Low thumping pulse sound in AirPods 4 when not playing music

I’ve had my set of AirPods 4 ANC for a few months, they were working fine until yesterday. I’m suddenly getting a low thumping pulse like sound when I’m not playing music, it’s super fast like 3 beats a second. It goes away when I switch off the listening modes. Just went to apple today and they told me everything is working as it should but I still hear the sound.

[Re-Titled by Moderator]

Original Title: Airpods 4 pulsating/thumping sound