Evaluation of TIMIT Sentence List Equivalency with Adult Cochlear Implant Recipients

Background: Current measures used to determine sentence recognition abilities in cochlear implant recipients often include tests with one talker and one rate of speech. Performance with these measures may not accurately represent the speech recognition abilities of the listeners. Evaluation of cochlear implant performance should include measures that reflect realistic listening conditions. For example, the use of multiple talkers who vary in gender, rate of speech, and regional dialects represent varied communication interactions that people encounter daily. The TIMIT sentences, which use multiple talkers and incorporate these variations, provide additional test material for evaluating speech recognition. Dorman and colleagues created 34 lists of TIMIT sentences that were normalized for equal intelligibility using simulations of cochlear implant processing with normal-hearing listeners. Adults with sensorineural hearing loss who listen with cochlear implants represent a different population. Further study is needed to determine if these lists are equivalent for adult cochlear implant recipients and, if not, to identify a subset of lists that may be used with this population. Purpose: To evaluate the speech recognition equivalence of 34 TIMIT sentence lists with adult cochlear implant recipients. Research Design: A prospective study comparing test-retest results within the same group of listeners. Study Sample: Twenty-two adult cochlear implant recipients who met the inclusion criteria of at least 3 mo device use and a monosyllabic word score of 30% or greater participated in the study. Data Collection and Analysis: Participants were administered 34 TIMIT sentence lists (20 sentences per list) at each of two test sessions several months apart. List order was randomized and results scored as percent of words correct. Test-retest correlations and 95% confidence intervals for the means were used to identify equivalent lists with high test-retest reliability. Results: Mean list scores across participants ranged from 66 to 81% with an overall mean of 73%. Twenty-nine lists had high test-retest reliability. Using the overall mean as a benchmark, the 95% confidence intervals indicated that 25 of the remaining 29 lists were equivalent (e.g., the benchmark of 73% fell within the 95% confidence interval for both test and retest). Conclusions: Twenty-five of the TIMIT lists evaluated are equivalent when used with adult cochlear implant recipients who have open-set word recognition abilities. These lists may prove valuable for monitoring progress, comparing listening conditions or treatments, and developing aural rehabilitation plans for cochlear implant recipients.