I didn't quite understand your question. Can you add a clarifying explanation? Wishes for a happy, peaceful and prosperous New Year.

si

I think that that the phonetic drift can go in either direction depending on the degree of phonetic overlap in the two languages. However, not only can a sound be lost, if it doesn't occur in one of the languages but it will be substituted for by another sound that does occur. To give two examples between Hebrew and English...The holiday Chanukah has just passed. [Ch] (the velar voiceless fricative) does not occur in English, so the holiday is pronounced Hanukah by many American speakers. Similarly, [th] both voiced and voiceless versions do not occur in Hebrew. The voiceless version is often substituted with [t] and the voiced version with [z]

Hello Abdul-Sahib,

The answer to your question is "no". An example is Turkish, which used to be written with the Arabic alphabet, but is now written with the Roman alphabet. The change in the writing system did not change the phonology of the language. And, of course, there were also speakers of Turkish who were illiterate, and their phonologogy is also not affected by this.

There are other similar examples which can be given: Vietnamese used to be written using Chinese characters and another set of indigenous characters, but now it is written with the Roman alphabet, and the phonology has not changed; also Korean used to be written with Chinese characters and hangeul (first half of the 20th century), but is now written using hangeul only, with no changes in phonology related to this.