Effect of Normobaric and Hypobaric Hypoxia on Formant Characteristics of Human Voice

Background: Hypoxia is an intensive environmental stressor which affects the psychophysiological state of an individual. It has been confirmed to influence the fundamental frequency of voice. This study aims to investigate the effect of different hypoxia conditions on formant characteristics of voice. Method: Eighteen volunteers recorded voice using a mobile phone in two phases. Study-1: Six subjects were exposed to normobaric hypoxia (NH) for four days in a normobaric chamber. For hypobaric hypoxia same subjects were airlifted to 11500 ft above sea level (SL) and stayed there for four days. Study-2: Out of twelve subjects, six test subjects exercised after NH exposure. Other six were control subjects. All 12 subjects were then airlifted to 11500 ft and stayed at this height for six days. Obtained data was analyzed using BLISS software. Result: No change in formant's frequency was observed after NH exposure or at high altitude (HA). Significant increase in formant's intensity was noted after NH exposure. Formant's intensity decreased on initial exposure to HA, however it increased after acclimatization. Percentage increase in the formant's intensity after NHE without exercise was more than that with exercise. Conclusion: Hypoxic stress changes voice parameters. Formant frequency is not affected by hypoxic stress.