My admittedly limited inderstanding of Tinitus Therapy is that they train you to not notice it so much. For example, if someone is listening to dinner conversation, they can hear the dog barking next door, but they usually block out the dog from from consciousness. They are not thinking about the dog, so the barking doesn't intrude into one's thoughts. If you think about it, there are many examples in everyday life where we exhibit selective listening. With all the mechanical noises in "modern" society, we have to.
I've had my Tinitus for so long, that I only notice it if I think about it.