The Impact of the Acute Hypoxia To Speech Inharmonicity

Abstract

When people that live at the small altitude (up to 400 m above the sea level) climb on the mountain, they are exposed to the effects of an acute hypoxia. As a result, their oxygen concentration decreases in the tissue. This paper presents the analysis of the acute hypoxia effects to the speech signal at the altitude up to 2600 m above the sea level. For the experiment, the articulation of vowels (A, E, I, O, U) from the test group of persons was recorded at different altitude, which creates the speech signal database. This paper presents an algorithm, which is suitable for the evaluation of the acute hypoxia degree by analysing the inharmonicity degree of the speech. The algorithm is based on the estimation of fundamental frequency and the irregular fluctuations of its harmonic components. These irregular fluctuations are defined as inharmonicity. The inharmonicity is quantitatively gauged by the inharmonicity coefficient β. The analogy between the vibrating strings in musical instruments and vibration of the vocal cords in humans was established. Furthermore, the acute hypoxia effect to the inharmonicity coefficient of the speech signal is analysed. At the end, the comparative analysis of the acute hypoxia effects shows that the level of the hypoxia can be determined by the change of the fundamental frequency and the inharmonicity coefficient of speech signal. Hence, it is possible to bring conclusions about the degree of hypoxia, which in many situations can be of importance for avoiding catastrophic consequences.

DOI: http://dx.doi.org/10.5755/j01.eee.20.5.4024