FAQ

Arrêté du 23 janvier 1997 relatif à la limitation des bruits émis dans l’environnement par les installations classées pour la protection de l’environnement.

The prefectoral authorization order sets noise levels for each period of the day (daytime and night-time), which must not be exceeded at the property limit of the facility. These levels are determined in such a way as to ensure compliance with admissible emergence values.

In all cases, the values set by the authorization order may not exceed 70 dB(A) during the day and 60 dB(A) at night.

Standard NFS31-010 – 12/1996

Emergence = ambient noise level – residual noise level

Emerging :

Temporal modification of the ambient noise level induced by the appearance or disappearance of a particular noise. This modification concerns the overall level or the level measured in any frequency band.

Ambient noise :

Total noise in a given situation over a given time interval. It is made up of all the noise emitted by all sources, whether near or far. In other words, industrial plants in operation.

Residual noise :

Ambient noise in the absence of the particular noise(s) which are the subject of the request under consideration. In other words, industrial plants at a standstill.

Special noise :

A component of ambient noise which can be specifically identified and which we wish to distinguish from ambient noise, particularly because it is the subject of a query.

Test our tool: Noise level generated by safety valves when venting to atmosphere

With the exception of pure sound, which is made up of a single frequency (for example, the sound emitted by your telephone before dialing), noise is made up of a superposition of multiple frequencies.

The sound spectrum is used to characterize noise more precisely. By analyzing a spectrum, it is possible to obtain the noise’s “identity card”. This makes it possible to propose solutions adapted to each spectrum.

The tool below calculates the overall level of a sound spectrum by logarithmically summing each octave band. The overall level is expressed both unweighted (dB Lin) and A-weighted (db(A)).

Sound level tool from a spectrum

Distance has a significant impact on measured noise levels. The further away from the source, the lower the noise level measured.

This little tool calculates the effect of distance:
How to calculate the effect of distance?

Noise levels are very commonly expressed in decibels (dB), which are logarithmic units. It is therefore not possible to “classically” add up these values.

Decibel addition tool

Test our tool: How do decibels add up?