Voiced and Voiceless Consonants
Both in English and in Russian, some consonants are voiceless and some are voiced. When the vocal cords are together, the air flow makes them vibrate, resulting in the production of voiced consonants, for example, English consonants D and Z and Russian consonants Other consonants do not rely on the vocal cords for pronunciation; think of the English consonants T and P and Russian consonants Φ and K. In Russian and in English, voiced and voiceless consonants can be classified into pairs as in the table below.
In contrast to English, Russian voiced and voiceless consonants are not always pronounced the way they are written. At the end of words, voiced consonants are pronounced like their voiceless counterparts.
Unlike English, Russian allows more consonant combinations within its words. This is why you will encounter words where you will see both voiced and voiceless consonants side by side, as in (rest). Because it would be difficult to articulate both voiced and voiceless consonants side by side without a lot of effort, the language developed a conservation technique, also known as consonant assimilation.
Whenever there are adjacent voiced and voiceless consonants, the first consonant takes on the voicing quality of the second. In this manner, a voiced consonant can become voiceless, and a voiceless consonant can be transformed into a voiced consonant. This assimilation occurs not only within a word, but also within phrases. The assimilation rule does not apply to the words or phrases where the first consonant is voiceless and the second one is the voiced consonant B, as in a word that does not undergo assimilation.