miller: the reason that you are not aware of the tinnitus when"out and about" is that there is so much other ambient noise for your brain to tune in to. Normally, you would become aware of it only in quieter environments.
That's how these Tinnitus sound relaxer machines work - they give your brain something to concentrate on, other than your "internal" noise- very useful when in quiet situations eg. bedroom at night, trying to sleep.