High-frequency click-evoked otoacoustic emissions and behavioral thresholds in humans

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Abstract
Relationships between click-evoked otoacoustic emissions (CEOAEs) and behavioral thresholds have not been explored above 5kHz due to limitations in CEOAE measurement procedures. New techniques were used to measure behavioral thresholds and CEOAEs up to 16kHz. A long cylindrical tube of 8mm diameter, serving as a reflectionless termination, was used to calibrate audiometric stimuli and design a wideband CEOAE stimulus. A second click was presented 15dB above a probe click level that varied over a 44dB range, and a nonlinear residual procedure extracted a CEOAE from these click responses. In some subjects (age 14–29years) with normal hearing up to 8kHz, CEOAE spectral energy and latency were measured up to 16kHz. Audiometric thresholds were measured using an adaptive yes-no procedure. Comparison of CEOAE and behavioral thresholds suggested a clinical potential of using CEOAEs to screen for high-frequency hearing loss. CEOAE latencies determined from the peak of averaged, filtered temporal envelopes decreased to 1ms with increasing frequency up to 16kHz. Individual CEOAE envelopes included both compressively growing longer-delay components consistent with a coherent-reflection source and linearly or expansively growing shorter-delay components consistent with a distortion source. Envelope delays of both components were approximately invariant with level.