Not surprising. Many millions have a mild enough case it's not a big issue for them, and often masked by everyday sounds, just as I had for many years as it worsened.
@Jupiterman He got it after smoking spice and still continued to work on helicopters so it seems like maybe a few things were at play. He's had it for 10 years now. He is habituated, and said he has a high pitched hiss.