When you are recording audio (or video with audio), there are often background sounds such as air conditioning (try to avoid that) or the sound of traffic from nearby busy streets. Sometimes you will also get electric guitar amp hiss.
If you are doing multitrack recording and these sounds are present on several tracks, that presence is multiplied when the tracks are played back together. If you are recording on tape, you may also get a static sound – what is commonly referred to as “tape hiss” that plays back along with your recording. It is important to know that there are ways to remove this background noise using programs like Audacity or Audition. (For video, you can use Adobe Premiere and an effect like DeNoiser)
If you are working with tape, you will first need to get your audio in the form of .wav files or similar high-quality audio. Be sure to leave some of the noise on either or both ends of the recording – don’t simply cut it out right before the recording, as many will often make the mistake of doing, as we need to reference the noise in the removal process.
If you are working with multiple tracks and not simply removing noise from a final mix, you can digitize the individual tracks as “stems” that will need to be realigned later. If you will be digitizing the tracks separately and realigning as stems, be sure you have a mark by which to align them, such as a 4-count or single clap before the song begins.
The noise reduction/removal process is almost identical in Audition and Audacity, and it is a two-step process. Once you have your audio as .wav files, you will need to choose a selection that only contains the noise you want to remove. In Audacity, go to Effect > Noise Removal. Click “Get Noise Profile”, which is the first step. This creates the noise “profile” or “signature” that the program will then search for throughout your entire clip in the second step.
Once you have clicked “Get Noise Profile” and Audacity has your noise signature, you will complete the second step, which involves first selecting your entire clip within which you are removing the noise. Once selected, again go to Effect > Noise Removal, and look at the bottom section that allows you to choose to remove “less” or “more” noise.
While you will be tempted to choose “more”, you almost always will want to slide the fader all the way to the left, reducing the “least” amount of noise during this step. The reason is that removing more than this will tend to negatively affect the sound of the recording you are trying to salvage.
You can preview what the track will sound like without the noise and adjust if necessary. Then click to finish the process. It may take a moment to complete the noise removal. If you do not like how it turned out, in most cases you can click Edit > Undo and restart the process.
Of course, you should take steps during actual production recording to remove or limit noise from the environment so this step will not be as necessary. The more noise you have in the original recordings, the more it tends to affect the quality of the audio after this process is completed.
