Influence of level control during adaptive determination of the speech reception threshold in noise and influence of contralateral ear masking in speech audiometry in normal hearing listeners and cochlear implant users

Testing speech intelligibility in noise is essential for outcome assessment and quality control of hearing devices such as cochlear implants (CI). Both fixed-noise and fixed-speech adaptive procedures are commonly used for this purpose. In many CI users with substantial residual hearing in the contralateral ear, reliable assessment of the newly implanted ear requires exclusion of the contralateral side. Similarly, contralateral masking is often necessary in general audiological diagnostics. This study compared adaptive speech-in-noise testing using the Oldenburg Sentence Test (OLSA) with fixed-noise and fixed-speech procedures in both CI users and normal-hearing (NH) listeners. In addition, speech intelligibility scores and speech reception thresholds (SRTs) were assessed under two methods for contralateral ear exclusion: occlusion and noise masking. Subjective preferences for the different methods were also evaluated. Results showed no significant differences between the fixed-speech and fixed-noise procedures in either participant group. No significant differences were found between occlusion and masking regarding intelligibility scores or SRTs in CI users, despite practical attenuation limits of occlusion, whereas noise masking produced significantly lower SRTs in NH listeners compared to occlusion. While CI users expressed a preference for the fixed-noise procedure, NH listeners expressed a preference for the fixed-speech procedure. However, both groups clearly preferred occlusion using earplugs and earmuffs over contralateral masking with noise. These findings support the clinical use of the fixed-noise procedure and recommend occlusion over masking for contralateral ear exclusion in CI users.