ORIGINAL: rcutdf
This lead me to ask a question that's been bugging me. When speaking of how to tune pipes, suggestions are often given in the form of specific dimensions, ''to the apex of the pipe''. Not too confusing, apex is biggest part of the pipe, technically point where the pressure wave is reflected. On a muffled tune pipe however, the apex is not a single point of the pipe, the pipe's largest diameter may extend for 6-10 inches.
Cheers,
DAVE
The reference point as I've always been told is the point where it first reaches maximum diameter. Get a flashlight and peer down the inlet of the pipe, you'll see things are different inside than out.
MJD