1 kHz is in the most sensitive, reliably-reproduced part of the range, survives any loopback path, and is easy to isolate from broadband noise with a narrow-band measurement that rejects unrelated noise.

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Audio Loopback Tester

Confirm that your output is routed back to your input. The tool plays a 1 kHz tone on your output and checks whether it returns on the input device you select — verifying a hardware loopback cable or a virtual loopback (Windows Stereo Mix, VB-Cable, BlackHole, etc.). It reports whether the loopback is detected, how strong the returned signal is, and an approximate delay.

↔ Pick the input that should carry the loopback in the dropdown. A clean electrical/virtual loopback returns a strong signal with very low delay; a weak, delayed return usually means the mic is just hearing your speakers (acoustic), not a true loopback.

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

Input device (loopback)

Capture input

Choose the input that should receive the loopback (e.g. "Stereo Mix", "CABLE Output", or your interface’s loopback channel).

Tone volume 50 %

The 1 kHz test tone is sent to your default output. Keep it moderate.

Idle — press Run loopback test.

Measurements

Loopback

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Return level (1 kHz)

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Strength

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Delay (approx)

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Result

Run the test to check your loopback

Strength is how far the returned 1 kHz tone rises above the input’s 1 kHz noise floor. A direct loopback typically gives tens of dB of strength with a strong return level; a faint, delayed return is usually acoustic leakage from speakers.

1 kHz level at the input — floor (tone off) vs return (tone on); the gap is the loopback strength

What a Loopback Test Tells You

A loopback routes your computer’s audio output back into an input so it can be captured — essential for recording system audio, streaming desktop sound, or verifying a signal chain. The route can be a physical cable (output jack → input jack on an interface), an interface’s built-in loopback channel, or a virtual device like Windows "Stereo Mix", VB-Audio Cable, or macOS BlackHole. This tool confirms the route is actually working.

It plays a steady 1 kHz tone on your default output and listens on the input you pick. First it measures the input’s level at 1 kHz with the tone off (the noise floor), then turns the tone on and measures again. If the 1 kHz level jumps well above the floor, the loopback is carrying your output — that jump is the loopback strength. It also estimates the delay between starting the tone and detecting its return.

Electrical/virtual loopback vs acoustic pickup

The tone can reach the input two ways: through the intended loopback route, or simply because your speakers are playing it and the microphone hears it (acoustic leakage). The tool can’t see your cables, so it infers the likely path:

Strong return + low delay ⇒ a direct electrical or virtual loopback. This is what you want.
Weak return + larger delay ⇒ probably acoustic — the mic hearing your speakers, not a true loopback. Mute the speakers (or use headphones) and re-test; if the return vanishes, it was acoustic.
No detectable return ⇒ the loopback isn’t routed. Set up Stereo Mix / a virtual cable, or wire output → input, and select that input here.

How this differs from the latency and echo tools

The Mic Latency Tester precisely measures acoustic round-trip latency (speaker → air → mic). The Echo Detection Tool looks for room reflections. This tool answers a different question: is my output wired/routed back into my input at all, and how cleanly? The delay here is approximate — for a precise figure use the latency tester.

Frequently Asked Questions

What is a loopback and why test it?

A loopback feeds your audio output back into an input so it can be recorded or streamed — for capturing system/desktop audio, re-recording, or checking a signal chain. Testing confirms the routing actually works before you rely on it for a stream or recording.

How do I set up a loopback?

Options: enable Stereo Mix in Windows sound settings; install a virtual cable (VB-Audio Cable on Windows, BlackHole on macOS) and route output to it; use your audio interface’s loopback channel; or run a physical cable from a line/headphone output to a line input. Then pick that input in the dropdown here and run the test.

It says "acoustic pickup, not a true loopback" — what does that mean?

The tone reached the input, but weakly and with delay — consistent with your microphone simply hearing the speakers rather than a wired/virtual loopback carrying the signal. To confirm, mute your speakers or switch to headphones and re-run: a real loopback still shows a strong return; acoustic leakage disappears.

Why can’t the tool choose my output device?

Browsers route Web Audio to the system default output and don’t let pages freely pick output devices, so the tone always plays on your default output. Set your desired output as the system default first; you only select the input (the loopback) here.

How accurate is the delay?

It’s an estimate — measured from when the tone starts to when its return is first detected, at roughly 5 ms resolution and including the tone’s onset ramp. For a direct loopback it reflects buffering latency; treat it as a ballpark. For a precise round-trip figure, use the Mic Latency Tester.

Why a 1 kHz tone?

1 kHz sits in the most sensitive, reliably-reproduced part of the audio range, so it survives any loopback path well and is easy to isolate from broadband noise with a narrow-band measurement. The tool measures specifically at 1 kHz, which rejects unrelated room/electrical noise.

Does it disable input processing?

Yes — it requests the raw input with auto-gain, noise suppression and echo cancellation off, so the returned tone is measured faithfully. Echo cancellation in particular would try to remove a looped-back signal; the tool turns it off, but if your OS forces it the return may read lower than reality.

Is any audio recorded?

No. The input is analyzed in real time to measure the 1 kHz level only; nothing is recorded, saved, or transmitted. The input is released when the test finishes or you press Stop.

Related Tools

← All Microphone Diagnostics Tools