Explanation

When making the [u] sound, your lips form a tight round shape. They push forward like you are about to whistle. This is called lip rounding.

Try saying [u] and watch your lips in a mirror. They make a small circle. This rounding helps create the specific [u] sound.

Lip shape affects vowel sounds. Round lips make back vowels like [u] and [o]. Spread lips make front vowels like [i] and [e].