Contralateral masking in cochlear implant users with residual hearing in the non-implanted ear

Contralateral masking was investigated in cochlear implant users with resid ual hearing in the non-implanted ear. Threshold elevations for acoustic pro bes were observed when electrical maskers were presented in the opposite ea r. Also, threshold elevations for electrical probes were observed when acou stic contralateral maskers were presented. The amount of threshold shift ex pressed in decibels charge or decibels sound pressure level produced by eit her contralateral acoustic or electric maskers was within the range found i n normal listeners for similar stimuli (i.e. 4-8 dB). There was a correlati on between the sensation level of acoustic maskers and the maximum amount o f masking observed which is consistent with data for normally hearing subje cts. The width of the masking patterns was similar to that expected from fo rward masking patterns in severely sensorineurally impaired ears and implan ted ears. The maximum amount of acoustic masking tended to occur for electr ode positions that were more basal than expected from characteristic freque ncy positions. However, where a relatively high-frequency 4-kHz masker coul d be used, there was a good match between the characteristic frequency posi tion of the maximum threshold elevation and that of the masker. Copyright ( C) 2001 S. Karger AG, Basel.