WAYYYY too many variables to call this one. Muzzle velocity, power, suppressor, efficiency, and caliber all play into this equation. I have a highly modified AF Condor in .25 that makes 81fpe at the muzzle. I use a DonnyFL Ronin in .30 to quiet it down. The slug hitting the target is louder than the rifle firing off. But it's still not "quiet" as the term in and of itself is ambiguous and subject to interpretation. In the EU, the limit is 12fpe. I would imagine those are super quiet, especially if suppressed. But if those guys stood next to my gun, they would probably comment on how loud it is. Then I would take off the suppressor, and let them hear what 81fpe sounds like un-throttled. Like I said, it's subject to interpretation. The only way to truly find out would be to set a standard with various rifles. Hypothetically...... 5 or 6 of the most popular high end rifles set at identical power settings in identical calibers achieving identical velocities. But at that point, the "bark" being silenced will depend solely on the suppression system being used. Then the question becomes, what's the quietest suppressor, and not what's the quietest rifle. Just my $.02 however.