Which is called tinnitus.
If you put anyone in a sound proof room for long enough, they will eventually hear noises.
The most common form of tinnitus is a high pitch ringing and the most common source is now believed to be in neural cortex (related to memory and overactive neurone feedback) rather than the ear, although the original source is often a defect in ear mechanism, such as a loss at a certain frequency where the brain is attempting to compensate.
In my case, it is 24x7 for the last 15 years. I can hold a hair dryer up to my head and still hear it.
The only medically accepted treatments are habituation(TRT)/masking which is teaching your brain to break the fight/flight response.
There are other techniques that have variable results, such as xanax, hypnosis, vegas nerve stimulation, notched music, and playing tones either side of the tinnitus frequency.
I heard a quote recently that if you could hear pain, that would be the sound of tinnitus.