What this means for learners
Sundanese and Bugis share 22 sounds — roughly 85% of Bugis's inventory overlaps with Sundanese. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 3 sounds found only in Bugis represent the greatest pronunciation challenge for Sundanese 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, Sundanese has 4 sounds not used in Bugis. Native Bugis speakers learning Sundanese 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.