Subjective test methodology for assessing speech intelligibility

Abstract

Recommendation ITU-T P.807 describes a subjective testing methodology for assessing Speech Intelligibility in communications settings, systems, and devices. The method provides a Percent Correct Intelligibility Score based on a two-alternative, forced-choice task where the stimulus is one of the two words from a pair of words, i.e., a test item. Half of the test items are rhyming word-pairs (i.e., differ only in the initial consonant) and half are alliterative word-pairs (i.e., differ only in the final consonant). The two critical consonants in each test item differ only in a single Distinctive Feature (see Annex A for a description of Distinctive Features). In addition to a score for Overall Intelligibility, the method provides scores for each of six Distinctive Features: Voicing, Nasality, Sustention, Sibilation, Graveness, and Compactness. These scores may be used to diagnose the specific cause of impairments leading to degradation of speech intelligibility.