The noise one's balls make during sexual intercourse as they slap against the body of the "penis-receiver."
OHHH! Who am I? While I receive your penis, your ballnoise is icing on the cake of my ears!!
B: So...I moan on the "off-beats?"
A: Yeah, because my ballnoise will fall on the on-beats, and I want to hear it this time!
Was that ballnoise I heard in your room last night, young lady?