Why speakers, not headphones?

The test is acoustic: the mic must physically hear the reference tone. With headphones the sound goes to your ears, not the mic. Use speakers and place the mic near them.

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Mic Distortion Analyzer

This mic distortion analyzer plays a pure reference tone through your speakers, captures it with your microphone, and measures total harmonic distortion (THD) — the energy that leaks into harmonics when something in the path distorts. See the harmonic spectrum, get a clean / moderate / heavy rating, and catch clipping in real time.

🔊 Use speakers (not headphones) and place the mic near them, in a quiet room. This measures the whole speaker → air → mic path — see the FAQ for how to tell mic distortion from speaker distortion.

🔒 Runs entirely in your browser. No audio is recorded, uploaded, or stored.

Microphone

Input device

Reference tone

Tone volume 40 %

Start moderate. Raise it gradually to find the level where distortion appears — that’s your path’s overload point.

Idle — press Start test.

Measurements

Captured fund. (rel.)

—

THD

—

2nd harmonic

—

Clipping

—

Total harmonic distortion

—%

play the tone to measure

Rough guide: under 1% is clean, 1–5% is moderate (audible on critical material), over 5% or any clipping is heavy distortion. Acoustic tests run higher than a wired loopback because the speaker and room add their own distortion.

Captured spectrum — fundamental (green) and harmonics (amber); distortion shows as tall harmonics

How the Distortion Test Works

A perfectly clean system reproduces a pure tone as a single frequency. When something in the chain distorts — most often by clipping when a level is too high — it adds harmonics: extra tones at exact multiples of the original (2×, 3×, 4×…). Total harmonic distortion (THD) is the ratio of all that harmonic energy to the original tone, expressed as a percentage. The more harmonics, and the taller they are, the higher the THD and the more "dirty" the sound. You may also encounter the term THD+N (THD plus noise) in lab measurements, which includes the noise floor as well; this tool reports pure THD measured against identifiable harmonic peaks. Running this audio distortion test at a range of volumes makes it easy to pinpoint the exact level where your path crosses from clean to distorted.

This tool plays a pure sine through your speakers, your microphone records it, and a Fast Fourier Transform (FFT) measures the level of the fundamental and each harmonic in the captured signal. It also watches the raw waveform for microphone clipping — samples pinned at the maximum, the flat-topping that screams "too hot." Together those tell you whether your capture path is reproducing sound cleanly. If you want to check your mic's gain staging before this test, the mic gain level meter helps you set input levels without clipping.

Telling mic distortion from speaker/room distortion

Because the sound travels speaker → air → mic, the measured THD includes all three. To isolate the microphone:

Sweep the volume. Distortion that only appears as you raise the tone volume — and especially anything that trips the clipping flag — is usually overload in your mic or its preamp/ADC. Note the level where it starts: that’s your overload point.
Low-level THD that’s present even quietly is more likely the speaker, the room, or background noise than the mic itself.
Compare the harmonics. Clipping produces strong odd harmonics (3rd, 5th); gentle overdrive favors the 2nd. The spectrum shows which are dominant.
Dynamic vs condenser mics. Condenser microphones (including USB condensers) have active capsule circuitry and a built-in preamp that can overload at high SPL. Dynamic mics are passive and generally handle loud sources better before distorting, but their lower output means preamp gain — which introduces its own noise and potential distortion — must be higher.

Getting a meaningful reading

Use speakers, mic close, quiet room. Headphones won’t reach the mic.
Make sure the captured fundamental reads a healthy level — if it’s near the noise floor, raise the tone volume or move the mic closer, or THD will be meaningless.
The tool keeps echo cancellation and noise suppression off; if your OS forces them, they will distort the result.
For USB microphones, the analog-to-digital converter (ADC) built into the mic body is part of the signal path measured here. Overdriving a USB mic's capsule overloads the internal preamp/ADC, which shows up as clipping or sharp harmonic spikes. To verify the signal path further, the audio spectrum analyzer can show you the live frequency content of any mic input in real time.

Frequently Asked Questions

What THD counts as good?

For this acoustic test, under ~1% is clean, 1–5% is moderate, and over 5% (or any clipping) is heavy. Don’t compare these to a microphone’s spec-sheet THD — those are measured electrically in a lab. Here the speaker and room add distortion too, so expect higher numbers; what matters is how THD changes as you raise the level.

Why must I use speakers, not headphones?

The test is acoustic: the microphone has to physically hear the reference tone to analyze it. With headphones the sound goes into your ears, not the mic, so there’s nothing to measure. Use speakers and place the mic near them.

Does this measure only my microphone’s distortion?

No — it measures the whole speaker → air → mic path, so the speaker and room contribute. The trick is to sweep the volume: distortion (and clipping) that appears as you turn it up points to overload in the mic or its preamp/ADC. See "Telling mic distortion from speaker/room distortion" above.

What is clipping and why is it flagged separately?

Clipping is the harshest distortion: the signal exceeds the maximum the system can represent and gets flat-topped, generating lots of harmonics. It’s detected directly from the waveform (samples at full scale), so it’s flagged on its own — if the clipping indicator lights, lower the tone volume or your mic gain immediately.

Why does THD jump around or read high at low volume?

If the captured fundamental is weak, background noise and room reflections dominate the harmonic bins and THD becomes unreliable. Raise the tone volume (or move the mic closer) until the captured-fundamental readout is well above the noise, then read the THD.

Which reference frequency should I use?

1 kHz is the classic THD test tone and a good default. 440 Hz and 220 Hz put more harmonics in the audible/measurable range and can reveal low-frequency overdrive. Try more than one — a path can distort differently at different frequencies.

Odd vs even harmonics — what do they tell me?

Hard clipping (overload) generates strong odd harmonics — 3rd, 5th, 7th. Softer, asymmetric distortion tends to favor the 2nd. The spectrum view lets you see which harmonics stand up, hinting at the kind of distortion in your path.

Is any audio recorded?

No. The captured signal is analyzed in real time to compute THD and detect clipping only; nothing is recorded, saved, or transmitted. The microphone is released when you press Stop or close the tab.

What is a good THD spec for a USB microphone?

Manufacturer spec sheets for USB microphones typically list THD measured electrically in a controlled lab, often under 0.5% at moderate SPL. Those figures are not directly comparable to this acoustic test, which includes speaker and room distortion. As a rough field guide: if this tool reads under 2% with the reference tone at a moderate listening volume, your microphone capture path is likely clean. Values above 5%, or any clipping, suggest the input gain is too high or the mic capsule is being overloaded.

Can phantom power or gain settings cause distortion?

Phantom power (+48V) itself does not cause distortion in a correctly wired condenser microphone — but insufficient phantom supply voltage (from a cheap interface) can cause subtle preamp instability. More commonly, excessive gain at the interface or in software is the culprit: it amplifies the signal into clipping before it ever reaches the ADC. If you see clipping in this test, first reduce the interface gain knob before lowering the tone volume, to confirm the overload is in the preamp stage rather than the acoustic path.

How does this differ from a wired loopback THD test?

A wired loopback connects your audio interface's output directly to its input with a cable, bypassing speakers and a microphone entirely — that isolates the interface's own DAC and ADC. This acoustic test includes the whole speaker → room → microphone chain, so THD will always be higher. Use the loopback method (with a separate loopback tool or audio analysis software like REW) to benchmark your interface in isolation; use this acoustic test to evaluate the real-world recording path including your microphone.

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