This is a Russian mystery signal known commonly as the buzzer. It is on 4625 kHz, transmitted in AM with a suppressed lower sideband. This recording was made in upper sideband mode.
The station identification is МДЖБ, but is commonly referred to by hobbyists as UVB-76 (based on an earlier callsign) or simply as The Buzzer.
The reason for the broadcast is not known. Many believe that it has a military purpose, but even that is not certain. There have been some rare voice transmissions on the frequency.
This has been transmitting for decades.
