Evaluation of the speech intelligibility rating (SIR) test for hearing aid comparisons

The SIR test was created for use in hearing aid comparisons. The test protocol obtains listener judgments of the intelligibility of connected speech passages. This study was conducted to evaluate the effectiveness of the SIR test in differentiating among hearing aids. Specific research questions were (a) Is the sensitivity of the SIR test sufficient for differentiating among very similar and slightly dissimilar hearing aids? (b) Does the SIR test result in reliable hearing aid rankings? and (c) What are the effects of using shortened connected speech passages? Ten listeners with hearing impairments rated the intelligibility of both full-length and shortened SIR test passages while wearing each of four individually selected hearing aids representing three different frequency/gain prescriptions. Results suggested that the SIR test is capable of differentiating among slightly dissimilar hearing aids and that hearing aid rankings resulting from speech intelligibility ratings were reliable. The decision to use full-length or shortened SIR test passages depends on the outcome the user wishes to maximize. Under the conditions used in this study, maximum sensitivity was achieved with ratings from five shortened passages, whereas maximum reliability was obtained with three full-length passages.