I have a shower that recently has started to whine or hiss really loud when the shower gets turned on. It's a tub shower and the noise happens when the pull knob gets pulled up on the spout and the shower turns on. Apparently if you don't pull the knob all the way up, the noise isn't as loud.

It seems to me that there is some kind of pressure that is building up in the line that is making the noise. Is the shower-head to blame, the tub spout, or do I have a much larger problem?

It probably has to do with shower head and the pressure water pressure behind it. Changing shower heads would likely solve the issue. I recently changed shower heads in a similar tub/shower combo and experienced basically the same problem. The only difference was that I had to pull the faucet knob all the way up to get the whine to stop.

Agree. We had a similar issue and it's all better now!