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.
On a bass, a small amount of reverb (or wet sound) is created by the tailpiece in conjunction with the string afterlengths and the tailpiece wire. If a player desires a dry sound, this reverb unit needs to be calmed down, either with more weight, a change in afterlength tuning, or a more absorptive tailpiece wire.