May 13, 2013
The Public Safety Communications Research Program (PSCR), a joint effort of ITS and the National Institute of Standards and Technology (NIST) Law Enforcement Standards Office (OLES), has posted over 20 GB of audio clip files for download by researchers. The PSCR MRT Library created by ITS includes 150,000 processed recordings used as stimuli during a series of tests conducted between 2008 and 2012 to measure the intelligibility of digital land mobile radio (LMR) communication systems when used in the high background noise environments experienced by firefighters.
The Modified Rhyme Test (MRT) is preferred by both the National Fire Protection Association (NFPA) and the American National Standards Institute (ANSI) as the testing mechanism for quantifying audio intelligibility. In an MRT trial, a subject must identify the word heard from a set of six words that rhyme. The PSCR MRT Library contains "processed" test files as well as the source files that were mixed to create them. The source files include clean, high-quality, talker-only recordings by a variety of male and female talkers and high-quality background noise loops. The processed files consist of voice recordings mixed with background noise and passed through various public safety communication systems. All the audio clips are freely available for use by other researchers for internal research and development purposes to test audio processing methods and assess audio quality.
These audio files were used by ITS researchers to conduct tests reported in NTIA Technical Report TR-13-495, Intelligibility of Analog FM and Updated P25 Radio Systems in the Presence of Fireground Noise: Test Plan and Results, May 2013; NTIA Technical Report TR-13-493, Intelligibility of the Adaptive Multi-Rate Speech Coder in Emergency-Response Environments, December 2012; and NTIA Technical Report TR-08-453, Intelligibility of Selected Radio Systems in the Presence of Fireground Noise: Test Plan and Results, June 2008.