In addition to being painful, acoustic noise at the higher end of this range may cause temporary or permanent hearing loss. Even noise of lower intensity may cause anxiety or distress in patients, especially infants, young children, and the elderly. This may manifest as patient motion artifacts and degraded image quality.
More significant are permanent threshold shifts (PTS), typically caused by noise levels ≥ 130-140 dB. These result from disturbances in microcirculation to the organ of Corti with ischemic cell death. Children have a lower sensitivity for hearing damage, and restricting exposure to less than 120 dB is recommended.
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An interesting auditory phenomenon associated with pulsed electromagnetic radiation is called “RF hearing”. This is described as a buzzing, clicking, hissing, or knocking sound and is thought to be due to periodic thermoelastic expansion of tissue with a pressure wave transmitted to cochlear hair cells. Patients seldom notice this phenomenon, however, because its magnitude is small compared to the many other noises the scanner makes during image acquisition.
Frey AH. Human auditory system response to modulated electromagnetic energy. J App Physiol 1962; 17:689-692. (First description of RF hearing). [DOI Link]
International Electrotechnical Commission. IEC 60601-2-33:2010: Medical Electrical Equipment - Part 2-33: Particular Requirements for the Basic Safety and Essential Performance of Magnetic Resonance Equipment for Medical Diagnosis. 3rd ed. with amendments. International Electrotechnical Commission; 2015. (accessed July 2020)
McJury M. Shellock FG. Auditory noise associated with MR procedures: a review. J Magn Reson Imaging 2000; 12:37-45. [DOI Link]
National Electrical Manufacturers Association. NEMA Standards Publication MS 4-2010 Acoustic Noise Measurement Procedure for Diagnostic Magnetic Resonance Imaging Devices. 2010 (accessed July 2020) - describes details of performimg noise measurement
OSHA Standard 1910.95. Occupational noise exposure. Revised 12/12/08. (See Table G-16 for permissible occupational noise exposures)
Röschmann P. Human auditory system response to pulsed radio frequency energy in RF coils for magnetic resonance at 2.4 to 170 MHz. Magn Reson Med 1991; 21:197-215. [DOI Link] (RF hearing caused by MRI)
What's all that noise the scanner is making?
What safety concerns relate to gradient fields?