Hi! I am 43 years old and have to bear a hum-like sound in my head since maybe 10 years now, and it is more than strange since all its properties are those of an artificial sound and quite 'unbiological' in my opinion:
- it's around 100-120 Hz (estimated)
- it's a tad more on the right half of my brain but not much
- never changes frequency
- never changes volume (subjectively it appears louder in a silent environment of course)
- goes on and off seemingly randomly, but actually it's not that random, because ...
- it's triggered by other low sounds, e.g. if chatter my teeth, or if a door shuts
- a trigger changes the hum to off if it's on and to on if it's off
- this 'triggering' doesn't work all the time, but often enough that imagination can be ruled out