You can control some of the pheromones you produce, the amount of blood in your skin, pupil dilation and the timbre of your voice. The net effect is that the signals and body language you produce need not match your true emotional or physical state.
The main effect of the shroud is to confuse automated sensors. Lie detectors, automated alarms and robot targeting systems can't get a good fix on you. The special bonuses of a Killseeker, Stress Analyzer or ThreatAnalyzer won't work against you, nor will similar functions of regular technology.