Sound Waves: Characteristics and Applications · Lesson 4 of 14
Energy of Sound Waves
“Sound waves transfer energy through a medium, allowing them to make other objects vibrate.”
• Explain experimental evidence that sound carries energy. • Describe energy transfer through particle vibration and collisions. • Distinguish energy transfer from particle transport. • Explain the energy conversions in microphones and speakers.
A sound can make a lightweight object move even when the sound source never touches it. This provides a direct clue that a sound wave carries something physically transferable: energy.
Energy of Sound Waves
Activity: Making Grains Move With Sound
Stretch a thin cellophane or rubber sheet tightly over a wide container and sprinkle small grains on it. Produce a loud sound nearby without touching the container. The grains can move or jump because the sound wave reaches the sheet and makes it vibrate.
When the sound source vibrates, it transfers energy to nearby particles of the medium. Those particles vibrate and interact with neighbouring particles. In this way energy is passed through the medium.
This observation supports the statement that sound is a form of energy. It also reinforces the earlier distinction: what is transferred over distance is energy, not a stream of the same air particles leaving the source and arriving at the ear.
Microphones and Speakers
A microphone converts sound energy into electrical energy. Sound waves make a thin membrane called a diaphragm vibrate, and these vibrations are converted into an electrical signal.
A speaker performs the reverse energy conversion. An electrical signal causes a cone or diaphragm to vibrate, producing sound waves in the surrounding air.
Microphone: sound energy → electrical signal. Speaker: electrical signal → mechanical vibration → sound energy.
Quiz
Which statement is a key takeaway from this lesson?
Which additional statement is also a key takeaway from this lesson?
Which further statement is also a key takeaway from this lesson?
Which another statement is also a key takeaway from this lesson?
Which statement correctly applies to the lesson “Energy of Sound Waves”?
Practice Problems
- Why do grains placed on a stretched sheet move when a loud sound is produced nearby?
- What actually travels from a tuning fork toward your ear: the original air particles or energy carried by the wave?
- Describe the energy conversion in a microphone.
- Describe the energy conversion in a speaker.
Key Takeaways
• A sound wave transfers energy from one place to another. • The particles of the medium oscillate but do not travel along with the wave over large distances. • Energy transferred by the wave can make other objects vibrate. • The ability of sound to produce vibrations elsewhere shows that sound carries energy.