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

This audio loopback tester confirms your output is routed back to your input. It 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 system audio capture, 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 serves as a routing test: it confirms the output-to-input path is actually carrying signal before you depend on it for a recording or live stream.

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.

Loopback for streaming and recording

Software such as OBS Studio, Zoom, Microsoft Teams, and most DAWs rely on a working loopback route to capture desktop audio alongside a microphone. On Windows, the most common software loopback is Stereo Mix (sometimes called "Wave Out Mix" on older drivers) — a virtual device built into many sound cards that re-captures whatever is playing through the speakers. If Stereo Mix is absent from your sound settings, your driver may have it hidden: right-click the device list and choose "Show Disabled Devices" to reveal it. Alternatively, free virtual audio cable applications such as VB-Audio Cable create a pair of virtual endpoints — route your application's output to the cable's input, then select its output as the capture device here.

On macOS, the system has no built-in loopback equivalent; third-party kernel extensions like BlackHole (free, open-source) or Loopback (commercial) are the standard approach. Once installed, they appear as regular audio devices and can be selected in this tool's input dropdown. If you use a hardware audio interface, check its control panel or mixer software for a dedicated loopback channel — many USB interfaces from Focusrite, Behringer, and MOTU expose one at no extra cost. You can also verify that interface loopback is active using the Sound Input Monitor to watch signal level before running this test.

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.

Stereo Mix doesn’t appear in my Windows sound settings — how do I enable it?

Right-click the speaker icon in the system tray, open "Sound settings", switch to the Recording (or Input) tab, right-click in an empty area of the device list, and tick Show Disabled Devices. Stereo Mix should appear — right-click it and choose Enable. If it still doesn’t show, your audio driver may not support it; install the official Realtek or OEM driver (not the generic Windows one), or use a virtual audio cable application such as VB-Audio Cable as an alternative loopback route.

Can I use this to test a hardware audio interface loopback or USB loopback?

Yes. Many USB and Thunderbolt audio interfaces — from manufacturers like Focusrite, MOTU, PreSonus, and Behringer — include a hardware loopback channel in their driver or mixer software. Enable it in the interface’s control panel, then select the loopback channel from the dropdown here and run the test. A clean hardware loopback at low buffer sizes typically returns a strong signal with just 5–20 ms of buffering delay, confirming the driver and USB bus are passing audio correctly.

What does a high delay reading mean — is my loopback broken?

Not necessarily. Delay depends on the audio buffer size your operating system and driver use — larger buffers reduce CPU load but add latency. A software loopback (Stereo Mix, VB-Cable) typically reads 30–150 ms of delay at normal buffer sizes; a hardware interface loopback is usually 5–30 ms. If the delay is in the hundreds of milliseconds, suspect a large WASAPI or ASIO buffer, or the signal going through a Bluetooth device. The tool flags acoustic pickup (the mic hearing your speakers) when delay exceeds a reasonable threshold and the return is weak; if your loopback genuinely needs a large buffer, increase your speaker volume or lower the detection threshold by bringing the tone volume slider up.

Related Tools

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