الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Sound localization is generally regarded as a binaural phenomenon, but monaural localization is possible (95) Normal hearing listeners generally rely on binaural acoustic cues for localization; the interaural time difference (ITD) and interaural intensity difference (ILD)
The spectral cues contained in speech sounds help identify them. In normal hearing listeners, these cues can be degraded to a certain degree without affecting speech recognition, while CI patients are more likely to receive a reduced set of speech cues due to diminished neuronal survival, incomplete insertion and frequency-place mismatch.
Current commercial cochlear implants speech processors have a series of bandpass filters by which the incoming signal is degraded to its basic frequency components to be delivered to the corresponding site in the cochlea. Each electrode stimulates a certain region of the cochlea and hence the auditory nerve according to its tonotopicity.
The current study comprised 40 prelingually or perilingually deafened children aged 7-18 years. Patients used the unilateral CI for at least 2 years and had satisfactory aided PTA response with their CI. All patients were tested for both sound localization and speech discrimination using high frequency monosyllabic list with the patients’ default map and two test versions derived from the default map: low pass map and a high pass map.
All results of sound localization and speech discrimination were in favor of the default map across all patients. Second to come were the results of the low pass map consonant recognition accuracy, where patients were using only the low frequencies below 1 KHz, which were always better in all consonant classes than for the high pass map. And this can be explained by many reasons; 1. Temporal cues are as important in perception of consonants as in perception of vowels. 2. Post meningitis hearing loss, short electrodes or incomplete insertion of electrodes due to any cause are more likely to affect consonant perception due compressing a large spectrum of frequencies within a narrow range and the resultant frequency-place mismatch. 3. Not only is the low frequency information of importance for vowels perception, but also has a great impact on consonant recognition as well as residual hearing reflected on the neural survival.