In music, an adjective referring to harmony and its principles. In acoustics, when a vibrating object, such as a string, is set in motion, it vibrates both as a whole, with a frequency called the fundamental, and, with lesser intensity, in sections as well. If these smaller lengths are integer fractions (1/2, 1/3, 1/4, ...) of the total length of the string, their frequencies of oscillation are called harmonics, and are integer multiples of the fundamental.
Other resonating frequencies which are not whole multiples of the fundamental may also be present, and are called partials. Bells, for instance, have many partials in their spectra, more than strings or pipes. It is the presence and relative strengths of harmonics and partials in a spectrum that are largely responsible for the tone quality (timbre) of any sound-producing body.
Note: In some texts, the term ’partial’ refers to both harmonic and inharmonic resonating frequencies. In other words, all harmonics are then partials, but not all partials are harmonics. Overtone is often used to designate both harmonics and partials.
The harmonics generated by a vibrating body, if they are integer multiples of the fundamental, may be represented in an ordered series called the harmonic series. (Source: Barry Truax - Handbook for Acoustic Ecology CD-ROM Edition. Cambridge Street Publishing, 1999 - CSR-CDR 9901)
See also:Frequency, Inharmonic, Noise, Spectrum