Automatic, mobile system for evaluation of human hearing abilities

At present two main methods of examination of the human hearing system are applied. The first one is based on close cooperation between the physician and the patient and its examination result is the classical audiogram. The second one, which is an objective method, comprises the analysis of the auditory brainstem response (ABR) signals. In the second case the cooperation between the physician and the examined patient with hearing impairments is not necessary. The present paper contains a description of a method allowing a construction of a system evaluating the patient\´s hearing abilities in an automated manner, without the necessary presence of highly trained audiological staff. The system leads to elimination of a subjective human factor from the diagnostic process. It should be noticed that diagnosis of human hearing impairment based on the registration of ABR signals and the analysis of the morphology of the recording as well as the latency periods and amplitudes of individual waves as functions of the stimulus intensity is very difficult and requires extensive practice. The ABR potentials emerge as electrophysiological reaction to an acoustic stimulus, usually being a short crack, or a tone, the intensity of which is gradually decreasing during the examination. After completing the examination a series of recording is obtained. Each ABR recording usually contains three to five dominant maxima. The amplitudes and latency periods of these maxima depend on the stimulus type and its intensity as well as the patient\´s age, sex and type of the hearing impairment. It is widely assumed that the hearing threshold coincides with the extinction of the fifth wave. The system described below operates in sequential mode, ie. at first the acquisition of the ABR signal is done, then the data are subject to preprocessing and in the next stage the analysis of the data is carried out. It has been implemented on the Pocet PC platform in connection together with "Kuba micro" device.