Electrical hum is a low, steady tone that leaks into recordings from mains power: through a cable, an amplifier, a charger, or a nearby appliance. It sits at the frequency of the local power grid, 50 Hz in most of Europe, Africa, and much of Asia (including Kazakhstan), and 60 Hz in North America and some other countries, including parts of Japan.
Remove Hum targets that tone. Leave it on Auto and Wavli finds the hum for you, or choose 50 Hz or 60 Hz yourself if you know where the recording was made. Preview the result, compare Before and After, and export.
Auto listens to the start of the recording (about the first 1.5 seconds) to tell whether the hum is at 50 or 60 Hz.
Hum often sounds like a buzz because it carries overtones above the base tone. Remove Hum cuts those too: it filters the base frequency and every overtone below 1 kHz, and leaves the rest of the sound alone.
Hum and background noise are different problems, which is why they’re separate tools. If a recording has both, like an air conditioner that whooshes and hums, run Remove Hum first, then tap Use in another tool and choose Remove Noise. Export only the final file and it uses one export.
Everything runs on your iPhone. Nothing is uploaded.
Remove Hum doesn’t fix crackle or buzzing from a damaged cable. Those are short bursts, not a steady tone, so replace the cable and re-record if you can.