This easy to make demonstrator can be made 2 ways. Attach a string and swing it in circles or throw to others to show the effect of perceived frequency when objects are moving away or toward you.

Supplies

9v battery holder

6v buzzer

optional supports:

A foam ball

spare piece of foam that can be cut as needed

paper clip

string

Step 1: Initial Assembly

Assemble the battery box and buzzer.

Step 2: Consider Ways to Support the Buzzer

Using some foam, a support can be built for the buzzer with a space to turn it on or off. Alternatively, the foam ball can be cut and the buzzer can be inserted directly into the ball and turned on and off as needed.

To finish, attach a string to a paper clip and slide the paper clip into the foam ball. Or just throw the things around to each other! A fun demo when talking about waves and frequency.