Press Start Test and allow microphone access. Speak normally and watch the level meter and peak readout respond, then press Stop when you are satisfied.
No. The live signal is analysed to draw the level meter and is then discarded. Nothing is written to a file, stored, or sent anywhere, so the test is safe to run before a confidential call.
First confirm you allowed microphone access when prompted. Then check that the right input device is selected in your system settings, that the microphone is not muted in hardware, and that no other application has exclusive use of it.
Browsers hide device labels until a page has been granted microphone permission, to prevent silent fingerprinting. Allow access once and the list fills in with the real device names.