Basically, when a submarine slips beneath the surface of the ocean it becomes blind. At the depths where a submarine travels under the waves, virtually no natural light can penetrate. Because of this, a submarine must rely on several different things to navigate from one place to another. One of these is sonar.
When a submarine is traveling under water, it can actually use sonar to help it orient itself. It does this by bouncing sound waves off of known objects such as rock shelves and underwater formations. By determining the exact position of the submarine relative to these stationary objects, the submarine’s operators can consult charts and re-calibrate the exact position of the submarine.
A submarine also uses active and passive sonar to locate other vessels in its immediate vicinity. This is how military submarines locate enemy ships. Active sonar consists of bouncing waves into an area where a vessel is believed to be located. The returning waves will tell the submarine operators the position of the vessel. Passive sonar allows submarine operators to listen for sounds around the sub without actively emitting sonar waves.
There are many other sounds that submarine sailors will hear besides the classic sonar ping. These include a general alarm, a dive alarm, a surface alarm, a torpedo alarm, an all hands man your battle stations sounding, and a ship’s whistle.
Additionally, some submarines have actually recorded the audio from military engagements. During WWII, the USS Sealion made recordings or its attack on a Japanese convoy, which resulted in the sinking of the Japanese battle sip Kongo. These historical records provide incredible insight into the operational protocol of a submarine during a military engagement.