Atmospheric Spherics (Fundamental)
Directly measured, standardized, or well-supported in mainstream scientific or technical literature.
The underlying cycle is measurable, but the audible tone is an octave-transposed mapping used for comparison, listening, and practice rather than a naturally audible emission.
Review the evidence modelElectromagnetic atmospheric impulses (spherics) measured by Hans Baumer at Pfaffenhofen/Ilm. The spectral maxima occur at frequencies that are exact octave tones of Earth's rotation. The fundamental spheric at 4150.84 Hz corresponds to the note C (129.71 Hz when octave-shifted down 5 octaves), matching Earth rotation's diatonic tone within 0.73 parts per thousand.
Sources
Used for atmospheric resonances, Earth-ionosphere cavity behavior, and related geophysical frequencies.
W.O. Schumann (1952) and later geophysical literature.