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.
Hand Dryer Sound [edit]. Many people object to the noise created by the modern hand dryers. A recent paper showed that the typically installed hand dryer creates over 80 dBA of noise, and that the manufacturers' reported sound intensity levels as measured in the lab are often exceeded in typical installations.