If you’ve read any audio recording tips, machinima-related or otherwise, you’ve probably heard two key points referenced:

1. Get a decent quality microphone.
2. Record in a quiet, noise-dampened room.

In this article, we’re going to focus on point # 2… what if you have a good microphone, but it’s impractical to acoustically treat your room, and you don’t like the idea of draping a big blanket over your head to achieve a similar effect? Or, what if you have contracted voice work from someone else, and their acting performance is good but you’ve got some background noise / hiss / that kind of thing?

There is a very easy technique you can try which may help you salvage a noisy recording, I’m going to detail it below.

Requirements for this tutorial:

• Windows operating system.
• The latest version of GoldWave Digital Audio Editor (free trial or full version).
• This audio file (.wav). You’re welcome to use your own, but for optimum “follow-along” value, I’d recommend you use this one.

Install GoldWave, then run the program. Use File > Open and select the noisy .wav file.

You should see a graphical representation of the .wav file, similar to this:

Go ahead and press Play to listen to the file once or twice. (If you don’t see playback controls, open them under Tool > Control.) Do you hear that static? Notice that you can see a visual indication of the static, in between the peaks where speech is going on.

What we want to do is select the longest sample of consecutive pure noise within this file. In other words, there should be nothing else going on except the static; no talking, no lip-smacking, nothing. Just the undesirable noise. It looks like the best place to grab that is at the following location:

To select that area, simply left-click and drag a selection to encompass it. If you don’t select the right area the first time, you can adjust the Start and Finish markers by left-clicking them and dragging them to new locations. Try to set your selection to look similar to the above.

To make sure you have selected only noise, press Play. GoldWave will now play only the selected slice. If you can hear anything other than static (noise) then adjust your selection so you hear only noise. (I’ll explain the importance of this later.)

Now, press CTRL-C to Copy this selection to the clipboard (or use Edit > Copy). Once you’ve done that, press CTRL-A to Select All (or use Edit > Select All).

Next, choose Effect > Filter > Noise Reduction. A window like the following should pop up:

In this window, the only thing you need to do is click Use clipboard under Reduction Envelope. Then click OK.

You should notice an immediate change to the shape of the waveform, and those areas which were once heavy with static are now completely or very nearly flat.

Press Play to hear the changed sound. You should notice an immediate and dramatic improvement in the noise level of the entire file. If you’d like to hear the improved file without doing these steps yourself, you can download it here.

That’s it! Simple, huh? Keep in mind, the sample file we used here was an 8-bit mono recording - very low quality. But these same kinds of results are possible with high-fidelity wav files too. It’s always desirable to have the cleanest possible source material… that will ALWAYS sound better than any noise filter… but when you’re in a pinch, this tool can be a lifesaver.

Here are a few tips to keep in mind when using this technique:

1. The longer the piece of pure noise you are able to grab to the clipboard from the file, the more data the filter has to compute its algorithm, hence the better the quality of the end result. You can still get decent results even if there’s only a small sample to grab, but longer samples will work better.
2. In some cases, you’ll hear some digital distortion in your fixed file, for example when the person uses an “s” sound, it may come across with a digital crackle which you dislike. Often this is because the noise sample you grabbed had the tail end of the person making an “s” sound, or perhaps they sniffled, or rubbed their clothing. If any “legit” sounds make it into your noise sample, then those frequencies will also be filtered out of the sound, creating that weirdness. Use the Undo feature, adjust and try again.
3. If the noise you’re trying to filter out happens to share a lot of frequencies with either the vocal of the person or their sibilance noises (the letter “s” is the most pronounced sibilance), then filtering the noise can have the same result as #2 above. A re-recording is likely in your future in this case.
4. In some rare cases, the recording is SO noisy that the noise is competitive in decibels with the vocal itself; filtering the noise completely distorts the vocal. In those cases, there really is no viable option but to re-record.

Even given these disclaimers, I have found that in a great majority of cases, with a little experimentation a vocal track with noise can be greatly improved using this technique. I am sure there are other programs which can pull this off… a good commercial noise filter plugin, for example… but among the extremely low cost alternatives, GoldWave is a shining star in this area. I have a lot of commercial audio software which I use for my projects, but GoldWave is still a big part of my toolkit, and this filter is one of the reasons.