Hirohito's August 15, 1945 surrender broadcast is commonly called Gyokuon-hōsō. The Japanese term is often translated as “Jewel Voice Broadcast,” referring to the emperor's voice reaching the public by radio.
Hirohito recorded the speech late on August 14, and the recording was transmitted by NHK at noon the following day. It was not a live address; technicians played the emperor's phonograph recording.
The message used formal classical Japanese rather than everyday speech. Because the recording quality was poor and the language was unfamiliar, many listeners did not immediately understand that Japan had surrendered.
The broadcast announced acceptance of the Potsdam Declaration, but the formal surrender document was not signed until September 2. Gyokuon-hōsō therefore identifies the public announcement, not the later legal ceremony aboard USS Missouri.