At 17:18 every Saturday, my Samsung HW-MS650 Soundbar plays the tune in the attached "video" file.
It does it really loud and there is nothing that can be done to stop it (except disconnecting power!). It happens when the sounder is on or off and if it is playing any other source, such as Bluetooth, Wifi, Din or any other connection it interrupts playback.
It must be triggered by the time because when the clocks change, the playback still happens at 17:18 local time.
The soundbar is running firmware version HWMS650WWB-1147.2