9x19 -> 350-400 m/s, max. effective range: <100m, sound level: 159.8 dB
.45ACP -> 250-270 m/s, max effective range: <75m, sound level: 157.0 dB
5,56x45 -> 900-950 m/s, max. effective range: <700m, sound level: 155.5dB
6,5x39 Grendel -> 760-880 m/s, max. effective range: <730m, sound level: no data
7,62x51 -> 740-850 m/s, max. effective range: <800m, sound level: 156.2dB
.408CheyTac -> 880-1100 m/s, max. effective range: <2000m, sound level: +170dB
12,7x99 -> 860-930 m/s, max. effective range: <1800m, sound level: +175 dB
Now let's assume a suppressor reduces the sound level by 30dB average. An decrease by 10dB is perceived as half as loud.
A spoken conversation is about 70-80 dB, a slam shut door 120dB. Now go figure how far the sound travels (I can not be held responsible for broken doors or angry neighbours).
The range is not affected by the suppressor. The accuracy can be increased by up to 30%, depending on weapon and caliber. Let's say 10% average.
The kinetic energy does not suffer and therefore the damage potential.
The supersonic crack (up to 120dB!) can not be traced to the origin and should make the AI at least duck and cover. They should investigate the surroundings. If there is light, movement or noise, they will be alerted.
A suppressor reduces the muzzle flash entirely or at least makes it neglectable.
Using subsonic loads reduces the effective range depending on bullet weight and speed. High kinetic mass does travel farther and offers longer effective ranges. For example a subsonic 7,62x51 load is effective up to 300m.
Subsonic means a muzzle velocity (v0) of <340 m/s. That is more than half the velocity of a supersonic load of the same caliber.
That being said, you can not suppress long range calibers and expect the same ranges with a subsonic load.
So the conclusion of this little write up:
Subsonic loads only make sense for a few calibers and purposes. 5,56x45, 7,62x51 and 9x19. The rest of the above listed calibers are not suited for subsonic loads or are already subsonic (.45ACP).
What buggers me is the way of setting muzzle velocities in ArmA games. It's not the gun that dictates the velocity, it is the ammunition. But to be precise, the barrel length should factor the v0. You could load a 9x19mm with 350m/s into a long barreled gun and still get 350m/s. Did BIS change that in ArmA3? Do longer barrels generate higher v0? This would be essential in ammunition calculations. A carbine will not generate as much v0 as a marksman variant (14,5" to 18 or 20"). So my notion would be to make the gun dictate the v0 or at least add a factor for barrel length to increase/decrease the muzzle velocity accordingly.
But this might be another issue not directly related to "stealth" and "suppressors".
That's all folks, thanks for taking the time to read my thoughts on that matter.