Why Does the Coat Hanger Sound So Different?

When you tap the metal coat hanger, it vibrates.

Those vibrations can travel through the air to your ears as sound. But as the sound spreads through the air, it becomes weaker. From a distance, you usually hear only a small clunk.

Add the string, though, and something surprising happens.

What Does the String Do?

When the hanger vibrates, it makes the attached string vibrate too.

The vibrations travel along the stretched string, through your fingers and towards your ears.

Instead of relying only on sound travelling through the air, you have created a new pathway for the vibrations to travel.

That is why the hanger suddenly sounds much louder and richer.

Why Does It Sound Like a Bell?

A metal coat hanger doesn't just vibrate in one tiny spot.

After you strike it, vibrations move through the metal and continue for a short time. These vibrations produce the ringing, bell-like sound you hear.

Different parts of the hanger can vibrate in different ways, which helps create its surprising mixture of sounds.

Scientists Say...

Sound begins with vibrations.

Those vibrations can travel through different materials — including gases, liquids and solids.

In this investigation, the same vibrating coat hanger can reach your ears by different pathways:

Through the air → your ears

or

Coat hanger → string → your fingers → your ears

Changing the pathway changes what you hear.

Think Like a Scientist

What else could affect the sound?

Try changing one thing at a time:

• the length of the string

• the type of string

• where you tap the hanger

• the material the hanger is made from

Can you discover which change makes the biggest difference?