New procedure of vowel acoustic space (VAS) (of vowel acoustic triangles) transformation for the purpose of characterization of vowel production in individuals with long-term hearing loss (HL) was developed. Objective. To characterize VAS of adult Russian speakers with long-term HL using newly developed acoustic indicators. Material and methods. Recordings of sustained Russian cardinal vowels /a/, /i/, /u/ of 10 women and 10 men with long-term HL were acoustically analyzed. For each participant, two first formants of each vowel were measured and log-transformed (logF1, logF2). VAS was transformed into right triangles, their /u/ corners were moved to the origin, and their legs were aligned with axes. VAS was almost symmetrical, equal and have a maximum size in the control group consisted of subjects without hearing impairment while these of long-term HL group VAS size tended to have reduced and VAS stretched along one axis. Results. Our study showed that a new VAS normalization approach can distinguish at least three groups of people with long-term HL. Conclusion. There are those with vowel triangles stretched along logF1-axis, with vowel triangles stretched along logF2-axis, and with symmetrical vowel triangles. Causes of the VAS differences require further investigation. © 2021, Media Sphera Publishing Group. All rights reserved.