What this means for learners
FASU and Auyana share 11 sounds — roughly 52% of Auyana's inventory overlaps with FASU. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 9 sounds found only in Auyana represent the greatest pronunciation challenge for FASU 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, FASU has 10 sounds not used in Auyana. Native Auyana speakers learning FASU 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.