That's interesting you say that about the fan. Tinnitus masking is using something external to create a white noise type thing. The tinnitus doesn't go away, but the brain focuses on the external noise rather than being ever conscious or at least less conscious of the tinnitus.
Those with tinnitus may want to check out this Stanford University site where you can listed to some sound files with a headset. I've been trying the sound of sitting in the rear of a Boeing 747. It doesn't drown out the tinnitus for me, but it does seem to help a bit. I was able to keep the sound playing in the background when I made calls from my PC (I use my PC as my office phone).
Here's the link
Chris L