Acoustic explanation of voice onset time of initial oral plosives in the speec h production of cochlear implanted children and normal hearings

The acoustic explanation of Voice Onset Time (VOT) in initial oral plosives produced by Cochlear Implanted (CI) children and Normal Hearings (NHs) showed that in both voiced and voiceless plosives، the mean amount of VOT was morein the production of CIs. The reasons of this condition are as follows: CIshave less control on the vibration of vocal cords، phonological awareness is increased in CIs and they apply it unnaturally، CIs don’t have enough sensory input in the critical period oflanguageacquisition، and in the production of prevoicing more acoustic cues are necessary. In most cases،labial place of articulation had the least amount of VOT; and palatal place had the most amount of VOT because of having the greatest contact area with the roof of mouth. Comparing with NHs، CIs utteredvoiced plosive withless prevoicing. Furthermore، the amount of VOT in girls was more than boys. Its reason is thatvocal cords sizeis different in boys and girls،and this haseffect on the pressure differences of under and above larynx. It has been proved that early acquisition of language is important in identifying phonological boundaries and acoustic cues. But CIs have lost the first two critical years of language acquisition and have less language experiment.