I have got a brilliant app on my android phone called Relax and Sleep (sorry if this has been posted before). I think it is free ( or really cheap).
It is a lifesaver for me when my tinnitus is so bad I can't sleep. There are loads of different sounds on there to help you to relax, and I just go through them till I get the right combination to help mask the ringing /humming/ whooshing I have at the time. It has a timer, and each sound can be set at a different volume, up to 5 at once.
Take care, Becky