Unfortunately I have been to ENT’s a lot over the last 2 years. Even had ear surgery to see if it would correct my problems. Which it did not.
Anyway, that is water under the bridge. My experience with an ENT is that they will want you to have a set of hearing tests from their in house Audiologists. This test should be conducted in a sound proof room and will be comprised of several tests. The Audiologist on here can better tell you about that than I can.
After the hearing test you should get to see the ENT Doc. The doc will usually discuss with you the problems you are having. Ask what external factors have happened recently, such as the incident you mention at the firing range. And other Q&A type of conversation. Make sure you give the doctor as many details as you can as the more info they have the better diagnosis they can make.
After the Q&A they should give you a visual examination. I have been to several different ENT’s and the examination has been different. Most commonly they look in your ear with a light and scope. May use some tuning forks to do on the spot testing.
I have also had a Ear Specialist use a microscope to examine my ears. Had me lay down on a chair that tilted. Kind of like a dentist chair. Then they stuck a machine in my ear. The machine was huge!! Doc kept tugging on my ear lobes and pulling this way and that way to get the machine down farther into my ear. He joked and said he was trying to see the backside of the other ear!!! After he got it in he took pictures of the ear.
That visit was back in the early 90’s when I was just starting to have hearing problems. So hopefully the machines have shrunk since then!
I have also had a CT Scan of my ears. But that was after my surgery and they were trying to diagnose why it had failed. So I get the feeling that it is not part of the standard battery of testing an ENT does.
After all testing is done the doc should give you the diagnosis and discuss treatment options with you. Make sure to get copies of your test results. Especially hearing tests. That way you can keep a history of your hearing to see if it is getting worse. I have my hearing tests going back to the early 90’s and can see the slope getting worse over time.
Hope that helps.