Then pack the stock cans with a little C-4 and see how loud they really are.
Funny story (at least to me):
Several years ago, I was invited to go with a friend to test his new outboard boat racing engine on the dyno - running a low percentage nitromethane/methanol mix of about 35% and help tune it with the new 180 pound per hour injectors, that they had bought from the Penske F1 team.
We ran about 6 pulls on the dyno, and got the tune nearly dialed in. Then we did a full power pull.
It seems that each pull was building up nitro and methanol in the dyno's exhaust and muffler. On the full power pull, this fuel in the exhaust ignited!
The dyno exhaust blew into fragments (nothing bigger than 4 inches square), the metal door on the dyno room was blown off the hinges, and the bullet proof glass window that looks into the room from the operator's control station was blown loose in its frame.
The engine was fine. We unbolted it from the dyno and flushed it out with gas. As we were loading the engine and tools back into the truck for the ride home, the shop owners asked us not to bring a nitro engine back there again. ;D