The objective of the present work was to develop unified criteria for the evaluation of the severity of noise-induced hearing loss. Current approaches to taking expert decisions based on the results of medical examination of the patients with impaired hearing are substantially different due to the considerable difference between the criteria for the estimation of hearing envisaged by the international classification, occupational pathology classification, and the national system of medico-social expertise. We undertook an attempt to correct and harmonize the existing criteria for the estimation of severity of occupational hearing loss based on the integration of all the three classification in order to "reduce them to a common denominator" and thereby to ensure the basis for the unified diagnostic and expert decisions for the cases of hearing impairment of any etiology. The project proposed in this paper makes it possible to use unified criteria for the assessment of the degree of hearing loss caused by occupational noises for diagnostic purposes and expertise compatible with the internationally accepted approaches.