Janggu 장구 is the most representative drum in traditional Korean music
The first depiction of the instrument is on a bell belonging to the Silla (57 BC–935 AD) period and in a mural painting of the same period in Goguryeo (37 BC–668 AD) tomb. The oldest Korean historical records about an hourglass-shaped drum may be traced to the reign of King Munjong (1047–1084) of Goryeo as a field instrument. SOURCE Wikipedia
Silla and Goguryeo were two parts of the 3 kingdoms of Korea. The two heads produce sounds of different pitch and timbre.