Audio switches to Bluetooth - Not Wanted!

Re: Samsung S22, Android 12

Whenever I participate in a Zoom session using my smartphone, the audio is extremely muffled.  It's because some setting (and I don't know what!) switches the audio setting on my phone to Bluetooth.  Except there is no connection to an external BT device.

To participate, I need to turn off BT on my phone entirely.   This is really annoying.

Is this a Zoom App setting thing?