scope:

This standard 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. The scope also includes the evaluation of the factors that affect the intelligibility of speech.

In this standard 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.

Predictions made using the methods specified by this standard are limited by the degree to which the test conditions, talkers, and listeners are representative of the population to which they are applied. Unless the testing requirements indicate otherwise, both talkers and listeners should be clear speakers of English and have normal hearing.