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June 1974

Phase Distortion of Averaged Electroencepha

Author Affiliations

From the Department of Communicative Disorders, University of Wisconsin, Madison. Dr. Mendel is now with the University of Iowa, Iowa City. Dr. Kupperman is now with the Veterans Administration, Wood, Wis. Mr. Buchanan is now with the Eunice Kennedy Shriver Center, Waltham, Mass.

Arch Otolaryngol. 1974;99(6):428-432. doi:10.1001/archotol.1974.00780030442008

Analog filters employed in most averaged electroencephalic response (AER) recording systems impose some phase distortion on recorded AER. Phase distortion of the response results in a real time shift of peak latencies. The extent of this distortion, in general, is determined by the cutoff frequencies of the filter band in relation to the spectrum of the response. If the filter band employed is quite restrictive, the shift of latencies can be large. For purposes of threshold audiometry, filter-imposed phase shifts will not usually prevent simple response identification. However, if such time shifts in the data are not accounted for in interclinic or published communications, the response information could be misleading and confusing.

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