[Stonewall Jackson]

Passive sonar, which is the type submarines usually employ to track other vessels and subs, involves listening to the sounds generated by these targets. Active sonar, involves sending out a sound pulse and listening to its return. This allows a vessel or sub to accurately map the area around them, but also pinpoints their own location for anyone else who is out there, a big no-no when you are trying to be sneaky. Additionally, all types of sonar, active and passive, are completely useless when doing a high-speed run like the San Francisco was doing at the time of the crash. They could have run over my cousin's stereo system and not heard a thing.

[duk]

Why were they going so fast?

Is their stealth compromised at that speed?
If the sonar won't work at that speed because of all the "hull" noise, it seems other passive sonar would have picked them up!