UVB-76 is the name used to refer to a mysterious shortwave radio station that has been broadcasting continuously since 1982. Using the frequency 4625 kHz, the station broadcasts short, monotonous buzz sounds at a rate of approximately 25 tones per minute, 24 hours a day. Occasionally, the buzzing stops and a voice is heard, speaking in Russian, briefly before the steady buzzing resumes once more.
Some of the transmissions have revealed other names that could be call signs or some sort of station identification. UVB-76 was the common reference until 2010, when the station began to refer to itself as MDZhB. Though there are several theories about the nature and reasons for the broadcasts, the actual purpose has never been confirmed and remains a mystery and constant source of speculation.