title: Cartilage conduction efficiently generates airborne sound in the ear canal.
abstract: OBJECTIVE
  By attaching a transducer to the aural cartilage, a relatively loud sound is audible even with a negligibly small fixation force. Previous study has identified several pathways for sound transmission by means of cartilage conduction. This investigation focused on the relative contribution of direct vibration of the aural cartilage to sound transmission in an open and in an occluded ear.
  
  
  METHODS
  Thresholds with and without an earplug were compared for three experimental conditions: the transducer being placed on the tragus, pretragus, and mastoid. Eight volunteers with normal hearing participated.
  
  
  RESULTS
  The thresholds increased with distance of the transducer from the ear canal (tragus, pretragus, mastoid, in that order). The differences were statistically significant for all conditions except for the occluded ear at 4 kHz. With the earplug inserted, the thresholds for the tragus condition were most sensitive below 2 kHz, indicating a significant contribution of direct vibration of the aural cartilage.
  
  
  CONCLUSIONS
  Direct vibration of the aural cartilage can enhance sound transmission. At low frequencies, cartilage conduction can deliver sound efficiently across a blockage in the ear canal. Stray airborne sound radiating from the transducer dominates cartilage conduction in the open ear at high frequencies.
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: 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 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.
authors.forename: Ryota
authors.initials: R
authors.lastname: Shimokura
authors.affiliation: Department of Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaragi 305-8577, Japan.
authors.forename: Toshie
authors.initials: T
authors.lastname: Matsui
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
authors.affiliation: Professor Emeritus, The City University of New York, United States.
authors.forename: Harry
authors.initials: H
authors.lastname: Levitt
mesh_terms: D000328:Adult; D001309:Auditory Threshold; D001844:Bone Conduction / Q000502:physiology*; D004425:Ear Cartilage / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D013016:Sound; D014159:Transducers
keywords: Air conduction; Aural cartilage; Bone conduction; Cartilage-air; Cartilage-bone; Direct-air; Occlusion effect; Tragus