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Optimal Transmit Volume Conditions for Mission Critical Voice Quality of Experience Measurement Systems



Chelsea Greene, Jesse Frey, William Magrogan, Cara O'Malley, Jaden Pieper


Selecting transmit volume levels using a transmit volume optimization (TVO) process is the first calibration step in performing quality of experience (QoE) measurements developed by the Mission Critical Voice portfolio of the Public Safety Communications Research (PSCR) Division. As noted in prior publications, audio volume levels have an impact on output consistency while performing mission critical voice (MCV) QoE measurements with push-to-talk (PTT) communications devices. These measurements must be consistent, repeatable, and comparable. The goal of this project is to ensure that MCV measurements are consistent and repeatable; it specifically focuses on transmit volume levels and their impact on the system under test (SUT). To achieve this, a measurement that characterizes audio distortion levels, specifically caused by overdriven speech into a transmit device, was developed. This measurement is performed across a series of transmit volume levels. The results are then used to present the system user with optimal levels to ensure MCV measurements contain a minimal amount of uncertainty caused by distortion within a range of stable volume levels. This paper will discuss the development of this specific distortion measurement and the methods designed to find optimal transmit volume levels.
Technical Note (NIST TN) - 2171
Report Number


Analog, Audio, A-weight, Communications, Direct mode, Distortion, Frequency, Frequency slope fit (FSF), Key performance indicator (KPI), Land mobile radio (LMR), Mission critical push-to-talk (MCPTT), Mission critical voice (MCV), Mouth-to-ear (M2E), Optimal volume plateau identification algorithm (OVPIA), Project 25 (P25), Plateau, Public safety, Push-to-talk (PTT), Quality of experience (QoE), System under test (SUT), Transmit volume optimization (TVO), Volume.


Greene, C. , Frey, J. , Magrogan, W. , O'Malley, C. and Pieper, J. (2021), Optimal Transmit Volume Conditions for Mission Critical Voice Quality of Experience Measurement Systems, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed April 24, 2024)
Created September 22, 2021, Updated November 29, 2022