Why does 'в' have a special case in consonant voicing?

Question

As far as I learned the lesson about voiced and voiceless consonants and consonant clusters, voiced consonants voice the preceding voiceless consonant and voiceless consonants devoice the preceding voiced consonant. But why is the voiced consonant 'в' an exception to this rule? (for example: свобода stays pronounced as свобода instead of звобода, but автобус is pronounced as афтобус)

Also, when a word ends with a voiced consonant and the following word starts with 'в', does the preceding voiced consonant stay voiced, or does it go voiceless, as if 'в' has no effect? (example: меж вами; is it меж вами or меш вами?)

Answer 1

Russian в originates from Proto-Slavic non-syllabic vowel *w, as in English "well".

This sound was sonorant enough for the law of the rising sonority to put it after obstruents in a single syllable, as well as another semivowel й and the sonorants (liquids р and л and nasals м and н).

That's why the modern Russian в, being an obstruent, does not vocalize preceding voiceless obstruents either: съезжать, сватать, слать, смотреть, снимать and срубать are all pronounced with initial [s].

Devocalization of в itself is a relatively recent Russian innovation. Ukrainian and Belorussian, as well as most southern Russian dialects, don't do that but rather replace it with the semivowel [w] in positions where it would have been devocalized.

Answer 2

First, "в" is a bit similar to sonorants like м, р, й and others. The second reason that might have played part in the peculiarity of this consonant's behaviour is that [ф] appeared pretty late comparing to other consonants. So, essentially, В was a consonant that existed in one variant only: Russian used to not draw any distinction based on voicing there.

In the beginning, Old East Slavic only had [в]. There was no devoicing back then because two consonants in a row of final consonants weren't possible: every consonant had a following vowel. Then, the short vowels disappeared, which changed the phonetic system significantly. It is here that [ф] should have appeared as a devoice version of [в]. Then, Greek influence eventually introduced [ф] as a separate sound, which is what we have now.

Regarding pronunciation:

• devoiced consonants are not voiced before В
• voiced consonants stay voiced (both inside the word and at word boundaries)
• Щ, Х, Ч, Ц behave as usual devoiced consonants, and they also have voiced counterparts [ʑʑ], [ɣ], [d͡ʑ], [d̪͡z̪] that are obvious at word boundaries (помощь бы, их даже, отец Бори, меч брата). Russian has no letters for these sounds, but the sounds do exist.

Answer 3

When you pronounce автобус like [афтобус] the voiceless consonant т devoice the preceding voiced consonant в like you said in your question.

As for меж вами there is no need to devoice ж when the next word starts with voiced consonant в (see the difference: меж собой will be [меш сабой])