Why does my iPhone play a specific tune randomly that are not stoppable as the cause is unknown.

Why does my iPhone play a specific tune randomly that are not stoppable?

The cause of this phenomenon is unknown, I tried checking which app had triggered the tune playing, like alarm settings, calendar events or reminders nothing like stands out and no app pops up, nothing appears to be playing in the background too when it sounded.

Has anyone encountered this or does anyone has any solutions or suggestions to fit this please? Thanks folks!