Leo and Nina were sitting in the grass behind the house, the sun warming their backs pleasantly. Bees buzzed around them, and the air smelled of freshly cut grass. They had a big plan for today. In front of them lay two empty yogurt cups and a long, long ball of thin string.
"Do you think it will work?" Nina asked, eyeing the cup with distrust. It looked so ordinary.
"Of course!" Leo replied, his voice full of confidence. "I saw it in a very clever book. It said we can make our own telephone. A completely real one."
The first step was to make the holes. "Wait, we need help with this," Leo said responsibly. "The string is soft, but the cup is hard." He called out to his dad, who was watering the tomatoes in the garden. Dad came over, smiled at their invention, and carefully used the tip of his scissors to make small holes right in the center of the bottom of both cups.
"Thank you!" they shouted in unison.
Now it was time for the string. Leo unrolled a very long piece so they could stand far apart from each other. He threaded one end through the hole in Nina's cup and tied a firm knot in it so it wouldn't slip out. Nina did the same on the other end with Leo's cup. Done! It looked strange. Two cups connected by a long white thread.
"Right, I'm going over to that apple tree, and you stay here," Leo commanded, running off with his cup in hand. The string unspooled cheerfully behind him across the grass. When he was far enough away, he shouted, "Now!"
Nina put the cup to her ear. Leo put his to his mouth and whispered something. But Nina heard nothing. Only the quiet rustle of the wind.
"I can't hear anything!" she shouted to him, disappointed. The string lay between them in the grass, coiled like a lazy snake.
Leo thought for a moment. He scratched his head. "Wait! The book said something else... Ah! I know!" he called out. "The string has to be tight! Completely straight!"
They both took a few steps back until the string between them was stretched as taut as a guitar string. It looked much better.
"Let's try again," Nina suggested, holding the cup tightly to her ear. She could feel its thin plastic touching her cheek.
Leo cleared his throat, put his cup to his mouth, and whispered very quietly, "Nina, can you hear me?"
Nina gasped. She heard it! She heard it as clearly as if Leo were standing right beside her, whispering in her ear. It was a thin, slightly funny, but perfectly clear voice. "Yes! I can hear you!" she burst out with joy into her cup.
On the other end, Leo jumped. "It works! It really works!" His voice traveled along the taut string straight to Nina's ear. They exchanged a few more secret messages. About the big ant Leo saw crawling up the tree, and about the beautiful butterfly that had just landed on a flower near Nina. They laughed, thrilled.
"But... how is that possible?" Nina wondered when they met again in the middle of the garden. "There are no batteries, no wires. Just an ordinary string. It's like some kind of magic."
Just as she finished speaking, the taut string they were still holding trembled gently. And right in the middle of it, something tiny and shimmering like a dewdrop appeared. Gradually, it took shape. It was a tiny little man, no bigger than a thumb, dressed in a cobweb coat and a bellflower cap.
The children were so surprised they couldn't even breathe.
"Magic? Not at all!" came a thin, tinkling voice. "It's not magic, it's me! Well... a little bit me. I'm Tinkle, the sound sprite. And I live wherever things vibrate."
Leo and Nina stared at him with their mouths open.
The sprite Tinkle sat on the string as if on a swing and dangled his feet merrily. "Your voice isn't magic. Your voice is vibration. That's a clever word for shaking."
"Shaking?" Nina repeated quietly.
"Exactly!" the sprite agreed. "Try putting a hand on your throat and saying a long Mmmmmmm."
The children obeyed. They immediately felt a gentle buzzing under their fingers. "Wow!"
"See? Your voice makes everything vibrate. When you speak, the air around you vibrates, and those little waves of vibration travel to other people's ears. But the air is a bit lazy and can't carry them very far on a long journey," Tinkle explained, hopping along the string.
"And when you speak into the cup," he continued, pointing to Leo's telephone, "you make the bottom of it vibrate. That shaking, that vibration, then jumps onto this taut string. And it travels along it like a speedy little messenger. Much faster than through the air!"
Tinkle ran along the string to Nina's cup. "When the vibration arrives here, it makes the bottom of this second cup vibrate. And that cup turns it back into the sound you hear in your ear." He finished his lecture and smiled proudly.
Leo looked at it with completely new eyes. "So my voice actually travels like a wave along the string?"
"Exactly! It's like a little sound highway. But it only works if it's taut. If the string is lying on the ground, the vibration gets lost in the grass and doesn't get anywhere," the sprite explained. "And I'll show you something else. Nina, say something into your cup now. And you, Leo, gently touch the string in the middle with your finger."
Nina put the cup to her mouth and said, "Testing, testing, one, two, three..."
Leo, who had the cup to his ear, suddenly heard only "Testing, tes..." and then silence. As soon as his finger touched the vibrating string, the sound stopped instantly.
"Why?" he asked in surprise.
"Because you stopped the waves. Your finger absorbed all that vibration, and nothing more got through," Tinkle laughed. "Sound is very sensitive."
The children were amazed. It wasn't magic anymore; it was something much more interesting. It was science they could hold in their own hands. They thanked the sprite Tinkle for the wonderful explanation. He just waved his bellflower cap at them and, with a soft tinkle, disappeared.
Leo and Nina played with their cup-and-string telephone for a long time afterward. They tried to see what the longest string that would still work was and tested whether the sound could travel around the corner of the house. They discovered that if the string touched the wall, the sound became weaker. It was the best invention in the world. Not only was it fun, but it had also taught them the secret of how a voice can travel.
And what about you, children? Will you try to make a cup-and-string telephone like this with your parents' help? It's great fun, and you might even meet a little sound sprite while you're at it.