But, pretty soon you'll have to have O2 tanks mounted on your SUV.I still don't get the selling air part. Air's free! (at least for now)
I think I was just anticipating the dull roar from the my shell is better than your shell crowd. You really couldn't test my formula by tapping on the shell without heads on it. The Helmholtz equation applies, only to a closed ported volume.
I am curious if any one else has tried calculating the frequency of their drums with that formula, and whether the frequency was reasonable for tuning.