Good, ol' fashioned, deep-bone diggin' sex. Specifically at a faster pace creating a slapping sound because the balls 'slap' the lady's ass.
John says to Bill: "Man, my balls are stingin' today."
Bill replies: "How come, John?"
John explains: "Well me and the Mrs. got it goin' real good last night...you know, slapadapadingdong like, and I swear I had my balls slappin' so fast off her ass that it sounded like we had an entire audience clapping for us!!"