I haven't kept any hawk-headed parrots myself but I have been doing some research on them, and I have met a few of them. From what I have learnt and observed, they are not loud, but they do have a very distinctive shrill call (which doesn't sound annoying to me). They seem quite strong-willed and bitey, so I think they should be for experienced parrot handlers only. Despite their small size, they are very active and therefore need large cages, but with bar spacing that should not be more than 2.5 cm apart. I suspect that they can do well in an apartment, provided that you are good at reading their body language and good at managing any problematic behaviors, in order to avoid being bitten, because their bites have a reputation for hurting a lot, so it's the screams when the humans are bitten that might create disturbances for the neighbours. But, I would strongly suggest that you talk to the actual hawk-headed parronts on those websites I mentioned before to do your own research. Cheers!