Short of measuring in a soundproofed, climate controlled environment it is impossible to have a standardized dB reading for vehicles – but even then the results would vary in the real world. There are many conditions which affect sound: distance, measuring angle, weather, sensitivity of the testing device, other sources emitting noise, and even reflection from the environment nearby. We’ve had reports of cars registering louder during the morning than in the afternoon at Laguna Seca due to sound retention from the thicker air / fog in the AM!
If you’re worried about sound levels and / or passing sound restrictions at track we invite you to give us a call to discuss your unique situation. We’ve put work into helping GT3’s pass sound with various exhaust setups and it’s important to us that you get to use your products on the track – we don’t want you to get black flagged.