Sound is a wave that travels in the air. Is that it? No. There are many interesting facts about sound. Like: Did you know that the speed of sound is faster in solids is produced by rapidly heated air surrounding lightning which expands faster than that in liquids or gases? The speed of sound also is affected by temperature. Dogs can hear at a higher frequency than humans, allowing them to hear sounds that we cannot. The sound of thunder an the speed of sound. The loud noise you create by cracking a whip occurs because the tip is moving so fast it breaks the speed of sound!
So, what did we learn today?
1. Sound can travel through solids.
2. How to use the '2 cans and a string' device.
3. Sound travels in waves.
4. Vibrations can be felt along the string and the cups when we talk.
5. When we paste the tape on the cup, we cannot hear the sounds clearly.
6. If we put 2 different strings together, we cannot hear it.
7. Sound is a type of energy.
8. With an extremely thin string, the receiver is unable to hear the message clearly and vice-versa.
9. With a long string (abt 40 metres), the message is also unclear to the receiver and vice-versa.
What are the best conditions for talking using cups and string?
1. Straight string
2. Short string
3. Loud voice
4. Must hold the cup
5. Tape the knot to the cup.
How does this work?
When one person talks into his/her cup, the bottom of the cup vibrates back and forth with the sound waves. The vibrations travel through the string by pulling the string back and forth. Therefore, the bottom of the second cup should start to vibrate back and forth just like the bottom of the first cup is vibrating, producing sound waves. The second person can hear the sound waves and can therefore hear what the first person says.
