The theaters of Ancient Greece enormous, when, for example, the nearest seat was almost 10 meters away from the performer, large movements and loud voices were critical to conveying the full story.
As such, it is widely accepted that the performers would wear very simple, plain masks which made their facial features more clear and obvious for the audience to see. Some theater historians assert that these masks also had a type of megaphone built in for amplification, although this point is disputed.
In conjunction with their enlarged faces, the performers were often on stilts and wearing heavy robes of fabric to accurately convey their character. These amendments to their body meant that every move they made and every sound they created needed to be worth it. There was no “stage whispering” in this theater which limited but also inspired Euripides to write plays with more dynamic and complex plotlines, ones filled with action and confrontation to futher add to the experience.
In addition, the chorus of some twelve men (playing women in Medea) would constantly dance around the orchestra (derived from the Greek term for dancing) during their scenes. The dancing was entertaining but also allowed the group to spread around the wealth so to speak of their odes, so that all might be privy to hearing their sound and seeing their dance.
Source: Didaskalia