title: Gain affected by the interior shape of the ear canal.
abstract: OBJECTIVE
  This study investigated the correlation of gain distribution and the interior shape of the human external ear canal.
  
  
  METHODS
  Cross-sectional study of gain measurement at the first bend and second bend.
  
  
  METHODS
  Chang Gung Memorial Hospital and Chang Gung University.
  
  
  METHODS
  There were 15 ears in patients aged between 20 and 30 years (8 men/7 women) with normal hearing and middle ears. Stimulus frequencies of 500, 1000, 2000, 3000, and 4000 Hz were based on the standard clinical hearing test. Measurements closer to the tympanic membrane and the positions at the first and second bends were confirmed by using otoscope. Real ear measurement to analyze the canal resonance in human external ears was adopted.
  
  
  RESULTS
  This study found that gain at stimulus frequencies of 4000 Hz was affected by the interior shape of the ear canal (P < .005), particularly at the first and second bends, whereas gain was only affected by the length of the ear canal for stimulus frequencies of 2000 Hz (P < .005).
  
  
  CONCLUSIONS
  This study found that gain was affected not only by the length of the external auditory canal (EAC) but also by the interior shape of the EAC significantly. The findings of this study may have potential clinical applications in canalplasty and congenital aural atresia surgery and may be used to guide surgeries that attempt to reshape the ear canal to achieve more desirable hearing outcomes.
authors.affiliation: Graduate Institute of Medical Mechatronics, Chang Gung University, Taoyuan, Taiwan. dr.jfyu@gmail.com
authors.forename: Jen-Fang
authors.initials: JF
authors.lastname: Yu
authors.forename: Yen-Sheng
authors.initials: YS
authors.lastname: Chen
authors.forename: Wei-De
authors.initials: WD
authors.lastname: Cheng
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001301:Audiometry, Pure-Tone; D003430:Cross-Sectional Studies; D004424:Ear Canal / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008297:Male; D013016:Sound; D013997:Time Factors; D055815:Young Adult