Paper cup telephone

We will make a paper cup telephone using two paper cups and a thread (at least 10 meters long). We will work in a group of 4.

                                               
Image 3.1: The end of the thread is passed through a hole and tied to a small ball of paper or a matchstick. This way the paper cup will not tear.

Holding the cups, walk away from each other till the string is stretched taut. Ask your friend to speak softly in one paper cup and listen to it at the other end by putting the second cup on your ear.

Can you hear your friend's voice?
Does your friend's voice change when you listen through the cup?
Can you still hear your friend's voice if the string is not taut?
Can you hear even if the thread is wet?
Is the sound different if you use cups of different sizes?