Only in Acehnese 42
What this means for learners
Acehnese and Garo share 13 sounds — roughly 24% of Garo'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 13 sounds found only in Garo 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 42 sounds not used in Garo. Native Garo 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.