Sound is all about vibrations

This term it is the senior classes turn to investigate sound.

In our first lesson we found out that sound is a form of energy that travels as a sound wave which makes a vibration.

We hear the sound when the sound wave reaches our ears.

Diagram from Kids' Health

The sound wave enters the ear and causes the ear drum to vibrate. The sound vibration is passed onto 3 tiny bones called the hammer, anvil and stirrup which pass the sound into the cochlea where the vibrations are turned into a signal that goes to the brain. The brain then works out what the sounds are and where they are coming from.

The investigations we did helped us to see and feel vibrations made by sound waves.

In this investigation we had to talk through the cardboard megaphone at the salt on top of a gladwrapped bowl. We observed that the salt moved around and sometimes jumped. The explanation for this is that the sound waves coming through the megaphone make a vibration that is passed onto the gladwrap. As the gladwrap vibrates the salt moves. When we talked quietly the salt hardly moved but when we talked loudly the salt jumped a lot. This is because loud noises create strong vibrations and quiet noises create weak vibrations.

During this investigation we used a tuning fork. When a tuning fork is hit it starts to vibrate and makes a ringing sound. We were able to see the vibrations by gently touching the tuning for on the water. When we did this the vibrations made ripples in the water and sometimes the water splashed out too.

When you talk at a balloon you can feel the vibrations made by the sound wave. Your fingers that hold the balloon start to vibrate and tickle a bit.

We could also feel the vibrations from the sound wave when we hummed against a piece of paper on a comb. Our lips went all tingly and it felt strange. We also discovered that we could make some pretty cool sounds (especially Mr Mills).