Regulations and standards, addition of decibels, operation of an engine silencer, calculation of a sound level…

BOËT StopSon, an expert in soundproofing, offers you all the technical explanations related to the field of acoustic performance and treatment.

Order of 23 January 1997 relating to the limitation of noise emitted into the environment by installations classified for environmental protection.

The prefectural authorisation order sets, for each period of the day (day and night), the noise levels not to be exceeded at the property limit of the establishment. These levels are determined in such a way as to ensure compliance with the admissible emergence values.

In all cases, the values set by the authorisation order may not exceed 70 dB(A) for the day period and 60 dB(A) for the night period.

Standard NFS31-010 – 12/1996

Emergence = ambient noise level – residual noise level

Emergence :

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

Ambient noise :

The total noise existing in a given situation during a given time interval. It is composed of the total noise emitted by all sources, whether near or far. In other words, industrial installations in operation.

Residual noise :

Ambient noise in the absence of the particular noise(s), which are the subject of the query. In other words, industrial installations that are not in operation.

Specific noise :

A component of ambient noise that can be specifically identified and that is desired to be distinguished from ambient noise, especially because it is the subject of a query.

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With the exception of pure sound, which consists of a single frequency (e.g. the sound your telephone makes before dialling), noise consists of a superposition of multiple frequencies.

The sound spectrum is used to further characterise noise. By analysing a spectrum, it is possible to obtain the “identity card” of the noise. This allows us to propose appropriate solutions based on the spectrum.

The tool below calculates the overall level of a noise spectrum by logarithmically adding up 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 the measured noise levels. The further away from the source, the lower the measured noise level.

This small tool allows you to calculate the effect of distance:

Distance Effect Tool

Noise levels are most commonly expressed in decibels (dB) which is a logarithmic unit. It is therefore not possible to “conventionally” add up these values.

Decibel addition tool

This formula is used to perform addition.

Formule calcul décibels