Why have noise limits at a race track?
It can seem a bit weird having a noise limit at a race track. Its a bit like telling a rock concert to keep the noise down. Race circuits by their very nature are going to be noisy – just like motorways. Most have been running since the 50’s and so anyone that moves near one should accept it or don’t move there in the first place in my opinion. But we are in a decade where law changes have enabled people to use the ‘letter of the law’ to satisfy their own selfish needs. As a result noise limits are the main limitation when it comes to taking your Car or Motorcycle on a track day, and for those that know their vehicle is ‘a bit close’, the noise test can be the most nerve racking part of the event! Regulations are much tighter these days and if a vehicle fails the test you won’t get on track or a refund.
The noise limits are set by the circuit but as a result of "discussions" with the local council. It is the local council who have to play middle-man between the grumpy local residents and the circuit owners. Some circuits will have more strict limits than others and many are limited to the amount of events they can run per year as a direct result of noise.
The noise testing by a circuit typically (but not always) follows the guide lines set by the MSA (Motor Sport Association) and ACU (Auto Cycle Union) which are explained below.
How is the noise level tested?
During a static noise test a decibel testing device (which looks a bit like a mini metal detector) is held at a 45 degree angle half a meter away from the exhaust exit. For cars the engine is held at ¾ of maximum revs. For bikes it will depend on the cc and number of cylinders.
The most common RPM needed for a static bike test will be:
7000rpm for a 4 cylinder 600cc. 5500rpm for a 4 cylinder over 750cc and 5000rpm for a 2 cylinder over 750cc.
The general limit for most UK Circuits is a max decimal limit of 105db which is a standard club race limit but there are several circuits and specific dates with more strict regulations and therefore lower limits.
A drive-by noise limit is often used as a secondary test carried out whilst the vehicles are on track. It’s more than likely to be done on the start/finish straight or at the point of a circuit that is closest or most exposed to the local residents and measured around 10 metres away. The drive-by limit will be less than the static limit so drivers and riders will need to be cautious if they know there vehicle makes a louder noise at certain gear changes, boost levels or RPM.
You will notice a lot of circuits have built banks, walls and other forms of sound absorbing to deflect the sounds waves at certain parts of the track in order to help with the restrictions set by the council.
How can I test my own vehicle?
There are several phone apps available on the market that will provide a reasonably accurate decibel reading up to 100db and your local garage might be able to provide the service. The best way is to pop along to a track day and get it done even if you are not booked on (check first). In most cases if your vehicle has the manufacturer’s standard exhaust with no modifications you will be fine anywhere.
What can I do if my vehicle is too loud?
If you have a modified or sports exhaust the simple answer is to fit a temporary silencer or baffle. On some track days they will be able to offer this service for you but you will need to check before booking. Performance cars may have ‘sports’ settings you can switch off or adjustable boost levels.
So now you are clear on noise limits you can get yourself sorted and book a trackday with confidence. The static noise limits are displayed on all the events on the Trackdays.co.uk calendar.
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