Has nothing to do with the drummer hitting hard... The guitar is most likely the primary source of your 105 dBA. He stated its an A-Weighted measurement.
OP: Are you trying to simulate a race with audio equipment?
If so, you're going to be hard pressed to find any audio system that can replicate the sound pulses and patterns of internal combustion engines that actually create the level of noise you'd be trying to measure... Its two extremely hard to compare types of sound generation.
Its also going to vary greatly depending on the number of cars, types of engines, type of fuel used, and the layout of the track... At first you'd be better off setting strict muffler requirements on the cars and relax them as your noise data grows.
That said, you might be able to get an approximation by using a pretty big setup. Most likely of similar size to your average stadium concert, but its going to be directional compared to an engine's exhaust going around a closed circuit. Be prepared to have a method of moving the rig in order to take samples in a 360 degree pattern.
Of course, I'm completely wrong about this.
I have to laugh at myself..... it's two years and change later, and we're still working on this project.
I wasn't thinking of simulating a race-- this is just a thought experiment to see how loud one of these races is compared to a band (I'm a rock/dirt/water/pollutants/things-that-go-boom engineer, not an audio engineer).
As a project, it's pretty sweet-- this is the first new track in this part of the country since the Kennedy administration. On the other hand, I'm desperately trying to avoid being appointed clerk of the works.
Most of the cars used at this track will be street-legal stuff like Corvettes and old Beemers-- this is not NASCAR. Actually, it's a national nonprofit sports car club who are building their own track because NASCAR has essentially taken over all the existing tracks in New England, and what they have to pay for a weekend at Lime Rock would pay the taxes on this site for a year. We looked at about 50 sites over 10 years for the client to find one that would work, mostly because of the noise issue. This place is basically a topographic bowl.
The 95 dba at 50' is the motor club's standard-- every vehicle gets tested at each event prior to racing, and vehicles louder than that can't participate.
We also have a point-of-compliance issue with the state air quality regs, which include noise pollution-- we have to predictive model noise levels at the property line and at the nearest residence to see what the increase in broadband noise above ambient background is-- somebody else is doing that, not me! If it's more than a 10dba increase, we have to mitigate. Background is at 45, which is weird because the surrounding area is very mountainous and rural.
