Only in Bulgarian 37
What this means for learners
Bulgarian and Ket share 12 sounds — roughly 24% of Ket'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 20 sounds found only in Ket 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 37 sounds not used in Ket. Native Ket 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.