How To Cure Making Noises During Sleep In Child?

Hi. My name is Amber, & are currently living with my boyfriend of about a year now. He has a son about 3, a single father. I have a daughter about 2, a single mother, and we now have another one on the way. His son apparently has the bad habit of rocking himself to sleep at night. He headbangs his head on the pillow, and groans & moans louder each time. I feel sometimes I have to tell him to be quiet every 15 minutes. I heard it was normal and that he'd grow out of it, he started around 6 months and he always uses this method to go to sleep. I can't sleep in the same room as him because it is something I am not used to, and sometimes gives me a headache. Is there ways to break this bad habit?