Ear rumbling is not the same as tinnitus. I can make my ear rumble, and I also have tinnitus (constant ringing or high pitched frequency sound). At least I assume, I have never bothered getting it diagnosed by a doctor because I can easily ignore it and have for many years, I only notice it when not focusing on anything else and I happen to pay attention to it.

I assumed tinnitus was mostly caused by damaging the little hairs that sense sound becoming damaged from loud sounds and not working anymore, which I would have done with headphone use in my teens/early 20s.