Home recording tip: save samples to speed up noise reduction

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Make better use of Adobe Audition or any software that offers noise reduction… save your offending sounds and speed up the noise reduction process in your home studio recordings.

If you record audio in a place where the same noises are often around, and you are not able to prevent them (air conditioning in South Texas, anyone?), then you’ve probably found yourself removing those noises from your audio recordings using noise reduction software. One of the disadvantages of recording in a home studio is that, unless you’ve built or purchased a sound-proof recording booth (difficult and expensive for most of us), there WILL be noise. The best thing is to record without the noise, obviously, but when that isn’t an option, you might rely on noise reduction tools to help out.

noise reduction home recording tip
Figure 1
The only way that most noise reduction software knows how to tell which audio is “the bad audio” – the noise – is for you to tell it! This is normally accomplished by highlighting a section of your recording that contains ONLY that noise. Once the program knows what the enemy sounds like, it knows what to get rid of and what to leave alone. [See figure 1]

Isolate and destroy

I mentioned above that you need to feed the noise reduction tool a selection of audio that is ONLY noise. This is absolutely vital. If your cat meows at the same time as you are singing, it will be difficult (in fact, probably impossible) to remove the noise (the meow, in case you were wondering). Your program will not be able to tell the difference between you an your cat, and you will both be eliminated. You will need to get Bubbles to meow again – at the same pitch – and record that. Only then can you load her solo meow into your noise reduction program so that whenever the cat/human duet occurs, the program will recognize and remove the cat and leave your dulcet tones alone.

Collect your noises

One problem is your recording might not contain a section that was ONLY the offending noise all by itself. Maybe the guy with the leaf-blower walked by just the once – right in the middle of your recording. That’s going to be a problem.

But what if you had a collection of the common noises that often intrude on your recording space? For example, in my case, the air conditioning is on and off all the time. In addition to that, there is the cat outside the door, the mourning doves in the trees outside, the leaf-blowers used by the neighbors, and the odd jackhammer. Rather than go through the process of sampling the noise in my recording every single time, it would really be useful to just load up a saved noise profile for any of those things.

noise reduction home recording tip
Figure 2

Fortunately for me, I can do just that.

I typically use Adobe Audition CC for noise editing. The Noise Reduction tool in Audition is excellent. It allows me to save my common noise profiles for use at any time. [See Figure 2]

You’ll notice in the picture that my saved noise profiles are currently: “Jackhammer,” “Bubbles Meow 1,” “Bubbles Meow 2,” and “Studio with AC Running.”

With these saved in the “Audition Noise Reduction” window, instead of using “Capture Profile,” which requires you to have the noise isolated in your current recording, I can simply click the “Load from File” button and select the noise I want to remove.

In order to create these noise profile files in Audition, you do have to have a recording of the isolated sound (no other sound along with it). Then all you have to do is select that sound, open Audition’s Noise Reduction window, and select the Capture Profile button. Once that is done, the “Save” button will become active (it will be grayed out until a profile is loaded). Just click the Save button and name your noise profile. [See Figure 3]

noise reduction home recording tip
Figure 3
Audition will save it as a file with an “fft” extension. That file extension is unique to Adobe and simply means “Adobe Audition Noise Print File.” If you’re super technical, and want to know WHY “fft,” you can do a little light reading on what “Fast Fourier Transform” means.

Most software that has noise reduction capability will offer similar options to save noise profiles for later. But even if they don’t – the free Audacity audio editor does not, for example – if you make an audio recording of these noises (wav, mp3, etc.), you can open those in the program and then pretend they were alone in your recording. It’s a workaround, but it could come in handy.

Once you have your common noises sampled and saved, your editing process will be faster and easier. And who isn’t a fan of faster and easier?

Ken Theriot is a singer, guitarist, and recording enthusiast who runs the Home Brew Audio blog, whose mission is to demystify audio recording for all the regular people out there who thought home recording was limited to the realm of tech geeks and audio engineers with lots of school and tons of expensive gear.

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4 thoughts on “Home recording tip: save samples to speed up noise reduction

  1. I am a longtime Audition user, and use this technique. HOWEVER, it’s very important that when creating noise profiles, there will be a different profile for each mic, for obvious reasons. And the way that the mic picks up noise, and thus the exact sonic quality of that noise, will vary with any substantial change in mic position (i.e. closer or farther to/from the noise source, angled differently, etc). For that reason, I don’t create stock profiles, just as Brian alludes in this thread.

    My method is that when I’m ready to record, I first make sure (or try to remember, duh!) that static noise sources are removed (like running A/C), then when I finish the take, I let the recording continue a bit longer with no input other than ambient noise. I sample that noise and save it as a profile for any more takes on that specific mic in that position. It only takes a few seconds to capture and save. This is not an onerous or difficult task to do on a regular and good-habit basis. ALSO, regarding sample capturing… when highlighting a section of waveform to be sampled, be sure to use the Zero Crossing button (in the same button group is Undo/Redo), before doing the Profile Capture, so that your captured sample is “clean” and does not start or end with an improper zero crossing… otherwise a click or artifact may be induced during your noise reduction process using that sample.

  2. Doesn’t the noise profile use amplitude as one of its criteria? If so, it would seem that profiling actual offending noise would do a better job than calling on a library of stock profiles. But there’s no question that having those profiles would speed things up.

  3. seems like a good idea but i am not convinced that it will work unless the recording chain is static and even then it will not be as effective as simply doing it manually each time. this is only an opinion since i have not tried your suggestion.

    brian

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