Lips
Round your lips tightly and push them forward into a small circle, like whistling. Match the strong rounding in the animation.
The vowel in "goose". A long "oo" with lips pushed into a tight circle.
Example words: goose, who, blue, food, school

Round your lips tightly and push them forward into a small circle, like whistling. Match the strong rounding in the animation.
Raise the back of your tongue very high, close to the soft palate. The front of the tongue stays low and out of the way.
Long. Hold it. This is the tense partner of the short "u" in "foot": "fool" stretches with tight lips, "full" is quick and loose.
Mirror check: while holding "oo", your lips should form a small, clearly forward-pushed circle. Then record "fool, full". "Fool" must be visibly and audibly longer and tighter than "full".
Two things go wrong: the rounding is too weak, so the sound turns flat and dull, or the vowel gets clipped short so "pool" sounds like "pull". If your lips aren't working, the vowel isn't either. You should feel them pushed forward.
🔊 plays the app's native voice. 🎤 records you so you can play it back next to it. Your recording stays in your browser.