Demonstration of the Doppler Effect.

There are primarily two ways to do this demo (see this Pasco page for the instruction manual). I start by holding the 'football' stationary in my hand, then flipping on the switch so that students hear the annoying tone at a constant frequency. Then choose one of the following motions:

1. If your classroom is large enough, have two people hold each pair of handles, and stand so as to take up the slack in the cord. With the football at one end, flip the switch to turn it on and have that person separate their hands quickly to send the football down the cord. Students will hear a change of frequency as the football approaches and recedes.
2. I have found that the Astro lab isn't large enough to do the demo effectively this way, so I put the football roughly in the middle, grasp the four cords with one hand and swing the football in a circular motion above my head. Point out that students hear the frequency increase/decrease as the football approaches/recedes from them in a circular orbit. You just need to make sure you have enough clearance, Clarance.

As a final demo, with the sound still on I'll wave the football back and forth towards groups of students. As you go around the room doing this, students will realize they hear the difference in frequencies most dramatically when the football is moving directly at them.

Now turn the damn thing off before you have a mutiny on your hands.

LDL-C2. Everything is kept in a white box (pic below). Try not to tangle the cords too much.