What this means for learners
Bisa and Ket share 12 sounds — roughly 29% of Ket's inventory overlaps with Bisa. 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 Bisa 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, Bisa has 29 sounds not used in Ket. Native Ket speakers learning Bisa 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.