How Sounds Travel

Sounds are very common in our life. Every single second we hear some sort of a sound, even at night. Sounds can be either soft or loud. Too much of loud sounds can turn into noise. Any kind of sound needs to travel through a medium such as solids, air and liquids. In this lesson, let’s talk about how sounds travel.

How sounds travel?

Sounds travel in a wavy (curly or curvy) way.

What are sound waves?

The way sounds travel through air, solids or liquids.

Sound waves
The way that sound travels

Now we know the way how we can hear sounds.

When something vibrates, sound waves are made and they move the air around them and make the air vibrate. These air vibrations enter our ears which we hear as sound.

E.g. –

1) If you ring a bell, the bell vibrates and makes sound waves. These sound waves make the air around them vibrate too and we can hear the bell is ringing.  

2) Following picture shows us the way how we can hear the sound of a horn.

Sounds travel through ear
 

How we hear the sound of a horn

Features of sound waves

• Sound travels in a wavy way.
• When sound travels very far it becomes weaker. (The further sound waves travel, the weaker they become)

E.g. – You can clearly hear the rumble (a loud continuous noise) of a train when it travels near by, but when it travels further, little by little the sound decreases and cannot be heard clearly. That is why we cannot hear a distant sound.

Different types of sound waves

Tuning Fork

 
A tuning fork is a two-pronged steel device. When struck it vibrates to give a note of specific pitch.

A Tuning Fork

Sound Waves from a Tuning Fork

Flute

A flute is a wind instrument. It is made from a tube with holes. The player covers the holes by the fingers, vertically or horizontally, so that the breath of the player strikes a narrow edge. As a result, a sound is made.
 

A Flute

Sound Waves from a Flute

Violin

A Violin

Sound Waves from a Violin

Piano

A Piano

Sound Waves from a Piano

Singer

A Singer

Sound Waves from a Singer

Thunder and lightning

Can you name a loudest sound we hear?  Thunder

What is thunder?

 
Thunder is the loud sound made by lightning. We hear thunder like an explosion. Lightning causes thunder.

What is lightning?

 
Lightning is a huge electric spark.

In a storm, why we often hear the thunder after we see the flash of lightning that made it?

 
The speed of light is faster than the speed of sound. Therefore in a storm we often see the thunder after we see the flash of lightning.

Sounds travelling through air, solids and liquids

• Sounds travel through air, which is a combination of gases very well
• Sounds travel through liquids such as water very fast
• Best of all, sounds travel  through solids such as metal, stone, glass, brick and wood very well

What is the fastest medium through which sound can travel?

Solids

E.g. – 1) They travel very well along metal pipes.

         2) They travel better through solid ground than through the air.

Underwater sounds

Sounds can be heard well underwater. 

E.g. – 1) A diver can hear the engines of a boat before someone on the surface can.

            2) Whales use sounds called, ‘songs’ to communicate with each other. These whale songs carry many hundreds of kilometres underwater. 

Hearing and space

What is a vacuum?

 
A vacuum is a completely empty space. It has nothing, not even air in it.

Can sounds travel through a completely empty space or a vacuum?

 
No, they cannot. Sounds cannot travel through a completely empty space or a vacuum.

If there is a vacuum between a sound-making object and our ears, we won’t be able to hear the sound.

E.g. – 1) On the moon there is no air. You could talk to people right next to you and they wouldn’t be able to hear you.

2) If you want to talk to someone in space, you have to change sound vibrations to electrical or radio signals.