[ltp] Sound devices on my A21P

[Constant Brouerius van Nidek]

Was working on Skype and found out that under sound devices they offer 7 
choices for each Sound in, sound out and ringing. The choices are

Default device
Sound Fusion CS46xx (hw:CS46xx.0)
Sound Fusion CS46xx (plughw:CS46xx.0)
Sound Fusion CS46xx (hw:CS46xx.1)
Sound Fusion CS46xx (plughw:CS46xx.1)
Sound Fusion CS46xx (hw:CS46xx.2)
Sound Fusion CS46xx (plughw:CS46xx.2)

I have played around with them but did not find any difference so I am back at 
Default.

Could somebody explain what these choices mean and why do we have those?