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. If a particle of air undergoes 1000 longitudinal vibrations in 2 seconds, then the frequency of the wave would be 500 vibrations per second. A commonly used unit for frequency is the Hertz (abbreviated Hz), where Your N o. 1 Choice for Stone and Pavers. Featuring 15 acres of inventory, Oklahoma Stone features a vast selection of landscaping, paving and building stone, including: Moss rock An increasing series of frequencies emitted from a speaker below a piece of cardboard covered with salt forms this pattern of the oval cross. The frequency of this cymatic pattern is 3,835 hertz. (3) Note the two cymatic symbols of the concentric circles and oval cross combine to form the symbol in the center.