Cymatics is the study of visible sound and vibration. This is usually evident on the vibrated surface of a plate, diaphragm, or membrane. A thin layer of sand or salt particles, paste, or liquid reveals symmetrical patterns in regions of maximum and minimum displacement. Different patterns emerge on the surface depending on the shape of the surface and the frequency that is produced.
When sand is placed onto the membrane to show these distortions, it is displaced by the vibrational peaks and troughs, causing it to settle along the nodal lines, areas with no movement. The image on the bottom right is a negative of the wave shape moving through the plate as the sand congregates where the wave is absent, thus revealing these striking patterns. When water is used, the same phenomenon causes its surface to displace, and finer patterns occur if the frequency is increased.
Waves are periodic (regular and repeating) disturbances that transport energy, not matter, through a medium. This sinusoidal vibration, based on the graph y = sin(x) where y is position and x is time, follows a pattern of crests and troughs with an intermediary equilibrium or resting position in-between.
The period of a wave is equal to the mathematical reciprocal of its frequency (period = 1 / frequency, measured in seconds per cycle). This is the time for the wave to complete a cycle of crests and troughs.
The frequency of a wave is equal to the mathematical reciprocal of its period (frequency = 1 / period, measured in cycles per second). This is the number of cycles completed per second.
Sound can be categorised as three different types of waves: mechanical, longitudinal, and pressure.
A mechanical wave disturbs a medium through particle-to-particle interaction. The motion of particle vibration in a longitudinal wave is parallel to the direction in which energy is being transported. Lastly, a pressure wave consists of the repetition of compressions (high-pressure areas or a wave’s crest) and rarefactions (low-pressure areas or a wave’s trough) of a pressure wave through a medium in a pattern.
Wavelength is the distance travelled by the wave over one period, or one complete cycle. It is measured from compression to compression, or rarefaction to rarefaction. The period of a sound wave is the time between successive compressions or rarefactions.
The frequency of a sound wave is measured in Hertz with one Hertz equal to one vibration per second. High frequencies have small periods and short wavelengths whilst low frequencies have large periods and long wavelengths. Pitch is our perception or sensation of frequency.
“The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium. The frequency of a wave is measured as the number of complete back-and-forth vibrations of a particle of the medium per unit of time” (Henderson, 2014).
Humans can hear anything from 20 Hz to 20,000 Hz. Anything below this range is called infrasound, and anything above this range is called ultrasound.
References
Henderson, T. (2014). Sound. Physics Classroom. Retrieved February 10, 2014,
from http://www.physicsclassroom.com/class/waves/
Henderson, T. (2014). Waves. Physics Classroom. Retrieved February 10, 2014,
from http://www.physicsclassroom.com/class/waves/