Development and Standardization of Digit in Noise Test in Indian English in Young Adults with Normal Hearing Sensitivity

Abstract

Background: The digit-in-noise (DIN) test is a quick and efficient method for hearing screening that can detect hearing loss at early stages. In a country like India, where there is a shortage of hearing care professionals and limited resources, there is a clear need for a simple and accessible screening tool for the Indian population. Objective: This study aimed to develop a digit-in-noise test in Indian English and standardize it in young adults with normal hearing sensitivity. Methods: The digits, 0-9 were recorded and were quasi-randomly constructed into digit triplets, which were binaurally presented to participants with normal hearing thresholds from 250 to 8 kHz in the presence of speech-shaped noise. The digits were homogenized using speech intelligibility functions to ensure that all digits were equally difficult. Following optimization, the final set of stimuli was evaluated by measuring speech recognition thresholds in 50 individuals across six test lists at three signal-to-noise ratios (-11, -13-, and -15-dB SNR). Results: The mean SRT-50 across subjects was -12.13 ± 0.25 dB SNR with a slope of 16.2 ± 1.3 %/dB. The lists were equivalent with a performance variation of just 0.08 SD. Test-retest reliability was excellent, with Cronbach's α values ranging from 0.88 to 0.97 across all test lists. The performance measures were comparable to other language versions of the DIN test, confirming the validity of the developed material. Conclusion: The digit-in-noise test developed in Indian English was constructed according to current international standards and provides reliable speech intelligibility measurements. It demonstrates excellent psychometric properties and can serve as an effective tool for evaluating the auditory system integrity.