Evaluation of the effect of electromagnetic waves on speech intelligibility from electrophysiological signals

While developing technology provides convenience in people's lives, it also brings some environmental problems. Considering the widespread use of mobile phones and the widespread use of wireless communication systems, it is important to determine the physiological effects of exposure to electromagnetic fields on individuals in daily life. In this thesis study, Galvanic Skin Response (GSR) and Electroencephalogram (EEG) based examination and analysis of the effects of mobile phone use on speech discrimination in individuals were carried out. Decreased speech intelligibility can lead to misunderstanding, frustration and loss of interest by those communicating. Within the scope of this study, EEG and GSR recordings were taken from the volunteers in the resting state and during the audiological test. These data were analyzed and the results were correlated with factors such as the average daily use of mobile phones by individuals and how many years they had been using mobile phones. According to the results obtained, the electrical activity of the brain near the ear, which is frequently interviewed, showed more significant changes. In addition, at this stage of the study, it was determined which frequency sub-band and which GSR feature of the EEG signal were more distinctive in terms of average interview time. In addition, the physiological effects of the audiological test process on individuals were investigated on the basis of galvanic skin response. The resting status of the volunteers participating in the study and the GSR data obtained during the audiological test were analyzed and the effects of the audiological test process were evaluated. At this stage, it was observed that the audiological test process showed significant differences in terms of average value, average power, RMS (Root Mean Square), Kurtosis and Skewness characteristics, according to the resting state. The findings obtained here show that these differences in the GSR data on individuals during the audiological test process can be evaluated according to the physiological effects of the emotional changes created by the test. In the continuation of the study, in order to determine the changes caused by the audiological test process in the brain activity of the individuals, the resting state of the volunteers and the EEG data obtained during the audiological test were analyzed and the effects of the audiological test process according to the resting state were evaluated. Dual electrode coherence analyzes were performed for the theta, alpha, beta, delta, and gamma sub-frequency bands of EEG signals. In the study, neural activation in frontal and temporal positions was also investigated using wavelet coherence during audiological testing. The results showed that there was a high consistency in the changes in delta, theta and alpha bands, especially in the symmetric temporal region, during the audiological test process. The study also investigated which channels were more effective at rest for different wavelet entropy types in order to determine the channel-based differences of the audiological test process from the EEG signals. The results showed that the wavelet entropy approach can be used to determine in which region of the brain the audiological test increases the activity in individuals and also to determine which electrode region the audiological test process shows more difference compared to the resting state.