Planning policy guidance notes set out the Government's policies on different aspects of planning. Local authorities must take their content into account in preparing their development plans. As a result these may be material to decisions on individual planning applications and appeals.

PPG 24 gives guidance to local authorities in England on the use of their planning powers to minimise the adverse impact of noise and builds on the advice previously contained in DOE Circular 10/73.

• It outlines the considerations to be taken into account in determining planning applications both for noise-sensitive developments and for those activities which will generate noise
• introduces the concept of noise exposure categories for residential development, encourages their use and recommends appropriate levels for exposure to different sources of noise
• advises on the use of conditions to minimise the impact of noise.

BS4142 1997 Method for Rating Industrial Noise Affecting Mixed Residential and Industrial Areas

This standard is used to support planning applications for the introduction of industrial type noise sources in to mixed residential areas. The  assessment  compares  the noise source with existing background noise.

The noise source is either measured or  acoustic data taken from the manufacturer's information for the item or plant of interest. A background noise survey must be performed during the proposed operating hours. The worst hour during day time is taken, and the worst 10 minutes at night.

Following analysis and corrections to the data in accordance with BS4142 the difference between the source and existing noise level is determined.

A difference of +10dB is a positive indication that complaints are likely. A difference of -10dB is a positive indication that complaints are unlikely. A difference of +5dB is said to be of marginal significance.

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