Ableza
Headphoneus Supremus
I have read the argument that even if the noise is inaudible, its presence does degrade the overall sound quality. I have no opinion one way or another, but it does seem kind of kooky.
Again, refer to my sig line. Noise that is below the level of audibility exists in every system. It does not matter if one cannot hear it.
A quote I've seen attributed to audio design guru Henry Kloss: "Everything that matters can be measured, but not everything that can be measured matters."