eavesturbate
to get yourself off while listening to someone else's messy and probably very loud sex
He eavesturbated through the floor and got a full-blown erection when he heard his neighbor having sex with their cat.
She eavesturbated from the hallway and started crying when she heard her brother's whole group chat having sex at the same time.
He eavesturbated through the window and got so turned on he started peeing on the neighbor's lawn.