What this means for learners
Slovene and Croatian share 29 sounds — roughly 78% of Croatian's inventory overlaps with Slovene. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 7 sounds found only in Croatian represent the greatest pronunciation challenge for Slovene 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, Slovene has 8 sounds not used in Croatian. Native Croatian speakers learning Slovene 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.