who pitch is high

Dear Student

Pitch depends on the frequency of vibration of the waves.
If the frequency of vibration is higher, we say that the sound is shrill and has a high pitch. On the other hand, if the sound is said to have a lower pitch then it has a lower frequency of vibration.
The vocal folds produce sound when they come together and then vibrate as air passes through them during exhalation of air from the lungs. This vibration produces the sound wave for our voice. The muscles of the larynx change the elasticity and tension of the vocal folds to determine the pitch of the sound.
So sound produced by Bubbly depends how quickly her vocal cords are vibrating.
When vocal cords vibrate more quickly then she produce a higher pitch,
Regards