Total Harmonic Distortion (THD)

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Updated2024-06-07
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LabVIEW Sound and Vibration Toolkit
User Manual

To determine the total amount of nonlinear distortion, also known as total harmonic distortion (THD), a system introduces, measure the amplitudes of the harmonics the system introduces relative to the amplitude of the fundamental frequency.

The following equation yields THD:

THD = \frac{\sqrt{A_{2}^{2} + A_{3}^{2} + A_{4}^{2} + \dots}}{A_{1}}

where A₁ is the amplitude of the fundamental frequency, A₂ is the amplitude of the second harmonic, A₃ is the amplitude of the third harmonic, A₄ is the amplitude of the fourth harmonic, and so on.

You usually report the results of a THD measurement in terms of the highest order harmonic present in the measurement, such as THD through the seventh harmonic.

The following equation yields the percentage total harmonic distortion (%THD):

% THD = (100) (\frac{\sqrt{A_{2}^{2} + A_{3}^{2} + A_{4}^{2} + \dots}}{A_{1}})

LabVIEW Sound and Vibration Toolkit User Manual

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Total Harmonic Distortion (THD)

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