opera by mozart(????) soprano voice?

Today in my music class we listened to an example of a soprano voice. Our professor played a clip from what I think she said was an opera by (I think, I could be wrong) Mozart. I wanted to know the name of the opera, one part, the soprano singer wasn't really singing, just making noises.

I'm sorry I can't be of more help, but if this sounds at all familiar, just post the name and I'll look it up to see if it's the one I want.

Thank you.