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.
The White Noise app helps generate a soothing audio soundscape to help its users fall comfortably to sleep. The app comes with a variety of looped sounds, such as blowing winds, burning camp fires or ocean waves, with additional tracks available as in-app purchases.