Energy released as sound waves

Sound is a type of energy made by vibrations. When any object vibrates, it causes movement in the air particles. These particles bump into other particles close to them, which makes them vibrate too, causing them to bump into more air particles. This movement, called sound waves, keeps going on, until they run out of energy. If your ear is within range of the vibrations, you hear the sound.

Picture a stone thrown into a still body of water. The rings of waves expand indefinitely. The same is true with sound. Irregular repeating sound waves create noise, while regular repeating waves produce musical notes. When the vibrations are fast, you hear a high note. When the vibrations are slow, it creates a low note.

Sound can travel under the water. It moves four times faster through water than through the air. It can travel such long distances that whales can hear each other when they are nearly a hundred miles apart. There is no sound on the moon or in space. Sound needs something to travel through, like air or water. Sound travels through air at 340 metres per second.

How do wind instruments make sound?

In wind instruments, like the flute and trumpet, vibrating air makes the sound. The air particles move back and forth, creating sound waves. Blowing across a flute's blow hole sets up smooth waves in the tube.

In the clarinet, a vibrating reed (a thin piece of wood set in the mouthpiece) gets the waves started. Different pitches are played by pressing keys that open or close holes in the tube, making the air column inside the tube longer or shorter. Longer air columns produce lower pitches.

How do string instruments make sound?

Stringed instruments are played by pressing the fingers down on the strings. This pressure changes the strings' length, causing them to vibrate at different frequencies and making different sounds. Shortening a string makes it sound higher. Strings produce different sounds depending on their thickness.

Science vocabulary

Respiration - Using oxygen to turn food into energy
Dissolve - This is when a solid mixes into a liquid and leaves a new liquid
Carbohydrate - Food that gives the body energy
Approximation - A guess about the size or amount of a number or group of things
Area - The space covered by a shape
Weight - The measurement of the force of gravity on an object
Width - The shorter side of a quadrilateral (geometrical figure with four sides)

Now, let us do an experiment on sound:

Making water chimes

Materials needed
Eight glasses
Teaspoons
Water

Directions

* Line up eight glasses of about the same size and shape.

* Fill the first glass about 1/8 full of water for the high note; the second glass should be 1/4 full; the third glass should be 3/8 full for the next note, and so on.

* Each glass should sound like a note on the music scale (do, re, mi, fa, sol, la, ti, do). You may need to tune your music scale (add or remove water with a teaspoon) until each note rings true.

* Use a metal teaspoon to gently tap out the scale and any other melodies you know.

Hints for water chimes

* Do not use expensive crystal glasses to make water chimes.

* Add a bit of food colouring to help children identify which glass is which sound.

* Changing the amount of water will change the musical note. The amount of water in the glass changes the pitch of the sound wave. Can you use the notes to play a simple tune?

Compiled by Janani Amarasekara