Fundamentals
Sound, Frequency, and Biology
How sound waves interact with biological tissue, and why specific frequencies produce therapeutic effects.
Sound is a mechanical wave, molecules compressing and rarefying through a medium. Every sound has frequency (Hz), amplitude (loudness), and timbre (tonal quality).
When sound waves reach biological tissue they create micro-vibrations at the cellular level. This is mechanotransduction: mechanical stimuli converting to biochemical signals. Cells respond to specific frequencies by altering gene expression, protein synthesis, and metabolism.
Every physical structure has a natural resonant frequency. When an external tone matches it, energy transfer is maximized, that's where therapeutic potential lives.
Hearing range matters. Humans hear from ~20 Hz to ~20,000 Hz. Dogs hear from ~40 Hz to ~60,000 Hz. Cats hear from ~40 Hz to ~85,000 Hz. Our pets perceive harmonic content we can't, which is why frequency selection for animals is its own discipline.
Wavelength matters too. Lower frequencies have longer wavelengths and penetrate deeper. A 20 Hz wave is ~17 meters long in air; a 1 kHz wave is ~34 cm. That's why sub-bass frequencies are felt throughout the body, not just heard, they reach deep tissue and organs.