When setting up microphones, your top priority is to remove microphone background noise to ensure you get the best sound quality. This is as vital to live performances as it is to recording in the studio. As a sound engineer, you’re aware that different spaces, performers, and mics can influence quality. To help you remove undesirable noise from live and studio recordings, we’ve got nine solid pieces of advice. Before we get to these tips, we’ll take a closer look at the problem of unwanted sound.
Types of Background Noise
Level and duration define the three main types of background noise.
- Impulse noise is short and has a high frequency. It consists of sharp sounds like pops, scratches, and clicks.
- Broadband noise distributes acoustic energy over a wide spectrum of frequencies. Also known as continuous noise, it includes sounds like static and hissing.
- Narrow band noise is an unwanted signal with a steady level. Confined to a narrow spectrum of frequencies, this type of background noise is typically the result of faulty grounding and badly shielded cables.
Noise can be defined as “unwanted sound”. Basically, the duration and level of the noise determine the characteristics of noise. There are three main noise types.
- Broadband Noise (or continuous noise) is the noise in which the acoustic energy is distributed over a wide range of frequencies. The sounds like hiss and static belong in this category.
- Narrow Band Noise is limited to a narrow range of frequencies. This kind of noise has a constant level usually caused by incorrect grounding and poorly shielded cables. Narrow Band Noise is basically any unwanted signal that remains steady over time.
- Impulse Noise includes sharp sounds such as clicks and pops. It has a high frequency and short duration.
Other common forms of audio noise include:
- Irregular noise can come from, for instance, road traffic, electrical appliances, or people talking in the background. Their inconsistent volume levels and frequencies make these background noises quite hard to remove.
- Electrical noise can also spoil recordings with a 60/50 Hz hum. To prevent it, connect all your recording gear to the same power source, and keep your mic cables away from electric cables.
You should also be aware of the noise floor, which is the background noise level in a signal or the noise level your sound system creates.
These nine methods of removing microphone background noise will help ensure your recordings are clear.
1. Use the Right Mic Sensitivity and Gain Settings
When you’re choosing microphones, be mindful of their sensitivity, or sens. This is typically determined using a 1 kHz sine wave at a sound pressure level (SPL) of 94 dB.
While sensitivity varies from mic to mic, it has no relation to microphone quality. When recording the same sound, different mics can produce different output levels. To determine the best mic for your specific needs, look at their distortion, sens, clipping point, and noise level. For instance, a high-sens mic could need less preamp gain, and it might offer less headroom before clipping than a low-sens mic.
Condenser microphones are typically high-sens while dynamic microphones tend to be low-sens. You can adjust the mic signal level to your required input level easily with the right preamp gain. Bear in mind that you’ll incorporate some noise into the signal with each gain level. You need to ensure that the input noise of every gain stage won’t interfere with the audio signal.
Use balanced audio connections and adjust your sound source’s input level correctly to keep noise out of your mic. State-of-the-art gear will help prevent environmental noise from entering live recordings.
2. To Record Outside, Use a Microphone Windscreen
To keep wind out of outdoor recordings, you can use a foam or fur windscreen; for the best results, we suggest combining these two variants. When you put a windscreen over the head of your mic, you’ll eliminate interference from the wind, as well as disruptive mouth sounds like popping and heavy breathing. Windscreens can reduce wind noise by up to 12 dB. Of course, these shields create a lower overall input volume and reduce the level of some higher frequencies. The trade-off, however, is a clearer recording with less ambient interference from the air.
3. Remove Microphone Background Noise With a Pop Filter
Designed for indoor use, a pop filter keeps sibilance and plosive sounds off your studio recordings. Setup is easy – all you need to do is mount this disc-shaped filter on the mic stand, positioning it between the vocalist and the microphone. Pop filters have flexible booms so you can place them exactly where you need them. Alternatively, you could get a mic with a built-in pop filter.
In addition to preventing your mic from recording vocal explosions and hisses, pop filters ensure your mic stays dry, protecting your gear. Check out Amazon’s selection of pop filters.
4. Get Yourself A Shock Mount
Modern mics are extremely sensitive. You must protect yours from vibration and shocks to achieve the highest quality recordings. Easy to fit to your mic stands, shock mounts minimize noises caused by handling microphones. Take a look at this excellent shock mount for studio sessions.
Once you’ve reduced potential recording disruptions, you’re ready for the next stage of removing microphone background noise: sound processing.
5. Apply Filters
You won’t change or add new frequencies to your audio input signal when you apply filters. You can use filters to emphasize signals in specific frequency spectrums and cancel signals in other frequency ranges.
Apply a high-pass / low-cut filter to get rid of low-frequency rumble and DC offset. To get rid of DC offset, adjust your frequency control to 10 Hz. You can easily remove AC hum by setting a harmonic notch filter cut to 50 or 60 Hz.
There are five fundamental filters:
- A bandpass filter separates a solitary signal at one frequency, or within a spectrum of frequencies, from signals at other frequencies.
- A notch or band-reject filter is the opposite of a bandpass filter. You can use this filter to rid a signal of an undesired frequency with little to no effect on all other frequencies.
- A low-pass filter allows low frequencies to pass through while rejecting audio signals that are higher than the filter’s cut-off frequency. Apply low-pass filters when you want to remove high frequencies from a signal.
- A high-pass has the opposite function of a low-pass filter, removing signals that are lower than its cut-off frequency. Use this type of filter when you want to remove low-frequency signals.
- An all-pass (or phase-shift) filter has no effect on the signal’s amplitude. Use this to change the signal’s phase without altering its amplitude.
Available on every mixer, low-cut (high-pass) is the most popular filter type. You can use it to reduce low-frequency rumbling. Start at 20hz and increase it until you hit the sweet spot without affecting the input sound. For instance, you can go up to 100hz for male vocals and 120hz for female vocals. The best way to remove microphone background noise with this and any other filter is simply to experiment. This helpful article covers filters in greater detail.
If you can still hear background noise after applying filters, you can fine-tune the signal with an equalizer.
6. Equalize It
You can modify the frequency of specific signals with a hardware or software filter known as an equalizer, or EQ.
Equalization is the optimization of sound frequencies. You can use this process to adjust the volume of selected frequencies.
Every sound has its own specific frequency, some of which are quite loud while others are difficult to hear. An EQ enables you to balance, or equalize, these frequencies. You can turn down overbearing frequencies and turn up less dominant ones to optimize the quality of your recording. Equalizers are easy to use, especially those that have a built-in analyzer, which shows you which frequencies are causing problems, helping you optimize sound quality.
For instance, if a voice recording contains hiss or white noise and the analyzer indicates 7khz is the dominant frequency, use your EQ to select and decrease that frequency. The difference in quality should be immediately obvious.
Alternatively, if you’re handling the sound for a live performance without a digital mixer, you’ll need to depend on your ears. Every tone has a specific frequency, so you should practice identifying frequencies that are either missing or excessively loud.
The first thing to attempt with an EQ is to reduce the frequency level rather than raise it.
A noise gate is a handy sound processing app. If you have the option of using one in the form of a digital mixer or external unit for a live performance, you’ll have a much easier time removing undesired sounds. It’s also a valuable post-production tool.
7. Reduce Unwanted Sounds With a Noise Gate
To remove undesired background sounds, use a noise gate, which only allows an audio signal of a level above a threshold noise level to pass through. When you set it correctly, your noise gate reduces power supply humming and steady amp static without affecting your sound source. With your noise gate and minimal adjustments, you can remove microphone background noise in live as well as studio settings.
Typically, a noise gate has five parameters:
- Threshold controls the dB level above which audio signals pass through the gate.
- Attack controls how soon the gate opens after the audio signal exceeds the threshold.
- Hold controls how long the noise gate remains open once the signal exceeds the threshold, even after the signal goes down.
- Ratio controls the balance between the original and gated sounds.
- Release controls how soon the gate closes after the signal drops below the threshold – a fast release stops the signal abruptly; a slower release fades the signal out gradually. If your release is too quick, you’ll end up with a clicking sound.
8. Be Careful Using Noise Reduction Software
Use noise reduction software with caution, as you could end up losing audio data while removing background noise. In some cases, you’re actually better off keeping a bit of noise in your recording rather than deleting a considerable amount of your audio tracks.
In the simplest terms, audio noise reduction is a system that helps get rid of unwanted noise from an audio signal. The objective of this process is always to isolate a clear audio signal from noise.
The market has an overabundance of noise reduction software plugins, each one of which fundamentally works on the same principle: “Capture noise print and apply”. Additional parameter settings are the only feature that differentiates them. For sound restoration, you can even get full-featured digital audio workstations (DAW). The popular Izotope, for instance, comes with state-of-the-art rx7 audio editing software for post-production work. Other notable audio restoration software providers include Sound Forge, Waves, Audacity, and Adobe.
Partly because it’s free, Audacity is an especially popular software solution. It has a respectable noise reduction plugin that does a good job of removing microphone background noise. The function is easy to use. Simply open the plugin, select a region that only contains the noise, and click on “Get noise profile”. Then select the audio you want to remove noise from and click “OK” – you’ll hear your audio track improving immediately. You can adjust other parameters if you need an even better sound.
9. Apply Adaptive Noise Reduction
This method of noise removal uses a reference audio input signal that only contains noise. You transmit the signal through an adaptive filter, which enables you to reduce it from the main input signal. You can apply adaptive noise cancellation to swiftly get rid of noises from, for instance, traffic, weather, and background conversations. Pretty much every modern noise reduction software solution offers this capability. You’ll find it handy when you want to remove microphone background noise in real time.
All audio recordings contain unwanted noise; you must use ambient noise reduction to achieve the highest quality sound. Until relatively recently, this process was costly and complicated. Advances in sound card technology and software have simplified noise removal immensely. This tech, plus the handy guide you just finished reading, will ensure you keep as much noise as possible out of your recordings, both live and in the studio.
You should also check out this recording gear over on Amazon:
- Rode Shotgun Mic – Thanks in part to its shock mount, this amazing microphone is ideal for reducing noise. Put a windscreen on it to get excellent outdoor recordings.
- Pop Filter – This keeps plosives and sibilance out of your recordings. It’s great for capturing vocals from close up.
- Rode NT1 Mic and pop shield – Delivering high-quality sound, this microphone and pop shield combo is perfect for studio recording, podcasting, and interviews.
- Acoustic Noise Panels – These cancel room noise, saving you time in post-production. Great for podcasting.