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 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, use Remove Hum for the tone and Remove Noise for the steady air sound.
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.