overharmonics

Overharmonics are the higher-frequency spectral components of a periodic signal that lie above its fundamental frequency. In a typical periodic sound, the spectrum includes a fundamental at frequency f0 and a series of harmonic partials at integer multiples: 2f0, 3f0, 4f0, and so on. These higher partials are frequently referred to as overtones or harmonics; some authors use the term overharmonics to stress their status as successive higher-order partials beyond the fundamental.

In practice, the presence and relative strength of overharmonics depend on the source and its physical properties. In ideal linear systems producing a pure sine wave, only the fundamental is present. Real-world instruments and signals, however, generate non-sinusoidal waveforms that contain multiple harmonics. Nonlinearities in sound sources, voice production, or electronic processing can also introduce additional overharmonics or alter their amplitudes, sometimes creating non-integer or inharmonic components.

The distribution of overharmonics strongly influences timbre. The relative weights of the partials determine brightness, warmth, and instrument character. For example, steeper decay of higher harmonics yields a mellower sound, while stronger high-order harmonics can produce a brighter or more metallic quality. In audio synthesis and signal analysis, identifying and shaping overharmonics helps control perceived sound color.

Terminology varies by field. While overharmonics are often treated as a subset of harmonics or overtones, some sources distinguish between harmonic partials and non-harmonic content. Regardless, the concept describes the higher-frequency content that accompanies the fundamental in a periodic signal.