Background noise is the bane of all recording efforts. It comes in many flavors and has many solutions. Of course, the perfect solution is to record in place that is absolutely silent with a high quality microphone. For example, just picking one at random, a ModMic!
However, life isn't perfect, and many times background noise is going to be a part of your life. Before we dig into how to fix them, let's identify the various types of noise we'll be encountering.
Types of Noise
Line Noise: This is interference between the microphone and the recording device. It is not audible in the room you are in, it only exists in the transmission. It's almost always a constant static hiss, hum, or buzz, depending on the type. Causes of this noise can be faulty or low quality components, nearby electrical equipment, or ground loops.
Real Background Noise: For lack of a better term, this is just noise in your environment. Your PCs fans running, a heater, air conditioner, just "everyday stuff" that is making small amounts of noise you'd only notice if your power went out.
Self Created Noise: Keyboards, mouse, movement, or in music pressing the pedals of an instrument, anything you are creating in the process of your recording that you do not actually want as part of the recording.
Outside Noise: Children, roommates, dogs, a TV in the other room, traffic, the list is practically endless, but these are things outside your recording environment that are going to be picked up in recording.
Noise Reduction Options
Now that we have these definitions out of the way, let's talk about the various options of noise reduction and how we can use them to fix the various issues above.
Before we dive too deep, noise reduction isn't a miracle cure. Unless you're literally building a soundproof booth, nothing we do is going to eliminate a police siren driving past your house or someone detonating firecrackers in your living room. The less consistent the noise, the less we can do about it. Additionally, the worse the background noise the bigger impact removing it will make on your mic quality.
Physical Noise Reduction
In short, using a real life object to reduce noise. This can be as simple as a cardioid (uni-directional) pickup pattern, using quieter fans, or putting sound absorbing material on your walls, using heavy curtains, and sealing gaps under your door. In particular physical noise reduction is best at reducing outside noise and reverb/echo in the room.
Pros: It's always "on" and generally works very well.
Cons: It can get very expensive to treat your walls, replace components, and cardioid pickup patterns tend to sound less natural than full pickup patterns.
Tips: You don't need to go spend thousands to treat your walls. Putting up some (cheap) decorative rugs and similar soft materials can add both aesthetic and have a surprisingly positive impact on noise reduction. In particular ensure door gaps are sealed and if the noise is coming from outside a window, heavy sound absorbing curtains will help a lot.
Static Noise Reduction
Instead of using an equalizer to adjust the way your mic sounds, we subtract certain frequencies from the signal permanently. If the subtractions are not severe, the overall mic quality change is minimal, but the reduction in noise could be immense. The more we subtract, however, the worse the mic will sound. This subtraction method is best for Line Noise and Real Background Noise. In short, anything that is doesn't change it's pitch or frequency. It is ineffective at removing complex noises like keyboards or voices in another room.
Pros: Free and has minimal impact on your system and recording quality. Because the subtraction doesn't change from moment to moment, you can also combine it easier with other features, like EQ and noise gating.
Cons: Absolutely worthless at removing complex noise and can severely harm mic quality if pushed beyond "medium" background noise levels.
Tips: We have a fantastic tutorial on removing background noise via subtraction in our article on Noise Reduction via Light Host and Reafir. It's also easy to add a noise gate to this method via our tutorial on Reagate. Combining these two will prevent most "Self Created Noise" as well! Finally, if you do not need real-time noise static noise reduction you can just remove the noise in post-processing. Programs like Audacity can do this for free as well, and generally speaking the results are better than real-time efforts.
Active Noise Suppression
Last but not least is active noise suppression. This works like an AI constantly monitoring your mic signal and activates automatically when it detects 'bad' input. This is the only way I know of to remove Outside Noise by any degree. It will also absolutely fix Line Noise and Real Background Noise, as well as noise gate or reduce most Self Created Noise. So why even talk about the other methods?
Pros: By far the most versatile, always on and can fix unexpected problems.
Cons: AI is never perfect. Because it's constantly changing the input line, you can't ever know 'exactly' how your mic is going to sound. This means your voice quality may change slightly (or massively) during the recording based on what the AI thinks is best and what is going on around you. In short, it takes control away from the user, but unless you're doing professional recordings, this is probably not important.
Tips: Despite that big "cons" section this is probably the best method for most users. It's not harder to setup than static noise reduction and fixes a much wider range of issues, including unexpected issues. It isn't magic though, just like with static noise reduction, the more work the AI does the worse you're going to sound. Our recent article on using Real-time Noise Reduction powered by RNNoise is our current recommendation for active noise suppression.
The best solution, as always, is not to have any noise to begin with. A high quality mic, a quiet room with quiet components, and nobody making noise outside or in the next room is the ideal situation. However, short of a recording studio, you're unlikely to have that combination in real life. So take heart, whether you've got a mechanical keyboard, a TV playing in the next room, or just an annoying ground loop problem, there are plenty of fixes!
If you have any questions about how to best use this software or hardware with an Antlion Audio product, drop by our Discord at https://discord.gg/AntlionAudio for help!