Phthalates are another class of chemicals that are often used in deodorants and antiperspirants that you may want to avoid. Phthalates are used in cosmetics, synthetic fragrances, plastics, body care products and medical goods. They help to dissolve other ingredients and to create a better consistency.
A harmonic is a signal or wave whose frequency is an integral (whole-number) multiple of the frequency of some reference signal or wave. The term can also refer to the ratio of the frequency of such a signal or wave to the frequency of the reference signal or wave.
In physics, resonance is a phenomenon in which a vibrating system or external force drives another system to oscillate with greater amplitude at specific frequencies. Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies or resonance frequencies. At resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations, due to the storage of vibrational energy.