gms | German Medical Science

A recent study by Oetting et al. [1] revealed increased binaural broadband loudness summation (BBLS) in some listeners with hearing loss. The source of this increased loudness summation is still unclear and it is unclear whether binaural speech intelligibility and binaural detection is also affected in these listeners. This study investigated the effect of increased BBLS on binaural speech intelligibility and binaural psychoacoustic detection experiments. Categorical loudness scaling was conducted with monaural and binaural conditions in combination with narrowband and broadband stimuli. Based on these screening measurements, 24 listeners with hearing loss were divided into three groups with different amount of BBLS. Data for eight normal-hearing (NH) listeners serve as reference. The main experiments were binaural masking level difference (BMLD) and spatial release from masking (SRM), all in presence of a fixed noise level at 70 dB SPL. The SRM measurement included another dichotic condition. Detection and speech reception thresholds were determined for monaural, diotic, and dichotic conditions. Signals were presented via headphones using virtual acoustics. In all experiments the NH listeners performed better than the majority of the hearing impaired listeners. BBLS did not show any significant effect on binaural speech intelligibility (SRM) or on binaural psychoacoustic detection experiments (BMLD). Therefore, it can be assumed that the mechanisms underlying increased BBLS are not affecting binaural speech intelligibility and binaural detection. However, a relationship between binaural speech improvement and binaural detection improvements was revealed (r=0.86, p<.001). This indicates that both might rely on the same underlying mechanisms.