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Seeing the Speed of Sound

Diana Hall, Bell High School, Nepean, Ontario

This demonstration allows students to get an idea for how slow sound actually travels. Read More...

Pressure vs. Particle Movement — The Dance

Diana Hall, Bell High School, Nepean

When discussing standing waves in air columns most textbooks focus on the movement of particles and show nodes at closed ends and antinodes at open ends. When thinking about the loudness of sound we have to remember that the sound is loud when the pressure difference is the greatest and that sound is a longitudinal wave. This occurs at nodes (where particles move the leave) and not the antinodes (where particles move the most). I use my students to demonstrate this difference. Read More...

Superposition Principle-Kicking the Canister

Diana Hall, St. Charles North HS, Illinois

My students have fun predicting which canisters will get knocked down in an interference demonstration. We stretch out a long spring across the classroom floor. We then line up film canisters (or other substitutions) alongside the spring. Students predict which ones will get knocked over and which will be left standing. They must also say why. Read More...

Acoustical Wheel with Christmas Tree Balls

Christian Ucke, Technical University Munich

Figure 1 was taken from an old German physics textbook1 dating from 1906. So-called Helmholtz-resonators are fixed on a cross which can rotate easily on a needle bearing. With the right resonance frequency of the Helmholtz-resonators and enough acoustical power from a loudspeaker, this device starts to rotate anticlockwise (view from above). Read More...
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