my hummer has begun to produce a noise that sounds like it could be a loose belt or something hitting the fan shroud. It sounds like it is coming from the middle of the engine.

Yes I would describe it as a humming noise.

I believe it may be the water pump.

You can remove the serpentine belt and run the engine for a minute, see if the noise goes away. Don't run it any longer than that or it'll overheat, and you'll get some check engine lights, battery light, since alternator won't be turning. If the noise is gone then you know it's a belt driven pulley or accessory. You can also spin each pulley by hand, try to feel if there is any unusual resistance or vibration.

Thank you. It ended up being the water pump along with the serpentine belt and the water pump bearing.