He sounds like a typical male p'lett. If he is out as long as you say he is and you do interact with him, is he vicious all the time towards you or your boyfriend? That sound you hear sounds like, to me, like a warning sound that he uses to kind of protect his territory or tell an object that he is the boss!
Does he step up? Does he talk at all? Do you ever give him treats? Have you ever taken, let's say, hemp seeds and fed them to him one at a time while he is outside the cage? Do you know who he has bonded with the most? Does he get 12 hours of darkness at night?
These are just questions you can answer for us so we can get to know him a little. Tell us what he likes or dislikes for you to do to him, etc..
David and Vicki