It would seem that the years of being a working musician have taken it's toll on my hearing.  I am often kept from falling asleep by a high pitched ringing in my ears - not noticable above the humdrum background noise of the day but quite intrusive at night. 

I have found that if I use an electric fan (even in winter!!) then the gentle whirring of the motor is just sufficient to override the ringing in my ears as the dominant sound and yet is not too loud to be distracting in itself.  Obviously, in the summer having a fan pointing at your head can be very nice but in the winter, all I do is angle it at the wall so I only feel a gentle breeze. 

Hope this helps... it works for me!