BrainStuff has the answer to that question in the following video.
Exploratorium offers a related lesson that explains why you think your voice sounds great when you're singing in your shower.
BrainStuff has another related video lesson titled Why Do Men Have Deeper Voices? Through this video students can learn how vocal cords change during puberty and how the length and thickness of vocal cords changes the sound of your voice.
Try a service like Vizia or EDpuzzle to create interactive quizzes based on these video lessons. You can learn more about both of those tools on page 20 of the free Practical Ed Tech Handbook.