Why are nuclear-armed submarines difficult for an enemy to locate?

Nuclear-armed submarines are difficult to locate primarily due to advanced silencing technologies designed to minimize their acoustic signature, which is the main target for passive sonar detection.12

To remain undetected, modern submarines employ several design strategies:
* Machinery Silencing: Engineers have redesigned reactor coolant pumps to be quieter and mounted machinery on sound-absorbing supports to prevent vibrations from reaching the hull.12
* Acoustic Coatings: Hulls are often covered with sound-absorbing materials that reduce the submarine's acoustic profile and limit the effectiveness of incoming homing torpedoes.12
* Natural Circulation: There is a design preference for natural-circulation plants, which reduce the need for noisy mechanical pumps.12

Furthermore, detection is inherently difficult because sonar range is limited by environmental factors such as sound attenuation, temperature-induced bending of sound waves, and background noise. While active sonar can locate objects by bouncing sound off a hull, it is often avoided by hunters because it reveals their own position to the target.312