Improvement of cochlear implant performance: changes in dynamic range

Theoretically, a wide input dynamic range (IDR) will capture more of the incoming acoustic signal than a narrow IDR, allowing the cochlear implant (CI) user to hear soft, medium, and loud sound. A narrow IDR may restrict the CI user’s ability to hear soft speech and sound because less of the incoming acoustic signal is being mapped into the CI user′s electrical dynamic range. The overall goal of the study is to provide guidelines for audiologists to efficiently and effectively optimize performance of CI recipients for two difficult listening situations: understanding soft speech and speech in noise. Two variables were studied; the independent variables were IDR and the electric dynamic range of the channels. The dependent variables were six Ling sounds, monosyllabic word test, and speech in noise test. Fourteen patients participated in the study. For each patient, seven programs were created. In each program, dependent variables were assessed in different independent ones. A restricted IDR resulted in poor speech recognition compared with the relatively wide IDR. Subjectively determined T level and most comfortable level (MCL) at the most, not the maximum, comfortable level appears to have a positive effect on both soft sound recognition and speech discrimination. Dynamic range is an important factor -among others- to improve the ability of CI users to understand soft speech as well as speech in noise.