What’s Harmonic Distortion?

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Harmonic distortion is the unwanted distortion of a waveform by multiples of an original frequency, causing disruptions in electrical circuits and sound quality. Total harmonic distortion (THD) is used to measure the degree of distortion, and various tools can be used to control it. Technicians need to pay close attention to installation, maintenance, and repair to avoid causing problems.

Harmonic distortion is the distortion of a waveform by unwanted multiples of an original frequency, causing disruptions in the way the waveform behaves in electrical circuits, or sounds, in the case of music and sound waves. Not all multiples, known as harmonics, are bad; for example, the rich and complex sound of musical instruments is the result of harmonics, where they produce sound waves at multiples of their original frequency. In distortion, multiples interrupt the signal and can cause problems.

With electrical circuits, harmonic distortion causes waves to change shape and deform as they move through the system. This results in voltage fluctuations. Sensitive equipment can be damaged by such fluctuations, and if they spike high enough, a system could shut down to protect itself. In music, harmonic distortion can interfere with sound quality, causing something to sound wrong or create a lot of background noise.

There are a number of tools that people can use to control this phenomenon. Building systems with appropriate materials, including items such as wiring that have excellent conductivity, is an important step. Sometimes, people may use a filter to prevent interference and problems with the signal. It may also be possible to make changes to the way the system processes waveforms, and the equipment may require shielding to protect it from interference.

A measurement known as total harmonic distortion (THD) is used to express the degree of distortion that occurs with a single percentage measurement. People want to keep this number low, typically below one percent. High-fidelity stereo systems use a variety of technologies to control the amount of harmonic distortion, keeping it below levels that the human ear can detect. Even a very high quality system will experience some sound wave deformation, but often people are unaware of this because it occurs at a low level.

Measuring harmonic distortion is sometimes difficult. In electrical installations, special equipment is needed to detect unwanted harmonics, while with stereo equipment, sensitive instruments are made specifically for controlling harmonic distortion. Once a technician can identify it, the problem could be very frustrating to fix. Fine-tuning and small adjustments are a key part of the process, as is exploring the possibility of changing equipment or components to see if this gets to the root of the problem. Especially when the equipment is in a highly sensitive environment with low distortion tolerance, technicians need to pay close attention to installation, maintenance and repair to avoid causing problems.




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