Do Some irregular nouns change their vowel sound to form the plural?

Yes, some irregular nouns change their vowel sound to form the plural. This is often called vowel mutation or umlaut.

Here are some examples:

* Foot - Feet (vowel changes from short "u" to long "ee")

* Tooth - Teeth (vowel changes from short "u" to long "ee")

* Mouse - Mice (vowel changes from short "ou" to long "i")

* Goose - Geese (vowel changes from short "oo" to long "ee")

* Man - Men (vowel changes from short "a" to long "e")

* Woman - Women (vowel changes from short "o" to long "e")

It's important to note that these changes in vowel sound are not always predictable and are based on historical language changes. You'll need to learn these irregular plurals individually.