We once heard one of our neighbours going hard at it on our baby monitor. Obviously cross talk from their monitor. We couldn't work out exactly who it was though, as a few of our close neigbours had young babies.
When we lived in Staffordshire, one of our neigbours were heavily into the swinging scene. Once a month, they had a party which often went on into the wee small hours. In the summer months, when the windows were open all night, we often heared the goings on, and our bedroom overlooked the back of their house, so we could often catch a good eyeful of action.........