eavesturbate
to pleasure yourself while listening to someone else's very loud and probably very bad sex
He eavesturbated through the ceiling and nearly exploded when he heard his mom's loud moans.
She eavesturbated from the hallway and got a nosebleed from the sheer amount of bad sex.
He eavesturbated through the wall and got a stiffy when he heard his neighbor having sex with their pet parrot.