You don't even need to be playing anything or be plugged in, if the device is turned on it activates the white noise feature to cancel out the surrounding noises. Be away that you will need batteries handy. They say you will need to swap out the battery every 10 hours or so; although, I have gotten longer. Either way, you may need to swap out batteries more than I do. I use it 1-2 hrs a day, which is enough to get me through crunch time especially if the spreadsheet I am working on is complicated. Hope this helps.