One theory suggests that the link between tinnitus and hearing loss has to do with auditory deprivation – in other words, depriving the brain of sound. We actually hear with our brain, which interprets the sound that comes through the ears.
If you have a hearing loss, sound at certain frequencies is not reaching the brain. The brain tries to compensate for the missing sound and turns up its own “volume” to find the sound (i.e. becomes more attentive). By doing this, the brain might mistakenly detect signals that it would have previously ignored and interprets them as sound – the tinnitus that you hear.
This is why using hearing aids to amplify those frequency regions can be so helpful in managing tinnitus – your brain gets access to the sound again and no longer has to overcompensate.