Forest Walk is a white noise productivity track with the calming sounds of the forest. It plays continually for 52 minutes, which correlates with the concentration span of adults.
 
When the track stops, the listener should get up and take an active break. 
No TV, reading, electronic games, etc. 
Go outside if at all possible, take a walk, do some stretches, make some coffee, etc. for 10-15 minutes before resuming work.