Performance and test-retest reliability of the digits-in-noise test used in the sound field

Abstract

There are approximately 1.7 billion smartphone downloads of health surveillance applications, which have become vital in modern day living (Economist, 2016). The smartphone Digits-in-Noise (DIN) test was developed with South African English digits and was released and marketed in 2016 as a smartphone application allowing for an accessible hearing screening solution (Potgieter et al., 2016). Typically, the test is completed with coupling to headphones/earphones. However, due to several limitations, such as the lack of availability or inability to utilise headphones/earphones, performing tests with earphones/headphones may not always be possible. Therefore, this study aimed to determine if the results obtained via earphones would be comparable to those obtained in the sound field via various transducers. The study employed a cross-sectional, quasi-experimental research design. Fifty normal hearing participants (bilateral pure tone thresholds 0.5 – 8kHz ≤ 15dB HL) between the ages of 18 to 25 years (mean 20; SD ±1.93) were recruited. The study consisted of two test sessions over two days and used a repeated measure design where the conditions were counterbalanced using a Latin square setup. The first test session compared the SRTs of the smartphone DIN test across Samsung Fame Lite earphones, two smartphone speakers and two external loudspeakers in a sound booth. Test session two determined the test-retest reliability of the above conditions. Results of this study indicated that there was no significant difference (p > 0.05) between the SRTs across the four different loudspeakers and earphones. It also demonstrated that the test-retest differences across the various loudspeakers was not significant (p > 0.05). Findings indicate that test-retest results in the sound field using various transducers is reliable. This study demonstrated that a smartphone version of the DIN test can be utilised in the sound field using various transducers with equivalent results compared to an earphone condition. Therefore, the smartphone DIN test can be implemented in any practice which has access to a controlled testing environment for screening and rehabilitation purposes. A limitation of the current study is that the smartphone DIN test is designed for users to utilise the application in a home environment where ambient noise and reverberation is not controlled. Therefore, a future research priority is to conduct the testing in a home environment. Based on the findings of this study, it is expected that the smartphone DIN test performed through the sound field will be a promising tool in a home environment if the noise and reverberation is low.