Objectively - less gas escaping the muzzle, the quieter the weapon will be at the muzzle end. The less gas escaping the ejection port, the quieter the weapon will be.
I'm not an otologist so I can't say for sure what is safe. Let's just take the OSHA standard -
https://oshwiki.eu/wiki/Noise#Acute_...ustic_shock.29
Apparently, 155db peak is enough for acute hearing loss that could be permanent.
Maybe some of our suppressor guys have ideas of what non-suppressed muzzle blasts are like @
Hansohn Brothers @
kedminster