Background: The Digits-in-Noise (DIN) test is an adaptive speech-in-noise assessment measuring speech reception thresholds (SRTs) using digit triplets. While DIN tests are available in multiple languages, studies on the effects of second-language (L2) proficiency, particularly combined with hearing loss, on DIN outcomes are limited. This study compares Turkish (L1) and Dutch (L2) DIN test outcomes in native Turkish speakers of a wide age range (19-68 years, mean age: 31.43 ± 15.0 years) with varying Dutch proficiency and hearing levels, to investigate these effects.

Methods: Forty native Turkish individuals (self-reported gender: 22 female; 18 male) were included. Most had normal hearing (n=36), with four having mild to moderate hearing loss. Participants’ Dutch proficiency ranged from A0 to C2 (CEFR). All participants underwent pure tone audiometry (0.25-8 kHz), performed the Turkish Child-friendly Coordinate Response Measure (T-CCRM) test, and DIN tests in both Turkish and Dutch. The DIN test implementations had two variables (1) Sound presentation: diotic or antiphasic; and (2) Speaker: Dutch male, Turkish male (S01), or Turkish female (S02). For all six DIN tests, speech level was adapted and starting SNR was -6 dB.

Results and discussion: Preliminary data from 40 participants indicate several observable trends. Consistent with previous studies with Dutch DIN, antiphasic sound presentations appear to result in lower (better) DIN SRTs compared to diotic across both Turkish speakers (S01 and S02). Observable differences also exist between the two Turkish speakers, with participants listening to S02 tending towards slightly better antiphasic DIN SRTs and for S01 towards slightly better diotic DIN SRTs. Participants’ Turkish (L1) DIN SRTs seem better than Dutch (L2) DIN SRTs. Regarding the effect of L2, participants with higher CEFR levels tend to show better performance on the Dutch DIN (both diotic and antiphasic). An interesting trend observed is that higher Dutch proficiency also appears related to slightly better performance on some Turkish DIN tests (S01 diotic and antiphasic, S02 diotic). Increased hearing loss appears associated with poorer performance on the Turkish DIN tests. However, a clear relationship between degree of hearing loss and Dutch DIN performance seems less apparent. Turkish T-CCRM scores show a tendency to be poorer for participants with worse L1 Turkish DIN scores, but a similar relationship with L2 Dutch DIN scores is not evident. Data collection is still ongoing, focusing on recruiting particularly more participants with hearing loss. Updated results will be presented at the 16th Speech in Noise (SpiN) Workshop.