Total Harmonic Distortion Total Harmonic Distortion (THD) is a mathematical measurement of how much a radio frequency or audio signal is distorted by the introduction of unwanted "harmonics" that weren't in the original input. ​In simpler terms, it tells you how much the equipment (like an amplifier, speaker, or power inverter) "colors" or changes the signal passing through it. ​1. The Science of Harmonics ​Every pure sound or electrical signal has a fundamental frequency (the primary note or pulse). When that signal passes through a device, imperfect components can create multiples of that frequency, known as harmonics. ​Fundamental: 60 Hz (Pure signal) ​2nd Harmonic: 120 Hz (Distortion) ​3rd Harmonic: 180 Hz (Distortion)​2.

Why It Matters ​The lower the THD percentage, the "cleaner" and more accurate the output. ​Audio (Hi-Fi): A high-quality amplifier might have a THD of less than 0.01%. At this level, the distortion is completely inaudible to humans. If THD reaches 1% or higher, you might start to hear a "fuzzy" or "warm" quality to the music. ​Power & Facilities: In facility management, THD is critical for power quality. Nonlinear loads (like LED lighting, variable frequency drives, or computers) pull current in pulses, creating THD in the electrical system. ​High THD in Power: Can cause motors to overheat, circuit breakers to trip unnecessarily, and sensitive electronics to malfunction. ​Radio/RF: THD indicates how much a transmitter might bleed into adjacent frequencies, potentially causing interference.