I just got some AirPods and was trying them out with various apps and devices. When I tried listening to a file in Audacity, I ran into the no sound issue in this thread. I tried the suggestions I saw (restart Audacity, rescan devices) but they didn’t work for me.
Here’s what worked:
With the AirPods on/in your ears, go to Preferences > Devices > Playback, then choose your AirPods.
Now audio played (yay!) but with loads of crackle noise (waah!). So I looked in the forum and saw the buffer length comments. Again in Preferences > Devices > Playback I increased buffer length to 400ms. Worked like a charm.
I’ll still use a wired headset most of the time with Audacity but it’s good to have the option for quick listening.
(Audacity 2.4.1. 2015 MacBook Pro running Catalina)