@gameragodzilla Depends on the enemy.  That's the nuance to it in System Shock 2, really.  For example the zombie enemies are very simple so they miss anything that isnt basically right in their face, but they are attracted to sound.  They aren't aggressive until engaged though so can be worked around.  The cyborg midwives (theres a name for ya) meanwhile are aggressive and much more perceptive but because they're cyborgs are subject to interference (emp grenades or being around certain electrical machinery like the reactor in the one section)