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State-of-the-art cochlear implants perform a frame-based signal processing on the incoming audio signal with a fixed frame-size. In the end of the signal processing chain, a stimulation pattern is generated for the current frame. As a consequence, the electrodes in the array are stimulated with a fixed rate independent of their frequency bands. In other words, the stimulation rate is dependent on and mostly equal to the frame rate of the incoming audio frames. In the context of the ABCIT (Advanced Binaural Cochlear Implant Technology) project, we have developed a research interface for cochlear implants (Adiloglu et.al. IWAENC 14), which is now being extended with a capability to stimulate at a variable rate. Different methods of adapting the stimulation rate depending on the input signal are possible and will be evaluated with subjects in the future. One possible strategy to adapt the stimulation rate depends on fundamental frequency (F0) tracking. Here, we present how the adaptive stimulation part has been implemented and present first objective measurement results. [ABSTRACT FROM AUTHOR]

Using current speech processors, Cochlear Implant (CI) users already reach up to 100% speech intelligibility in quiet. Listening in noisy environments however, still remains a challenge. The increasing supply of profoundly deaf patients with two independent implants (bilateral supply) already provides improved speech intelligibility in noise compared to unilateral supply. In this study, the potential of binaural speech enhancement strategies to further improve speech intelligibility of bilaterally implanted CI users in noise was assessed. Instrumental measures as well as perceptual (listening) tests were used to evaluate 2 monaural and 6 binaural noise reduction schemes. All algorithms were implemented in the Master Hearing Aid framework and run online in real-time. 4 spatially distinct noise scenarios were created in a reverberant environment (T60 ≅ 1250 ms) using virtual acoustics. The Oldenburg matrix sentence test (Oldenburger Satztest OLSA) was used as speech material. Several instrumental measures were applied to evaluate the algorithms' potential in improving speech intelligibility independent of inter-subject variability. Results from this instrumental evaluation demonstrate the ability of the tested algorithms to provide improvements in speech intelligibility as well as sound quality. For the perceptual evaluation, speech reception thresholds (SRT50) were determined using a maximum likelihood adaptive measurement procedure. 8 bilaterally implanted CI subjects, using processors from 3 different manufacturers have participated in the evaluation. The results show substantial and significant improvements in perceptual speech reception threshold (SRT50) in reverberant, spatial testing conditions using the algorithms presented here. [ABSTRACT FROM AUTHOR]