Japanese · Pronunciation Guide
A single quick beat: a dental d and a pure short e, with no glide toward "day."
de
One mora, no accent, fused to the preceding noun. Like every particle it borrows its pitch from the phrase around it; on its own it has no melody worth describing. What it does have is a fixed, short duration that shouldn't stretch even when the sentence slows down.
Listen: で
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家で仕事をします。
Ie de shigoto o shimasu.
I work at home.
Listen: 家で仕事をします。
Free browser voice. Hear it read by a real native speaker inside the LingoDrop app.
家で仕事をします opens with 家 (i-e), two vowels in a row that must each get a beat, then で attaches directly to it. So the phrase 家で is three morae, i-e-de, said as one smooth run. English speakers routinely fuse i and e into a single "yay" sound and lose a count before the particle even arrives.
The vowel is where this goes wrong: "day" instead of "deh." English e in an open syllable almost always diphthongises, so learners import that automatically. Freeze the tongue for the duration of the vowel. The second issue is stress — treating で like an emphasised English preposition. It's a clitic; keep it short, flat and attached.