Cymatics
Cymatics is the science of observing the effects of sound and frequency on matter, usually in the form of liquid or powder. The term was coined by Swiss scientist Hans Jenny, who used specialized equipment that allowed a viewer to observe shapes formed in a medium under the influence of sound wave frequencies.
Each Solfeggio frequency contains “nodes” and “antinodes” representing the peaks and valleys of visible standing sound waves, representing their fluctuating amplitude.