Грамматика русского языка. Часть 3. Различие согласных звуков по глухости / звонкости. Глава 1. Звонкие и глухие согласные. Russian Grammar. Part 3. Voicing and Devoicing of Consonants. Unit 1. Voiced and Voiceless Consonants.

You've learnt how the soft vowels and the soft and hard signs affect the sounds around them. Now you'll see how the position of the consonant in the word affects its sound.

Voiced and Voiceless Consonants

Russian consonants are divided not only into hard and soft sounds, but also into voiced and voiceless consonants. Voiced consonants are produced with the aid of the vocal chords, which give to the consonants a buzzing sound; in the production of voiceless consonants, however, the vocal chords remain inactive.

The same distinction exists in English: the English b, v, d, and z are voiced or buzzing sounds; the p, f, t, and s are voiceless sounds.
Study the differences in the production of these letters in the following sets of words:

bat / pat
van / fan
die / tie
zeal / seal

You'll notice that when you form each pair of words, your mouth is in the same position, yet the sound is different. The difference can be clearly put: in each word on top, the vocal chords are used in the production of the initial letter; in the corresponding word on the bottom, they are not.

Most voiced consonants in Russian have their voiceless counterparts, just as in English the b is related to the p, the v to the f, the d to the t, and the z to the s. However, in Russian pronunciation, unlike English, this relationship is functional; for under certain circumstances, voiced consonants become devoiced (i. e. pronounced like their voiceless counterparts), and vice versa.

Study the following table:

ALWAYS VOICED	VOICED AND VOICELESS COUNTERPARTS	ALWAYS VOICELESS
л	б [b] – п [p]	ц
м	в [v] – ф [f]	ч
н	г [g] – к, х [k, kh]	щ
р	д [d] – т [t]
	ж [zh] – ш [sh]
	з [z] – с [s]