Voice of the Process is the statistical data that is feedback to the people in the process to make decisions about the process stability and/or capability as a tool for continuous improvement.(The Quality Portal)
Other Definitions
Voice of the Process (VoP) – results of the historical performance of the process (or system). Normally a control chart is used to show the capability of the process. The VoP details what the process is capable of producing. (Curious Cat Management Improvement Library – Dictionary)