title: Effects of electrical stimulation rate on speech recognition in cochlear implant users.
abstract: OBJECTIVE
  The stimulus signals delivered in cochlear implant (CI) systems are generally derived by sampling the temporal envelope of each channel at some constant rate and using its intensity to control the stimulation current level delivered to the corresponding electrode site. The objective of the study was to investigate speech recognition performance of cochlear implant users in quiet and noisy environments using either moderate or high rates of electrical stimulations.
  
  
  METHODS
  Six post-lingually deafened adult users of the Nucleus CI24 cochlear implant (Contour® electrode array, Cochlear™, Macquarie Park, Australia) with the Freedom® speech processor participated in the study. Stimulation rates of 900 and 2400 pulses-per-second/channel (pps/ch) were used after both stimulation programs were balanced for loudness. Monosyllabic word and sentence recognition scores in quiet and noisy environments were evaluated for each stimulation program after two months of practice. Subjects were also asked to respond to a questionnaire to examine their preference to any stimulation rate in different hearing conditions.
  
  
  RESULTS
  Word recognition scores for monosyllabic words in quiet conditions with the 900 stimulation rate was better than that of the 2400 stimulation rate, although no significant differences between them were found for sentence test in noise. A survey questionnaire indicated that most subjects preferred the 900 stimulation rate to the 2400 stimulation rate, especially in quiet conditions.
  
  
  CONCLUSIONS
  Most subjects indicated a preference for 900 pps/ch rate in quiet conditions. It is recommended to remap at 900 pps/ch for those CI users whose performance in quiet conditions is less than ideal.
authors.affiliation: Department of Otolaryngology, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Sung Hye
authors.initials: SH
authors.lastname: Park
authors.affiliation: Department of Otolaryngology, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Eunoak
authors.initials: E
authors.lastname: Kim
authors.affiliation: Department of Otolaryngology, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Hyo-Jeong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Otolaryngology, Hallym University College of Medicine, Chuncheon, Korea.
authors.forename: Hyung-Jong
authors.initials: HJ
authors.lastname: Kim
keywords: Cochlear implants; Rehabilitation of hearing impaired; Speech perception