The mysterious radio station · 1:29pm May 15th, 2020
UVB-76, aka The Buzzer, started broadcasting in Russia since 1973. A short buzz tone is repeated at a rate of 25 tones per minute, 24 hours a day and sometimes, a voice transmission takes place with messages consisting of numbers and names. It typically starts with Mikhail Dimitri Zhenya Boris (MDZhB, the station's callsign).
Read more about it here and watch a news clip that explains the mystery of the station.