The 1945 radio broadcast in which Emperor Hirohito announced Japan’s surrender was called Gyokuon-hōsō.
The Japanese term is often translated as “Jewel Voice Broadcast,” referring respectfully to the emperor’s voice. The broadcast aired at noon on August 15, 1945, and relayed the emperor’s acceptance of the Potsdam Declaration.
The speech was not delivered live. Hirohito recorded it at the Imperial Palace on August 14, and the recording was replayed the next day. Palace officials secretly protected the records during an attempted military coup by officers who wanted to prevent the surrender announcement.
Because the speech used formal Classical Japanese and had weak sound quality, many listeners found it difficult to understand. The term Gyokuon-hōsō refers to the broadcast, not to the later surrender-signing ceremony aboard USS Missouri.