Devoiced Vowels: Why です Sounds Like “des” and 好き Like “ski”
Your textbook romanizes です as desu, but listen to a native speaker and you can barely hear that final u. There’s a name for this disappearing vowel: vowel devoicing (母音の無声化). Once you notice it, your Japanese starts sounding a lot less stiff.
What Devoicing Is
The vowels i and u can lose their voice, meaning your vocal cords stop vibrating, when they sit between two voiceless consonants (k, s, t, h, p) or at the very end of a word after one of them.
Here’s the part learners miss: the vowel isn’t actually deleted. Your mouth still forms it, so the timing stays the same. It’s whispered rather than voiced. That’s why です still feels like two beats to a Japanese ear even when you can hardly hear the u.
Words You Already Mispronounce
When It Happens
Two reliable triggers cover most cases:
- Between two voiceless consonants: the i in 〜した (shita) and the u in 靴 (kutsu) sit between k/s/t/h sounds and go quiet.
- At the end of a word, after a voiceless consonant: the u in です and 〜ます, the i in 〜です sentences spoken quickly.
It’s strongest in standard Tokyo speech. Kansai and some other regions devoice less, so you’ll hear a fuller desu there — both are correct.
How to Use It
- Don’t add a full vowel. Saying “de-SU” or “su-KI” with a strong final vowel is one of the clearest markers of a beginner accent.
- Keep the beat, drop the voice. Whisper the vowel without cutting the timing. です is still two moras.
- Learn it by ear. Shadow native audio for です, ます, and した, plus the “ski / kts” words, until the whisper happens on its own.
Teacher's Note
The romaji is what trips up most of my students. “Desu” on the page tells your mouth to voice that u, so you do. Trust your ears instead. The u is written, and it counts as a beat, but most of the time you’re not supposed to actually hear it.
Hear it the way natives say it
Nihongo Pass plays native audio for every word, so devoiced vowels become second nature instead of a surprise.
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