I take out a collection of 5.56mm suppressors, a Bruel & Kjaer impulse sound meter and a bunch of IWI 5.56mm ammo to find out how well each of them performs following the Mil-Std 1447D protocols.

Suppressors used (and where you will find them in the timeline): AAC M4 2000 - 4:34, AAC Mini 4 - 5:32, Silencerco Saker - 6:16, Silencerco Specwar - 7:07, Silencerco Specwar K - 7:51, Surefire SOCOM - 8:33, Griffin Armament M4SDII - 9:15, Griffin Armament M4SD - 10:02, Griffin Armament M4 SDK - 10:46, Griffin Armament Recce 5 - 11:30, Griffin Armament SPR - 12:15

Information on decibels and what it all means: http://www.acousticsbydesign.com/acoustics-blog/perception-vs-reality.htm

As the link above explains, 3db is technically a substantial increase in sound however what we hear as humans (perceived sound) it's not quite noticeable (+5db and most people can hear an increase in sound). When talking about damage caused to your hearing, 3db can be meaningful even if the noise doesn't sound louder to you as the shooter.