Study of the Role of Hearing Aid on the Area of the Acoustic Field of Vowels

The method of transformation of acoustic vowel triangles (AVT) /a/, /i/, /u/ was used for an objective assessment of the acoustic features of vowels in the speech production of 20 persons with long-term hearing impairment (LHI). The logarithm of the values of the first two formants of each vowel (logF1, logF2) was determined for each subject. AVTs were transformed into the right-angled triangles, the vertices of the sound /u/ of which were moved to the origin of coordinates and the legs were aligned with the coordinate axes. In patients with LHI, the size of the triangles usually decreased, and they were stretched along one of the axes, which probably depends not only on the hearing loss severity but also on the duration of hearing aid use. The presented approach to the normalization of AVTs makes it possible to distinguish at least three groups of persons with LHI: in the first group, vowel triangles are stretched along the logF1 axis; in the second group, vowel triangles are stretched along the logF2 axis; and in the third group, AVT are symmetric.