4 types of background noise
To learn how to get rid of background noise on mics, it helps to know the four main types of noise that can diminish the sound quality of your recordings:
- Broadband noise. Broadband noise occurs over a wide range of frequencies. When these frequencies produce noise all at once, it creates the familiar hissing and buzzing sound commonly known as background noise.
- Narrowband noise. Compared to broadband noise, narrowband noise occurs over a much smaller range of frequencies. Electrical circuits can cause narrowband noise that creates a hum in your audio recordings. You can often trace narrowband noise to a poorly grounded mic cable or an instrument’s pickups.
- Impulse noise. Audio engineers group the clicks and pops you hear on certain audio recordings into a broad category called impulse noise. These include plosives from consonant sounds like “p” and the loud crackle that happens when you plug in an audio cable.
- Irregular noise. True to its name, irregular noise occurs on an irregular basis. Examples include rain, wind, thunder, traffic, and ambient conversations — sounds that come and go depending on the recording environment.
How to get rid of unwanted background noise when recording
The best way to get rid of background noise is to block it out during the recording process. Noise cancellation software can help you in post-production, but nothing beats a clean, noise-free recording to start with. Here are six ways to use your audio hardware and sound recording skills to produce noise-free audio:
- Get close to the mic. The pros in the podcasting business describe a recording done with the speaker talking right into the mic as one with a “high speech-to-noise ratio.” To achieve this ratio for your own podcasts, place podcast mics near each speaker’s mouth — ideally about a palm’s length away. This reduces the need to boost mic sensitivity to make up for the distance. In other words, if the speaker is too far from the mic, you’ll need to boost the mic’s sensitivity, which, as a consequence, boosts noise levels as well. A mic that’s less sensitive, on the other hand, is less likely to pick up background noises or amplify unwanted line noise.
- Find a sturdy mic stand. You might not have to look far to find the source of those annoying impulse noises — they might be coming from your creaky old mic stand. Use well-maintained mic stands and swap out your old ones if they start making unwanted noises. You can also use a shock mount mic clip (particularly for condenser microphones), which lets your mic hover just off the stand, eliminating certain creaky sounds that might happen without a clip.
- Use pop filters to block out plosives. A pop filter is a thin membrane of fabric that blocks plosives created by certain consonants (particularly the “p” sound). To knock out certain impulse noises, clip a pop filter to your mic stand so it hovers right between you and your mic.
- Opt for dynamic mics in noisy environments. Both dynamic microphones and condenser microphones offer many benefits to a recording artist, but the average dynamic mic is less sensitive than the average condenser mic, giving dynamic mics the edge in noisy situations. By using a dynamic mic and holding it close to your mouth, you’ll increase your speech-to-noise ratio.
- Use clean electrical sources. Electrical circuits can cause narrowband noise that creates a hum in your audio recordings. This notably occurs in buildings with old, outdated electrical wiring; these buildings often have poor grounding, overloaded circuits, or strange wiring paths that create ground loop antennas. A hum can also happen when your audio gear shares a power socket with high-powered lights (particularly lights with dimmer switches). You can get around this by using a power conditioner, an electrical box that removes the alternating current ground loops that cause narrowband noise.
- Record in the quietest room in your house. No one said noise suppression for microphones has to be high-tech. Sometimes the best technique is the most obvious one: Record in the quietest space you can find. For many people, this might be a clothes closet, since the hanging clothing naturally absorbs sound. If you’re recording in a normal room — which may be more comfortable for podcasts with multiple hosts — you can achieve ambient noise reduction by closing windows and doors. Carpeted rooms also absorb more noise than rooms with hard floors.
- Check your plugs. In many cases, the culprit behind unwanted headphone noise is a bad plug connection. Check all headphone jacks and make sure that the plugs are pushed in all the way. Then, do the same with your mic inputs.
- Watch your gain levels. Your audio signal may pass through multiple gain stages, i.e. places where extra power is added to the signal to make it louder. When you add too much gain to a signal, particularly near the top of your signal path, you can distort it. If your audio tracks sound noisy and distorted, turn down the volume (particularly on your preamp if you’re using one).
- Use noise-canceling headphones. If the noise is coming from your environment, consider using a pair of noise-canceling headphones. These use ambient noise reduction technology to cancel background noise coming from nearby sound sources. Noise-canceling headphones work best on steady ambient noises, including both broadband noise and narrowband noise. They won’t do much for intrusive noises and irregular noises that quickly come and go, though.
How to reduce noise using a computer
Your computer is your last line of defense in your fight against unwanted noise. Thankfully, many software applications can turn noisy audio recordings into high-quality final products. Here are a few ways to reduce noise with your computer:
- Using Windows’s built-in tools. The Windows operating system has built-in tools to help you whittle away background noise. Find them in the Hardware and Sound section of your computer’s control panel. Once there, click on the Recording tab, select your recording device, and then click the device’s Levels tab. You can then reduce the “boost" that Windows gives to your mic. Depending on your machine, you may also see an Enhancements tab, where you can tick a box for “noise suppression.”
- Using MacOS’s built-in tools. If you have a Mac, go to the Sound section of your System Preferences. There, you can adjust the input level on your computer’s audio devices. Older Macs have a checkbox for “ambient noise reduction,” but this feature was discontinued on newer models with Apple Silicon chips (like the M1 chip).
- Using background noise reduction software. If you’re recording directly to your computer, you can use software specifically designed to remove background noise while you record. One such program is Krisp, which has a free tier. It features tools like acoustic echo cancellation (to remove obnoxious echoes on video calls) and voice cancellation (to block out all sounds except the primary speaker’s voice) — particularly helpful when recording audio from a video chat.
- Using the built-in tools in your DAW. All the leading digital audio workstations (DAWs) have noise reduction tools to cut unwanted sounds from your mix. Look for this feature in programs like Audacity, Adobe Audition, Pro Tools, Logic Pro, and GarageBand. These tools work by isolating the audio frequencies of the unwanted noise, then filtering out these frequencies using a band-reject filter.
- Using manual audio filters. You don’t need a preset microphone background noise filter. Applying high-pass filters and low-pass filters to certain audio tracks can reduce many of the ambient sounds that turn up as background noise. A high-pass filter allows high frequencies to pass through, but filters out frequencies below a certain threshold (which you set in your DAW software). Use a high-pass filter (also known as a low-cut filter) to cut low rumbling sounds. On the other hand, a low-pass filter (also called a high-cut filter) lets low frequencies through while filtering out frequencies above a given threshold. These can be useful for removing high, ambient hums.
- Using Descript’s industry-leading features. If you’re a podcaster who needs to turn raw recordings into high-quality audio tracks, Descript has the solution. Its powerful Studio Sound feature (which we mentioned above) uses AI and machine learning to enhance voices while reducing and removing background noise, room echo, and other sounds you don’t want. Studio Sound makes flawed recordings sound like they were made in a studio. It takes a single click to do what would otherwise take several steps (and some expertise) in a traditional DAW. Once Descript does its work, your final product will be a mix of the original recording and the cleaned-up AI version.