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.
(August 2016) (Learn how and when to remove this template message) In acoustics and specifically in acoustical engineering, background noise or ambient noise is any sound other than the sound being monitored (primary sound). Background noise is a form of noise pollution or interference. Background noise is an important concept in setting noise regulations. See noise criteria for cinema/home cinema applications.