I kinda get it now, it's more of a way of studying induced deafness at certain frequencies that might be similar to the effect of tinnitus.

If your tinnitus is at say 13khz, and someone turns on a sound at that frequency, you don't react to it because your mind is effectively masking it.

I once played my tinnitus tone from this site https://www.szynalski.com/tone-generator/ for my partner, when i turned it off i had the odd sensation that i couldn't tell if the sound actually stopped or not.

I used to get some temporary relief from dialing in the tone on that site and listening it to a few minutes.