Nuclear submarines are designed to operate quietly to minimize their acoustic signature and remain undetected. The noise level of a nuclear submarine can vary depending on its operational mode, equipment, and circumstances. However, it is challenging to provide an exact decibel level without specific information about the submarine in question.
In general, a modern nuclear submarine operating in a quiet mode would emit very low levels of noise. These submarines are designed to reduce the radiated noise from their propulsion system, machinery, and other onboard equipment. The primary source of noise is typically the submarine's propulsion, which can include the noise generated by the nuclear reactor, steam turbines, or electric motors. Additionally, auxiliary systems such as cooling pumps, ventilation, and other machinery can contribute to the overall noise level.
While it is difficult to provide an exact decibel measurement, it is estimated that a quiet nuclear submarine could have a noise level in the range of 60 to 80 decibels (dB) at a distance of a few hundred meters. To put this into perspective, a quiet library or a residential area during the night typically measures around 30 to 40 dB, while a conversation at a normal level is around 60 dB.
It's important to note that the noise level can vary depending on the specific circumstances and the distance from the submarine. Also, keep in mind that the ability to detect the submarine's noise depends on the capabilities of the sonar systems and sensors used by other vessels or systems attempting to detect or track it.