Correspondence amongst microstructure patterns observed in otoacoustic emissions and Bekesy audiometry

Similar patterns of microstructure have been reported in normal ears for Be kesy threshold recordings and various forms of otoacoustic emissions (OAE). It has been suggested that they have a common origin associated with the a mplifying function of the outer hair cell system and wave interactions occu rring within cochlear mechanics. Fine-frequency Bekesy audiometry was condu cted in ten normal ears and its microstructure was compared with that recor ded using two OAE techniques: stimulus frequency (SFOAE) and distortion pro duct (DPOAE). All sweeps encompassed the frequency range from 992 to 2000 H z in 16-Hz steps. The same probe was used for all Bekesy and OAE recordings to eliminate transducer effects. SFOAEs were obtained with stimulus intens ities of 0, 3, 6 and 9 dB. DPOAEs were obtained for 2F1-F2 with primary lev els (L1/L2) of 40/30, 45/35, 50/40 and 55/45 dB. Reliable microstructure was recorded in all ears. Mean values of microstruc ture peak spacing ranged from 5.6 to 9.3 per cent amongst methods, consiste nt with published data. Microstructure was similar within each OAE method f or different stimulus intensities for each subject. However, comparisons be tween Bekesy and OAEs, or between OAE methods, did not show the strong corr espondence that would be expected if there were a simple common origin to t he microstructure. There was weak support for the expected correspondence b etween Bekesy and SFOAE, but no support for any correspondence between Beke sy and DPOAE. It is concluded that the various forms of microstructure cann ot be explained by a simple common origin.