bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental validation of a chirp-based underwater acoustic communication method
Authors: Palmese Maria , Bertolotto Giacomo , Pescetto Alessandro , Trucco Andrea
Published: May 2008

A wireless underwater acoustic communication algorithm based on the combination of chirp modulation and direct-sequence spread-spectrum signaling is presented. In this paper, the processing chain design is proposed, discussed, and demonstrated using real data. The communication algorithm is made of a transmission block encoding the bits with adequate linear chirps multiplied by pseudo noise (PN) sequences, and a rake receiver that allows one to positively exploit the energy present in the most significant propagation paths. The use of chirp signals takes advantage of the low Doppler sensitivity in the matched filter operation whereas the choice of PN sequences allows one to reduce narrowband interference arising from other users and self-interference due to multipath propagation. Moreover a tracking procedure that allows an adaptation to the instantaneous Doppler shift has been devised and tested. Some experiments have been carried out changing the distance and the speed between transmitter and receiver. Results show that the developed communication method is able to handle the multipath phenomenon and the Doppler effect, allowing one to achieve a bit error rate less than 10 (-3) for long ranges for bit rates of about 15 and 230 bit/s.
Concurrent detection, classification and localization of seabed targets using virtual time reversal
Authors: Dumortier Alexis J. , Schmidt Henrik , Sabra Karim G.
Published: May 2008

During the last decade, the use of unmanned vehicles to detect seabed objects has been revolutionized by the rapid development of AUV technology. The reduced power budget imposed by autonomous operations limits the amount of processing allowable onboard and calls for simple and efficient detection algorithms. Time reversal techniques have proved to be a robust way of focusing sound on reflective objects in complex environments and only require minimal computation. The method proposed here uses a virtual time reversal mirror in monostatic configuration to localize the origin of the field scattered by objects located on the seafloor. The waveguide is insonified with a low frequency source (∼kHz) mounted on the AUV and the resulting scattered field is sampled by a receiving array towed behind the vehicle. The recorded signals are then used to simulate the time reversed transmissions onboard, generating a map of reflectors present on the seabed. The rejection of clutter using singular value decomposition and the sensitivity of this method to environmental misknowledge are addressed along with the presentation of experimental results. [Work supported by ONR.]
Integrated sensing, modeling, and control in undersea sensor networks
Authors: Balasuriya Arjuna , Schmidt Henrik , Benjamin Michael B.
Published: May 2008

The way forward in adaptively sampling the vast ocean environment is by deploying a network of sensors with different capabilities. Due to the complex nature of the environment, covering such an area cannot be achieved by simply deploying underwater sensor nodes at predefined locations. The undersea network topology should dynamically adapt to the events and changes in the environment. However, the main challenge for undersea network autonomy is due to the limitations in underwater acoustic communication. In order to overcome such limitations, Nested Autonomy architecture is being developed and demonstrated in programs such as PLUSNet and Ocean Observatories. This paper looks into the implementation of such autonomy architecture in different sensor nodes with different capabilities. This is achieved by separating the "low-level" tasks of a sensor node with its "high-level" tasks. Low-level tasks will be sensor specific while the high-level tasks looks into the autonomy required for the adaptive sampling applications, which here refers to as the "Backseat-driver paradigm". The "backseat" carries the on-board intelligence required for the mission at hand. Behavior-based autonomy architecture which is used in the back-seat significantly improves the sensor performance by selecting the best behavior for the given state of the vehicle, mission at hand and the observations being made.
Global synthesis of superdirective frequency-invariant beam patterns
Authors: Crocco Marco , Repetto Stefania , Trucco Andrea
Published: May 2008

Frequency-invariant beam patterns are often required by systems using an array of sensors to process broadband signals. If the spatial aperture is shorter than the involved wavelengths, the use of a superdirective beam pattern is essential to attain an efficient system. In this context, robustness to array imperfections is a crucial feature. In the literature, only a few approaches have been proposed to design a robust, superdirective, frequency-invariant beamformer, based on a filter and sum architecture: in all of them, the frequency invariance is achieved imposing an a priori desired beam pattern. However the choice of a suitable desired beam pattern is not trivial and depends on the specific design case: an improper selection of the desired beam pattern can produce unsatisfactory performances. We propose a new method of global synthesis, computationally inexpensive, allowing to design a robust broadband beam pattern with an optimal trade-off between the frequency invariance and the directivity, without the need of imposing a priori a desired beam pattern. The results show that the synthesized beam patterns have a directivity, a frequency-invariance, and a robustness that are very similar to or better than those of the beam patterns obtained by the literature methods.
The generation of binaural signals from a regularly sampled soundfield using a beamforming approach
Authors: Poletti Mark , Svensson Peter
Published: May 2008

Auditorium designs can be evaluated prior to construction by numerical modeling of the design. Subjective assessment of the design requires auralization of the computed soundfield at a desired listener position and the binaural format is dominant for representation of the soundfield. For high accuracy the modeling is based on solving the wave equation numerically, which typically produces the sound pressure on a rectangular grid. Such a sampled soundfield is not straightforward to convert to a binaural format. This paper investigates binaural conversion from the sound pressure at a selected number of grid points using a least squares beamforming approach. Low-frequency axisymmetric emulations are derived assuming a solid sphere model of the head, and an open spherical array of 640 microphones is used to emulate ten measured HRTF data sets from the CIPIC database for half the audio bandwidth. The microphone positions might be displaced from the exact spherical surface to fit the mesh sample points. The spherical array can produce high-accuracy band-limited emulation of any human subject's measured HRTFs for a fixed listener position by using individual sets of beamforming impulse responses.
New measurements of head-related transfer functions with an optimized ear-canal microphone
Authors: Haut Christopher , Rausch Jacqueline , Mellert Volker
Published: May 2008

Affecting the ear-canal impedance by inserting a microphone produces considerable changes in the directional characteristics of the ear with increasing frequency. Head-related transfer functions (HRTFs) are measured in the horizontal and median plane under systematic change of the ear-canal microphone more or less blocking the ear-canal entrance. A microphone arrangement is developed which minimizes the influence on the given impedance of the ear canal entrance. New measurements of HRTFs are reported and compared with well-known literature results. The "undisturbed" HRTFs serve as objective functions for a microphone array which substitutes the dummy head in head-related (stereophonic) recordings. The (complex) objective functions are modified for the microphone array according to the relevance in directional hearing.
Model-based signal processing for hearing aids
Authors: Hohmann Volker
Published: May 2008

The aim of the work presented in this talk is to investigate potential applications of models of human auditory processing to signal processing in hearing aids. In particular, it is shown that auditory models may be used as objective indicators of the perceptual quality of single- and multichannel noise reduction strategies. Furthermore, a general framework for computational auditory scene analysis (CASA) is introduced and applied to the problem of estimating spatial direction and spectral envelope of super-imposed sound sources from a binaural input signal. Finally, implications of using nonlinear peripheral models for the design of compression systems in hearing aids are discussed. In particular, results from a multiband instantaneous compression scheme are presented, which is based on a novel nonlinear auditory filterbank controlled by the instantaneous frequency calculated in frequency sub-bands.
The sound field in life-size replicas of human ear canals occluded by a hearing aid
Authors: Stinson Mike R. , Daigle Gilles A.
Published: May 2008

In addition to the longitudinal sound pressure distributions that form in the human ear canal, large transverse variations can arise in the vicinity of an occluding hearing aid. These effects are being studied, numerically and experimentally, making use of life-size ear canal replicas. Using digital representations of real ear canal geometries [Stinson and Lawton, J. Acoust. Soc. Am. 85, 2492-2503 (1989)], a polyjet fabrication process forms replicas with a spatial accuracy of better than 0.1 mm. A hearing aid test fixture, with vent, receiver, and an inner microphone, occludes the replica canal and provides the acoustical input. The sound field inside the canal is measured using a 0.2 mm o.d. probe microphone. In parallel, the interior sound field is calculated using a boundary element method, using the same ear canal geometry as the replicas and accounting for the acoustical boundary conditions presented by the eardrum and the hearing aid. In the current series of ear canal replicas, the eardrum is rigid. Measurements and calculations are in good agreement. Large transverse variations of sound pressure level, as much as 20 dB at 8 kHz, are observed across the inner face of the hearing aid, particularly near the receiver and vent ports.
High sound quality and concha headphones: where are the limitations
Authors: Blanchard Lola
Published: May 2008

Concha headphones (the small type of headphone that rests at the entrance of the ear canal) are the most popular type of headphones for every-day use. However, the sound quality produced by even "high quality" concha headphones is rather poor. This paper gives an overview of the different factors that affect the quality of this type of headphones, describes the measurement difficulties, and presents a model. The leakage between the headphone and the ear changes every time the headphone is inserted in the ear. This alters the perceived sound quality, especially at low frequencies, and makes measurements very difficult. Moreover, because of energy efficiency considerations, a typical transducer design is prone to nonlinear behaviour, and a high distortion rate can be measured for most concha headphones. The measured transducer parameters and leakage have been implemented in a model realised in Simulink. The simulation model, which makes it possible to study the influence of the various parameters including the uncontrolled leakage, is the first step towards developing a compensation technique.
Advanced application-motivated design techniques for high performance piezocomposite underwater sonar transducers and arrays
Authors: Cochran Sandy , Demore Christine E. , Marin Pablo , Marsh Richard , Mayne Keith , McRobbie Graeme , Wallace Michelle , Walsh Mark P. , Wright Richard
Published: May 2008

Developments in areas as diverse as advanced piezoelectric materials and low cost digital electronics continue to offer new possibilities to the designer of high performance underwater sonar transducers and arrays. Many of these are likely to be realised with complex composite materials comprising a polymer matrix with rods of piezoelectric ceramic such as PZT 5H or crystal such as PMN-PT which require advanced design techniques. This paper first briefly reviews relevant capabilities of conventional equivalent circuit and wave equation transducer models, and the composite homogenisation technique of Smith and Auld. The increasing possibilities offered by finite element analysis (FEA) running on relatively low-cost computing hardware are also considered. Whichever design technique is adopted, accurate material properties are crucial and this is reported through reference to a range of piezoelectric and passive materials. The potential variation of such properties across the operating temperature range of underwater transducers is also considered, illustrated with experimental measurements. As understanding of high performance transducer structures grows, future possibilities also become evident, such as the 3-1 connectivity multilayer composite. The paper is therefore completed with an outline of these complex structures and a stochastic mathematical technique that can be used to optimise their designs automatically.
Broadband tonpilz transducers based on single crystal relaxor ferroelectrics: Design and modeling
Authors: Meyer Richard J. , Markley Douglas C.
Published: May 2008

Very broad bandwidth transduction capability has been made possible by high coupling piezoelectric single crystal materials. Recent work has shown that PMN-PT based tonpilz elements with a single resonance have a device electromechanical coupling coefficient greater than 0.86 and can easily achieve more than two octaves of source level bandwidth. Implementing single crystal based tonpilz elements reduces array packaging volume and weight while maintaining source level. In addition, high coupling projectors reduce transmit system complexity when compared to traditional materials. This paper will describe approaches to creating broadband SONAR projectors using single crystal materials. Crystal anisotropy plays a key role in transducer design. This anisotropy requires final designs to be modeled in three dimensions. ATILA finite element code was used to capture all of the modes of vibration and performance predictions. Motor section geometries and material compositions will be compared. The model predictions will also be compared to measured data.
A new impedance sensor for wind instruments
Authors: Dalmont Jean-Pierre , Le Roux Jean Christophe
Published: May 2008

Our aim was to build a low cost but accurate portable impedance sensor. The adopted technique is the one using a source with a back cavity. A first elctret microphone on the front of the source measures the pressure at the input of the instrument weather a second one measures the pressure in the cavity, which is proportional to the volume flow supplied by the source. By choosing a sufficiently small sealed cavity and a small piezoelectric source the system do not exhibit any cut-off frequency in the measurement range. The calibration is then simplified and only few parameters are needed to model the three complex calibration functions. This calibration is performed with three nonresonant calibration loads. Moreover, it is shown that the geometry of the sensor being known, the measurement with a rigid wall is sufficient to calibrate the sensor. Results show that it is possible to achieve a measurement with an accuracy lower than 1dB in the range 50-4000 Hz.
Improved precision in acoustic impedance measurements by using calibration loads without resonances
Authors: Dickens Paul , Smith John , Wolfe Joe
Published: May 2008

Although the input impedance of a one-dimensional waveguide is simply defined by the ratio of pressure to volume flow measured at its input, the deficiencies of available transducers require a more complicated approach for precise measurements. These can involve multiple transducers at points within an impedance head connected to the measured load. However, resonances and/or singularities during calibration and/or measurement often limit the precision of acoustic impedance spectra. This paper reviews and compares several established techniques, and describes a technique that incorporates three features that can considerably improve precision. The first feature involves minimising the problems due to resonances by calibrating the instrument using up to three different acoustic reference impedances that do not themselves exhibit resonances: an acoustically infinite waveguide, an acoustic open circuit and an acoustically infinite flange. The second feature involves using multiple pressure transducers to reduce the effects of measurement singularities. The third involves iteratively tailoring the spectrum of the stimulus signal to control the distribution of errors across the particular measured impedance spectrum. Examples are given of the performance of the technique on simple cylindrical waveguides and some wind instruments, including the saxophone and clarinet.
Acoustic pulse reflectometry for the measurement of horn crooks
Authors: Kemp Jonathan , Chick John , Campbell Murray , Hendrie Darren
Published: May 2008

The echo-based technique of acoustic pulse reflectometry can be used to measure tubular objects to determine the bore profile. In this paper, measurements of historic orchestral horn crooks are presented showing how the technique can help to determine the method of construction of historic crooks and can provide valuable information to manufacturers of reproduction period instruments. Comparison of the bore profile measured by pulse reflectometry and the known exit radius of the crook can be used to determine the presence of leaks. The technique is shown to be sensitive enough to find a leak in a horn crook that behaves reasonably under playing conditions and was not suspected of having a leak prior to testing.
Industrial applications of acoustic pulse reflectometry
Authors: Amir Noam , Barzelay Oded , Pechter Tal
Published: May 2008

Acoustic pulse reflectometry (APR) has been used extensively in the study of wind instruments, for measuring input impedance, bore reconstruction, and fault detection. Industrial applications have often been mentioned in the literature, though they have barely been exploited. Academic APR systems are extremely bulky, which limits their industrial use severely. Two requirements from such an industrial system are that the source tubes be as short as possible, and that they be able to measure long objects, often much longer than most musical instruments, e.g., condenser tubes which are at least 8 m long. This creates difficult calibration problems and difficulties in obtaining sufficient SNR levels, especially at low frequencies. In this paper we describe a system with the necessary adaptations for industrial use. We demonstrate the problems that are encountered, and introduce solutions which we have implemented. Modifications to the deconvolution phase improve low frequency SNR, which is further improved using nonlinear filtering. Adaptive filters are then used to discriminate between a faulty and intact system. When faults are detected, they are identified using several identification algorithms based on matched filtering and local inverse scattering.
Influence of the bocal on the sound of the bassoon
Authors: Baumgart Johannes , Grothe Timo , Grundmann Roger
Published: May 2008

The bocal of a bassoon is characterized by geometrical parameters such as the bore, the outer contour and the wall-thickness as well as material parameters and the coating. Professional bassoonists select bocals extremely carefully and report influences on the playability and sound colour. In order to understand the underlying effects, several experiments were performed with bocals of the same bore bent in two different shapes and with two different materials. Images of a high-speed camera show a periodic motion of the bocal tip while the instrument is artificially blown. A modal analysis of the bocals was performed experimentally and numerically to investigate the dynamic behaviour of the structure. The first bending mode of the bocals is around 70 Hz. While the material properties shift the modal frequencies less than 2%, the shift due to the geometry is more than 10%. The experimental program included playing experiments with professional bassoonists. The setup was fixed and the players used the same reed. For each player, slight shifts in the sound spectra could be found due to the use of different bocals. The harmonic structure showed changes in the frequency bands where the bending modes differ.
Influence of the edge tone (mouth tone) on the sound of flue organ pipes as a function of pipe scaling
Authors: Angster Judit , Miklos Andras
Published: May 2008

The sound quality of an organ pipe is mainly influenced by the attack transients. This onset is first dominated by the edge tone, while later the pipe resonator will play a more important role. To understand the physics of a flue organ pipe, it is necessary to analyse the edge tone, the acoustic properties of the pipe resonator, the attack transient and the stationary sound of the pipe. Several pipe ranks have been investigated in the anechoic room of the Fraunhofer IBP: Nachthorn, Diapason, Gamba, Octave, Flute, Geigenprinzipal, Salizional. By the evaluation all physical effects contributing to the production of sound were taken into account. In the present paper about the physical effect of the edge tone on the production of the pipe sound will be reported.
Voicing documentation of a pipe organ
Authors: D'Alessandro Christophe
Published: May 2008

The paper begins with a brief presentation on the Parisian organ landscape, and then focuses on sound documentation of the historical organ of Sainte Elisabeth (Suret 1853, 3 keyboards and pedal, 40 stops, about 2500 pipes). Calibrated recordings of all the notes have been performed inside and outside the organ case, using several microphone positions. The methodology proposed by Pollard (J. Acoust. Soc. Am. 106(1), July 1999, 360-370) is extended and applied to sound analysis for all the notes of the instrument. The analogies between the proposed sound description (or “voicing quality,” described in terms of sharpness, loudness, tristimulus coordinates, transient building, and spectral centre of gravity) and human voice quality description are discussed. Both voicing of individual pipes and voicing of the instrument are analysed. “Voicing of the instrument” means voicing variations of the pipes for different notes or registers of a same stop, for different stops of a same division, and for different divisions of the instrument. This methodology may be applied to documentation and characterisation of the “style” of the instrument in terms of its acoustic signature, provided additional information on recording conditions and room acoustics are available.
The physical characteristics of mechanical pipe organs and how much they allow the organist to influence the initial transient
Authors: Grossinho Jose
Published: May 2008

It has been accepted by organists that one can change the timbre of the organ simply by varying the velocity of the key. Previous research (Nolle, 1941, 1992) shows clearly that there is a change in the initial transient of the sound with different pressure rise times (PRT) on the foot of the pipe. More recent research (Woolley, 2006) shows that in mechanical action organs there is no major difference in the velocity of the key when the organist thought there was. The velocity of opening of the pallet is one of the main aspects that influence the PRT. Calculations of the flexibility of mechanical parts from organs in Mafra, Portugal, were taken, as well as motion of the key, pressure on the pipe's foot and sound measurements on a model organ, using human touch on the key. Due to the pressure differences in the wind chest and the groove, it is difficult to control the pallet movement after it starts to open. The results show that there is a more efficient control of the velocity of opening of the pallet on more rigid actions, giving a better control to the organist over the timbre of the instrument.
Reduced-order models for jet noise
Authors: Dowling Ann P. , Afsar Mohammed , Karabasov Sergey , Hynes Tom P.
Published: May 2008

The research reported here leads to a simple prediction methodology based on a reduced-order model for jet noise. The approach is a hybrid one made up of three components. Each component uses modeling and numerical techniques optimised to suit a particular purpose. The propagation of noise to the far field is captured via a new method for solution of the adjoint linearised Euler equations, describing how sound emitted by the jet is modified by propagation through the time-averaged but spatially varying jet flowfield. The directivity of the quadrupole sources is more general than is usually assumed and their statistical properties are modeled based on a RANS solution for the jet: the cross-correlation of the turbulent quadrupoles is modelled as Gaussian with length and time parameters proportional to the local length and timescales from the RANS solution, The constants of proportionality are determined through comparison with correlations from LES and from experimental data. Hence the source model is determined entirely from near field data and the far-field sound is then predicted with no empirical constants. Comparison between this predicted noise and experimental data is very good, across a wide spectral range and even at angles close to the jet axis.
Coupled oscillations in the aeroacoustics of a Katana blade
Authors: Roger Michel
Published: May 2008

The paper investigates experimentally the tonal characteristics of the aerodynamic sound of a Katana blade handled at high speed. Katana is the name of the Japanese sword used in martial arts. It is designed with a sharp cutting edge, a thick black-edge, and sometimes so-called blood-grooves. When handled through the air, the blade radiates sound at different frequencies. First a low-frequency, dominant sound is heard due to the von Karman vortex shedding in the wake of the blade. Second high-frequency tones are produced in the case of a Katana with grooves. The tones result from the self-sustained oscillations of the detached shear layers over the grooves which behave like cavities under a grazing flow. In the case of a Katana with no groove, other high-frequency tones are heard due to acoustic back-reaction on the Tollmien-Schlichting waves growing in the boundary layers. The variations of the acoustic signature with varying angle of attack and relative flow speed are analyzed in the paper, with emphasis on the coupling between the different mechanisms. The main trends are compared to simple self-sustained oscillation formulae. Finally the possible use of the sound as a criterion of inaccuracies in the handling of the Katana is discussed.
The mechanisms of roughness noise
Authors: Devenport William J. , Glegg Stewart A. , Alexander Nathan , Smith Ben
Published: May 2008

The interaction of turbulence and a rough surface results in the radiation of sound that is not produced in smooth wall flows. The mechanisms by which this sound is generated are not well understood. Scattering of the convected turbulent pressure field by the surface irregularities seems to be a probable source when the roughness size is small compared to the boundary layer. The bluff body mechanisms of vortex shedding and unsteady drag from the roughness elements appear more likely to be dominant sources when those elements are large compared to the boundary layer. Demonstrating the existence of these mechanisms, their range of dominance, the extent to which they are distinct and can be characterized in terms of flow parameters that can be realistically modeled (such as the surface pressure spectrum), are all pre-requisites to the development of a robust prediction method. New insight into these issues has been obtained through measurements made with using a purpose built roughness noise facility in combination with fundamental theoretical analysis of the problem. The measurements include roughness noise spectra, wall pressure spectra and aerodynamics for a large variety of rough surfaces. This work is supported by the Office of Naval Research.
Design of a low noise radial fan with computational aeroacoustics
Authors: Sorgüven Esra , Dogan Yilmaz , Arslan Ergin
Published: May 2008

Aim of this study is to employ computational aeroacoustics methods in order to design a fan system. Design objectives of this study are to decrease the flow-induced noise, to provide the necessary flow rate and pressure increase. During the design, modern computational methods will be employed in addition to traditional turbomachinery design methods. The design procedure begins with a baseline fan system design, which is based on traditional semi-empirical correlations. Flow through this fan system is analyzed via computational fluid dynamics. Pressure fluctuations on rotating and stationary solid surfaces are determined to calculate sound sources of the system. The baseline design is improved by eliminating the areas where powerful sound sources occur. Flow analysis and sound prediction is repeated to improve fan system further. This step is repeated until the desired sound power level is achieved. This design procedure employs numerical analysis instead of experiments. Therefore it will be more effective and less time consuming than the experimental trial and error design procedures. The number of prototypes and necessary measurements are decreased dramatically.
Strategies for noise action plans
Authors: De Vos Paul
Published: May 2008

Following the requirements of the Environmental Noise Directive, Noise Action Plans should have been produced. The plans are supposed to build on two important pillars: the strategic noise maps and the consultation with the local residents. In some cases, the plan is considered as a mere statement of the long term policy of the authority under concern. In other cases, it is set up as an implementation plan with clear and measurable targets. Also the focus varies: only the highest noise levels could be attacked or the large numbers of exposed citizens, or even the overall annoyance. Target noise levels may lead to confusion both for local decision makers and citizens. Also, the preservation and possible creation of quiet areas can be envisaged. The use of an equal annoyance indicator helps to set the targets in the right perspective. Translation into different levels of quality of life is recommended. In terms of cost and benefits, the options for city councils are very limited. Due to a lack of European legislative power, cities tend to set their own rules, e.g. for road vehicles. Several initiatives to propose toolkits for action plans, comparable to the best practice guide for noise mapping, are welcomed but require harmonization and dissemination.
Urban and building acoustics management in the next decades: a matter of prevention, simplification and education
Authors: Baring João G.
Published: May 2008

In Brazil, in cities like São Paulo and Rio de Janeiro, noise pollution control has been carried out mainly in the form of repression. In the seventies and eighties, people joined together to fight against noisy government projects, and government fought noisy industries and commercial establishments. Since then, people have become aware of their rights, but have learned little about their own obligations on the matter. The author researched this process in order to find a better way for the future and concluded that prevention must be enforced through noise codes, standards must include easier survey methods, and low cost devices for noise control must be available. Most important, education must be improved in all levels, to make every citizen a partner of noise control at home, at work and elsewhere in the cities. This paper points out some ways of dealing with this process.
NERS-analysis extended to include the existence of neighbouring quiet areas
Authors: Stenman Åsa , Malm Peter , Lindqvist Magnus
Published: May 2008

One of the goals for the EC financed Integrated Project Quiet City Transport (QCITY), is to provide European city administrations with validated analysis tools and technical noise control solutions for the efficient production of noise action plans. A part of the QCITY project work is to produce complete noise maps and hot-spot analysis for a part of Stockholm. This paper will focus on the Noise Environmental Rating System (NERS), a tool for performing hot-spot analysis on noise maps, developed within the QCITY project. The input parameters that have been used in previous studies [Internoise-07_411, Å. Stenman, P.-Malm, 2007] are outdoor noise on all floors, number of inhabitants per building and the facade sound insulation index. Previous studies, such as the "Stockholm score rating model (Trafikbuller och planering II, Stockholm, 2004) show a strong correlation between noise annoyance and the existence of quiet nearby areas. The NERS-analysis in this work has therefore been extended to include quiet areas.
Calculations of low height noise barriers efficiency by using Boundary Element Method and optimisation algorithms
Authors: Baulac Marine , Guillou Arnaud , Defrance Jérôme , Jean Philippe A.
Published: May 2008

Nowadays, roads and railways are often quoted as the most annoying source of noise for the living environment. This problem of ground transportation noise is present in extra-urban environments as well as in town centres. Traditional noise barriers are in many cases not suited for acoustic protection in urban areas mainly because of their height. Previous studies have shown a significant efficiency of low height noise protections (kind of urban furniture) for the decreasing of noise levels in semi-opened areas such as city parks, places, and large avenues. However, the simulations of low height noise protections requires specific numerical codes since ray tracing methods are not suited for barriers lower than around 2 m. This paper proposes a way to implement an approach with allow to simulate low height noise protections in engineering calculation methods. This can be done by creating a database using a Boundary Element Method numerical code combined with optimisation algorithms. Work is still in progress since only 2D configurations are considered at the moment.
Status of noise abatement measures for roads in Switzerland
Authors: Cosandey Laurent , Ingold Kirk , Meloni Tommaso , Luethi Nicole , Pestalozzi Hansueli
Published: May 2008

In 2006, a comprehensive survey on the status of noise abatement measures for all roads was carried out in Switzerland for the first time. This survey recorded the costs of remedial work and noise protection measures completed to date (approx. CHF 1 billion) or still outstanding (approx. CHF 3 billion). An account is also given of the distribution among different types of measures, and of the protective effects on the public. As well as indicating the financial resources required for remediation of the Swiss road network on schedule, the survey highlights measures for controlling noise emissions at source which need to be implemented urgently.
Influence of noise source representation on the estimation of specific descriptors close to traffic signals
Authors: Can Arnaud , Leclercq Ludovic , Lelong Joel
Published: May 2008

Considering traffic dynamics greatly improves noise estimation in urban area. This can be achieved by coupling a dynamic traffic model with both emission laws and sound propagation calculation. This paper focuses on the influence of noise source representations in the combination with the traffic model. Several representations are tested: point sources and homogeneous line sources of different sizes. We aim at evaluating how these representations correctly estimate classical descriptors (LAeq and statistical descriptors) and specific descriptors able to capture noise dynamics at a traffic signal scale. Three typical urban situations are studied: in front of, upstream and downstream a traffic signal. Noise source representation can be coarse for classical descriptors calculation if traffic dynamics is precisely described. On the contrary, noise source representation should be refined to precisely assess noise dynamics.
Environmental impact of noise from mobile outdoor equipment
Authors: De Roo Foort , Gerretsen Eddy , Borst Jeroen
Published: May 2008

As part of an evaluation study of European Directive 2000/14/EC relating to the noise emission by equipment for use outdoors, an environmental impact assessment was required to investigate the need for new or tighter noise limits. In contrast to other environmental noise sources, the operating location of outdoor machines is not fixed. As conventional environmental noise mapping could not be used for this purpose, an environmental indicator was developed. This indicator takes the following factors into account: numbers of equipment in use in the EU, typical average sound power level, tonal/impulsive/intermittent sound content, annual duration of operation, day/night operation and typical areas of use. The numbers of people affected were assessed by means of a series of noise maps, resulting in distribution curves characteristic for different types of environment (urban, suburban, rural, and others). The newly developed environmental indicator is a relatively simple quantity taking all relevant factors into account including annoyance.
Challenges and opportunities for noise mapping in the United States
Authors: Kaliski Kenneth
Published: May 2008

Primarily through the impetus of European Union Directive 2002/49/EC, EU cities have been on the forefront of noise mapping and the community planning that results from it. The United States has no similar legislation at federal or state levels. As a result, noise mapping for towns and cities in the U.S., and indeed, awareness of noise issues by planners, appears to lag behind their European counterparts. However, metropolitan areas in the U.S. have invested a great deal in transportation modeling. As a result, the data foundation for noise mapping, that is, road and rail geometry and traffic volumes, is in place in many metropolitan areas. In addition, digital terrain elevation data, aerial photography, and GIS data are generally available on a state or national basis at no charge over the internet. The Chittenden County, Vermont noise map is one example of how publically available data can be used to create a useful community noise map over a large area. Other examples will be discussed.
A noise mapping study of a large metropolitan city with a heterogeneous traffic
Authors: Alur Ramachandra , Ramasamy Kalaiselvi
Published: May 2008

Traffic noise characteristics in some of the cities in a developing country like India are slightly varied by virtue of the fact that the composition of the traffic is heterogeneous accompanied by variance in road geometry and varying density of the buildings on the either side of the road. To study the feasibility of noise reduction in some of the areas a noise mapping study has been attempted along with field measurements of L10, L50, L90 and Leq. In the noise mapping parameters such as Ld, LN, Lden have been arrived at by taking into consideration the geometrical features of the roads and varying heights of the buildings. In this study noise mapping through computer simulation model (soundplan) is used by considering several noise sources and propagation of noise to the receiver point. This paper describes how the local characteristics of the city affect the propagation of noise and describes an integrated approach to control noise pollution in these areas. A three dimensional acoustical model has been developed for two locations of the city. Methodologies of noise control through noise contours around traffic are illustrated.
Nonlinear acoustic acceleration waves in porous media flow
Authors: Jordan Pedro M.
Published: May 2008

Acoustic acceleration waves are defined as jumps in the first derivatives of the velocity, pressure, or density across a propagating singular surface (or wavefront). In this talk, the temporal evolution of the amplitude and the propagation speed of such waves are investigated in the context of finite-amplitude acoustic propagation in Darcy-type porous media. It is shown that there exists a critical value, α*(>0), of the initial jump amplitude such that the acceleration wave magnitude either goes to zero, as t ← ∞, or blows up, in finite time, depending on whether the given initial jump amplitude is less than or greater than α*. In addition, a connection to traveling wave solutions is noted and the linearized case is examined. Finally, the numerical solution of a (1D) nonlinear IBVP involving sinusoidal signaling in a fluid-saturated porous slab is used to illustrate the finite-time transition from acceleration wave to shock wave, which occurs when the initial jump amplitude is greater than α*. [Supported by ONR/NRL funding (PE 061153N).]
Deduction of porous material properties using a point source
Authors: Allard Jean François , Dazel Olivier , Boeckx Laurens , Geebelen Nathalie , Lauriks Walter
Published: May 2008

The acoustic field created by a point source above the plane boundary between two semi-infinite fluid layers has been previously studied by Brekhovskikh. A straightforward generalization can be performed by replacing the fluid under the source by the fluid equivalent to a rigid-framed porous medium. This leads to a method of evaluating, from pressure measurements, the surface impedance close to grazing incidence and the Brewster angle of total refraction of the porous medium. The model by Brekhovskikh can also be generalized when a thin porous layer is set under the point source. A pole of the reflection coefficient exists for an angle of incidence close to grazing incidence. This pole is related to an acoustic field similar to a surface wave above the layer. The measurement of this angle provides an evaluation of the surface impedance close to grazing incidence. The point source induces frame vibrations that can be predicted with the Biot theory. The rigidity coefficients of the frame at audible frequencies can be evaluated from measurements of the frame velocity with a laser velocimeter.
Low frequency implementation of the full Kramers-Kronig relationships for the description of dispersion and attenuation of acoustical waves in porous media
Authors: Castagnede Bernard R. , Lafarge Denis , Depollier Claude , Sebaa Naima , Henry Michel
Published: May 2008

It is well known that the causality principle which applies during the acoustic propagation of a wave packet inside any material should be described by the universal Kramers-Kronig (K-K) relationships, enabling to formally link dispersion to attenuation curves. The application of the K-K formalism to porous networks has been studied lately, but unfortunately, the metrology of dispersion features at very low frequency is intricate. The use of parametric arrays of nonlinear acoustics enables to get at the same time, some precise information on dispersion and absorption on various porous media, for instance in the frame of the “equivalent fluid” model. In the present work, we describe some very recent findings obtained along these ideas for a truly relevant application of the full KK formalism in various fibrous materials. We have checked numerical predictions of the absorption versus frequency computed from the dispersion curves with the K-K modeling, as well as confrontation of these numerical predictions with experimental data on absorption obtained with various set-ups, on different fibrous materials.
Analytical microstructural model for acoustical porous materials with single or double porosity
Authors: Gourdon Emmanuel , Jaouen Luc
Published: May 2008

An analytical model of sound propagation for porous materials with single or double scale of porosity is described. For each scale, pores and interconnections between them are modeled by a serie of two cylinders; a cylindrical periodical cell is thus considered. Scales are supposed to be separated, the porous medium is supposed to be periodic and to have a motionless skeleton. The geometrical parameters needed to quantify visco-thermal effects are directly related to the microstructure of the material. These parameters: lengths and radii of pores and interconnections can be extracted from image analysis for example. From additional conditions on cell morphology, independent parameters per porosity scale can be reduced to a number of three. Good comparisons between theoretical calculations of the sound absorption coefficient at normal incidence and impedance tube measurements are obtained for single and double porosity (meso-perforated) materials.
A new setup for measuring the mechanical properties of porous materials
Authors: Dauchez Nicolas , Doutres Olivier , Genevaux Jean Michel , Lemarquand Guy
Published: May 2008

A new device for determining complex Young's modulus of porous materials in a extended frequency range is proposed. Classical methods are based on quasitatic or dynamic response of porous material. These methods generaly neglect the coupling between the surrounding fluid and the porous frame so that they are restricted to low frequency range (<100 Hz) or specific sample shape. Dynamic methods provide relevant information only at the resonance frequencies of the frame. The proposed method extends the quasistatic method towards high frequencies: 1. the porous sample is setup in a cavity in order to avoid the coupling with the external fluid, 2. a specific electrodynamic transducer has been developped to get the mechanical impedance of the sample from the measurement of the electrical impedance, 3. mechanical properties of the frame are derived by inverse method using Biot theory so that the frequency range is not restricted to the quasistatic domain. First results obtained with a prototype validate the method in comparison with two classical methods.
Quasistatic evaluation of mechanical properties of poroelastic materials: static and dynamic strain dependence and in vacuum tests
Authors: Bonfiglio Paolo , Pompoli Francesco , Shravage Paresh
Published: May 2008

A complete description of the vibro-acoustical behavior of a poroelastic material requires the knowledge of both geometrical quantities, related to the structure of the fluid-filled pores to account the sound propagation within them, and mechanical parameters (i.e. Young Modulus, Poisson's ratio, and loss factor) in order to model the wave propagation through the elastic structure constituting its skeleton. Because the nonlinear nature of poroelastic media, those mechanical properties are shown depending on static preload and dynamic strain applied to them. In the present work a well established quasi-static method, based on the measurement of mechanical impedance and the use of adequate polynomial relations, has been used to determine the dependence of the mechanical properties on the applied deformations. Furthermore, tests have been also carried out in a vacuum chamber in order to evaluate the real contribution of the filling fluid on the total vibro-acoustical response of the material.