Enlarge the experimental kit sound boosters with the addition of test frequency patterns:

This app can be generated, as with music much more uniform pattern. All you need is the same experimental setup as in the experiment "sound make visible" from the manual.

Just connect your smartphone or tablet to the sound booster, fire up the app and press the button in the app "On". You can adjust the volume with the controls and the frequency. The frequency can be quite accurately by entering the numbers set.

Can you find a frequency at which to start the grains of sand or water droplets to dance?