I think it must be so. It is not a requirement for BIS, this is just my reasoning:
1) The minimum distance for instant detection of a fighter with a sound supressor (primary weapon) should be not more than 85 -100 m. If a shooter with a sound supressor (primary weapon) will be located closer than this distance, only then it can be detected quickly. At night or in the fog/smoke this distance should be even less.
2) The terrain, weather, time of day, the presence of a smoke cover or visual cover, should have affect the probability of detection. So for example in the woods, in the fog, at night or in smoke detection probability AI should decrease significantly.
3) A specific weapon, that uses soldiers also should affect the probability of detection. So for example a machine gunner with a sound supressor, should always have a greater chance of being detected (because of the high rate of fire) than a rifle , that fires single shots. Thus the minimum detection for machine gun, can be increased with 85-100 by approximately 120-150 meters. At that time, if a shooter uses a pistol with a sound supressor, should not be detected up immediately, even at close range! (within 20-30 m)
4) If a player uses a primary weapon with sound supressor and is located on free place map (without any visual shelters) and distance to enemy within 150-200 m, then this marksmen must be detected within not earlier than approximately 10-20 seconds , even if the enemy AI has 100% skill. The game should not be super-human abilities!
5) Presence of visual hiding place, near to the marksmen, should have an impact on detection. Thus, if a player uses a sound supressor and uses at one time visual shelter (e.g. bushes) and up to enemy within 150-200 m, then the detection of such a player must be complicated. This shooter should be detected not earlier, than within a approximately 30-70 seconds.
And just in case the shooter will not change self position!
6) The Presence of a ghillie suit(expecially at large distances more > 200-250 m) should also have an impact on detection. If the player uses the sound supressor and at the same time uses a ghillie suit and distance to enemy > 200 m, then the AI-detection of such a player must be complicated. This marksmen, should be detected within not less than within 60-120 seconds. And only if he doesn't change fire position!
7) Increase the distance, should be harder to detect. So for example, if a marksmen with a sound supressor, shoots from distance > 350-400, then this fighter, should not be quickly detected. This marksmen should have the all chances to be found no earlier than 5-10 minutes!