The sounds were hot and dirty and gave Barty an even clearer image of how it had to look, combing with the image from earlier, one that wasn't leaving Barty's mind for a long time. Oh, that mouth making those sounds, yes Barty saw it clear as day. And he further chose to make a mental image of what his arse looked liked, getting so thoroughly fucked.
His mouth opened to release a low moan, shallow but repeating like a strong echo, rebounding off the walls.