What this means for learners
Goajiro and Japanese share 27 sounds — roughly 59% of Japanese's inventory overlaps with Goajiro. 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 Japanese represent the greatest pronunciation challenge for Goajiro 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, Goajiro has 19 sounds not used in Japanese. Native Japanese speakers learning Goajiro 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.