Lev Shcherba and the theory of phoneme

Phonetics was one of the main objects of study for Shcherba throughout his entire scientific career. Lev Vladimirovich Shcherba was the founder of the Leningrad Phonological School, stood at the origins of the formation of such a science as phonology. Suffice it to recall his work on the development of the cabinet of experimental phonetics. From 1909 until the end of his life, Shcherba tirelessly develops the work of the laboratory, which was his favorite brainchild.
The foregoing determined the relevance of the chosen topic.
The aim of this work is to study the contribution of L. Shcherba to the theory of phonemes.
In the field of phonology, Shcherba is known as one of the founders of the phoneme theory. He was the first in the history of science to analyze the concept of background-we as a word-distinctive and morpheme-distinctive unit, opposed to a shade (variant) as a unit that does not have such a distinc-tive function. This analysis was the subject of the introduction to Shcherba's master's thesis, published in 1912 under the title “Russian vowels in qualita-tive and quantitative terms”. At that time in the West, scientists had not yet dealt with the problem of phonemes, and Shcherba, although sometimes in a very condensed form, considered all the most important aspects of phonology that still concern researchers [1].
Shcherba begins his analysis of the concept of a phoneme, showing that speakers come to the concept of a separate sound only through the phoneme due to its connection with the semantic units of the language. He considered the problem of dividing the stream of speech to be the most important and most difficult problem of phonology until the end of his life.
Shcherba conducted systematic studies, either in the form of a course, or in the form of a seminar on experimental phonetics. Even before the revolu-tion, he taught the pronunciation of Western European languages at the uni-versity using phonetic techniques. In the 1920s, he develops these techniques and develops them into a whole system, widely popularizing it. Together with S.K. Boyanus, he organized various courses of foreign languages in Leningrad, including the Phonetic Institute for the Practical Study of Languages and the State Courses of Foreign Languages.
All phonetic phenomena received scientific coverage from Shcherba, therefore they were deliberately assimilated by students. Students worked only on transcribed texts, bypassing spelling. Shcherba believed that a complete understanding of a foreign speech and a foreign text is inextricably linked with the correct, up to intonation, reproduction of their sound form.
Shcherba says that a lot of sounds can be observed in the speech stream, but not always we can isolate them, for example, in the words that and that we hear one sound t, but it will be different before a and before y: before a - ru-ined, but in front of y - no. But in the case of a difference in vowels in front of hard and soft consonants, it is more obvious: we feel the difference in the pro-nunciation of the words steel and steel, sat and sat, etc. Shcherba gives an an-swer to the question why we do not always notice these differences: because these differences are not semantised, that is, this sound difference is not con-nected with morphological difference.