Sometimes, USB speakers do not produce any sound, even though the driver is attached and the volume is set to high. Hot-plugging the device might not change this behavior.
To restore sound, power cycle the USB speakers.
When you plug in a USB audio device while logged in to the console, the console is the owner of the /dev/* entries. Therefore, you can use the audio device provided you remain logged in. If you were not logged in, then root is the owner of the device. However, if you log in to the console and attempt to access the USB audio device, then device ownership changes to the console. For more information, see the logindevperm(4) man page.
The behavior is different with remote logins. If you attempt to access the device remotely, the ownership does not change and therefore the device is secure. For example, unauthorized users cannot remotely listen to conversations over a microphone that is owned by someone else.
You might observe that after removing the USB device, the /dev/audio does not point back to /dev/sound/0. This error indicates that the system did not revert to using the on-board audio device as the primary audio device. Do one of the following workarounds:
Shut down the system, and use the boot -r command.
As root, issue the devfsadm –i command.