What this means for learners
Sango and Yorouba share 28 sounds — roughly 64% of Yorouba'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 4 sounds found only in Yorouba 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 16 sounds not used in Yorouba. Native Yorouba 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.