What this means for learners
TOL and Sundanese share 13 sounds — roughly 46% of Sundanese's inventory overlaps with TOL. 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 Sundanese represent the greatest pronunciation challenge for TOL 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, TOL has 15 sounds not used in Sundanese. Native Sundanese speakers learning TOL 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.