title: Importance of bone-conducted sound transmission on patient hearing in the MR scanner.
abstract: OBJECTIVE
  to evaluate the influence of bone-conduction in the MR environment compared to a standardized acoustic environment.
  
  
  METHODS
  Acoustic noise is an unwanted side effect of MRI that is commonly tackled with passive hearing protection. In an MR scanner, however, with the patient completely surrounded by the MR sounds and in close contact with the vibrating MR table and gantry, bone-conduction may increase subjective sound levels, restricting the efficacy of passive protection that reduces air-conducted noise only. A total of 10 volunteers were subjected to pure MR tones, covering the frequency range relevant for hearing and at 60 dB, generated through the MR system's gradient coils. Bone-conduction was determined for various passive damping conditions in an MR scanner and was compared to that acquired in an acoustically-calibrated environment. The contribution of mechanical vibrations to bone-conduction was determined. Also, with a microphone in the ear canal, the objective efficacy of the passive protection was measured.
  
  
  RESULTS
  We found no difference between the bone-conduction experiments executed inside the imager and in the acoustically-controlled environment. The overall insertion loss of the passive hearing protectors was over 20 dB with strongest effects at 0.4 and 2.5 kHz.
  
  
  CONCLUSIONS
  As bone-conduction is not more pronounced inside the MR scanner than outside, the previous reports on the subjective evaluation of protection devices in MRI hold their validity.
authors.affiliation: Department of Radiology, Erasmus MC-University Medical Center Rotterdam, Rotterdam, The Netherlands. a.moelker@erasmusmc.nl
authors.forename: Adriaan
authors.initials: A
authors.lastname: Moelker
authors.forename: Ronald A J J
authors.initials: RA
authors.lastname: Maas
authors.forename: Mika W
authors.initials: MW
authors.lastname: Vogel
authors.forename: Mohamed
authors.initials: M
authors.lastname: Ouhlous
authors.forename: Peter M T
authors.initials: PM
authors.lastname: Pattynama
mesh_terms: D001844:Bone Conduction / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D009622:Noise