Sound Energy and Mediums

In this lesson, students build on their knowledge of forces by exploring how forces can produce a disturbance that causes sound. Students begin by investigating how the volume of sound relates to the amount of energy it has by observing the motion of vibrating sand particles and then test how quickly sound energy moves through solids and liquids.

• Energy can be transferred from place to place by moving objects or through heat, electric currents, or sound.
• Sound is one form of energy that is carried in waves of vibrating molecules.
• A medium is matter that a wave travels through, and it can be a solid, liquid, or gas.

• What are some of the different kinds of evidence that indicate when energy has been transferred from one place to another?
• Why are doctors able to hear their patients’ hearts beating through their bodies?
• What do all sounds have in common?
• How can you make a sound softer?
• What causes one sound to be louder than another sound?
• Why can sound only travel through matter?
• How are the molecules of a solid, liquid, and gas different from one another?
• What is the relationship between sound energy and matter?

Ear : the part of the body that senses sound

Hearing : the brain’s interpretation of information carried by sound waves

Medium :  the matter that waves travel through; can be a solid, liquid, or gas

Sound :  energy that is carried in waves of vibrating molecules

Sound Wave :  a pattern of vibrating molecules caused by the movement of sound through a medium

Vibrate : to move back and forth quickly

Volume : how loud or soft a sound seems; a loud sound carries more energy than a soft sound

Listening to a Heartbeat

Your body is a noisy place. Your heart always beats. It makes a thumping sound. Your lungs always breathe in and out. They make a whooshing sound.

Your doctor can listen to these sounds with a stethoscope. A stethoscope has a part that is shaped like a disc. This part goes on your body over your heart or lungs.

The disc is connected to tubes. These tubes connect the disc to the earpieces. The earpieces go in the doctor’s ears. The sound from your heart or lungs travels through the stethoscope to the doctor’s ears.

Sound is Energy

The doctor hears these sounds because sound moves from one place to another. Sound is energy that is carried in waves by vibrating molecules. To vibrate means to move back and forth quickly.

When your heart beats, it makes the molecules of matter around it vibrate and bump into the molecules closest to them. This passes on the energy and makes them vibrate too. Then those molecules bump into more particles, and so on.

The vibrations travel out in all directions. Molecules stop vibrating once they have passed on the energy. The doctor hears those vibrations through the stethoscope as the sound of your heart.

In this lesson, students investigate how the volume of sound relates to the amount of energy it has by observing the motion of vibrating sand particles. Students then test how quickly sound energy moves through solids and liquids. In the first part, students use a cup covered with tissue paper to test how loud and soft sounds cause matter to vibrate. In the second part, students use a stethoscope and a tuning fork to observe how sound moves through solid and liquid matter. Students use the data from the investigation to construct an explanation about the relationship between a sound’s volume and the amount of energy it has, and about how sound moves differently through solids and liquids.