The development and validation of the speech quality instrument.

Objective: Although speech perception tests are available to evaluate hearing, there is no standardized validated tool to quantify speech quality. The objective of this study is to develop a validated tool to measure quality of speech heard. Study Design: Prospective instrument validation study of 35 normal hearing adults recruited at a tertiary referral center. Methods: Participants listened to 44 speech clips of male/female voices reciting the Rainbow Passage. Speech clips included original and manipulated excerpts capturing goal qualities such as mechanical and garbled. Listeners rated clips on a 10-point visual analog scale (VAS) of 18 characteristics (e.g. cartoonish, garbled). Results: Skewed distribution analysis identified mean ratings in the upper and lower 2-point limits of the VAS (ratings of 8-10, 0-2, respectively); items with inconsistent responses were eliminated. The test was pruned to a final instrument of nine speech clips that clearly define qualities of interest: speech-like, male/female, cartoonish, echo-y, garbled, tinny, mechanical, rough, breathy, soothing, hoarse, like, pleasant, natural. Mean ratings were highest for original female clips (8.8) and lowest for not-speech manipulation (2.1). Factor analysis identified two subsets of characteristics: internal consistency demonstrated Cronbach's alpha of 0.95 and 0.82 per subset. Test-retest reliability of total scores was high, with an intraclass correlation coefficient of 0.76. Conclusion: The Speech Quality Instrument (SQI) is a concise, valid tool for assessing speech quality as an indicator for hearing performance. SQI may be a valuable outcome measure for cochlear implant recipients who, despite achieving excellent speech perception, often experience poor speech quality.