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Re: [Phys-l] Harmonics vs Overtones



Greetings,

I think there is an important but at times subtle difference between overtones and harmonics. On stringed instruments and organ pipes these two ideas often overlap.

Harmonics are integer multiples of the fundamental, but for a given system these may not be present in the sound produced.

Overtones deal with the sound actually produced. An example, given by Wikipedia, is a drum head in which case the first overtone is 2.4 times the fundamental. Another example is brass horns. Their overtones are shifted a bit higher than the harmonics of the fundamental, because the shorter wavelength sound decouples from the flare of the horn earlier in the flare. (The pressure node of sound wave at the open end organ pipe, is actually just beyond the end of the pipe. When the wavelength of the sound wave becomes comparable with the diameter of the pipe or the part of the flare things get complicated.) This shift of the overtones from the harmonics produces the characteristic "bright" sound of a brass horn.

Sincerely,
Roger Haar