Document Detail

Analysis of the coil generated impulse noise in extracranial magnetic stimulation.
MedLine Citation:
PMID:  1380916     Owner:  NLM     Status:  MEDLINE    
An intense impulse noise artifact is generated by the coil used in extracranial magnetic stimulation (EMS) of the brain and cranial nerves. In this study we measured and analyzed the sound pressure level (SPL), spectral content, wave form, and time course of the magnetic coil acoustic artifact (MCAA) impulse noise in the sound field and in the ear canal of life-size models of the human cranium. Two different clinical magnetic stimulators and coils were used. Sound field measurements from both coils showed the MCAA to be a transient impulse noise with a rapid rise-time, brief duration, broad acoustic spectrum, and high intensity. Measurements made on models of the human head with the magnetic coils positioned at selected standard clinical positions for EMS, particularly the peripheral facial nerve, auricle and mastoid areas, indicated that the MCAA may reach sound pressure levels that exceed noise damage-risk criteria limits for sensorineural hearing loss. The maximum peak energy in the acoustic spectrum of the MCAA measured in the ear canal of the model heads was from 2 to 5 kHz, the range of highest sensitivity in human ears. Ear protectors were found to attenuate the SPL of the MCAA, reaching the ear canal of the model heads by 15-22 dB SPL, and were recommended for use by patients and subjects exposed to EMS.
S A Counter; E Borg
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Electroencephalography and clinical neurophysiology     Volume:  85     ISSN:  0013-4694     ISO Abbreviation:  Electroencephalogr Clin Neurophysiol     Publication Date:  1992 Aug 
Date Detail:
Created Date:  1992-09-30     Completed Date:  1992-09-30     Revised Date:  2008-09-09    
Medline Journal Info:
Nlm Unique ID:  0375035     Medline TA:  Electroencephalogr Clin Neurophysiol     Country:  IRELAND    
Other Details:
Languages:  eng     Pagination:  280-8     Citation Subset:  IM    
Neurology Department, Harvard University, Biological Laboratories, Cambridge, MA 02138.
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MeSH Terms
Brain / physiology*
Ear / physiology*
Models, Anatomic
Noise / adverse effects*
Signal Processing, Computer-Assisted

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