What this means for learners
Sango and Ket share 11 sounds — roughly 25% of Ket's inventory overlaps with Sango. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 21 sounds found only in Ket represent the greatest pronunciation challenge for Sango 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, Sango has 33 sounds not used in Ket. Native Ket speakers learning Sango 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.