>> Do they need a "buddy?" I'd be happy keeping just one, but if I need to get 2 to make them happier, I can do that too.
>>

No. I've kept one by itself for over 4 years. It eats, it moves around, it soaks, it tries to eat my hand, and it rarely hides. Seems happy and healthy. See photo below.

>>Also, how loud are they?

I think I've heard him call less than a dozen times in 4 years. It's not that loud. He seems to react to certain sounds, like a vacuum cleaner or the sound of the hand misting pump.

Good luck!