Originally, Tinnitus Retraining Therapy was developed as a method to cause unhabituated individuals to become habituated to their tinnitus. There's evidence that this works, but it won't lower the volume of your tinnitus.
Habituation is a process whereby an individual's tinnitus tone no longer bothers them. Habituation has been shown to lower the distress caused by tinnitus, but unfortunately, many people do not experience habituation.
If you're interested in sound therapy for tinnitus check out AudioNotch.com. We offer a service to treat tinnitus and ringing ears through sound therapy online. If you have any questions feel free to contact us.