We are looking for an open source voice quality test tool. The tool should be able to measure the quality of voice (not just audio) on a call. Tool should also suggest the level of background noise and tell that quality of voice on call is good or below standard.
VoIP codec quality measurements are made by using a panel of human listeners. Overall quality is then calculated from these.
Apart from codec limitations, background noise is a function of the analogue part of the terminal equipment, not the VoIP system.
In particular see en.wikipedia.org/wiki/Mean_opinion_score for the human testing that is done on VoIP codecs.