Only in Bulgarian 29
What this means for learners
Bulgarian and Chuvash share 20 sounds — roughly 41% of Chuvash's inventory overlaps with Bulgarian. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 19 sounds found only in Chuvash represent the greatest pronunciation challenge for Bulgarian speakers. The adult brain tends to map unfamiliar sounds onto the closest native equivalent — a process that produces the characteristic "accent" of a second-language speaker. Learning to hear and produce these sounds as distinct requires focused ear training, not just repetition.
Conversely, Bulgarian has 29 sounds not used in Chuvash. Native Chuvash speakers learning Bulgarian will face the mirror-image challenge with these sounds.
Phoneme inventories from PHOIBLE. Data reflects one documented inventory per language; some variation exists across dialects and sources.