Objective calibration of bone conductors using otoacoustic emissions

Objective: To demonstrate a technique for objectively calibrating bone conductors on an individual basis using distortion product otoacoustic emissions (DPOAEs). Design: Individual calibrations were obtained using DPOAEs recorded from a single ear of 21 normally hearing adults. Validity and robustness of the technique were investigated through subjective phase cancellation measurements and sensitivity analysis. Results: Calibrations obtained using the DPOAE method were well supported by phase cancellation results. Intersession repeatability was good, and manipulation of the DPOAE data showed that the calculated calibration is relatively insensitive to small variations of emission magnitude. Bilateral stimulation through bone conduction did not display an apparent effect on emission magnitude in a single individual, Conclusion: Bone conductors can be accurately calibrated on an individual basis with good repeatability using DPOAEs. The technique is robust and offers an objective, noninvasive calibration method for research and specialized clinical applications. No training and only passive cooperation are required, making the procedure ideal for special groups such as children. A number of limitations will reduce the clinical utility of this technique. Important audiometric frequencies below 1 kHz cannot be tested because of noise, because individuals with significant hearing loss are unlikely to produce sufficient DPOAEs, and because commercial bone conductors typically have poor high-frequency response above 4 kHz.