What this means for learners
Catalan and Indonesian share 25 sounds — roughly 64% of Indonesian's inventory overlaps with Catalan. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 6 sounds found only in Indonesian represent the greatest pronunciation challenge for Catalan 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, Catalan has 14 sounds not used in Indonesian. Native Indonesian speakers learning Catalan 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.