Industrial noise zone

In spatial planning, the authorities designate a noise zone around industries and other noise sources, where the noise level exceeds the recommended noise limit. Below is a review of recommended noise limits for industries.

Noise from industry 

The recommended noise limits for industries, enterprises etc. are published in Guidelines from the Danish Environmental Protection Agency, no. 5/1984 "Environmental Noise from Industry" (in Danish).

The recommended noise limits are mainly used in processing environmental permits or bans related to noise. However, they are also used for spatial planning. The recommended limits differ in the day, evening and night periods.

The limit values apply to the corrected, A-weighted equivalent noise level (noise rating level L _r ).

The equivalent noise level is the average of the noise level over a long period of time, the reference time interval (eight hours for the day period 7am-6pm, one hour for the evening 6pm-10pm, and half an hour for the night period 10pm-7am). In case the noise has clearly audible tones or impulses, a 5 dB penalty is added to the equivalent noise level to obtain the noise rating level.

The limit values are to be kept out of doors in the adjacent area, not only in areas near dwellings or at the area's border. For dwelling areas a supplementary noise limit applies to the maximum (instantaneous) noise level during the night period. This is 15 dB above the corresponding L _r – limit for these periods, namely L _max = 50 or 55 dB.

Other limit values apply to the situation where the enterprise and the dwelling are in the same building. In such case the noise is to be measured indoors.

Since the recommended noise limits differ in the day, evening, and night periods, the drawing of a manageable noise zone around an industry is not straightforward. A set of recommended noise limits for purpose of general (and strategic) planning, each expressed as a single-figure Lden was published in Guidelines from the Danish Environmental Protection Agency, no. 4/2006 "Noise Mapping and Noise Action Plans" (in Danish).