Rios can get pretty loud, this I can attest to! They are kinda cheep.
What model Rio is on it? You should be able to get another comparable GPH
powerhead no problem. Heck I think they sell Penguins at WalMart.
Good luck I will watch this post and see what you end up doing... I do not like loud obnoxious continuous noises either.. I always wonder how it affects the fish too..