Decibels ... how low can you go?

My Vulcan .25 with the Petr mod and LDC is measuring 79-80dB at 45 degrees and 6 feet from the end of the barrel. Shooting a tuned velocity of 900fps. Gun was shooting 945fps as delivered and the noise is really about the same.
As a comparison the sound of cycling the action to chamber a round was registering at 68dB.
My hand clap was registering about 70dB at this same distance. Ambient noise was registering 30dB.
 
After being assessed with hearing loss beyond what would be acceptable for my age I bought a dB meter out of curiosity and started testing everything.
Gamo CFR .22cal- 78dB measured at 2 metres and 45* from muzzle.Pellet hitting a piece of pine at 25 metres measured same way-94dB.Ambient noise in my house averages about 40dB.My twin 8 year old girls scared by their brother scream at 120dB.Think I know where my hearing went.
I will test my rimfire and centrefire rifles when I get a chance.