Robotic voice while using Bluetooth headsets including airpod

When I have connected Bluetooth headset to iPhone 13 Pro including airpod or other brand headsets, mostly when on calls (voice call or FaceTime or zoom meetings or teams), the voice turns robotic. Not just my voice; both sides. I hear it robotic as well as other side they hear me robotic.

when I switch to wired headset, this never occurs.

I connect the same AirPods to Mac, never an issue. It’s just with my iPhone.

I had similar issue with my previous iPhone XS as well.

how do I fix this?