title: Is it necessary to occlude the ear in bone-conduction testing at 4 kHz, in order to prevent air-borne radiation affecting the results?
abstract: OBJECTIVE
  To re-evaluate the current BSA recommendation that the test ear should be occluded during the bone-conduction procedure at frequencies above 2 kHz to prevent audible air-borne radiation.
  
  
  METHODS
  Pure-tone audiometry was undertaken during routine hearing tests. The audiograms of fifty-two ears met the criteria for the study and were included. Bone conduction at 4 kHz was tested in three different conditions: test ear open/occluded by earplug and occluded by circumaural earphone.
  
  
  METHODS
  Forty-four adults aged 41-77 years with average hearing levels from normal to severe loss. All complied fully with the test procedure. No audiogram had a significant conductive element.
  
  
  RESULTS
  There was no significant difference in each of the three test situations. Only two audiograms showed any (5 dB) difference at 4 kHz when bone conduction was retested with the ear occluded.
  
  
  CONCLUSIONS
  The errors that result in a false air-bone gap at 4 kHz would not appear to be due to air-borne radiation. Failure to occlude the ear canal at 4 kHz, where air-borne radiation is greatest, makes no significant difference to the audiometric results. It is therefore suggested that it is unnecessary to block the test ear during routine pure-tone bone-conduction testing to prevent audible air-borne radiation, and that this should no longer form part of normal clinical practice.
authors.affiliation: a Vision and Hearing, Anglia Ruskin University , Cambridge , UK.
authors.forename: Maryanne
authors.initials: M
authors.lastname: Tate Maltby
authors.affiliation: b Methley Park Hospital , Leeds , UK.
authors.forename: David
authors.initials: D
authors.lastname: Gaszczyk
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000368:Aged; D000388:Air; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology; D001844:Bone Conduction; D004056:Differential Threshold / Q000502:physiology; D004424:Ear Canal; D004430:Ear Protective Devices; D005260:Female; D034381:Hearing Loss / Q000175:diagnosis*; D006320:Hearing Tests / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D006801:Humans; D008297:Male; D008875:Middle Aged; D060205:Therapeutic Occlusion
keywords: Air-bone gap; air-borne radiation; bone conduction; earplug at 4 kHz; recommended procedure