Simple Explanation

The percentage of distortion added to the original signal, caused by harmonics produced by the audio equipment. Lower THD means clearer, more accurate sound reproduction.

Concise Technical Definition

Total Harmonic Distortion (THD) is the ratio of the sum of the powers of all harmonic components (frequencies that are multiples of the fundamental frequency) to the power of the fundamental frequency itself. THD is a measure of how much distortion is added to the original signal by an audio device. A lower THD indicates a cleaner, more accurate reproduction of sound. THD is commonly used to assess the quality of audio equipment, and lower THD values generally correlate with better sound fidelity.

Layman-Friendly Analogy

Imagine you’re listening to music, and there’s a slight buzzing or "fuzziness" that wasn’t in the original recording. That unwanted "fuzz" is caused by harmonic distortion. The less of this distortion, the clearer and more faithful the sound will be to the original music. Think of it as a photograph: the sharper and more detailed the image, the more accurate it is. Similarly, a lower THD results in a "sharper" or cleaner sound.

Industry Usage Summary

THD is a widely used metric in audio equipment testing and comparison. Audio engineers, manufacturers, and audiophiles use THD measurements to evaluate the performance of components like amplifiers, speakers, and digital devices. A lower THD value indicates that a device produces sound that is closer to the original recording, making it a key factor in high-fidelity systems. THD measurements are especially important when assessing the linearity and quality of audio devices, with values often measured across a frequency range of 20 Hz to 20 kHz to provide a comprehensive picture of the device's distortion characteristics. High-end audio products typically strive for very low THD values to ensure maximum sound accuracy and clarity.

Engineering Shortcut

A measure of the distortion added to the audio signal, where a lower THD indicates clearer and more accurate sound reproduction.

Full Technical Explanation

Total Harmonic Distortion (THD) is a key measure in audio testing, quantifying the distortion introduced by a device when processing a signal. It is defined as the ratio of the sum of the powers of all harmonic components (multiples of the fundamental frequency) to the power of the fundamental frequency itself. THD is typically expressed as a percentage or a ratio, with lower values indicating less distortion. The THD+N measurement includes noise in addition to harmonic distortion, providing a more complete assessment of the device’s performance. To measure THD, a sine wave of known harmonic purity is passed through the device under test. The output signal is then compared with the original signal after filtering out the test frequency, leaving only the distortion and noise components. The results are displayed using a true RMS voltmeter, and THD can be measured across frequencies to evaluate a device’s performance over a broad range of audio signals. The goal is to minimize distortion for the most accurate and transparent sound reproduction.