While fishing this year I have been hearing a groaning noise coming from under the boat.  It seems you only hear it when you are right over top of whatever it is that is making the noise.  I have heard this a few times in past years, but this year I am hearing it a lot. I am mostly fishing between East Brady and Emlenton.
 
Anyone else hear this?  Does anyone know what is making the noise?

Anywhere in the area of the power plant??

Not at all.   It has to be a fish or some other water critter.  As you drift towards it, the noise is faint and it gets louder once you get over top of it and then it fades as you drift from it.   or it will stay faint if you don't drift directly over it.  Once you pass it you wont hear anything until you drift down the river and maybe approach another one.  The noise seems to be in slow deep pools.

Are there air bubbles coming up.

Loch Ness monster on her migratory path deciding if she wants to eat you....or just let you keep fishing 😉

Drum maybe?
 

No bubbles.   I was also maybe guessing drum.