The extract below is from a New Zealand study.
"To prepare this noise management plan an event schedule was developed in an attempt to achieve a balance between how loud each motor racing event was and how often they occur. In the example given, Council decided that 50 events with a noise level of “background plus 5dB” would be permitted in any 12 month period. Where events were likely to be noisier than this, the number of events would reduce in accordance with Graph 1 below which is taken from the Guide. An event that exceeds the background noise level by 8dBA would count as two events. An excess of 30dBA is deemed to have a noise exposure equivalent to 10 events."
|dB above background vs annual events|
Citation: Marshall Day Acoustics (2007). Ruapuna Park and Christchurch Kart Club Noise Assessment. Christchurch, New Zealand. http://resources.ccc.govt.nz/files/TheCouncil/policiesreportsstrategies/districtplanning/cityplan/proposedplanchanges/PC52AcousticsReportOctober2007.pdf