What happens to the French word ta when there is a vowel in front of it?

When "ta" is followed by a word which begins with a vowel sound, it is transformed in ton (as if it were masculine instead of feminine). This is done for pronounciation purposes.

Ta maison (no change) but ton histoire (not ta histoire), ton habitude, ton amie, ton élève, ton origine, ...

When there is a vowel in front of "ta", nothing happens; Ex: à ta santé - ou ta voiture.