This activity takes a look at a simple toy, called a sound tube. I've also seen them called noise tubes, or gravity tubes. They aren't hard to find online, but I can sometimes find them for much cheaper at our local Dollar Store/Tree, etc.
The idea is that the students will investigate what makes this simple kid's toy work. What's really happening when you spin it that causes it to make sound. This can be used to explain concepts such as sound (vibrations), frequency (the faster air moves through the tube, the higher the frequency (pitch)), or even air pressure (the faster moving end of the tube is a LOW pressure zone, and the end held in your hand is a HIGH pressure zone).
I have a few basic questions for students to address as they "experiment" with the toy. These questions can easily be expanded, made of a higher level, etc. to match the needs of your class.
I've included a basic explanation video as well, either for student, or teacher use.