I take out a collection of 30 caliber suppressors, a Bruel & Kjaer impulse sound meter and a bunch of PPU .308 Winchester ammo to find out how well each of them performs following the Mil-Std 1474D protocols.
Part 1 of this series: https://www.full30.com/video/d559c7570e13a9dd160dea9383d8e51e
Suppressors used (and where you will find them in the timeline): AAC SR-7 - 5:08
SilencerCo Saker 7.62 - 5:41
SureFire SOCOM 762 - 6:11
Griffin Armament Recce 7 - 6:46
Dead Air Sandman-L 762 - 7:24
SilencerCo Omega 30 Cal - 7:59
Tested on a 5.56mm Rifle:
Griffin Armament Recce-7 - 8:53
SilencerCo Saker - 9:20
SilencerCo Omega - 9:50
SureFire SOCOM 762 - 10:19
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.
For impact or short duration pulses, OSHA considers 140 dB or less to be hearing safe. https://www.osha.gov/dts/osta/otm/noise/standards_more.html