Tapping My Ear Increases Volume of External Sounds?

I dunno if it's maybe just normal or not but anyone else come across this situation?

My unexplained hearing loss and tinnitus has been gradually getting worse over 2 years but I've realised that when I tap my ear, or around the ear, any sound around me comes through significantly louder and clearer. I can also achieve this through scrunching my face and tensing my eyes etc... sounds gets noticeably louder. Once I stop, the sounds get quieter again.

It's really bizarre but if anyone's had this I'd appreciate advice if it suggests any particular condition. I theorised it could be me helping the sound vibrations along and might be suggesting something like otosclerosis. This doesn't work on my right side as much but that ear's been the worst for the longest so I might not be able to get the same benefit.

 

I was mowing the grass with earmuffs on and realized that I could open my eustachian tubes and actually hear through my mouth. I confirmed this by opening and closing my mouth and pinching my nose.