"honking" regulator

[chrisw]

Hi all,
I just got OW certified two weeks ago so I am loaded
with questions!

Why does my octo regulator sometimes make a "honking"
noise when I inhale on the surface to test it?

I was told by my instructor and by the head dude of
ScubaDiving Magazine's ScubaLab that it is normal.

But I would really like to know WHY it does it and/or
what is happening to make it do that.

thanks,
-chrisw

[Chris]

I asked this question too when I first got my regulator... I think it has something to do with the water pressure against a valve or diaphram. I know someone here will have a better or more precise answer, all I know is that it IS indeed normal.

[nomads]

Chrisw, I think what you are referring to is that your backup regulator is detuned so it won't freeflow. It is not supposed to breath as easily as your primary regulator.

[lrmoll]

My guess is as follows. When you test breath out of water the diaphram can move much easier than when it is in the water. So it tends to oscillate some when you breath from it in air. A side effect of the detuning.

[chrisw]

so, can such oscillation occur underwater too?
is that what "overbreathing" is?

[JoelW]

Overbreathing is trying to pull more air out of the regulator than it will supply, due to a valve not being opened, lower perfomance reg, balanced vs. unbalanced, diver overworking, panicked, etc.

[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