Mon, 29 Aug 1994

Listening to a town's heartbeat

By Antoine Bauer

NANTES, France: In their everyday lives, more than six million French people suffer from a level of noise which is harmful to their health. Most of them are city-dwellers. The public authorities, supported by the town councils, are fighting this scourge.

The city of Nantes, which is the capital of the Loire region (with half a million inhabitants), has taken an original approach to the problem, based on the idea that, in order to fight the enemy, it is better to know it well first.

For that purpose, a qualitative study of the sound environment in the city's historical center was made with the help of modern acoustic equipment. It is a technical "first".

It was carried out by a psycho-acoustician from the French National Scientific research Center (CNRS), together with urbanists, local technicians and several specialists from the nuisance department at the Ministry of the Environment.

The noise-analyzer in question can be compared to a medical stethoscope. It enables the "heartbeats" of the city, its rhythm, its silence and its discords to be listened to, recorded and interpreted.

From data gathered in a given street or a given square, it is then possible to draw a picture of the sound landscape which can be used by the municipal service.

In the course of several series of walks, each lasting two hours, with 30 specific points for making sound recordings, the equipment registered sound sequences representing different times of the day. These walks, which were repeated in the morning, the afternoon and the evening, created a sound picture of the noises of the city from the quietest to the most deafening.

The "urban stethoscope" consisted for the most part of a digital recorder with microphones which were specially designed to ensure the accurate location of the noises during the playback.

As all sound phenomena can be broken down into a series of elements that can be listed, the sound sequences recorded were arranged in six different sources.

* Background noise, which measures the moments of silence or "false silence" (residual noise)

* The sounds of nature (birds, wind, fountains etc.)

* Urban activity, linked to mechanical noise (cars, buses, motorbikes, road and building works)

* Human presence (commercial and leisure activities and general bustle)

* Language and communication (intelligible voices, music, sound signals).


Using this data, a computer program created a "sound map" which was combined with a street map of the area concerned. Different colored zones appear on it. Blue indicates areas with pedestrian-type noises.

Red shows traffic sounds. Green reveals combined noise areas dominated by humans. Orange shows areas in which urban noise predominates and yellow indicates areas where people stay and live.

"This inventory of sounds proves to be extremely useful for town councils which wish to improve the quality of life of their fellow citizens," explains one of the CNRS researchers who worked on the project. "It helps them to know their town better and to deal with one of its major problems".

Several French and foreign towns are already interested in the Nantes experiment. The urban stethoscope will be a precious instrument when, for instance, a decision has to be made concerning the development of a district, the deviation of main traffic or the organization of a street function.

Moreover, it will make it easier to overcome that feeling of discomfort and insecurity felt in various places by the inhabitants or by passers-by, and to do something about it.

Thanks to this instrument, it will finally be possible to forestall many of the conflicts arising from neighborhood noises which so often envenom relations between city-dwellers.

-- AFI