I'm sorry, I was vague. I meant that the noise has no peaks or troughs; as long as your batteries are charged, it is a constant volume that doesn't change on cable wiggles or the volume of the music played from the source. It is exactly the sort of noise that you want- if you have to have it. My Walkmans and AMP3Pro not to mention one or two other amps, have noise that modulates even when you are not touching the chassis or twiddling the volume pot. Those non-neutral noise signatures are annoying.
Got it. I have mild tinnitus, and you basically described what I hear in near or total silence. The slightest sound overrides it and it is not noticeable.