The processing of the otoacoustic emission responses provides a valuable and powerful tool to study the effects on the forward and backward sound propagation, from the external ear to the cochlea. Any obstacles in the sound transmission result in an alteration of the recorded otoacoustic emission responses. Within this context, any factor influencing the sound propagation to the cochlea can be monitored successfully.

        Although the standard emission protocols refer mostly to effects within the auditory periphery, new emission protocols can provide information on the status of the efferent system identifying possible hearing complications in the central nervous system. Verification of the latter is derived by the information obtained from recordings of evoked auditory potentials, which monitor the course of the sound stimuli from the external ear up to the brainstem.