How do submarines stay so quiet?

Submarines are the ultimate “stealth weapon. Remaining underwater to attack or use its sensors, quietness is critical. Through design, modern nuclear submarines have equipment mounted on special mounts to isolate the noise from the outside and reduce the noise signature of the sub in the ocean. Rotating equipment is checked from the design through operation so it is always quiet and it is immediately repaired if it is not operating quietly. The sub checks itself with its own acoustic sensors and establishes the most quiet lineup of equipment for normal or critical operations. Overall, the reason the submarine is so quiet is because every member of the crew knows how important it is to remain quiet and undetected ensuring the submarine can perform all of its mission.