prosthetic devices, consisting of implanted electrodes and a signal processor and are designed to restore partial hearing to the profoundly deaf community. August 2002 An understanding of how information about the speech signal is spread among the various frequency bands of the spectrum is essential in numerous communications, audio and hearing related applications. Overall, the data from the present dissertation highlight the importance of preserving the acoustic landmarks present in the speech signal for improved speech understanding by cochlear implant users in noisy conditions. Several studies have suggested that electrical-field interactions can disrupt the acoustic properties of the signal and severely degrade speech intelligibility, however this relationship has not been directly tested. Such knowledge could potentially help us develop better speech enhancement algorithms. Two noise estimation algorithms are proposed for highly non-stationary noise environments. Understanding the effect of various factors on melody international trade essays in theory recognition in the context of cochlear implants is important to improve the existing coding strategies. A second experiment was conducted to examine the reasons contributing to the CI users inability to perceive reliably the acoustic landmarks embedded in the signal. This thesis proposes a modification to the conventional spectral subtraction approach in order to address the problem of musical noise and speech distortion that is inherent to the conventional spectral subtraction based approach. The following experiments examine electrical-field interactions and speech recognition performance for three electrode designs: patients implanted with the Enhanced Bipolar Clarion electrode array without a positioner, patients implanted with the Clarion Electrode Positioning SystemTM (EPS) and the Enhanced Bipolar electrode array, and patients with the.
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Active Noise Cancellation (ANC) is one such approach that has been proposed for reduction of steady state noise. The most recent studies examined speech recognition either for a single hole varying in frequency location and size or for a single hole in the middle of the spectrum. Download thesis: pdf - 572 Kb analyses OF speech processing strategies FOR cochlear implants AND THE effects OF electrode interaction Ginger Stickney PhD Dissertation May 2001 Multichannel cochlear implants electrically stimulate the auditory nerve to restore partial hearing to the profoundly deaf patient. . This thesis addresses the problem of reduction of additive background noise in speech.
To make the residual noise perceptually inaudible, we propose two methods for incorporating psychoacoustical models. When less current is required, current spread and electrical field overlap is reduced. . The pattern of results also suggests that, with acute listening trials, patients achieve the highest speech recognition scores with the speech processing strategy most similar to their own. . Based on previous research, susceptibility to electrical-field interactions is expected to vary as a function of electrode design, the speech processing strategy used in the device, and factors specific to each patient. . In these methods, the speech signal is first enhanced using the noise reduction method and the enhanced signal is then processed using the speech processor. To minimize speech distortion, we propose subspace methods which can be generally applied for colored noise environments.