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The effect of ear-canal air pressure on click-evoked otoacoustic emissions was measured for pressures ranging from 200 to -200 daPa and stimulus levels ranging from 60-90 dB PeSPL. Positive and negative ear-canal pressures (relative to ambient pressure) reduced the emission amplitude by 3-6 dB. A spectral analysis of the emissions revealed that the effect of ear-canal air pressure is that of a high-pass filter with a cutoff frequency of 2600 Hz and a slope of 4 dB/oct. The spectral changes are the expected effect of an increase in stiffness of the middle ear and were independent of pressure polarity and click level. Ear-canal air pressure substantially reduced the reproducibility of the emission waveform, in many cases rendering the emission indistinguishable from background noise. The implication of these findings for hearing screening applications is that a high false alarm rate may occur in normal-hearing patients with intratympanic air pressures that are significantly different from ambient pressure.

There has been increased interest in electrocochleography for the diagnosis and intraoperative monitoring of patients with endolymphatic hydrops. Attention has been focused on the determination of the summating potential:action potential (SP:AP) ratio from alternating polarity clicks. Review of this technique at the University of Minnesota led to a reevaluation of the usual interpretation of these recordings. Separate examination of the rarefaction and condensation click recordings provides insight into abnormal response patterns. Cases are presented to illustrate a variety of normal and abnormal patterns including abnormal differences in the latency of condensation and rarefaction-click-generated action potentials, increased summating potential, uncanceled cochlear microphonic, and reduced action potential and summating potential amplitudes. These response categories may be useful in understanding the pathophysiology of Meniere's disease.

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