20. A number of measures can be used to control the source of or limit exposure to noise. Such measures should be proportionate and reasonable. Possible measures include:
- Engineering - reduction of noise at point of generation ( e.g. by using quiet machines and/or quiet methods of working); containment of noise generated ( e.g. by insulating buildings which house machinery and/or providing purpose-built barriers around the site); and protection of surrounding noise-sensitive buildings ( e.g. by improving sound insulation in these buildings and/or screening them by purpose-built barriers);
- Lay-out - adequate distance between source and noise-sensitive buildings or areas; screening by natural barriers, other buildings, or non-critical rooms in a building;
- Operational - limiting operating time of source; restricting activities allowed on the site and specifying an acceptable and reasonable noise limit. The implications of restricting hours of operation for the economic efficiency and operational capacity of a business over the longer term will need to be considered;
- Work sequencing - programming and phasing construction or extraction activities to limit noise impact; use of acoustic screens around plant; limiting vehicle noise through speed control, road surfacing and driving style;
- Baffle mounds - particularly relevant to mineral and landfill workings where they can be constructed from the top soil, sub-soil and over-burden which need to be removed and stored;
- Acoustic fencing - an alternative to baffle mounds or used on top of a mound to increase acoustic protection;
- Alternatives to vehicle reversing alarms - include flashing lights during the night (but these may also cause a nuisance if not operated with care), radar-operated safety devices, audible "warble" devices, TV camera systems, and reduced level audible warnings for night time use;
- Off-site road traffic noise - restriction of lorry movements to particular times or particular routes; low-noise road surfaces and road surface maintenance;
- Rail traffic - low-noise rolling stock; low-noise tracks; and sensitive location of depots;
- Equipment selection - setting noise limits for specific items of plant and equipment, e.g. those with certain tonal noise characteristics;
- Acoustic double glazing and secondary glazing for existing development - this is unlikely to be appropriate as a response to noise caused by a new development. The use of double glazing and secondary glazing is not an alternative to other measures to control noise emissions or a means of legitimising higher noise limits.
21. Where appropriate, relevant and enforceable mitigation measures can be implemented through planning conditions and/or legal agreements. Conditions attached to a planning consent should meet the six policy tests set out in Circular 4/1998 Use of Conditions in Planning Permissions. The addendum to Circular 4/1998 contains some examples of model conditions relating to the control of noise. Planning Agreements must meet the policy tests set out in Circular 1/2010 Planning Agreements.