Matching Pursuit reveals the relation between transient and spontaneous otoacoustic emissions

Otoacoustic signals measured for time epoch of 80 ms after the click stimulus were decomposed by means of adaptive approximation by Matching Pursuit algorithm. High resolution time-frequency distributions of signal energy were calculated. Two types of responses were identified: Transiently Evoked Otoacoustic Emissions (TEOAE) characterized by the waveforms of the short durations appearing in first 20 ms and Synchronized Spontaneous Otoacoustic Emissions (SSOAE) characterized by the waveforms of very long duration and narrow frequency band. The results supported the thesis that the later were due to spontaneous emissions. The long lasting OAE were characterized by the almost constant energy in time. The exponential decay observed by some authors was explained by the superposition of TEOAE and SSOAE. The implications for the clinical applications were shown.