I go 4 fingers down from the collar on the front, and just under the front collar impression on the backside of the shirt. everyones fingers are different so I measured mine and the 4 fingers measure 3.5. I also use my left hand to guage where to put left chest logos.
Grey noise then, has a sound frequency that, if translated to a light frequency, would roughly be the color grey. Grey noise is a random sound that is distinguishable from other types of sound because it sounds the same, to the human ear, at all frequencies.
Pink noise, or 1/Æ, (one over frequency) is a low frequency wave-like pattern with equal energy in all octaves. a chart! (Yes that explains everything I'm sure.) Pink noise straddles the line between white noise and brown noise. White noise is entirely uncorrelated data, complete chaos, the snow on the tv screen. Brown noise is highly correlated data full of predictability. So pink noise is where the chaos of white noise and the order of brown noise meet. Some things send out the actual frequency of pink noise and some behaviors or patterns when tracked and put on a graph match up to the pattern of pink noise. I think pink noise sounds like a big waterfall. I'm listening to it right now. It's really good at drowning out the outside world, curing the ringing in your ears, or for just relaxing. Things with pink noise: wind; pulsating quasars; your heartbeat