Masks were always used by the actors of the ancient Greek theatrical plays. Their theatrical function indicates an integral connection between the performers, the plot and the acoustics of the open-air ancient theatres which has not been explored in the past. Although the exact form, shape and material of such masks can be only deduced from limited archaeological finds, based on these and other sources, a number of typical mask templates were constructed covering most of the potential alternative forms. For these mask templates, the acoustic frequency response, the angle-dependent radiation and the actor's voice self-perception were tested via use of a KEMAR manikin and appropriate post processing. The novel results illustrate important acoustic and voice communication aspects of these masks.