The term RAPS, TAPS can be summarized as two different types of knocks. RAPS stands for 'Rapid Acoustic Pulse Sounding' and is a type of sonar used to measure the depth of water. TAPS stands for 'Tactical Acoustic Pulse Sounding' and is a type of sonar used to detect objects in the water. Both types of knocks are used by the military and other organizations to detect underwater objects and measure depths.