Formant structure of the voice during the intensive acute hypoxia.

The influence of intensive acute hypoxia on the frequency-amplitude formant vocal O characteristics was investigated in this study. Examinees were exposed to the simulated altitudes of 5,500 m and 6,700 m in climabaro chamber and resolved Lotig's test in the conditions of normoxia, i.e. pronounced the three-digit numbers beginning from 900, but in reversed order. Frequency and intensity values of vocal O (F1, F2, F3 and F4), extracted from the context of the pronunciation of the word eight (osam in Serbian), were measured by spectral speech signal analysis. Changes in frequency values and the intensity of the formants were examined. The obtained results showed that there were no significant changes of the formant frequencies in hypoxia condition compared to normoxia. Though, significant changes of formant's intensities were found compared to normoxia on the cited altitudes. The rise of formants intensities was found at the altitude of 5,500 m. Hypoxia at the altitude of 6,700 m caused the significant fall of the intensities in the initial period, compared to normoxia. The prolonged hypoxia exposure caused the rise of the formant intensities compared to the altitude of 5,500 m. In may be concluded that, due to different altitudes, hypoxia causes different effects on the formants structure changes, compared to normoxia.