title: Perception of speech in cartilage conduction.
abstract: OBJECTIVE
  By attaching a transducer to the aural cartilage a relatively loud sound is audible even with a negligibly small fixation pressure applied to the transducer. This form of conduction is referred to as cartilage conduction (CC). Utilizing CC, novel audio devices can be developed, and one possible application is a CC hearing aid. However, there are no studies on speech perception in CC. In this study, CC speech recognition performance was measured and compared with that for air and bone conduction (AC and BC, respectively).
  
  
  METHODS
  Nine volunteers with normal hearing participated in the study. The performance-intensity functions were measured for AC, BC and CC. These measurements were performed in the conditions with and without an earplug.
  
  
  RESULTS
  Without the earplug, no differences in speech recognition scores were observed among AC, BC, and CC. With the earplug, the level at which the maximum speech recognition score was obtained did not increase in CC, which agreed with the result of BC but not AC. The maximum speech recognition CC score decreased with the earplug. The performance-intensity functions for AC and BC shifted in parallel with the earplug. These shifts approximated the average threshold shifts. In contrast, for CC, the performance-intensity function did not shift in parallel with the earplug. As for the CC threshold shifts with the earplug, although the threshold at 500Hz decreased by 15.4dB, those at 2000 and 4000Hz increased by 13.8 and 31.1dB, respectively. Compared with AC and BC, CC excessively emphasized low over high frequency sounds when the earplug was inserted. Confusion matrices analysis demonstrated that 4%, 22%, and 74% of the errors occurred at low, intermediate, and high frequency speech sounds, respectively. Thus, this excessive low frequency sound emphasis probably prevented the recognition of high frequency speech sounds.
  
  
  CONCLUSIONS
  The decrease in the maximum speech recognition score for CC with the earplug was derived from the biased frequency composition. It can be improved by frequency composition adjustment.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Miyamae
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan. Electronic address: t-nishim@naramed-u.ac.jp.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Nishimura
authors.affiliation: President's Office, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoi
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Saito
authors.affiliation: Department of Area of Architecture and Production Design Engineering, Interdisciplinary Graduate School of Science & Engineering, Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Shimokura
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Yamanaka
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kitahara
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001309:Auditory Threshold; D001844:Bone Conduction; D004425:Ear Cartilage; D005260:Female; D064368:Healthy Volunteers; D006310:Hearing Aids; D006801:Humans; D008297:Male; D013067:Speech Perception; D013069:Speech Reception Threshold Test
keywords: Aural atresia; Earplug; Low tone; Occlusion effect; Performance-intensity function