noise level during the flight; first of all a new passive insulation, and then verifying the possibility of an active noise control approach. The acoustic characterization was performed into two different step; in-flight acoustic and vibration measurements during a typical mission of the vehicle were initially measured, to characterize the acoustic levels and spectra elated to the different flight operations. Ground measurement were also performed to characterize the sound insulation properties of the aircraft structure. The next item was the partial re-design of the sound insulation pack for the vehicle by the use of innovative material; the choice of the best technical solution has been performed by the use of numerical prediction models and through experimental tests on modified samples of the aircraft structure. The in-flight acoustic and vibration measurement showed also the presence of dominant low frequencies tonal components related to the BPF's and upper harmonics. This situation suggested the possibility to implement an active noise control approach. All these activities will be herein presented and discussion of the main results will be performed within the paper.
A design-oriented approach to landing gear noise prediction
Authors: Morris Philip J. , Brentner Kenneth S. , Lopes Leonard V.
Published: May 2008

Landing gear noise is one of the most important sources of airframe noise. But it is the most difficult to predict. The difficulty is that the landing gear is made up of components of substantially different scales. The small-scale features such as tubes and hoses are known to contribute to the landing gear noise, especially in the mid to high frequency range. Existing semi-empirical models are only reliable for the range of landing gear geometries for which test data are available. The present paper describes a component-based landing gear noise prediction model. The method uses an application of simple, fast, and scalable models called acoustic elements that are used to represent the complex landing gear geometry with a high level of geometric detail. Extensions to an earlier model developed by the authors is described, including the replacement of the original time domain approach with a frequency domain method. The local mean flow is also taken into account through the use of low-fidelity computational fluid dynamics simulations. Estimates of the effects of acoustic shielding are also described. Comparisons are made with available experimental data to demonstrate the capabilities of the method. Future improvements are also described.
SOUND-SCAPE: A framework for characterising positive urban soundscapes
Authors: Cain Rebecca , Jennings Paul , Adams Mags , Bruce Neil , Carlyle Angus , Cusack Peter , Davies William , Hume Ken , Plack Christopher J.
Published: May 2008

People's assessments of urban soundscapes are dependent upon many factors. For example, perceptions of a soundscape may depend on the activity that the listener is doing and their associated listening state at the time. Temporal variations (daily, weekly, seasonal) can also affect perceptions of the soundscape, as can the type and usage of urban space, architectural characteristics and the cultural and historical setting. The context of listening is also a factor in terms of the cognitions that people bring to the listening situation by way of memories, preferences, attitudes, values and meaning. In order to inform the planning process with regard to assessing and creating positive urban soundscapes, a framework is under development. The framework attempts to bring together all the influencing factors in urban soundscape assessment in a new and novel way, and considers how the identification of sources and the variety and mix of sources interact to produce a soundscape. The framework presented in this paper forms the basis of multi-disciplinary soundscape research in the EPSRC funded "Positive Soundscapes Project", which seeks to develop a rounded view of human perception of soundscapes by combining methods from several disciplines.
Can urban squares be recognized by means of their Soundscape
Authors: Brambilla Giovanni , Di Gabriele Maria , Maffei Luigi , Verardi Patrizio
Published: May 2008

Squares have always played important functions in urban areas, being a reference place in the citizen's life. During last decades, road traffic noise has influenced the perception of the sonic environment in many squares. However, there are squares where historical and typical sound sources are still present. In both cases the sonic environment remains a feature of the square together with other factors, like the visual impact. The present paper deals with the above issue and describes an experiment aimed to study how the soundscape of a square can contribute to recognize the square itself. For this purpose some well known squares in Naples and Rome have been selected to cover a range of different characteristics. In each square binaural recordings and pictures have been taken simultaneously. Then the binaural recordings have been played back by headphone to a group of subjects in laboratory simultaneously to the display of the pictures of all squares on a screen. After listening each sound the subject was asked to choose among the pictures the one showing the square judged to have the sonic environment most appropriate to the sound just heard. The comparison between subjective responses and correct answers are in progress.
Fountains as a natural component of urban soundscape
Authors: Semidor Catherine , Venot-Gbedji Flora
Published: May 2008

Fountains play an important role in urban landscape as well as being a cultural mark in a city. They also have an environmental function. For example, their effect in the control of the microclimate is well known. The paper deals with the sound effects which big fountains located in large squares have on the urban soundscape of the area. In particular, we deal with how their natural character can change the global perception of the site. Indeed, the representation of water sounds is positively appreciated by most city-dwellers. Depending on their size and shape, they are able to give a quiet or a dynamic character to the site. But in the case of areas with a lot of traffic we ask ourselves what are the interactions with strong background noise level and others sound sources. GRECAU uses the soundwalk method to assess the acoustic environment. The following case studies, Plaza de Cataluna in Barcelona and Piazza Ferrari in Genoa, are two examples of such a situation. Some of the results we give here try to answer the previous questions.
Mesoscopic study of the enhancement of the nonlinearity of an ultrasonic wave in inhomogeneous media
Authors: Moura André
Published: May 2008

In quantitative nondestructive evaluation of materials it is not still clear why linear elastic waves often exhibit substantial nonlinearity when traveling through inhomogeneous medium, whereas this effect exists but remains minor in most homogeneous media. A current dominant thesis claims that when damaged, intact brittle materials become nonlinear mesoscopic elastic materials. Although this model is consistent with macroscopic observations in the framework of continuum mechanics, it eludes, however, a fundamental aspect, i.e., the detailed nature of the wave/microstructure interaction like scattering and transmission through microcrack. To construct a unified theory, from the mesoscopic to the macroscopic scale, that could take account altogether such so different mesoscopic elastodynamic effects is our objective. Toward this aim, many aspects of the wave/slit interaction are thoroughly analyzed among the clapping effect and nonlinear scattering, and experimental schemes are scheduled. At the current state of our knowledge, a first general postulate is claimed.
Microdamage detection and monitoring using nonlinear elastic wave spectroscopy over a wide frequency range
Authors: Van Damme Bart , Le Bas Pierre-Yves , Van Den Abeele Koen
Published: May 2008

Innovative diagnostic techniques based on Nonlinear Elastic Wave Spectroscopy (NEWS) have been implemented for global inspection of microdamage in intact and damaged aeronautical components using low and high frequency sound waves. For low frequency analysis, we focused on the amplitude dependent analysis of the resonance behavior, both in time and frequency domain. Alternatively, we have analyzed the time-windowed interaction of a hammer impact with a high frequency continuous wave. The results of both techniques agree extremely well, and prove their potential for quick and global microdamage detection. For local inspection, we have implemented a combination of the traditional elastic wave time reversal technique with a phase coded pulse sequence selective excitation. Alternatively, sparse array tomographic reconstruction with NEWS pre-treatment could be used. The nonlinearity based imaging techniques are illustrated on aeronautical components, and discussed in terms of the feasibility and usefulness of the methodologies as new tools for microdamage imaging.
Simulations of nonlinear ultrasonic NDT of plate-like structures
Authors: Geeraert Marieke , Janssen Els , Delrue Steven , Bou Matar Olivier , Blomme Erik , De Gersem Herbert , Van Den Abeele Koen
Published: May 2008

Inclusions in materials generally affect the linear wave propagation characteristics of sound waves, observed through scattering, and reduced reflection or transmission with respect to pure materials. The smaller the inclusions, for a fixed ultrasonic frequency, the harder it is to interpret these observations. Therefore, zones of microdamage initiated from fatigue or thermal loading might not induce any linear scattering at all. Nevertheless, the damage information is definitely carried along within the propagating sound wave. In this case, however, it is necessary to investigate the spectral changes of the propagating sound waves, in the form of harmonics and intermodulation frequencies. This contribution reports on simulations of the nonlinear signatures arising in Lamb, Rayleigh and bulk wave propagation in media with localised microdamaged zones. The simulations are performed with a Finite Difference Time Domain solver accounting for microdamage though the inclusion of hysteretic nonlinear stress-strain relations at the microscale. Depending on the configuration it is possible to obtain one or more harmonic images of the defect, their number and relative position containing information about the location and depth of the defect. The simulations allow simple prediction of the response images in complicated experimental conditions.
Nonlinearity, hysteresis, end-point memory, and congruence in sandstones
Authors: Claytor Kevin E. , Koby Joseph R. , Tencate Jim A.
Published: May 2008

Very low frequency stress-strain measurements on many rocks show definite and repeatable hysteresis loops. Much of the modeling of this behavior uses Preisach or Ising-like models adapted from models developed for magnetic systems which exhibit hysteresis. To date, the experimental data on many rocks showing end-point memory are noisy and only qualitative. The congruence property, in fact, has never been examined for rocks. Just how well does the behavior of a sandstone fit a Preisach model? To find the answer to this question, we performed a new set of careful stress-strain experiments on several sandstones to examine end-point memory (in detail) and also to see if the congruence property does indeed hold for these rocks. In addition we explored the dependence of measurement rate on the relaxation time of these rocks (the analog to magnetic aftereffect). For very slow measurement rates (low frequencies), hysteresis disappears, leaving only a simple nonlinear stress-strain curve.
Effect of Water Saturation on the Nonlinear Elastic Response of Concrete
Authors: Payan Cédric , Garnier Vincent , Moysan Joseph
Published: May 2008

Nonlinear interaction of a monochromatic elastic wave with a low frequency should be a good tool for non-destructive evaluation of existing concrete structures. This technique has already proofed efficient in detecting global damage. However, it is necessary to understand the influence of some structural parameters as porosity, stress state, or water saturation on the nonlinear processes. In this way, a thermodynamically based model containing all of them is presented in this paper. It is sustained by nonlinear interaction measurements in order to quantify the evolution of the nonlinear behaviour of concrete with water saturation state.
The Parametric Array in Berea Sandstone, Revisted
Authors: Le Bas Pierre-Yves , Tencate Jim A.
Published: May 2008

Previous measurements of the characteristics of the parametric array in sandstone by Johnson and Shankland [J. Geophys. Res., 94, 17729-17734 (1989)] were difficult to perform and, given the apparatus of the day, only qualitative. Since then, memory effects have been found to play a strong role in the dynamic behavior of rocks. This experimental study was performed to find out how well the "classical" theory of nonlinear acoustics, i.e., all compressional waves with no memory effects, works at describing the parameteric array in a granular solid. An array of PZT disk transducers (every other one broadcasting one of two frequencies) was epoxied to a large block of Berea sandstone (1.2x0.4x0.4 m). The two primary frequencies were near 100kHz and chosen to produce a difference frequency around 15kHz. Using a scanning laser vibrometer (Polytec), several scans of the beampatterns were made at the opposite end of the rock and the results compared with calculations based on those commonly used for parametric arrays in water. A narrow beam generated from the two primaries was measured and the beampattern compared with those of the primaries. The agreement is surprisingly good using a beta of around 200 and a Q of about 50.