Do you have a source for this? That is a pretty big claim. To be able to say that with certainty any data on successes would need to clarify how they got their results.
I have tried TRT with a therapist listed and recommended by those who invented TRT and it did not work. I know for a fact that those TRT clinics that are recommended tick like a sucess case the patients who do not come back. The clinic where I went recognised that. The "treatment", if you can call that thing "treatment" is very expensive, and the clinics make very simple and standard tests like an audiometric test be extremely expensive. I can give you specific numbers: for an audiogram and an eardrum test (this is like half an hour) they can bill you in the region of 300 euros. These test are FREE at most hearing-aid audiology clinic and they may even have better equipment, better audiometric cabins.
My private insurance is very expensive and covers
everything, including TRT, all the tests etc I can choose any doctor, clinic, and just send them the bill. They paid for everything but it did not work and the price is ridiculous if you have to pay it out of your own pocket.
When you read any study or article on TRT you have to read very carefully what they define as "success", because the results they get after their "treatment" is pretty much the same as the result you are going to achieve by just listening to a sound of your choice at home over many months. For them an increase in LDLs to way below normal levels is going to be tagged as "success".
Actually, I can tell you too that there is one particular audiologist in my country that has been trying to sell this sort of treatment for a good 15-20 years, and the clinics of this audiologists have been renamed like 4-5 times already. After some time, the service is offered at some other place.
Some clinics also say they have a 99% success rate and they have ENTs on a freelance basis in case you want to ask about the "treatment". Well, it seems not everyone goes to check with their ENTs because I have had some funny conversations with them, where they admitted that they cannot endorse TRT as an effective therapy. Even one of the ENTs said he hadnt seen any patient with hyperacusis referred by that clinic in his life!!!
Make a deep research and you are going to find plenty of information on this sort of "clinics" and "treatments". Also wonder why in Western Europe there arent many hospitals endorsing this sort of "therapy". Do you think that a country that spends thousands of millions on "free" healthcare (supported by taxes) for everyone is not going to carry an effective therapy?