Dynamic FM systems and Cochlear Implants: latest developments and study results

摘要

Introduction Communication in noise is often difficult for recipients of cochlear implants (CIs). In fact, speech-recognition scores in noise may be as much as 50 percentage points poorer than speech recognition in quiet (Schafer and Thibodeau, 2004; Wolfe and Schafer, 2008b). Additionally, recipients of CIs mention speech recognition in noise as one of their most significant challenges (Schafer and Thibodeau, 2004; Noble et al, 2008). Reasons for the difficulties users of CIs experience in noise include degraded spectral resolution (Nelson et al, 2003; Stickney et al, 2004) and poor fine temporal structure (Qin and Oxenham, 2003; Nie et al, 2006). Use of personal frequency-modulated (FM) systems significantly improves speech recognition in noise for users of cochlear implants (CIs). Previous studies have shown that the most appropriate gain setting on the FM receiver may vary based on the listening situation and the manufacturer of the CI system. Unlike traditional FM systems with fixed-gain settings, Dynamic FM automatically varies the gain of the FM receiver with changes in the ambient noise level. The purpose of this variable gain is to maintain speech intelligibility in very harsh listening conditions. A larger gain of the FM receiver has the effect in hearing instruments that the overall gain of all input signals, including the noise picked up by the ear level ambient microphone, is reduced and that the high signal to noise ratio of the FM signal is not 'polluted' by the ambient noise picked up the ear level microphone. As the systems design of CIs is markedly different from the systems design of hearing instruments, The purpose of the presented studies was to evaluate speech recognition of Advanced Bionics Corporation, Cochlear Corporation CI recipients or MedEl CI recipients using Dynamic FM versus a traditional FM system and to examine the effects of Autosensitivity on the FM performance of Cochlear Corporation recipients.