An application layer monitoring module is configured to monitor application layer packets for a call supported by a voice application and to detect an interruption in the call based on the application layer packets. A signaling layer monitoring module is configured to monitor signaling layer events associated with the voice application concurrently with monitoring of the application layer packets for the call. A correlation module is configured to correlate the interruption with the signaling layer events in response to the application layer monitoring module detecting the interruption. The correlation module is also configured to generate a key performance indicator (KPI) message including information indicating the interruption and at least one signaling layer event that is correlated with the interruption.