To reiterate 237SJ's description, I find that most of my cohorts in aviation, especially any one over , say 50 years old, are experiencing hearing-loss related tinnitus, including your's truly. Problem seems to have originated in the era in which most of us began learning to fly. At that time, sound related hearing loss wasn't well understood and most of us flew aircraft that had little or no insulation... jus a thin piece of metal firewall between the cockpit and the engine compartment. It wasn't until later that earphones for radio communication became the standard and much later still that sound reducing earphones were introduced. At roughly the same historical period, hearing tests were introduced as part of the First Class flight physical which transport pilots are required to hold.
The results of the hearing test, in its graphical depiction look like the ski jump at winter's Olympics... the lower ranges (equivalent to human voices) are fairly steady and straight line, but when the higher ranges are reached the ability to hear them dives.
In many cases, not only did most of us experience sustained loud noises but, as my Doctor explained after questioning me about hunting when I was young, loud, percussive sounds (such as gunfire) are equally debilitating.
Doc also confirmed what's been said here, that the brain, not receiving sounds at a given range, 'creates' its own sound in the form of ringing or other anomaly. I occasionally here chirping and/or musical notes (or so it seems) but mainly a constant ringing that never goes away... but like a sore thumb, becomes so common place that one becomes nearly unaware of it over a period of time.
Lotsa over-the-counter remedies advertised, but don't waste your money. I have had friends that began wearing hearing aids and have all stated that the ringing has subsided or actually gone away while wearing th devices... No scientific proof of that though... yet at least...