Total Harmonic Distortion. A measure of all the harmonic distortion components (i.e.,second harmonic, third harmonic,etc.) produced by an audio device, expressed as a percentage of the fundamental signal. Called "total" because it is the sum of all the individual harmonic-distortion components created by the component.

A measurement of the accuracy of an amplifier (or the amplifier section of a receiver). THD refers to the amount of internally generated noise. The lower the number, the better.

Total Harmonic Distortion. A number representing the total amount of distortion or misrepresentation of a sound passing through an amplifier or speaker; how much unwanted coloration the system adds to the original sound.

Total Harmonic Distortion. A term refering to how much distortion is introduced by a device at a given level. Used for rating the noise level of devices.