CAN A GIRL ANSWER THIS? WHAT WAS THE JOKE?

A girl was secretly hosting a party. Her mom came home early. The girl told the band to hide in the closet. The mom entered the house, but one of the band members accidentally played a tuba noise from the closet. The following dialogue happened:

Mom: What was that noise?
Girl: Excuse me.

What was the joke? Why did she say "excuse me" when the mom asked about the tuba noise?