What this means for learners
Icelandic and Madurese share 20 sounds — roughly 44% of Madurese's inventory overlaps with Icelandic. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 15 sounds found only in Madurese represent the greatest pronunciation challenge for Icelandic 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, Icelandic has 25 sounds not used in Madurese. Native Madurese speakers learning Icelandic 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.