Emperor Hirohito's recorded radio address announcing Japan's acceptance of surrender terms was called Gyokuon-hōsō.
The Japanese term is commonly translated as “broadcast in the Emperor's voice.” Broadcast at noon on August 15, 1945, the recording communicated the imperial decision to accept the terms of the Potsdam Declaration and end the war.
For most Japanese listeners, it was the first time they had heard the Emperor speak. The recording was difficult to understand because of its poor audio quality and the formal classical language used in the Imperial Rescript on the Termination of the War.
Gyokuon-hōsō was an announcement, not the formal surrender document. The legal signing occurred later, on September 2, aboard USS Missouri in Tokyo Bay. That distinction explains why August 15 and September 2 are both important dates in accounts of Japan's surrender.