Design
Project 4
Attentive to the needs of stations!
Rail & Recherche n°33 - October/November/December 2004
Who does not remember the station in the Monsieur Hulot film where you see a crowd of passengers dashing from one platform to another as they try to listen to incomprehensible announcements? Franck Poisson who works on acoustic phenomena willingly refers to this symbolic sequence himself. But times have changed. Sound and noise environment processing in stations and trains has been subjected to advanced studies which now are bearing fruit.
What exactly is sound design? “It is a way of optimising the function of a space by using the acoustic modality”, sums up Franck Poisson, project manager in the SNCF Research department. Today we are aware that improving acoustics also improves how a place is perceived and used. Three lines of research have thus been defined: the function of the space (is it a rest, transit or sales area?), its identity (station concourse, TGV high-speed train platform, TER regional train platform and so on) and finally, comfort. “The aim is not to create sound sculptures but to make hearing easy, to make announcements intelligible and keep customers from getting tired”, says Franck Poisson.
Sales, waiting and transit areas. The objective of the sound design project is to sculpt sounds to control the information they are carrying and thus better identify the different areas of the stations.
Towards sound signalling
Intervening signifies acting, from now on, on existing direct sources of noise, human and railway, and also on the transmission and absorption by the framework by modifying coverings, for example (wood, absorbent material), by reducing certain sources or by adding other sources. “The electronic notice boards and new generation ticket-stamping machines are now silent, hence we are designing sound signalling that will enable passengers to spot changes or that highlight ticket-stamping.” An example of this sound signalling is the “sonal” (announcement signal created by Louis Dandrel) tested in the Creusot-TGV station. It ensures a transition between the background noise of the surrounding countryside and the passage of a non-stop 300km/hr TGV train, thus warning passengers waiting on the platform of its passage. Regarding the intelligibility of announcements, for which a lot of progress has already been made, nowadays directivity-controlled speaker systems are installed. “A minimum amount of acoustic energy is advisedly distributed in the space to reduce reverberation. This new broadcasting system which is physically in the form of columns of speakers, enables you to focus the sound electronically in the exact desired area,” explains Franck Poisson. Whether it is a matter of reducing noise to improve comfort or sculpting sounds to control the information they carry, researchers need a real-time simulation tool. This is the case of Odas (noise environment design tool), a software program developed from an existing digital sound platform to synthesise the noise environment on-board trains this time. “Thanks to the simulation of an acoustic environment you can determine which source you need to act on.”
Identifying a space by sound
Improving this predictive method falls on the shoulders of Julien Tardieu who has devoted a thesis to the design of the noise environment in stations. After recording sounds* in six very different stations throughout France, he organised listening tests with some 100 listeners: “What do travellers perceive? Do they recognise spaces just by listening? That is what we wanted to know. The analysis grid which applied to sources, activities and architecture was confirmed by the tests. The errors were negligible and the identification was always relevant.”
The imperative of this research is to be able to define a method of action by comparing environments through simulation. “Acoustical recognition of spaces can be helpful in orienting travellers in transit,” stresses Julien Tardieu. Special signalling, sound identity, processing environments is work that is very close in its philosophy to that of the designers of luminous environments.
*The existing environments are captured with an ambisonic microphone which has the particularity of recording the whole sound field without favouring a reproduction mode (binaural, stereo, quadraphonic, 5.1, etc).