Hiss… unless you’re a reptile, it’s probably not a welcome sound, especially when it’s invading your music production. “Hiss” of course is just a vague term for any sort of undesired non-pitched noise. It might originate from the mic preamp, effects, plugins, or even the instrument itself (remember the original DX7?). As usual, an ounce of prevention is worth a pound of cure, so for example if you can adjust mic positions and cut back on mic preamp levels, you should do that before reaching for your de-noiser plugin.
The universe unfortunately is a little less than ideal (some would say a lot less), so you can’t prevent all hiss. Even if you’ve managed to eliminate all but the slightest trace of hiss on each track, if you’ve got 40 tracks playing back, all that hiss can add up. Of course, if you’ve got 40 tracks, chances are the music will overwhelm the hiss. After all, it’s not hiss per se that’s problematic; it’s the hiss/music ratio. So if you’ve got a tiny amount of hiss on each of your 40 tracks, it probably doesn’t matter if those 40 tracks are for an epic symphonic metal opus. But on the other hand, if you’ve got 40 very quiet tracks of sound effects for a movie soundtrack, then the hiss might be unacceptable.
I did mention de-noiser plugins. De-noiser plugins typically work by being shown a bit of audio that contains noise without music. The plugin “learns” what the noise looks like and can then hunt it down and remove it from the rest of the track even where there is music and noise playing at the same time. (The trick is to set the amount of de-noising so that the music doesn’t get damaged.) I swear by (and sometimes at) the iZotope Denoiser plugin.
Knowing how the de-noiser plugin works allows you to play a little trick. When recording, record some extra sound before the instrument starts playing. This will give you a chunk of noise with no music in it, which is there deliberately for the purpose of training your de-noiser plugin.
In some cases, there is such a wide separation in the frequency domain between the music and the hiss, that a simple low-pass EQ can remove the hiss without damaging the music. This might be true for example on a bass track.
Lastly, if all else fails, here’s a little trick that I’ve learned: Set each track to mute wherever there is no music on it. This is especially effective at the start and end of a song. For example, if you have an acoustic guitar solo to start off the song, then all the other tracks should be muted during it. Likewise, at the end of the song, if there’s a track that extends beyond the end of the music on that track, mute the track at the end of the music, not the end of the song. Note that muting a track is different from simply removing unwanted audio clips. Sometimes plugins add to noise, so even if a track contains no audio clips, a plugin inserted on that track generates noise. In that case, you have to mute the track to mute the noise.
Similarly, if there’s a section of a song that gets very quiet, with most instruments dropping out, mute the instruments that have dropped out during that section. Whenever muting a track, be careful not to mute before reverb tails have finished.
I hope you find these techniques useful. Until next time, may all your recordings be hiss-free.