Meinl Tuning fork - Schumann 250.56 Hz

The Schumann resonance refers to the phenomenon where electromagnetic waves of certain frequencies form standing waves around the circumference of the Earth. The sufficiently conductive surface of the Earth (mostly saltwater) and the highly conductive ionosphere above it create a spherical cavity resonator, from which possible resonance frequencies can be calculated based on its dimensions. Waves that return to the same phase after circling the Earth (i.e., the Earth's circumference is an integer multiple of the wavelength) are amplified, while others cancel out. This results in a fundamental resonance frequency of approximately 7.8 Hz. This tuning fork translates the Schumann frequency into the audible range through fivefold octave shifting, resulting in a frequency of 250.65 Hz.