Probe Microphone Placement for Real Ear Measurement Update on a Simple Acoustic Method Research Article
Research Article  |   July 01, 1997
Probe Microphone Placement for Real Ear Measurement
 
Author Affiliations & Notes
  • Grant D. Searchfield, MAud
    Audiology Section, Department of Physiology, University of Auckland, Private Bag 92019, Auckland, New Zealand
  • Suzanne C. Purdy
    Audiology Section, Department of Physiology, University of Auckland, Private Bag 92019, Auckland, New Zealand
Article Information
Hearing & Speech Perception / Acoustics / Hearing Disorders / Hearing Aids, Cochlear Implants & Assistive Technology / Special Populations / Genetic & Congenital Disorders / Research Articles
Research Article   |   July 01, 1997
Probe Microphone Placement for Real Ear Measurement
American Journal of Audiology, July 1997, Vol. 6, 49-54. doi:10.1044/1059-0889.0602.49
History: Received November 20, 1996 , Accepted May 23, 1997
 
American Journal of Audiology, July 1997, Vol. 6, 49-54. doi:10.1044/1059-0889.0602.49
History: Received November 20, 1996; Accepted May 23, 1997

Probe microphone measurement systems allow determination of sound pressure level (SPL) within the external auditory meatus (EAM). EAM geometry and middle ear impedance contribute significantly to the acoustic properties of the EAM, and consequently sound pressure distribution along the EAM is not uniform. Accurate measurement of SPL at the tympanic membrane (TM) requires probe microphone placement within 6 to 8 mm of the TM. A method of probe placement using the acoustical properties of the EAM (Sullivan, 1988) was investigated in 6 adults. Sullivan's acoustic probe placement method was found to overestimate probe distance from the TM, but with minor modification the acoustic method could be used to place the probe so that real ear measurements accurately predicted SPL at the TM. The difference between TM SPL and SPL at probe position was compared for the acoustic method and a constant insertion depth (25 mm) method. More accurate estimates of TM SPL were obtained with the acoustic method.

Acknowledgments
This work was supported in part by a grant from the Deafness Research Foundation of New Zealand. The authors would like to thank Ruth Bentler, Donald Dirks, David Fabry, Roy Sullivan, and three anonymous reviewers for their comments on earlier versions of the manuscript.
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