A human can start hearing at 0 decibels, which is the sound at which we are able to pick up noises as quiet as a mosquito buzzing10 feet away! At –4 decibels sounds are as quiet and detailed as the ticking of a wristwatch. This makes it all the more amazing that a nuclear submarine microphone can hear noises as low as –80 decibels, which in other words, is the sound of shrimp chewing their food from 100 metrs away!
The reason submarines have such an impressive microphone is due to their use of Sonar, which stands for Sound Navigation And Ranging. Sound is vital for submarines to navigate through the waters. Nuclear submarines in particular need to be as quiet as possible, and able to detect the slightest of sounds when avoiding hostile areas. For this they must use a technique known as ‘silent running’.
This is where many modern submarines use nuclear power to generate energy that is close to silent, and is what allows them to pick up such minute noises as a little shrimp chowing down on some grub! Of course, I’m sure that the crew of a nuclear submarine is probably more distracted looking out for the sound of enemies nearby though!