The purpose of communication systems is to transmit information via speech. As such, the intelligibility — or comprehensibility — of the transmitted speech is of utmost importance. One of the more precise definitions of intelligibility is the proportion of speech items (words and/or speech sounds) uttered by a talker, and sent via a communication system, that can be recognized by the listener. This is an important capability for the design of a wide range of systems, especially those related to public safety (e.g., police, fire, emergency).
ABC-MRT, or Articulation-Band Correlation Modified Rhyme Test, was developed by the Institute for Telecommunication Sciences (ITS) of the United States National Telecommunications and Information Administration (NTIA). It follows the paradigm of the Modified Rhyme Test, a technique for assessing speech intelligibility that involves subjective assessment by human subjects as detailed in ANSI/ASA Standard S3.2. To eliminate the time, complexity, and expense of the traditional human subject-based methodology, ABC-MRT uses a form of automatic speech recognition (ASR) to conduct an automated measurement that is closely correlated — greater than 95% — to a Modified Rhyme Test. An added benefit of ABC-MRT is its use of real speech (English only), allowing it to support the testing of systems that use noise suppression and/or codecs that only pass speech.
Using the ABC-MRT option allows developers to measure the speech intelligibility of their designs with AP’s industry-leading instrumentation and use that same equipment for the rest of their audio and electro-acoustic test requirements. Once installed, the ABC-MRT measurement can be easily incorporated into any test sequence.
“For designers and developers needing perceptual audio test capabilities, whether measuring quality or intelligibility, AP offers a wide range of options,” says Dave Schmoldt, Audio Precision Chief Executive Officer. “From PESQ and POLQA quality measurements to STI, and now ABC-MRT, intelligibility measurements, APx can meet their needs for analog, digital, electro-acoustic and perceptual audio test.”
The ABC-MRT software option (APX-SW-ABC-MRT) is available now and retails for US$2,100. It requires APx500 audio measurement software release v4.5.2 (or later) and is compatible with all analyzers in the APx500 Series.
For further information about ABC-MRT, visit the Institute for Telecommunication Sciences (ITS) website at https://www.its.bldrdoc.gov/