"honking" regulator

[FMT]

While the honking is annoying, it is normal for a regulator
to do it when breathed from out of the water. A second
stage works because you pull the diaphragm in when you
inhale thus moving the lever and opening the valve.
Unfortunately when there is air on the outside of the
second stage (on the surface) the air flowing through
it can set up an oscillation because of less resistance
on the outside than when the reg is in water. Second
stages that have thicker diaphragms tend to have less
honking because they resist this oscillation better. This
can account for the difference in "honking" abilities between
some brands of regs.
Hope that helps.
Todd