Only in Acehnese 30
What this means for learners
Acehnese and Yao share 25 sounds — roughly 45% of Yao's inventory overlaps with Acehnese. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 24 sounds found only in Yao represent the greatest pronunciation challenge for Acehnese 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, Acehnese has 30 sounds not used in Yao. Native Yao speakers learning Acehnese 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.