JayShadow
[12] Conqueror
The reason you take Adrenaline is for the speed boost. Zombie hits don't hold you back. You revive incapped teammates much quicker. You swing melee weapons quicker. Machete+Adrenaline=Harbinger of DeathAdrenaline (recovers only a small amount of temperary health, side effects is that you cant hear very clearly when your on this - sounds like eveyone and everything around has inhaled helium... lol?, taking pills or healing will recover you from the symptom.)
The sound is to let you know the speed is still active.