Hello,
when using the softphone - I presume this is being redirected to the guest desktop as a USB device.
In which case, instructions detailed here: VMware KB: How to improve audio quality when using USB headsets or speakers with a View desktop *might* help you get improved audio quality.
This is turned off by default, as it is not a fix-all solution and it might help you but it depends on your application and physical hardware.
Let me know how you get on,
cheers
peterB