The primary audio device, /dev/audio, points to the USB speaker.
% ls -l /dev/audio lrwxrwxrwx 1 root root 10 Feb 13 08:46 /dev/audio -> usb/audio0 |
(Optional) Remove the speaker. Then, plug it back in.
If you remove the speaker, the /dev/audio device reverts back to on-board audio.
% ls -l /dev/audio lrwxrwxrwx 1 root root 7 Feb 13 08:47 /dev/audio -> sound/0 |
Add a USB microphone.
% ls -l /dev/audio lrwxrwxrwx 1 root root 10 Feb 13 08:54 /dev/audio -> usb/audio1 |