Rudy,
I am not a medical person, but from what I've learned over the years, it can be either way. From what I understand, generally hearing loss happens over a long period of time. But traumatic hearing loss can occur instantly, like mine. My initial hearing loss and tinnitus was caused when I was exposed to an explosion while in a very confined space. This happened during a training exercise when I was in the Army and stationed in West Berlin in the spring of 1972. Over the years, with continuous exposure to loud noises (another four years in the service and then almost 30 years working in construction) my hearing continued to decrease and my tinnitus became louder.
I don't know if you have found this to be of any help, I can only relate to you the things that I have experienced in life or learned over the years in an attempt to understand what I was experiencing.
Good luck
Al