I went to an audiologist and an MD for my spontaneously developed tinnitus in my 30s. They did a hearing test, asked a couple of questions that didn't apply to me and they both said "I dunno why you have it" and were fairly useless.
The only hint was a dip in a hearing chart, which wasn't big enough to be considered hearing loss or otherwise. This list alone is a better list of potential causes than those useless doctors.