Sound and Pitch – Glass Bottle Xylophone

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Learn how to make a glass bottle xylophone and observe how the pitch changes when the bottles are struck with a metal spoon.

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What Causes Sounds?
We hear and make sounds all the time. We make sounds when we talk, clap or play a musical instrument. Objects like cars, sirens, phones and televisions make sound too.

Sound is a form of energy we can hear. All sounds are made when something vibrates. Vibrations are rapid back and forth movements.

When a bow is pulled across the strings of a violin, the strings vibrate and make sound. The vibrating strings cause the air around them to vibrate too. This creates sound waves. You hear the sound when the sound waves travel through the air to your ears.

Describing Sounds
We can describe the sounds we hear in different ways. One way to describe a sound is by its volume. Volume is how loud or soft a sound is.

The sound of an airplane jet engine and the sound of thunder are examples of loud sounds. The rustle of leaves and a whisper are examples of soft sounds.

A loud sound has more energy than a soft sound. Hitting a drum with a large force creates larger vibrations and a louder sound than if it were hit with a smaller force.

Compare the sound of a rooster crowing to that of a lion’s roar. The volume of the sounds are similar – they are both loud sounds. However, they are different in pitch. Pitch is how high or low a sound is.

The crow of a rooster is a high-pitched sound. The roar of a lion is a low-pitched sound.

The faster an object vibrates, the higher the pitch of the sound. The length and thickness of the vibrating object also affects its pitch. You can see this by making different sounds on a guitar. A thin, short string produces a much higher-pitched sound than a longer, thicker string.