Sinusoidal quantity of a frequency that is an integral submultiple of a fundamental frequency.

Even subharmonics are one-half, one-quarter, and so on. Odd subharmonics are one-third, one-fifth, and so on of the fundamental frequency.

They are sometimes called sub-synchronous components.

In the vibration spectrum of a rotating machine, there will normally be a component at the rotational speed along with several harmonics of turning speed. If there is any play in the machine, the spectrum will usually contain sub harmonics. Harmonics of one-half rotational speed are called half orders.

See also: Frequency, Harmonic, Subsynchronous.

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Subjects: Electronics Noise & Vibration