Jacques Chatillon’s research while affiliated with Institut National de Recherche et de Sécurité and other places

Geometric or acoustical irregularities induces acoustic scattering. In this paper, a generalization of the model proposed by Khanfir et al. [8](Journal of Sound and Vibration 332 (4) (2013)) to determine the scattered acoustic field above gratings of parallel rectangular cavities is developed, addressing the case of gratings of non-parallel rectangular cavities. The results provided by the model were compared both to numerical results, obtained with the finite element method, and to experimental ones. The observed agreement between the analytical predictions and the numerical and experimental results supports the validity of the proposed model. The coupling between the different cavities was investigated, in order to attain an explanation for its dependence on frequency and on the spacing between cavities.

The interior wall facings that delimit industrial rooms are often uneven, i.e. they often have relief, and that causes the sound propagating in such premises to be acoustically scattered. Acoustic prediction software making it possible to plot maps of the sound field in workplaces needs characteristics such as the sound absorption or the sound scattering coefficient of such surfaces. In this work, we propose to obtain experimental this sound scattering coefficient of vertical surfaces in situ thanks to a new measurement. The experimental technique that was originally developed under free-field conditions was adapted to attenuate the echoes coming from reverberation and the noise coming from sources and machines present on the site. For that purpose, a first device has been developed containing a multipolar acoustic array and an impulsive source used respectively for achieving spatial filtering and for separating in time the different echoes. The new device developed and presented in this paper has been used on several measurement campaigns, and it has thus been possible to study, among other things, the reproducibility of the results. Installing a large multipolar array made it possible to obtain good accuracy for the results at low frequencies. The scattering coefficient of a vertical surface containing a rectangular cavity was measured for various angles of incidence in a noisy and reverberant environment. Finally, those measurements made it possible to map the sound scattering coefficient in the XY directions and thus to highlight the highly variable scattering mechanisms of a uneven structure depending on the measurement point.

It is currently accepted that noise is one of the most important annoyance factors in open-space offices. However, noise levels measured in open spaces of the tertiary sector rarely exceed 65 dB(A). It, therefore, appears necessary to develop a tool that can be used to assess the noise environment of these offices and identify the parameters to be taken into consideration when assessing the noise annoyance. This article presents a questionnaire to be filled by people working in such environment, and a case study in different open plan offices. The majority of the 237 respondents consider that the ambient noise level in their environment is high and that intelligible conversations between their colleagues represent the main source of noise annoyance. This annoyance was significantly correlated with their evaluation of sound intensity, which could not be represented by A-weighted level measurements. Practitioner Summary: This article presents a short questionnaire aimed to evaluate the employees' comfort in an open-plan office and to propose optimal modifications of the office. Answers collected from 237 respondents showed that intelligible conversations represent the main source of noise annoyance; moreover, overall noise level is not related to this annoyance.

Open plan office users complain of two annoyances due to noise. The first annoyance is lack of concentration and the second annoyance is the reduction of the confidentiality of conversations. The rapid prediction of the acoustic work environment in open plan offices would give the possibility to optimize the acoustic comfort of the users during the design phase of the construction. To begin with, the calculation methods used by CSTB have been validated. For this, the efficiency of an acoustic table screen between two working desks by taking into account the acoustic properties of the ceiling has been studied. Since the desks are positioned in an open plan office, it can be assumed that the floor and the ceiling are of infinite extent. In this study the floor and ceiling are modeled as two parallel baffles in the BEM method MICADO3D. The ray-tracing simulation program ICARE has been used with the Capolino and Albani method along with double edge scattering. A comparison with the measurements done in the semi-anechoic chamber of INRS will be presented. The MEPAS project, a common 2-year project between INRS and CSTB funded by ANSES, aims to develop a rapid calculation method for the prediction of open plan office acoustics. This part of the paper presents the work realized in the MEPAS project at mid-term. Fictive open plan office models have been created and simulated with ICARE and MICADO3D. Real open plan offices are investigated by creating a model for acoustic simulations and measurements. In each office different acoustic criteria such as the spatial decay rate DL2 or the speech transmission index STI are calculated and measured.

Les occupants des bureaux ouverts expriment souvent une double gêne par rapport aux nuisances sonores : l'une due à une perte de concentration et l'autre due à une réduction de la confidentialité des conversations. La prédiction de l'ambiance acoustique de ces environnements de travail permet, dès la conception, d'optimiser le confort acoustique de leurs occupants. Dans un premier temps, la précision de l'outil de lancer de faisceaux développé au CSTB (ICARE) est estimée par comparaison avec une méthode de simulation acoustique de référence, la méthode des éléments de frontières. Les niveaux de pression acoustique dus à une source ponctuelle sont comparés dans deux cas d'étude simplifiés: deux postes de travail séparés par une cloisonnette absorbante et un espace contenant seize postes de travail. Dans un second temps, ICARE est confronté à des résultats de mesures effectuées par l'INRS dans un local réel. Différents critères acoustiques (indice de transmission de la parole, décroissance d'énergie par doublement de distance) référencés par la norme relative au mesurage des paramètres acoustiques des bureaux ouverts (NF EN ISO 3382-3:2013) sont simulés et comparés à leurs valeurs mesurées. Le travail présenté est effectué dans le cadre du projet MEPAS financé par l'ANSES dont l'objectif est de développer une méthode simplifiée de prévision acoustique afin d'étudier l'impact de différents paramètres caractéristiques de bureaux ouverts sur le confort acoustique de leurs occupants.

Désormais de plus en plus courant au sein des entreprises, le bureau ouvert est une forme déspace de travail qui permet un gain de place tout en facilitant l'échange verbal entre collègues. Cependant, il apparait que le manque d'intimité et l'augmentation du niveau sonore sont parmi les principaux inconvénients de ce type déspace de travail. Le projet GABO (Gêne Acoustique dans les Bureaux Ouverts) s’intéresse à l’évaluation de la nuisance sonore pour les travailleurs dans les bureaux ouverts et a pour but de définir des indicateurs de gêne qui tiennent compte notamment du type de la nuisance sonore. Dans la première partie du projet, il a été montré à partir d’enquêtes in-situ [1] que les conversations intelligibles et non intelligibles, les sonneries de téléphone et le bruit de machines (imprimantes) étaient parmi les sources sonores qui contribuaient le plus à la gêne totale ressentie par les utilisateurs. En s’appuyant sur ces résultats, la suite de l’étude a pour but d’évaluer en laboratoire la gêne occasionnée par ces différents types de source. Ainsi, trente cinq sujets ont réalisé une tâche de mémorisation à court terme dans cinq contextes sonores différents, à savoir quatre types de sources (imprimante, parole intelligible, parole non intelligible et sonnerie de téléphone) et un bruit de fond (ventilation), sans aucune source sonore supplémentaire (situation de contrôle). Ainsi, la gêne due au bruit a pu être évaluée de façon subjective, mais il a également été possible de mesurer la dégradation de la performance (sur la tache de mémorisation) suivant le type de source sonore subie par l’individu. Si les conversations intelligibles impactent significativement la performance, il n’y a en revanche pas de différence significative de la gêne ressentie entre les paroles intelligibles, les paroles non intelligibles et les sonneries de téléphones. Seules les imprimantes sont moins gênantes.

The NOMAD project was a survey to examine the noise-related content of instructions supplied with machinery offered for purchase in Europe. The project collected more than 1 500 instructions from machines covering 40 broad machine-families and from 800 different manufacturing companies. These instructions were analyzed to determine compliance with the requirements of the Machinery Directive, and assess the quality of information. The general state of compliance of machinery instructions with the noise-related requirements of the Machinery Directive was found to be very poor: 80% of instructions did not meet legal requirements. Some required numerical values relating to noise emissions were often missing. Where values were given, they were often not traceable to machine operating conditions or measurement methods, and not credible either against stated conditions/methods or as warnings of likely risk in real use. As a consequence, it is considered highly likely that, in making a machinery procurement decision, employers are prevented from taking noise emissions into account, and understanding what is necessary to manage the risks from noise relating to equipment that is procured. Recommendations are made for actions aimed at bringing about a global improvement to the current situation. Targeted actions are now proposed by “ADCO Machinery Group” aimed at raising awareness of the legal requirements, responsibilities and actions required among the various groups who have parts to play in the system - machine manufacturers, machine users, occupational safety and health professionals, and standards-makers. Recommendations are also made aimed at providing, or improving, tools and resources for all these actors.