What this means for learners
NGIZIM and Yao share 21 sounds — roughly 43% of Yao's inventory overlaps with NGIZIM. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 28 sounds found only in Yao represent the greatest pronunciation challenge for NGIZIM 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, NGIZIM has 19 sounds not used in Yao. Native Yao speakers learning NGIZIM 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.