the fence on the back straight is quiet close to the track so thats where you would have issues. They do get pretty anal there, couple of mates in a race series had to install silencers prior to race day after failing the noise testing on the friday.

your phone should be pretty good for it. just measure a distance in a clear bit of road and go past it at various distances to see how far away you have to be to get 95dB. Needs to be under full throttle too.