On Ubuntu, start with Sound settings so you know the right input and output are active before changing browser permissions.
Open Settings > Sound, then look at Input. Choose the microphone you expect and speak while watching the input level. If the level does not move there, the browser test will not hear it either.
USB microphones and webcams usually appear as separate input devices. Headsets can expose more than one profile, so try the other input if the first one is silent.
Open micandcam.com, press Start mic or Start camera, and choose Allow if the browser asks. If it says blocked immediately, use the site permission icon beside the address bar, remove the block, reload, and try again.
Some browsers installed through different package systems can have different sandbox or permission behaviour. If one browser fails and another works, keep the working browser for the call and update the failing one later.
For no sound, open Settings > Sound > Output, pick the right speaker or headphones, and use the system test before using MicAndCam. For a black webcam, close other camera apps and try another camera device if listed.
If the quick check works but Zoom, Teams, or Meet does not, select the same microphone, camera, and output inside that app.
Ubuntu may still be using the laptop microphone. Open Settings > Sound > Input, choose the USB device, and confirm the input level moves before testing in the browser.
Different browser builds can have different sandbox and permission behaviour. Use the working browser for urgent calls, then update or reinstall the failing browser later.
It can be when the tool runs locally. MicAndCam analyzes microphone levels, camera preview, snapshots, and recordings in your browser and does not upload media. You can verify this with the live counter or your browser's Network panel.