Simulation of the acoustics of coupled rooms by numerical resolution of a diffusion equation

Over the last few years, some studies showed that the acoustic energy density in closed or semi-closed spaces may be the solution of a diffusion equation. This theory allows non-uniform repartition of energy, and is especially relevant in room acoustics for long rooms or complex spaces such as networks of rooms. In this work, the three-dimensional diffusion equation is solved directly by using a finite-element solver. This approach is used to simulate the acoustics of coupled rooms in terms of spatial variations of intensity levels and sound decay. The obtained results match satisfactorily with a model based on the classical statistical theory of room acoustics, but it allows to perform a finer spatial description of the acoustics of coupled rooms

Validation of a numerical diffusion equation-based modelling of the reverberated sound field in long rooms

Many applications as corridors, railways tunnels or tube stations present a long room geometry. A fast and reliable modelling of such sound fields could be helpful for designers. In fact, the classical statistical theory based on the assumptions of diffuse sound field is not applicable in such cases because the reverberant sound energy along the room is not uniform. In this study, several models assuming diffuse reflections of sound by walls are used for predicting the reverberant sound field in long rooms. Two models based on a diffusion equation for the energy density (one numerical and one analytical based on an image approach for describing the sound reflection at the corridor extremity) are compared with a radiosity model, and with a ray tracing software. Predictions are compared in terms of sound attenuation and reverberation time with measured data. The long rooms considered in this study were two rectangular corridors of lengths 20.3m and 47.3m. All models overestimate the attenuation, reaching 6dB for the numerical diffusion based model. When a part of specular reflection (30%) is added in the ray tracing model, the predicted sound attenuation matches with the measured one: even in case of rough surfaces, specular reflections cannot be totally excluded. For reverberation time, the agreement between predictions and experiments is good with fewer than 15% of discrepancy. The best predictions of the reverberation time were given by the diffusion models, with discrepancy less than 2% for the numerical model. So, it could be concluded that it is difficult to find a prediction method which is consistent both in terms of steady state and sound decay for the acoustics of long halls

Experimental validation of a diffusion equation-based modeling of the sound field in coupled rooms

peer reviewedSound modeling in coupled rooms (i.e., two acoustically coupled rooms separated by an open area) has attracted considerable attention in the past. However accurate and operational models are still needed, principally when three or more rooms are coupled. In recent papers, a diffusion equation-based model has been applied to unusual room shapes. For the coupled rooms geometry, this diffusion model has been validated successfully by comparison with the classical statistical theory in a parametrical study of the coupling parameters [Billon et al., J. Acoust. Soc. Am. 116, 2553 (2004)]. In the present work, the diffusion model results are validated by means of a comparison with experimental results, both in terms of sound attenuation and reverberation time. A comparison is also provided with results given by the statistical theory and a ray tracing program. For this purpose, experiments have been conducted in two coupled classrooms with two different sound source locations. The results show a very good agreement between the diffusion model and the experiments. Conversely, the statistical model is not valid for modeling accurately the sound field distribution and decay in both coupled rooms. At last, the diffusion model runs much faster than the ray tracing program

Application de la méthode EF-modale à l'étude de réseaux périodiques ouverts

Ce travail présente l'application de la méthode EF-modale à l'étude de la propagation acoustique dans de quartiers, considères comme des réseaux périodiques ouverts. L'idée principale est de transformer le domaine original ouvert en un guide d'ondes équivalent, en remplaçant les ouvertures par de PML (perfectly matched layers). Ensuite, le processus se divise en deux étapes. La première est obtenir les modes périodiques transverses du guide par une méthode éléments finis (EF). Après, ces modes sont utilisés dans une formulation multimodale de la propagation dans la direction longitudinale

Noise mapping based on participative measurements

The high temporal and spatial granularities recommended by the European regulation for the purpose of environmental noise mapping leads to consider new alternatives to simulations for reaching such information. While more and more European cities deploy urban environmental observatories, the ceaseless rising number of citizens equipped with both a geographical positioning system and environmental sensors through their smartphones legitimates the design of outsourced systems that promote citizen participatory sensing. In this context, the OnoM@p system aims at offering a framework for capitalizing on crowd noise data recorded by inexperienced individuals by means of an especially designed mobile phone application. The system fully rests upon open source tools and interoperability standards defined by the Open Geospatial Consortium. Moreover, the implementation of the Spatial Data Infrastructure principle enables to break up as services the various business modules for acquiring, analysing and mapping sound levels. The proposed architecture rests on outsourced processes able to filter outlier sensors and untrustworthy data, to cross- reference geolocalised noise measurements with both geographical and statistical data in order to provide higher level indicators, and to map the collected and processed data based on web services

Crowdsourcing of Noise Map Pollution using Smartphones: Journées des Laboratoires SIG de Suisse romande

We present at the LSSR journey, the ENERGIC-OD project and the application developed by the LAB-STICC (CNRS) and LEA (IFSTTAR) laboratories to collect noise data from smartphones.We present the ENERGIC-OD project and the application developed by the LAB-STICC (CNRS) and LEA (IFSTTAR) laboratories to collect noise data from smartphones

NoiseCapture, une approche collaborative pour répondre aux enjeux de la maitrise des nuisances sonores

Les rencontres nationales de l'ingénierie territoriale, Les collectivités locales face aux enjeux de l'économie circulaire, Dunkerque, FRANCE, 13-/06/2019 - 14/06/2019NoiseCapture, une approche collaborative pour répondre aux enjeux de la maitrise des nuisances sonore

Effects of diffusion on the sound propagation in a street

Inter-noise 2004, 33rd International Congress and Exposition on Noise Control Engineering, PRAGUE, TCHÈQUE, RÉPUBLIQUE, 22-/08/2004 - 25/08/2004Many investigations have been carried out regarding sound propagation in urban streets. In most of them, multiple diffuse reflections by building façades are considered to be one of the most important effects on the sound propagation in streets. For instance, in a recent paper, J Kang has realized a systematic comparison between the sound level and reverberation time in urban streets resulting from diffusely (according to a Lambert's law) and geometrically reflecting boundaries, and has shown considerable differences. However, except for the Lambert's law, no result was given considering more complicated or realistic reflection laws. In order to evaluate the effect of diffusion for several reflection laws, a numerical model of sound propagation in a street was developed using the concept of sound particles. In this model, the building façades are defined by an absorption coefficient, a diffusion coefficient and a specific reflection law (specular, Lambert, uniform, "semi-diffuse" including the size and distribution of building façade irregularities). In this way, and using Monte Carlo methods, it allows simulating any type of reflection laws. Numerical simulations were then carried out, in order to compare the sound level and the reverberation time in the street for several reflection laws. As expected, these simulations show that the sound propagation in a street is function of the boundary conditions