Total Harmonic Distortion (THD) is a measurement used to quantify the level of distortion introduced by a device or system when processing or reproducing an audio signal. THD is commonly expressed as a percentage and indicates the proportion of additional harmonics (frequencies that are multiples of the fundamental frequency) introduced by the device or system relative to the original signal.
In the context of audio equipment, such as amplifiers, speakers, and headphones, THD provides insight into how faithfully the equipment reproduces the original audio signal. Lower THD values are generally preferred because they indicate that the equipment is producing less distortion and maintaining the integrity of the audio signal.
THD can be caused by nonlinearities in electronic components, impedance variations, clipping, and other factors. It's important to note that some level of distortion is inherent in all audio systems, and very low levels of THD are often imperceptible to the human ear. However, excessive THD can result in audible artifacts and negatively impact audio quality.
THD is often reported for different harmonic orders, such as THD+N (Total Harmonic Distortion plus Noise), which includes both harmonic distortion and other forms of noise present in the signal.
When comparing audio equipment, especially amplifiers and speakers, it's important to consider THD values, but also take into account other factors such as frequency response, signal-to-noise ratio, and dynamic range. While a low THD value is generally desirable, it's just one aspect of overall audio performance, and a combination of factors contributes to the perception of high-quality sound.
