Are submarines soundproof

Answer 1

No, the opposite is true. Sound travels through water much better than air,and the steel hull is very good at transferring sound from water to air, or vice versa.The sound of submarines is detected by AWAKS aircraft many miles away, and even from satellites.

Although that isn't completely incorrect, all submarines employ ways to reduce sound output (called transients). Some common ones are sound dampeners, floating sound mounts, and vibration reducers. All of these devices have the same objective: prevent vibrations and sounds from escaping the hull.

Submarines have always relied on stealth to complete their missions so we wouldn't be very useful if we could be detected by every awacs or fishing trawler passing by. True, some submarines are quieter than others, and any submarine can be given away by a poorly timed transient, but all in all they attempt to minimize sounds passing through the hull.

More:

Submarines are not sound proof at all. All measures are made to minimize sound transients. Similar to the way your car has motor mounts that are made of rubber to prevent loud sound and vibration from entering the cab a submarine has sound mounts on every piece of equipment that has moving parts. Pipes have small pieces of metal to stop vibrations as fluid passes through it. Motors have mounts. Solid pipes have rubber isolation hoses to separate them from pumps that move back and forth while running. Electronic equipment has sound mounts to prevent hum from entering the deck. Even the deck has its own isolators from the hull. The crew wear soft soled shoes even to reduce the amount of noise they make walking. The outer hull is even cover in rubber tiles to prevent active sonar pings from reverberating off the hull. Something as simple as paint on a sound mount can transmit sound through the hull.