Noise Exposure Through Mouth and Nose via Open Eustachian Tubes?

[Dogwhistlehead]

I have a noisy job. I work at a ship yard with lots of loud bangs and noisy work. I have tinnitus and some hyperacusis due to noise trauma. Because of this I always wear both helmet mounted earmuffs and and earplugs to be safe. This works well and the earplugs alone have been tested to attenuate about 40 dB for me. This provides highest possible protection under normal conditions.

But sometimes I experience some extra noise coming through. This typically happens when I move my jaw a certain way, or yawn, or even tighten certain muscles in my head. This happened the other day when I made a closed mouth yawn just as a colleague made a banging noise. Because of this I assumed that the movement caused a minor leak in the hearing protection. However, now I believe the sound might actually travel through my open Eustachian tubes through my nose!

If I listen to a steady sound with earplugs and recreate the sensation like listening to a faucet etc., I can hear the volume of what I listen to increase, not as much as with no earplugs, but noticeably. I notice a reduction again if I pinch my nose.

So my question is, does anybody know of any information of how many decibels can actually travel to the inner ear from the nose through open Eustachian tubes?