Individual differences in sensitivity lo loud-ness, and correlation between the sensitivity and the strength of the nervous system (I) and the individual psychophysical loudness scales (2) have been studied on 28 human subjects. Strenght of the nervous system has been measured in terms of RT. Loudness scales have been obtained by means of comparison of the presented sounds with the standard. The study shows that in majority of subjects (70 %) the index of differential sensitivity in the sub-region of weak sounds (40 db) is inversely correlated with that in the subregion of strong sounds (120 db). In 30% of subjects there has been established a direct correlation between the two indices. Subjects with a weak nervous system possess better differential sensitivity in the subregion of weak sounds and worse sensitivity in relation to strong sounds. Subjects with a strong nervous system, on the contrary, are characterized by better differential sensitivity in the subregion of strong sounds and by worse sensitivity in relation to weak sounds.