Comparing Digits-in-Noise Test Implementations on Various Platforms with Normal Hearing Individuals

Authors: Soner Türüdü1, Thomas Koelewijn1, Etienne Gaudrain2,Deniz Başkent1

1University Medical Center Groningen

2CNRS, Lyon Neuroscience Research Center

Background This study aimed to investigate the effects on outcome scores of the frequently used versions of the Digits-in-Noise (DIN), as was reported in the literature for onsite and online research.

Methods Different versions of the DIN test were created onsite and online using original Dutch DIN materials. Fifteen normal-hearing individuals participated in onsite, and eight of them also online. DIN tests had three variables: (1) Mixing Method set speech, noise, or a mix of both at 65 dB SPL (only onsite); (2) Starting signal-to-noise ratio (SNR) high (0 dB) or low (-16 dB); and (3) Sound Presentation diotic or dichotic (speech phase reversed in one ear).

Results A three-way repeated-measures ANOVA revealed significantly lower DIN thresholds for dichotic compared to diotic Sound Presentation in both onsite and online tests. Onsite DIN results showed a significant main effect for Starting SNR, Mixing Method, and a significant three-way interaction. However, this was a small effect, limited to a maximum of 1.3 dB SNR Post-hoc analysis of onsite data indicated that the Starting SNR, Mixing Method, and their interaction were significant only in the dichotic conditions. No significant effect was observed for the online session for Starting SNR or Mixing Method. There was a main effect of onsite and online platforms (see Figure 1).

Conclusions The lower DIN score with dichotic listening may be related to the additional cue introduced by the speech phase reversal in one ear, which helps separate speech from noise. Ideally, DIN measurements should be immune to variations in Mixing Method, Starting SNR, and the platform. The differences we observed were small in young normal-hearing participants, but when applied to different populations, the DIN test should be customized.

The figure shows the onsite DIN scores (dB SNR) for Sound Presentation (shown on the left and right sides for diotic and dichotic, respectively), Starting SNR (shown in the white or gray shade for low and high, respectively), and Mixing Method (shown in green, blue, and red colors for fixed-speech, fixed-noise, and fixed-level, respectively).