The Effects of Noise on Speech Recognition in Cochlear Implant Subjects: Predictions and Analysis Using Acoustic Models
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The Effects of Noise on Speech Recognition in Cochlear Implant Subjects: Predictions and Analysis Using Acoustic Models Jeremiah J. Remus Department of Electrical & Computer Engineering, Pratt School of Engineering, Duke University, P.O. Box 90291, Durham, NC 27708-0291, USA Email: [email protected]
Leslie M. Collins Department of Electrical & Computer Engineering, Pratt School of Engineering, Duke University, P.O. Box 90291, Durham, NC 27708-0291, USA Email: [email protected] Received 1 May 2004; Revised 30 September 2004 Cochlear implants can provide partial restoration of hearing, even with limited spectral resolution and loss of fine temporal structure, to severely deafened individuals. Studies have indicated that background noise has significant deleterious effects on the speech recognition performance of cochlear implant patients. This study investigates the effects of noise on speech recognition using acoustic models of two cochlear implant speech processors and several predictive signal-processing-based analyses. The results of a listening test for vowel and consonant recognition in noise are presented and analyzed using the rate of phonemic feature transmission for each acoustic model. Three methods for predicting patterns of consonant and vowel confusion that are based on signal processing techniques calculating a quantitative difference between speech tokens are developed and tested using the listening test results. Results of the listening test and confusion predictions are discussed in terms of comparisons between acoustic models and confusion prediction performance. Keywords and phrases: speech perception, confusion prediction, acoustic model, cochlear implant.
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INTRODUCTION
The purpose of a cochlear implant is to restore some degree of hearing to a severely deafened individual. Among individuals receiving cochlear implants, speech recognition performance varies, but studies have shown that a high level of speech understanding is achievable by individuals with successful implantations. The speech recognition performance of individuals with cochlear implants is measured through listening tests conducted in controlled laboratory settings, which are not representative of the typical conditions in which the devices are used by the individuals in daily life. Numerous studies have indicated that a cochlear implant patient’s ability to understand speech effectively is particularly susceptible to noise [1, 2, 3]. This is likely due to a variety of factors, such as limited spectral resolution, loss of fine temporal structure, and impaired sound-localization abilities. The manner and extent to which noise affects cochlear implantee’s speech recognition can depend on individual characteristics of the patient, the cochlear implant device,
and the structure of the noise and speech signals. Not all of these relationships are well understood. It is generally presumed that increasing the level of noise will have a negative effect on speech recognition. However, the magnitude and manner in which speech recogni
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