Siosal, here's an article explaining the research you're referring to.
- New research could help millions who suffer from 'ringing in the ears' https://www.sciencedaily.com/releases/2020/10/201015173126.htm

Date: October 15, 2020
Source: University of Minnesota
Summary: In the largest clinical trial of its kind, researchers show that combining sound and electrical stimulation of the tongue can significantly reduce tinnitus, commonly described as 'ringing in the ears.' They also found that therapeutic effects can be sustained for up to 12 months post-treatment.