Provided is a method and apparatus for objectively and non-intrusively measuring voice quality on live calls without disrupting the call session or the network. A communication system includes plural communities each including a switch that controls access to a packet-based data network for call sessions. Each of the communities is coupled to the data network by respective packet-based trunks. Quality of service (QoS) monitoring devices are coupled to the respective packet-based trunks to monitor quality levels of routes between any two given communities. Each QoS monitoring device receives packets containing streaming data (which may be actual packets or test packets). From the received packets, the QoS monitoring device can derive QoS parameters, particularly for audio and speech signals on live calls without disrupting the call session.