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Alternative Ear-Canal Measures Related to Absorbance

Neely, Stephen T.1; Stenfelt, Stefan2; Schairer, Kim S.3

doi: 10.1097/AUD.0b013e31829c7229

Several alternative ear-canal measures are similar to absorbance in their requirement for prior determination of a Thévenin-equivalent sound source. Examples are (1) sound intensity level, (2) forward pressure level, (3) time-domain ear-canal reflectance, and (4) cochlear reflectance. These four related measures are similar to absorbance in their utilization of wideband stimuli and their focus on recording ear-canal sound pressure. The related measures differ from absorbance in how the ear-canal pressure is analyzed and in the type of information that is extracted from the recorded response. Sound intensity level and forward pressure level have both been shown to be better as measures of sound level in the ear canal compared with sound pressure level because they reduced calibration errors due to standing waves in studies of behavioral thresholds and otoacoustic emissions. Time-domain ear-canal reflectance may be used to estimate ear-canal geometry and may have the potential to assess middle ear pathology. Cochlear reflectance reveals information about the inner ear that is similar to what is provided by other types of otoacoustic emissions, and may have theoretical advantages that strengthen its interpretation.

1Department of Hearing Research, Boys Town National Research Hospital, Omaha, Nebraska, USA; 2Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden; and 3Audiology and Speech-Language Pathology Service, James H. Quillen Veterans Affairs Medical Center, Mountain Home, Tennessee, USA.

ACKNOWLEDGMENTS: Contributions of the coauthors of the four reviewed studies (Michael Gorga, Rachel Scheperle, Judy Kopun, and Daniel Rasetshwane) are gratefully acknowledged. Some of the apparata used to measure reflectance was generously provided by Jon Siegel at Northwestern University.

The contents of this article do not represent the views of the Department of Veterans Affairs or of the U.S. Government.

Work on this review was supported by the National Institutes of Health grant R01 DC8318 to the first author.

The other authors declare no conflict of interest.

Address for correspondence: Stephen T. Neely, Boys Town National Research Hospital, 555 North 30th Street, Omaha, NE 68131, USA. E-mail:

Received January 22, 2013

Accepted May 13, 2013

© 2013 by Lippincott Williams & Wilkins