Aspects of the topic frequency ratio are discussed in the following places at Britannica.
Assorted References
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dynamic range of the ear (in sound (physics): Dynamic range of the ear)
...100 and 200 hertz sounds the same as that between 1,000 and 2,000 hertz or between 5,000 and 10,000 hertz. In other words, the tuning of musical scales and musical intervals is associated with frequency ratios rather than absolute frequency differences in hertz. As a result of this empirical observation that all octaves sound the same to the ear, each frequency interval equivalent to an...
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musical tuning and temperament (in tuning and temperament (music))
Two concepts fundamental to the theory of tuning are those of frequency ratio and of consonance and dissonance. A given musical pitch is determined by the frequency of vibration of the sound wave that produces it, as a′ = 440 cycles per second. An interval, or distance between two pitches, can thus be mathematically described as the ratio of the frequency of the first pitch to the...
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organ tone production (in keyboard instrument (music): Reed pipes)
...closing the opening. Immediately, the elasticity of the brass asserts itself, and the tongue reverts to its curved shape, thus uncovering the opening. This process is repeated rapidly. The frequency of the pulsations of air that enter the shallot is determined by the effective length of the reed and, in turn, determines the pitch of the note. Thence, the pulsations pass out into the...
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overtone series (in musical sound: Tone)
...thus creating partial wave forms in addition to the fundamental wave form. These partials are not fortuitous. They bear harmonic relationships to the fundamental motion that are expressible as frequency ratios of 1:2, 3:4, etc. This means that the reed (or string or air column as well) is vibrating in halves and thirds and fourths as well as a whole. Another way of expressing this is that...