What this means for learners
Finnish and Ket share 15 sounds — roughly 36% of Ket's inventory overlaps with Finnish. Shared sounds are ones a speaker already knows from their native language and will generally produce and perceive accurately without explicit training.
The 17 sounds found only in Ket represent the greatest pronunciation challenge for Finnish 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, Finnish has 27 sounds not used in Ket. Native Ket speakers learning Finnish 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.