# THD Analyzer Measure single-tone harmonic distortion per channel and download a ZIP report. > Canonical page: https://elysiatools.com/en/tools/thd-analyzer - **Category:** Media - **Keywords:** audio, harmonic distortion, single tone ## Overview Use a stationary sine test, not music or a sweep. Analyze 0.05–5 seconds with at least 20 cycles. Frequency refinement is limited to ±1%; at least 80% fundamental energy is required. Hann projections measure harmonic amplitudes below a guarded Nyquist limit. Noise at harmonic frequencies biases results; this is not THD+N. THD dBr is relative to the fundamental; dBFS is relative to digital full scale. A half-window phase/amplitude consistency screen returns inconclusive THD for detected contamination. It cannot resolve arbitrarily close interfering tones. ## Inputs - **Audio file** (file) - **Nominal frequency (Hz)** (number) - **Start (seconds)** (number) - **Window (seconds)** (number) - **Maximum harmonic order** (number) ## 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 - Upload a supported audio file (WAV, FLAC, MP3, AIFF, OGG, or M4A) and define the nominal frequency, analysis window, start offset, and maximum harmonic order. - The 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. - Amplitudes 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. - Results 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. ## Frequently asked questions ### 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. ## Related tools - [Bit Depth Analyzer](https://elysiatools.com/en/tools/bit-depth-analyzer): Inspect container precision and per-channel integer low-bit occupancy; download an offline ZIP report. - [Audio Chord Progression Detector](https://elysiatools.com/en/tools/audio-chord-progression-detector): Estimate an audio file's chord sequence locally and download CSV, JSON, SVG, and method notes in one ZIP. - [Audio SNR Estimator](https://elysiatools.com/en/tools/audio-snr-estimator): Estimate per-channel signal-to-noise ratio from separate program and noise-only regions, with an offline ZIP report. - [Audio Melody Contour Extractor](https://elysiatools.com/en/tools/audio-melody-contour-extractor): Extract a dominant melody path from audio and export MIDI, note events, a pitch contour, SVG, and JSON in one ZIP. - [Audio Noise Floor Timeline](https://elysiatools.com/en/tools/audio-noise-floor-timeline): Track a heuristic low-level RMS proxy over time, with separate digital-silence counts and per-channel change flags. - [Audio to Multitrack MIDI (Draft)](https://elysiatools.com/en/tools/audio-to-multitrack-midi): Split a full mix into stems (drums/bass/other/vocals) and transcribe each to MIDI — a multi-track starting point for transcription - [Image Particle Music Visualizer](https://elysiatools.com/en/tools/image-particle-music-visualizer): Turn a picture into an audio-reactive point cloud. Preview locally, then export a 30 fps MP4 with music, a PNG poster and settings JSON. - [DTMF Decoder](https://elysiatools.com/en/tools/audio-dtmf-decoder): Detect DTMF touch-tone digits in any recording and recover the keypad sequence with timestamps. Goertzel filter bank per ITU-T Q.23/Q.24 — measures both tone frequencies, twist and duration for every keypress. ## Samples - [Copyright-Free FLAC Audio Samples](https://elysiatools.com/en/samples/flac-samples): Lossless FLAC audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music - [Copyright-Free MP3 Audio Samples](https://elysiatools.com/en/samples/mp3-samples): Collection of royalty-free audio samples for testing and development purposes including nature sounds, meditation music, and ambient audio - [Copyright-Free WAV Audio Samples](https://elysiatools.com/en/samples/wav-samples): Uncompressed PCM WAV audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music - [Copyright-Free Raw PCM Audio Samples](https://elysiatools.com/en/samples/pcm-samples): Raw PCM s16le audio samples featuring nature ambience and relaxing music for waveform, playback, and conversion workflows ## Related content - [Audio Processing Regression Tests: Null, Distortion and Report Handoff](https://elysiatools.com/en/hubs/audio-processing-regression-null-and-distortion-review): Compare a fixed audio reference with separately processed outputs, document null-test coverage and suitable single-tone THD results, and deliver a reviewed regression record with files and hashes.