Development of the Mandarin Digit-in-Noise Test and Examination of the Effect of the Number of Digits Used in the Test

Objectives: The study aimed to develop and validate the Mandarin digit-in-noise (DIN) test using four digit (i.e., two-, three-, four-, and five-digit) sequences. Test-retest reliability and criterion validity were evaluated. How the number of digits affected the results was examined. The research might lead to more informed choice of DIN tests for populations with specific cognitive needs such as memory impairment. Design: The International Collegium of Rehabilitative Audiology guideline for developing the DIN was adapted to create test materials. The test-retest reliability and psychometric function of each digit sequence were determined among young normal-hearing adults. The criterion validity of each digit sequence was determined by comparing the measured performance of older adult hearing aid users with that obtained from two other well-established sentence-in-noise tests: the Mandarin hearing-in-noise test and the Mandarin Chinese matrix test. The relation between the speech reception thresholds (SRTs) of each digit sequence of the DIN test and working memory capacity measured using the digit span test and the reading span test were explored among older adult hearing aid users. Together, the study sample consisted of 54 young normal-hearing adults and 56 older adult hearing aid users. Results: The slopes associated with the two-, three-, four-, and five-digit DIN test were 16.58, 18.79, 20.42, and 21.09 %/dB, respectively, and the mean SRTs were −11.11, −10.99, −10.56, and −10.02 dB SNR, respectively. Test-retest SRTs did not differ by more than 0.74 dB across all digit sequences, suggesting good test-retest reliability. Spearman rank-order correlation coefficients between SRTs obtained using the DIN across the four digit (i.e., two-, three-, four-, and five-digit) sequences and the two sentence-in-noise tests were uniformly high ( r s = 0.9) across all participants, when data from all participants were considered. Results from the digit span test and reading span test correlated significantly with the results of the five-digit sequences ( r s = −0.37 and −0.42, respectively) but not with the results of the two-, three-, and four-digit sequences among older hearing aid users. Conclusions: While the three-digit sequence was found to be appropriate for clinical use for assessment of auditory perception, the two-digit sequence could be used for hearing screening. The five-digit sequence could be difficult for older hearing aid users, and with its SRT related to working memory capacity, its use in the evaluation of speech perception should be investigated further. The Mandarin DIN test was found to be reliable, and the findings are in line with SRTs obtained using standardized sentence tests, suggesting good criterion validity.