I've had my GCC in a dorm room and 2 apartments over the years, and never had any complaints. She's a pretty quiet bird. I think if she was in a cage and could hear me in another room, she would probably scream for me. But we are never in that situation. She is cage free and free to follow me around. If she can't be with me, I put her in her room (which is also my office/computer room) and shut the door and since she can't hear me, she will settle down for a nap.
She has a loud alarm call, which she uses only when she is truely frightened (pretty rarely), and then a hurry-up-with-dinner scream which can be annoying - but only lasts while I am getting her dinner ready. She also has a high pitched happy squeal she will occasionally use when happy and playing. It's not very loud and I like hearing it because it means she's happy, but my dad has commented that it can be painful to hear. So I guess older people with reduced hearing range may find some of the noises more irritating.
But in general, she is a very quiet bird. On the rare occasion she is screaming with the windows open, I can hear her outside the house, but her screams are not distinct among the wild birds and other outdoor noises - I would never notice her unless I was listening for her.