ANSI/ASA S3.2-2020: Speech Intelligibility
Loudspeaker systems can be used for sound reinforcement in theaters and concert halls; microphones are used in many applications, including telephones, hearing aids, public address systems for concert halls and public events, motion picture production, megaphones, and radio and television broadcasting. Speech intelligibility of loudspeakers and microphones is important because it directly impacts how clearly words can be understood by listeners, which is critical for effective communication. ANSI/ASA S3.2-2020: Method for Measuring the Intelligibility of Speech over Communication Systems provides methods for the subjective evaluation of speech intelligibility over entire communication systems and the evaluation of the contributions of elements of speech communication systems.
What Is Speech Intelligibility?
In general, speech intelligibility is a measure of how well a speaker is clearly understood by a listener in a given context. It refers to the proportion of a speaker’s output that a listener can easily understand, or in other words, how comprehensible a person’s speech is to a listener. For example, if a speaker says “My name is John” and the listener hears “My name is Tom,” then the listener understood 75% of the speech.
As you can imagine, reduced speech intelligibility can often cause misunderstanding, frustration, and/or loss of interest by the listener(s). It can also be a barrier to social engagement, education, and employment, as well as adversely impact one’s self-esteem.
What Is Speech Intelligibility in ANSI/ASA S3.2?
ANSI/ASA S3.2-2020 establishes uniform methods for measuring the intelligibility of speech over communication systems. The measurement process involves talkers, in their environment, who speak test words into a transmission path to listeners, who receive and identify the speech in their environment. The standard specifies how to design a test of speech intelligibility for tactical communication an Protection Systems (TCAPS) and how to provide insight on how to determine the appropriate amount of training for listener participants.
What Is ANSI/ASA S3.2?
ANSI/ASA S3.2-2020 specifies a method for subjectively evaluating the speech intelligibility of communication systems. It defines a speech communication system as “a combination of environment and, usually, equipment that transmits speech from a talker to a listener. In some cases, speech recordings or a device (vocoder) that produces speech-like sounds or their electrical equivalent, based on an analysis, coding, and reconstruction of a human utterance, may replace the talker.”
The American National Standard also specifies validated English word lists for performing the tests. It details methods for selecting and training the talkers and listeners, for designing, controlling, and reporting the test conditions, for calculating the intelligibility score, and for analyzing and reporting the test results. In ANSI/ASA S3.2-2020, the intelligibility of speech over a speech communication system is measured by comparing the monosyllabic words trained listeners receive and identify with the words trained talkers or vocoders speak into a communication system that connects the talkers (or vocoders) with the listeners.
Speech Intelligibility Testing
ANSI/ASA S3.2-2020 specifies that materials used in intelligibility testing should employ a representative sample of the critical speech sounds under all the conditions of speech communication under investigation. The materials should show validity and reliability and permit analysis of performance errors.
Moreover, ANSI/ASA S3.2-2020 details that the three sets of test material that meet its requirements are the Phonetically Balanced Word Lists, the Modified Rhyme Test, and the Diagnostic Rhyme Test. All three tests have demonstrated sensitivity to degraded speech and have been used successfully with human talkers and coders, with analog and digital speech, in reverberation and noise, and with bandwidth compression and encryption devices
ANSI/ASA S3.2-2020: Method for Measuring the Intelligibility of Speech over Communication Systems is available on the ANSI Webstore.
