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Mission Critical Voice Start-of-Word Correction for Access Delay Measurement System



William Magrogan, Jaden Pieper, Zainab Soetan


NIST's Public Safety Communications Research (PSCR) division previously developed an access time measurement method for push-to-talk (PTT) communications systems. This paper introduces a correction term, called the start of word correction, to address a systemic error in the original measurement method. This error can be caused by extraneous audio prior to the start of a Modified Rhyme Test (MRT) keyword in the test audio clips thatwere developed for the access time measurement. Example measurements were performed using the start of word correction to quantify its affect on access time measurements.
Technical Note (NIST TN) - 2166
Report Number


Access delay, Access time, Articulation Band Correlation Modified Rhyme Test (ABC-MRT), ABC-MRT16, Land mobile radio (LMR), Long term evolution (LTE), Mission critical voice (MCV), Modified Rhyme Test (MRT), Project 25 (P25), Public safety, Push-to-talk (PTT), Quality of experience (QoE), Trunked mode


Magrogan, W. , Pieper, J. and Soetan, Z. (2021), Mission Critical Voice Start-of-Word Correction for Access Delay Measurement System, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed July 16, 2024)


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Created June 24, 2021, Updated November 29, 2022