Development of the Speech Intelligibility Rating (SIR) test for hearing aid comparisons

The Speech Intelligibility Rating (SIR) Test has been developed for use in clinical comparisons of hearing aid conditions. After listening to a short passage of connected speech, subjects generate a rating proportional to its intelligibility using an equal-appearing interval scale from 0 to 10. Before test passages are presented, the signal-to-babble ratio (SBR) is adjusted to a level that elicits intelligibility ratings of 7-8 for a "setup" passage. Then, with SBR held constant, three or more test passages are rated and the results averaged for each aided condition. This paper describes the generation of recorded test materials and their investigation using normally hearing listeners. Based on these data, a critical difference of about 2 scale intervals is recommended. A future paper will deal with results for hearing-impaired subjects.