You get metered on a mic that is designed for SPL purposes. It measure the Sound Pressure Level inside the car. A decent audio shop should have some kind of SPL meter.
128 db....didn't quite reach the full spl cap in SQ.....but even if i did get the full 30 points i wouldn't have got first......but i ended up with a nice large trophy....
lets hope i can come close to 130 with 3 8's for the spl cap this year.
149.? on a audio control I think. I cant remember exacts but could not break 150. I was using 4 rockford 1810 power punch with a jbl1200.1. The box was sealed at .91 with pollyfill. This is what is on my sound domain. I am redoing now with 4 12" brahmas and 4800 rms.