Estimation of distortion product otoacoustic emissions.

Distortion product otoacoustic emissions (DPOAE's) are acoustic signals generated from the cochlea when stimulated by dual tone stimulus. The measurement of the DPOAE's is useful in objectively assessing the hearing functionality of humans. The parameter estimation of the DPOAE's has been based on the fast Fourier transform (FFT) technique, which may not guarantee optimum performance in general. In this paper, we investigate the optimal maximum-likelihood estimator (MLE) for the DPOAE's. Experiments showed that the performance of the MLE is superior to those of the conventional FFT estimators. Furthermore, it is proven that the unwindowed FFT estimator is essentially the MLE when the stimulus tones are constrained to exhibit complete cycle within the data frame.