[Captain Tom Coughlin]

His hearing, he can hear everything happening on the ship and can even isolate individual conversations and what not.

[Roysten]

Originally Posted by Saquist

how can he tell?

There's the season 6 episode Schisms where Crusher records strange noises in her quarters and Data separates them all out to be conversations and the like of the Enterprise crew, including obviously various members of the crew getting it on.

[starbase63]

Hi guys, happy 4th of July...

[Captain Tom Coughlin]

Hello SB63, and a happy 4th to you!