I have the answer. I found out that the volume control is there but it's a manual operation. When the volume increases with the speed going up, and it's not to your liking, you reach over and turn the volume down a little (counter clockwise). On the other hand, if you slow down, and the volume is too low, you reach over and manually turn it up (clockwise). I've actually done this and it works.

JUST KIDDING !!

The speed to volume compensation is there but not adjustable and you can't disable it. (unless you have a big hammer)

I don't have a clue where I got the idea that there was an adjustment section. Must have been on another vehicle that I owned. SORRY GUY'S.