Thd N Calculator

Total Harmonic Distortion and Noise (THD-N) is a key metric in audio and signal analysis that measures the quality of a signal by quantifying both harmonic distortion and noise. This calculator helps you compute THD-N from your signal measurements.

What is THD-N?

THD-N stands for Total Harmonic Distortion and Noise. It combines two important measurements of signal quality:

Total Harmonic Distortion (THD): Measures the unwanted harmonic frequencies generated by nonlinear components in a system.
Noise (N): Measures random variations in the signal that aren't part of the original signal.

THD-N is expressed as a percentage of the total signal power. Lower values indicate better signal quality.

In professional audio systems, THD-N is typically measured in dB (decibels) relative to the total signal power. However, for simplicity, we'll use percentage values in this calculator.

How to Calculate THD-N

The THD-N calculation combines THD and noise measurements using the following formula:

THD-N = √(THD² + N²)

Where:

THD = Total Harmonic Distortion (as a percentage)
N = Noise level (as a percentage)

Example Calculation

Suppose you have a signal with:

THD = 0.5%
N = 0.3%

Using the formula:

THD-N = √(0.5² + 0.3²) = √(0.25 + 0.09) = √0.34 = 0.583 or 58.3%

Using the Calculator

Enter your THD and noise values in the calculator panel to get the combined THD-N result.

Interpreting THD-N Results

THD-N results are typically interpreted as follows:

THD-N Value	Signal Quality	Typical Applications
< 0.1%	Excellent	High-end audio systems, professional recording
0.1% - 0.5%	Good	Consumer audio equipment, home theater
0.5% - 1%	Fair	Budget audio equipment, general use
> 1%	Poor	Low-quality equipment, testing purposes only

For professional applications, THD-N values are often expressed in dB. The conversion from percentage to dB is approximately:

THD-N (dB) = 20 × log₁₀(THD-N (%))

FAQ

What is the difference between THD and THD-N?: THD measures only harmonic distortion, while THD-N includes both harmonic distortion and noise. THD-N provides a more complete picture of signal quality.
How is THD-N different from SNR?: Signal-to-Noise Ratio (SNR) measures the ratio of signal power to noise power, while THD-N combines both harmonic distortion and noise. THD-N is often used in audio applications where distortion is also important.
What are typical THD-N values for different audio devices?: High-end headphones might have THD-N values below 0.1%, while budget speakers might exceed 1%. Professional audio equipment typically falls between 0.1% and 0.5%.
Can THD-N be negative?: No, THD-N is always a positive value representing the percentage of distortion and noise relative to the total signal power.