Audio loopback test
Before you start: Use an electrical connection and suitable attenuation. Never connect a speaker-level output to a microphone or line input. Check device ratings and keep monitor volume low before connecting anything.
Electrical path setup
Use a physical electrical output-to-input connection, not a speaker and microphone in a room. WaveLocus will capture the return locally, correlate it with a known chirp and withhold invalid metrics.
- Connect an output directly to an input.Use suitable attenuation and keep monitor volume low. Do not route headphone or line output directly to an input that cannot accept it.
- Select the returning input.Browser labels become available after permission is granted.
- Confirm the path and run the preflight.Each run repeats the same local stimulus to estimate variation.
Connect an electrical output to an input, then request the selected input.
No measurement yet
The result panel will not show a latency, level or polarity number until a local preflight produces a corresponding eligibility decision.
Why loopback uses a separate stimulus
Electrical loopback needs a correlated return with usable input headroom. This tool’s finite chirp and sine burst are separate from listening-test gain settings. Stimulus peak and RMS accompany new runs, and weak or near-full-scale returns limit interpretation. The connected interface and capture settings still require hardware validation; browser results are not converter specifications.
Source: REW soundcard calibration guidance. Read dBFS vs dB SPL to distinguish digital signal levels from physical sound pressure. Use the loopback validation requirements to check which measurement claims the current evidence supports.
How to interpret your audio loopback test results
A metric is reliable or limited: Read that metric's eligibility explanation. The reported latency includes the browser and connected round-trip path; it is not an interface-only specification.
A metric is invalid or unavailable: Do not interpret its withheld value. Check the return path, input headroom, processing settings and correlation before repeating.
Runs vary: Keep the wiring and levels unchanged and inspect repeated captures. Software-only repeatability does not validate the physical interface.
Source: REW soundcard calibration guidance.
Frequently asked questions
What does an electrical audio loopback test measure?
It captures a generated output through an electrical input connection and correlates the return with the reference. Eligibility and signal confidence determine whether a local round-trip estimate is shown.
Can I use speakers and a microphone instead of a cable?
No. This workflow is for an electrical output-to-input path. Room propagation, acoustic feedback and microphone processing make a speaker-to-microphone setup a different measurement.
Why is a loopback measurement unavailable or withheld?
The selected device, processing, return signal or confidence checks may not meet the method’s requirements. Read the displayed reason and check the electrical setup. A withheld value is not a zero-latency result and should not be replaced with an estimate from another setup.