A flashy experiment using a loudspeaker, tone generator, ferrofluid & food dye-water mixture
Step 1: Loudspeaker
The speaker needs to be able to play low frequences. Discant speakers wont work. I used Logitech computer speaker set with a 4" subwoofer the whole set priced at 30$. Place the speaker pointed upwards.
Step 2: Container
I used a Creme Bonjour creme cheese container, because its diameter is same size range as the speaker. The container needs to sit on the moving part of the speaker and it really helps that the size is similar with respect of the speaker - otherwise the container will move around. On the video I also use a metal lid from a candy box. I prefer the plastic container because it is lighter.
Step 3: Online Tone Generator
There are many tone generators around the net. I have used this one:
The cymatic patterns will show at around 0-300 hz range. Remember that humans won't be able to hear under 20hz.
Step 4: Adding Colored Water
Adding some desired color food dye to water will make the experiment
look even better. Using a syringe is convenient at this step. If you struggle to get the cymatic patterns to appear, there is most likely a problem with the container. It needs to sit gently on the moving part of speaker and balanced well enough. The volume doesn't need to be very loud at all to get the patterns visible. the depth of the water-food dye mixture was approx 1 cm
Step 5: Adding Ferrofluid or Other Type Oil
I used ferrofluid just because it is black - it gives a nice contrast next to colored water. Ferrofluid is just very expensive so you can try with any type of oil that floats on water. When using a mixture of food dyes and water the first drop of ferrofluid spreads out evenly to form a thin layer on the food dye-water mixture after this the second drop will stay together forming a black dot on the liquid. The cymatic surface currents look more distinct when using this second drop of ferrofluid. When done right this experiment looks really hypnotic. When the sound waves are observable, adding the ferrofluid or other oil on liquid will make surface currents visible. You can also try this with music - it will make an innovative and astonishing music video.