ACALES as a complement of the German matrix test in clinical measurement routine: Systematic variation of background noise and spatial separation

The ACALES (Adaptive CAtegorical Listening Effort Scaling) method for measuring listening effort was evaluated as a complement to the German matrix test (Oldenburg Sentence Test, OLSA) with regard to sensitivity under ecologically valid testing conditions. The aim was to obtain guidance for clinical testing routines and to expand the methodological evidence base in the future. The stationary background noise Olnoise, which is a speech-simulated noise based on the German Matrix Test, was compared with two fluctuating background noises: The first was ICRA5-250, developed by the International Collegium of Rehabilitative Audiology; the second was the International Female Fluctuating Masker (IFFM). Spatial separation of speech and background noise (S0N0, S0N90, S0N180, S45N-45) was also systematically varied. A total of 12 test conditions were evaluated with 17 cochlear implant (CI) patients. The results showed that ACALES demonstrated significantly lower listening effort values for stationary background noise (Olnoise < IFFM and ICRA5-250) in the positive, everyday-relevant SNR range; no effects regarding background noise were observed for the OLSA. The spatial separation of speech and background noise led to a significantly reduced listening effort (S45N-45, S0N90, S0N180 < S0N0) with higher effect sizes compared to the OLSA. Overall, a statistically significant sensitivity of ACALES was demonstrated to ecologically valid measurement conditions. However, measurements with larger and more diverse clinical samples are necessary to generalize the results presented here. We recommend using ACALES as a complement to speech audiometric testing as part of clinical measurement routine. For CI patients, we recommend using the S45N-45 or S0N90 measurement conditions with ICRA5-250 noise in addition to the guideline-compliant S0N0/Olnoise measurement setup.