Lofi-girl helps me too, it's completely out of my traditional musical tastes but there's something in it that makes me start working. I also have to turn it off eventually though, I find I need to revert to silence after a while for some reason. And if I notice a beat or tune I've heard before, it can rip me out of concentration.
Yes it's hard to say. Sometimes it's when I feel like it's a natural time for a break, but also maybe whatever it is (that the audio tickles in my brain) becomes fatigued or used up.
Either way the silence gives a great feeling of relief. I sleep with a noise generator in my room and can't really do without it (tiny noises fill me with adrenaline at night) but when I wake up and turn it off my body loves me for returning the silence.
