Vowel polygon efficiency induced by middle level psychological stress

This paper presents the comparison of six different methods for finding the most uniform changes in vowel polygons caused by psychological middle level stress. On created database containing real stress, each method cross-correlating two different vowel polygon parameters is applied for reaching the most appropriate formant plane vowel shape to stress detection. The best results have been reached by Method 5 and Method 6, the best vowel shape can be classified as EIOU vowel tetragon, AEI and AEU vowel triangles. The best formant planes contain the fifth formant, i.e. F1F5, F2F5 and F3F5. Further by created efficiency coefficient, the best vowel polygons for stress detection are AEU35 (Method 6), AIO25 (Method 1) and EIOU15 (Method 5). The worst results are reached by methods 3 and 4 which are absolutely unsuitable for stress detection as well as formant plains containing both lower formants.