1. Lesson 2
What is Sound Energy?

2. Sound Energy
Sound is a wave of vibrating particles that spread from their source.
The particles in a sound wave move in a pattern.
They get closer together and then move farther apart.
Sounds' loudness can be measured in decibels; more vibration gives a louder sound.

3. Sound Waves
The areas where particles are close together are called crests.
The number of crests that pass a point in one second is the frequency.
Pitch is how high or low a sound is. A sound’s pitch is higher when the sound has a greater frequency.

4. Sound’s Behavior
Sound can move through many different materials, but not a vacuum since there are no particles there.
When sound reaches a border between different materials they can:
Reflect: They can bounce back, which can cause an echo.
Absorb: They can be soaked up and muffled.
Transmitted: They can transfer to another object.
Moving from one material to another changes the speed of a sound wave.
Ex: Sound moves more slowly in air than water.

5. Transfer of Energy
We hear sound as the sound energy transfers from the air to your eardrum, causing it to vibrate.
Sound waves transfer energy from one object to another.
Ex: The kinetic energy of piano keys make the piano’s strings vibrate and creates sound energy. Soundproofing material on the music room’s walls causes the sound to reflect multiple times, which causes vibrations. Eventually thermal energy is created. The sound energy eventually absorbs, which causes the sound to lesson.

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