THD Analyzer | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Media
Input types: file, number
Output type: file
Sample coverage: 4
API ready: Yes

Overview

The THD Analyzer evaluates single-tone total harmonic distortion per channel from stationary sine wave audio recordings and compiles the results into a downloadable ZIP report.

When to use

Measuring harmonic distortion in stationary sine wave recordings from audio hardware or plugins.
Quantifying individual harmonic levels and fundamental tone purity across audio channels.
Generating multi-channel distortion reports and discrete harmonic metrics from test recordings.

How it works

1Upload a supported audio file (WAV, FLAC, MP3, AIFF, OGG, or M4A) and define the nominal frequency, analysis window, start offset, and maximum harmonic order.
2The tool isolates the specified segment, requiring at least 20 complete cycles, refines the fundamental frequency within ±1%, and verifies that the fundamental contains at least 80% of total signal energy.
3Amplitudes for harmonics up to the specified order are computed via Hann window projections below a guarded Nyquist threshold, accompanied by half-window phase and amplitude consistency checks.
4Results are calculated per channel in dBr relative to the fundamental and in dBFS relative to full scale, then exported in a downloadable ZIP report.

Use cases

Evaluating line output fidelity and harmonic distortion on audio interfaces using a 1 kHz test sine wave.
Measuring odd and even harmonic coloration produced by analog outboard preamps or tape emulation software.
Verifying that audio signal generators produce clean test tones with distortion within target tolerances.

Examples

1. Hardware Interface 1 kHz Sine Tone Audit

Audio QA Engineer

Background

A quality assurance engineer needs to verify the total harmonic distortion of a production run audio interface output using a recorded 1 kHz loopback tone.

Problem

Calculate individual harmonic levels and channel THD without manual spectral analysis calculations.

How to use

Upload the 1 kHz loopback WAV file, set Nominal Frequency to 1000 Hz, specify a 1-second analysis window starting at 0.5 seconds, and set Harmonic Order to 10.

Nominal frequency: 1000 Hz, Start: 0.5 s, Window: 1.0 s, Harmonic order: 10

Outcome

Downloads a ZIP report detailing per-channel THD in dBr and dBFS alongside individual harmonic amplitudes from H2 to H10.

2. Low-Frequency Sine Purity Verification

Sound Lab Technician

Background

A lab technician records a 100 Hz calibration tone generated by an analog bench signal generator.

Problem

Confirm whether low-frequency harmonic distortion remains low enough for calibration use before running acoustic tests.

How to use

FAQ

Can I analyze music or frequency sweep files?

No. The analyzer requires a stationary single-tone sine wave and will fail or yield inconclusive results on dynamic audio or sweeps.

What is the difference between dBr and dBFS in the results?

dBr measures harmonic distortion relative to the fundamental tone amplitude, while dBFS measures distortion levels relative to digital full scale.

Why does the tool return an inconclusive THD measurement?

A result is marked inconclusive if the fundamental contains less than 80% of the window energy or if half-window consistency checks detect signal instability or interference.

Does this tool calculate THD+N?

No. The tool measures discrete harmonic peak projections (THD) and does not calculate total noise and distortion across the full audio spectrum.

What are the duration limits for the analysis window?

The analysis window must be between 0.05 and 5 seconds and long enough to contain at least 20 full cycles of the test tone.

Nominal frequency: 100 Hz, Start: 0.0 s, Window: 2.0 s, Harmonic order: 8

THD Analyzer

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Hardware Interface 1 kHz Sine Tone Audit

2. Low-Frequency Sine Purity Verification

FAQ

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