Engineering Hearing Toys

In this lesson, students apply what they know about sound energy to design a toy that can be used to “trick” how their brain determines where a sound originates.

• Hearing is the brain’s interpretation of information carried by sound waves.
• Hearing is closely related to touch because of the relationship between sound and vibrations.
• Humans have two ears to help our brain figure out where sounds are coming from.
• All sound is caused by vibrating molecules.
• Ears are the parts of the body that sense sound. If you are within the range of these vibrating molecules, your ears pick up the vibrations and hear them as sound.

• How is sound related to vibrations?
• How do people hear sounds?
• What would happen to your ability to hear if you covered one of your ears?
• Why do people sometimes cup their hands around their ears?

Misconception: Sound can travel through empty space.

Fact: Sound moves in waves of vibrating molecules, so it cannot travel in empty space, where there are no molecules to pass along the energy.

Misconception: Sounds cannot travel through liquids or solids. 

Fact: Sounds can travel through any medium, which can be solid, liquid, or gas.

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 Music’s Vibrations

Evelyn Glennie is a percussionist. This means she plays musical instruments that are shaken or hit. Drums are percussion instruments.

Evelyn owns more than 1,300 musical instruments. One of these instruments is a set of cut and tuned car exhaust pipes. She has won several awards for her music.

Evelyn is also famous because she is profoundly deaf. This means that she cannot hear speech, but she can hear some sound. Hearing is the brain’s interpretation of information carried by sound waves. Evelyn lost her hearing when she was 12 years old. She didn’t let that stop her. She taught herself to play using the feelings of the vibrations made by different sounds.

How We Hear Sound

Evelyn has said that hearing is a special kind of touch. This is because of the relationship between sound and vibrations.

Remember that as forces transfer energy through a system, they disturb molecules at rest. This causes the molecules to vibrate. As energy is carried in waves of vibrating molecules, it produces sound. Sound travels outward from the source.

If a person who is not deaf is within the range of these vibrating molecules, their ears pick up the vibrations and hear them as sound. Ears are the parts of the body that sense sound. Humans have two ears. We use both ears to help our brain figure out where sounds are coming from. With two ears, we can hear sounds from opposite directions.

If you cup your hand around your ear, you can make some sounds appear louder. This is because you cause more sound waves to move through a smaller area.

Human ears have three parts that work together. Each ear has an outer ear, a middle ear, and an inner ear. The outer ear is the part we can all see. Its job is to collect sounds. When vibrating molecules reach the outer ear, they travel down a tunnel called the ear canal. The ear canal directs the sound waves so they are easier to hear. When the sound waves reach the eardrum, they make the eardrum vibrate.

In this lesson, students use information from a scenario to help them define the main problem facing a toy factory, which needs engineers to design a new toy for children that will trick their brain’s sense of sound. They work in teams to come up with possible solutions to solve the problem. Once they have built a prototype, they carry out a procedure for testing it to see how well it solves the problem. Students use the data and observations from their prototypes to describe how well their prototype solved the problem given the criteria and constraints, how their modifications positively or negatively affected their prototype’s ability to trick the brain, and to decide if they would refine or replicate any of their designs based on the data. Students use the data from their testing to communicate about how well their prototype solved the problem presented in the scenario.