Comment 22 for bug 1296425

I'm sorry that the previous post was too long.
This is the summary:

1) "aplay -l" gets called with an empty environment by a script in ubuntu-drivers-common which Kubuntu runs at startup, through the "DriverManager_DBus".
"aplay -l" doesn't find a pulseaudio and creates a new one (through libasound), because it has no environment and no way to know the session on which pulseaudio is already running.

2) The solution is to: Edit this file:
          /usr/share/ubuntu-drivers-common/detect/sl-modem.py
and replace this line:
        aplay = subprocess.Popen(['aplay', '-l'], env={},
with this line:
        aplay = subprocess.Popen(['aplay', '-l'],

NOTE TO MAINTAINERS: please evaluate if this solution is safe and sound, and if so, create a patch so that everyone benefits, and can have USB sound devices usable again (no more "device busy" errors while having an spurious extra pulseaudio instance).

Cheers,
Juan Manuel Cabo