My Audio Has Background Hiss: What Causes It and How to Fix It

The short version

Find out whether the hiss is there with nobody speaking; that is the noise floor.
Raising the gain late raises the hiss; set the gain properly at the start.
A steady hiss responds well to a noise reduction tool.
Fix the source on the next recording: a quieter room, a closer mic or a better cable.

Find out what is there

Record ten seconds of silence and listen on headphones. If the hiss is there, it is the noise floor of your setup. If it appears only when you speak, it is more likely the gain or the cable.

Gain

If the level was low and you raised it later, the hiss rose with it. Set the input gain at the start so the voice is strong, as the gain guide explains.

The room and the mic

A steady hiss often comes from a fan, the air conditioning, an audio interface or the mic’s own electronics. Turn off what you can, and move the mic closer to the mouth so the voice sits above the hiss.

The cable

A damaged or long cable can add hiss. Try a shorter, better cable and see if the hiss changes.

Clean what remains

A steady hiss responds well to noise reduction. Use the lowest setting that removes it, and check the voice for a watery sound. The noise removal guide has the steps.