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Discovering how all sounds are created by tiny back-and-forth movements called vibrations.
Have you ever touched a speaker while music was playing and felt it 'buzz'? Or noticed how a guitar string looks blurry when you pluck it? That buzz and blur are the secrets to every sound you've ever heard!
Sound is a type of energy. It isn't something you can grab with your hands, but you can definitely hear it with your ears! Sound happens when something moves back and forth very, very fast. This fast back-and-forth movement is called a vibration. If there are no vibrations, there is no sound. Think of a drum: when you hit it, the skin of the drum shakes up and down. That shaking pushes the air around it, creating sound waves that travel all the way to your ears. Even your own voice starts with vibrations in your throat!
Quick Check
What is the name for the fast back-and-forth movement that creates sound?
Answer
Vibration
You can see vibrations in action with a simple ruler! 1. Hold one end of a plastic ruler firmly on the edge of a desk. 2. Let the other half of the ruler hang off the edge. 3. Use your other hand to push down on the hanging end and let go! 4. Watch the ruler move up and down so fast it looks blurry. Listen to the 'boing' sound it makes. The blurry movement is the vibration creating the sound energy.
Every musical instrument has a special part that vibrates to make its unique sound. In a string instrument like a guitar or violin, the strings vibrate when you pluck them. In a wind instrument like a flute or trumpet, the air inside the tube vibrates. In percussion instruments like a xylophone or a drum, the surface vibrates when you hit it with a mallet. Even when you speak, your vocal cords (tiny muscles in your throat) vibrate to turn your breath into words!
Quick Check
If you hum a low note and touch your neck, what do you feel?
Answer
You feel vibrations (or a buzzing sensation) from your vocal cords.
Let's explore how changing a vibration changes the sound. 1. Stretch a rubber band between your thumb and pointer finger. 2. Pluck the rubber band and listen to the sound. 3. Now, stretch the rubber band much tighter and pluck it again. 4. You will notice the sound is higher! This is because the rubber band is vibrating faster. The more you put into the pluck, the louder the vibration will be.
Vibrations don't just stay in one place. They travel through things! Most of the time, sound travels through the air, but it can also travel through water or solid objects like a wooden door. Imagine a line of dominoes. When the first one falls (the vibration), it hits the next one, and the energy moves down the line. Sound waves work the same way by bumping into tiny particles in the air until they reach your ear. This is why you can hear someone calling your name from across a playground!
This experiment shows how vibrations travel through solids better than air! 1. Poke a tiny hole in the bottom of two paper cups. 2. Thread a long piece of string (about 10 feet) through the holes and tie a knot inside each cup. 3. Stand far apart until the string is tight (). 4. Have a friend whisper into one cup while you hold the other to your ear. 5. The vibration of their voice travels through the string as and turns back into sound in your cup!
What must happen for a sound to be made?
Which part of a guitar vibrates to create sound?
Sound can only travel through the air.
Review Tomorrow
In 24 hours, try to explain to a friend or family member what a 'vibration' is and give one example of something that vibrates.
Practice Activity
Go on a 'Sound Hunt' around your house. Find three different objects that make noise and try to touch them (carefully!) to feel the vibration.