Total harmonic distortion


The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. THD is used to characterize the linearity of audio systems and the power quality of electric power systems. In audio systems, lower THD means the components in a loudspeaker, amplifier or microphone or other equipment produce a more accurate reproduction by reducing harmonics added by electronics and audio media. In power systems, lower THD means reduction in peak currents, heating, emissions, and core loss in motors. When a signal passes through a non-ideal, non-linear device, additional content is added at the harmonics of the original frequencies. THD is a measurement of the extent of that distortion.

Related formulas


THDFTotal harmonic distortion frequency factor (dimensionless)
V2 The RMS voltage of second harmonic (V)
V3 The RMS voltage of third harmonic (V)
V1 The RMS voltage of first harmonic ( for fundamental frequency( (V)