I'm so sorry you got tinnitus from a slamming door. That incident certainly could be the cause of your tinnitus, even though most door slams don't seem like they would be loud enough to inflict damage. It depends on so many factors, such as the materials used to make the door and the door frame, the size of the room you were in, the acoustics of that room, how hard the door was slammed, and how close you were to the door at the moment it slammed. (The fact that you were only a foot away from the door when it happened tells me that yes, the sound was horribly loud for you, and not so loud for people at the other side of the room. What terrible luck.)
It's also possible that you had previous exposures to loud noises that made your ears somewhat vulnerable to injury and that the door slam was just the proverbial straw that broke the camel's back.
We may never know all the reasons why you got tinnitus from that incident, but what matters more is that you're looking for ways to heal.
Since you asked, I can't think of anybody on this website who said they got tinnitus from a slamming door. The closest example I can recall is this person who wrote about a storage bench that had a hinged lid that got slammed down very hard:
Hey Everyone, I am brand new to Tinnitus Talk. I have read some posts and found support over the last couple of days. I was exposed to a loud sound Friday night, a bench slamming shut. Since then I’ve had increased bilateral ringing and I felt a bit nauseous and slightly off-balance. I went...
www.tinnitustalk.com
Are you seeking treatment now from any doctors or audiologists or mental health therapists? I really hope that your tinnitus dies down, or that you find ways to manage your symptoms if it does not.
EDIT: I typed the words "slammed" and "door" into the search engine of this website, and it pulled up several more instances of people experiencing ear issues from that type of sound. So it's definitely a triggering event for some people.
