Cecile B DeMille was the first director to use a megaphone on the movie set.

Theatrical costumes were an innovation from Thespis, Greece in the 6th century BC. Theatrical costumes are still called "the robes of Thespis." The most important feature of the Greek costume was the mask, which indicated the character's age, sex, station, and customary mood. The masks were made of linen, cork or wood and were skillfully carved and painted. Their funnel shaped mouths are thought to have acted as megaphones to amplify the voice.

Many primitive cultures employ masks with which to disguise the voice in magical or religious  rites. Such megaphones are still used today in as widely dissimilar cultures as those of Switzerland and the Brazilian Indians.

Important disclaimer information about this About site.