Retired Vice Admiral Masao Kobayashi commanded Japan's submarine fleet from 2007 to 2009. In a recent interview in Tokyo with The Japan Times, when asked to explain one of the country's most tightly guarded military secrets, he seemed reflective.

Kobayashi pointed to the ceiling lights in the quiet interview room and said: "Take those fluorescent lights, for example. Any fluorescent light generates sound."

Other than our voices, there were no other sounds in the room.