As you can see by the video it seems there’s something going on with water pressure/vacuum because the sound is in synch with the water flowing into the tank. Could still use some explanation though. EDIT: Fixed. (See below the video for more.)
Well, good news, I didn’t have to replace anything. Even though I couldn’t find anything to adjust on it I figured I’d have to take the thing to Home Depot to make sure I got one to match anyway. So I took it out and decided to take it apart to see if I could figure out what was wrong with it.
I couldn’t take it apart completely due to the way it’s manufactured but I was able to break it down into about 5-6 parts. I rinsed water through it while figuring out how it works and just on a hunch I decided to put it back in to see if I’d washed out any debris while messing with it … sure enough it works fine now.