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.
Delay is one or more distinct sound images. Here is where reverb and delay are related. Stand in a huge room and yell hello.. The very first sound you hear reflected off the walls is an echo. That echo quickly turns into reverb as the sound is reflected off a second, third, and fourth surface.