The amount of noise in a microphone signal can ruin an otherwise perfect sound capture. Low noise levels separate the pro from the amateur audio recordings and should be strived for by everyone.
How To Reduce Microphone Noise:
- Choose A Condenser Or Active Mic With Low Self-Noise
- Choose A Dynamic Mic With A Humbucking Coil
- Place Mics Closer To The Sound Source
- Use A Shock Mount
- Use A Pop Filter
- Record In Quiet Or Soundproof Environments
- Use Balanced Mic Cables
- Do Not Run Mic Cables Alongside Power Cables
- Use An RF Filter
- High-Pass Filter The Mic Signal
- Use A Pad When Approaching Max SPL
- Plug The Mic Into A Mic Input
- Use Clean Preamps
- Use An In-Line Preamp Before The Mic Preamp
- Use A Noise Suppression Plugin In Your DAW
Let's discuss each of these methods in greater detail.
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1. Choose A Condenser Or Active Mic With Low Self-Noise
Condenser microphones (and other active microphones) have what is known as “self-noise.”
Self-noise is defined as the noise introduced into the mic signal via active components (like transistors, vacuum tubes, and printed circuit boards) and as the noise emitted from these components that are captured by the mic capsule.
In fact, signal-to-noise ratio (SNR) ratings are given to active microphones based on their self-noise ratings.
When choosing a condenser or active microphone, check out the self-noise rating. Any rating above roughly 20 dBA means the microphone will output a noticeable hiss of noise.
Sticking to mics with low self-noise is the way to go if we're looking to reduce microphone noise.
For a deeper read into self-noise, check out my article What Is Microphone Self-Noise? (Equivalent Noise Level).
2. Choose A Dynamic Mic With A Humbucking Coil
Passive moving-coil dynamic microphones do not have active components, so they do not have self-noise ratings.
That being said, the components of these microphones do draw noise into the microphone signal. The magnets and conductive coils of dynamic mics are particularly sensitive to electromagnetic interference (EMI).
A dynamic microphone that features a humbucking coil is often less noisy than another dynamic mic without this humbucker.
This covers the section on choosing quieter microphones. Chances are, though, that you're looking to reduce noise in the microphones you already have. In that case, let's move on to mic positioning and accessories.
3. Place The Mic Closer To The Sound Source
Although this may not technically reduce the noise in the microphone, it will certainly help improve the signal-to-noise ratio of your microphone.
A higher SNR will certainly yield a mic signal that sounds as if it has less noise. That is because:
- The signal will require less gain (the noise floor will not be boosted as much).
- The intended sound in the signal will be perceived much louder than the noise.
Placing a microphone closer to a sound source increases the amount of that sound source (we'll call it the signal) relative to the amount of noise in the mic output. This is explainable with the inverse-square law.
The inverse-square law states that as sound moves away from its source, its sound pressure drops by half (- 6 dB) for every doubling of distance.
This tells us that if we halved the distance between our mic and the sound source, our “signal” (being the intended sound source) would be 6 dB louder at the microphone capsule!
Therefore, if we look strictly at the signal-to-noise ratio (rather than just noise), moving the microphone closer to the sound source will reduce the noise in the microphone's output signal.
For more on microphone positioning, check out my article Top 23 Tips For Better Microphone Placement.
4. Use A Shock Mount
Mechanical noise is a major type of noise that affects microphones. It is defined as any vibrations through solids that reach the microphone capsule and cause noise in the mic signal.
Examples of this could be handling noise (from holding the microphone), vibrations from the instruments on a stage, footsteps on the floor of a studio, and even the naturally low rumbling of the Earth.
A shock mount helps isolate the microphone from these mechanical noises, thus reducing the noise in the mic.
There are two main categories of microphone shock mounts:
- Internal shock mounts: the shock mounts are built into the microphone itself and help to mechanically isolate the capsule/cartridge from the body of the microphone.
- External shock mounts: these are the “basket” type microphone clips you see in studios. External shock mounts hold the microphone in place while connecting to a stand and act to mechanically isolate the entire mic. They use different fabrics to help reduce the mechanical noise transfer from the stand to the microphone.
The mechanical isolation provided by these shock mounts can greatly reduce the strength of the vibrations that reach the microphone capsule through solids.
For more information on microphone shock mounts, check out my article What Is A Microphone Shock Mount And Why Is It Important?
My top recommended shock mounts are:
To read more, check out my article: Best Microphone Shock Mounts.
5. Use A Pop Filter
I was hesitant to add this to the list, but I decided to in the end.
The reason being that many people use microphones to record or reinforce the human voice and that vocal plosives (“P-pops”) can certainly be considered unwanted “noise” in the microphone signal.
Pop filters act to dissipate the blasts of air causes by vocal plosives before they reach the microphone capsule and overload it.
Plosives, in English, happen on the hard consonant sounds of P, B, D, T, G, and K. Part of the vocal path closes (lips; tongue and palate; or tongue and throat) momentarily and opens back up, causing a blast of air known as a plosive.
By placing a pop filter between the speaker/singer and the microphone, we can greatly reduce the risk of plosives in the microphone signal and, in this way, reduce the “noise” in the microphone.
My top recommended pop filters are:
To read more, check out my article Best Microphone Pop Filters.
6. Record In Quiet Or Soundproof Environments
This may seem like an overly obvious tip, but it's worth mentioning.
To reduce noise, reduce the ambient noise of the environment.
The best example of this is the typical soundproof studio isolation booth. These booths are soundproofed so that no sound will enter them from the outside. They also have padded walls on the inside to create an acoustically dead environment where sound will not reflect off the surfaces.
There will be much less extraneous noise with a single sound source in a soundproof iso-booth than in other environments.
The most extreme example of a soundproof room is an anechoic chamber, which is designed to have no ambient noise whatsoever.
So it goes without saying that moving to a quieter environment will reduce noise. Let's look at some other not-so-obvious methods to reduce the noise of our environments.
If possible, try the following to reduce ambient noise in your microphones signals:
- In buildings, record away from fans, heat pumps, refrigerators, etc.
- Outdoors, record away from street traffic, construction, etc.
- Hang blankets on the walls in a non-soundproof room to reduce room reflections.
- Use a vocal isolation shield to reduce room reflections.
- Record in a separate room from your computer if you're using a DAW to reduce computer noise.
- Get the talent to stay relatively still while performing into the microphone to reduce noise from clothing, footsteps, etc.
- On location records, see if you can get the people to be quiet during recording. Sometimes this is not possible.
7. Use Balanced Mic Cables
If you're using professional microphones, you're probably also using balanced mic cables.
The most commonly used balanced microphone cable is the 3-pin XLR.
Balanced cables work by carrying the audio signal on two pins rather than one (in unbalanced cables). The audio signal is carried with positive polarity on one pin and negative polarity on the other.
At the mic preamp, a differential amplifier sums up the differences between these two audio pins while rejecting the commonalities. This is known as common-mode rejection.
Any electromagnetic interference (EMI) the cable will experience should cause the same noise on each of the audio wires. With common-mode rejection, this noise will be eliminated at the mic preamp!
Check out my take on the Top 11 Best XLR Cable Brands In The World.
The EMI induced on a balanced cable is nearly identical on both audio wires/pins. In the real world, there will be slight differences (because the cables cannot both be in the same exact space), but these differences are minor relative to unbalanced cables.
My top recommended balanced mic cables are:
To read more, check out my article Best Microphone Cables.
8. Do Not Run Mic Cables Alongside Power Cables
Because any cable is susceptible to EMI, running mic cables alongside power cables is not recommended. It's always best practice, if possible, to cross a mic cable and a power cable at a single point rather than running them together.
This is because the power mains (and their cables) emit electromagnetic noise. The closer the power cable is to the mic cable, the more likely the mic cable is to pick up this noise.
In the US and most of the Americas, this is known as the dreaded “60 cycle hum” because the AC power mains have a frequency of 60 Hz. In many other places in the world, the power mains run at 50 Hz.
So to reduce the likelihood of power mains hum, try crossing your mic cables and power cables as few times as possible. This will reduce the noise in the microphone signal.
9. Use An RF Filter
Radio frequency interference (RFI) is another culprit when it comes to EMI in a microphone signal.
If you're using a microphone in a city or anywhere near a radio station, you run the risk of RFI in your microphone signals.
Note that some microphones are more sensitive to RFI than others. For example, I work in an audio production house across the street from a radio station and a television station. Our Rode NT1-A is barely affected by RFI in my studio room, whereas our Neumann U 87 Ai picks up the radio station noise clear as day.
The noise caused by RFI is bad enough. Even worse is hearing radio pop music in the mic signal when you're trying to record a voiceover!
To further reduce EMI and eliminate RFI from the mic signal, try using an RF filter. These filters go in-line (I typically plug them directly into the microphone and connect the filter to the XLR).
The RF filter we use at the studio, which I would highly recommend, is the Shure A15RF.
10. High-Pass Filter The Mic Signal
If low-end hum (from power mains) or rumble (from traffic, footsteps, machines, etc.) is unavoidable, we can try reducing noise from our mic signal with a high-pass filter.
A high-pass filter takes out the low frequencies of the microphone signal (it “allows the highs to pass”).
High-pass filtering a mic signal at 100 Hz or above can really reduce the amount of low-frequency noise, including:
- AC mains hum (50 or 60 Hz).
- Mechanical noise (the vibrations that reach the microphone through solids) including low-end rumble.
- Low-end rumble (rumbling from street traffic, machines, etc.).
Caution must be taken when high-pass filtering a microphone signal. Setting the filter at too high a frequency will cause the signal to sound thin. When recording high-pitched sound sources, this isn't as big of a deal. When recording bass sound sources (low voice, tuba, kick drum, bass guitar, etc.), high-passing the signal may not be a great choice.
That being said, if you find there is too much low-end noise in the mic signal, try engaging an HPF on the signal.
Some microphones have built-in HPFs (like the aforementioned Neumann U 87 Ai).
HPFs can also be found in/as the following:
- Standalone “in-line” units (both mic level and line level units).
- Built into microphone preamplifiers.
- As software plugins in for use in you computer/DAW.
For more info on high-pass filters, check out the following My New Microphone articles:
• What Is A Microphone High-Pass Filter And Why Use One?
• Audio EQ: What Is A High-Pass Filter & How Do HPFs Work?
High-pass filters can sometimes be found in the microphone itself and are sometimes found in the mic preamp.
If not found there, the EQ in the channel strip of analog and digital consoles will have an HPF. In digital audio workstations, there are plenty of EQ plugins to effectively high-pass the audio signal.
That being said, Shure does make an inline high-pass filter that I feel comfortable recommending, though I've never had to use it myself. This HPF is the Shure A15HP.
11. Use A Pad When Approaching Max SPL
This is an interesting point. Generally speaking, the louder the sound source, the better the signal-to-noise ratio in the microphone that captures it.
However, in active microphones, a loud sound source may exceed the microphone's maximum sound pressure level (max SPL).
A microphone's max SPL rating tells us the point at which the microphone signal will start to distort. Usually, this is measured with a 1 kHz tone, and the distortion threshold is set as 0.5% total harmonic distortion.
Although distortion is not technical noise (it's an alteration to the signal), it does add harmonics to the signal, which could be considered noise.
Sometimes exceeding a max SPL rating will yield a somewhat pleasant saturation to the signal. Other times it can really distort the signal and make it sound terrible.
But distortion is not the main culprit here; it's the ambient noise in the environment.
By engaging a pad (passive attenuation device) on a loud sound source, we effectively reduce the extraneous noise in the mic signal while still capturing a strong sound source.
A pad (passive attenuation device) is an audio device that reduces the microphone signal level.
It's important to note that pads will not change the mic's natural signal-to-noise ratio. Lowering the mic signal with a pad will lower the noise in the signal by the same amount that it lowers the intended signal.
If there is no pad in your microphone or your mic preamplifier, then I'd recommend yet another in-line processor by Shure. The Shure A15AS has 3 switchable pads at -15, -20, and -25 dB.
12. Plug The Mic Into A Mic Input
A sure-fire way to cause unnecessary noise in your mic signal is to connect your microphone to an input that is not designed for it.
A mic input expects a mic level signal and is typically balanced (these are most often the female XLR connectors on mixers, recorders, interfaces, etc.).
Plugging a microphone into a mic input means the signal will be transferred to a circuit that works well with it.
If we were to plug a microphone into a line input, we would have a terrible noise issue. This is because line inputs expect a signal 10 to 1000 times stronger than a microphone's mic level signal. The inherent noise in the input could be as loud or even louder than the mic level signal.
For more information on microphones and mic level, check out my article Do Microphones Output Mic, Line, Or Instrument Level Signals?
Mic inputs typically include microphone preamplifiers, which brings us to the next point.
13. Use Clean Preamps
Clean preamplifiers are essential if we are to have pristine audio quality from our microphones.
The good news is that many mic preamps (and nearly all professional mic preamps) will supply enough clean gain to boost an active microphone's signal to line level without introducing a noticeable amount of noise.
It's important to know that, for better or worse, some professional preamps do add colour to the mic signal. In fact, any analog circuitry (in this non-ideal world we live in) will colour the mic signal.
The issues really start coming up when we use passive microphones with low sensitivity ratings (most notably ribbon microphones).
Low sensitivity dynamic microphones require a lot of gain (sometimes upwards of 80-100 dB) to get boosted to line level (an active mic may only require 30-60 dB). Not many preamps can supply that much clean gain, and most introduce a noticeable amount of noise to the audio signal.
So if you are using low-sensitivity microphones (especially on quiet sound sources) and want low-noise, choosing a high-end preamp is a good call.
High-end preamps of this sort cost a lot of money. A cheaper method of supplying clean gain to your mic signal is to put an extra (low-noise) preamp inline between your microphone and your mixer, recorder, interface, etc.
To learn more about microphone preamplifiers, check out the following My New Microphone articles:
• What Is A Microphone Preamplifier & Why Does A Mic Need One?
• Complete Guide To Microphone Preamplifier Specifications
• Best Microphone Preamplifiers
• Top 13 Best Microphone Preamplifier Brands In The World 2021
14. Use An In-Line Preamp Before The Mic Preamp
Consider a low-noise inline preamp if you really need the gain and cannot afford the high-end preamps.
These preamps can offer extra clean gain before the signal reaches the main preamp of the mixer, recorder, interface, etc.
15. Use A Noise Suppression Plugin In Your DAW
If all else fails and you end up working with a noisy audio signal in your digital audio workstation (DAW), you can also pick up a noise reduction plugin.
As an additional tip, if your computer has the processing power, you can track the microphone through a noise suppression plugin when recording or monitoring your mic signal.
Sometimes we cannot get our microphone signal clean on the way in. Luckily for us, we live in the age of plugins that can help to digitally reduce the noise within our mic signals.
If you've already recorded audio and have noisy multitracks, please check out this article for help: How Do I Get Rid Of The Noise In The Multitracks Of My Mix?
Related article: Top 7 Best Noise Reduction Plugins For Your DAW
So we've covered 15 methods to reduce noise in our microphone signals. Clean mic signals can make a huge difference in the quality of our recordings and should be strived for by professionals.
In discussing these 15 tips, I've written about choosing the proper mic; positioning the mic and cables (environment, proximity, and hardware); signal flow/gain, and audio processors.
Let's recap the 15 steps in these categories:
Choosing A Microphone
- Choose a condenser or active mic with low self-noise
- Choose a mic with a humbucking coil
Positioning The Microphone
- Place directional mics closer to the sound source
- Use a shock mount
- Use a pop filter in front of the mic for vocals
- Record in quiet or soundproof environments
- Do not run mic cables alongside power cables
- Use balanced mic cables
- Plug the mic into a mic input
- Use clean preamps
- Use an in-line preamp before the mic preamp
Using Audio Processors
- Use an RF filter
- High-pass filter the mic signal
- Use a pad when approaching max SPL
- Use a noise suppression plugin in your DAW
How do I lower my mic sensitivity? The sensitivity rating of a microphone is set (unless you alter the microphone components). However, Windows OS refers to mic gain/volume as “sensitivity,” and in order to change that value, do the following:
- Open Control Panel
- Open Sound
- Click the Recordings Tab
- Click on Microphone
- Change the Sensitivity Levels
For an in-depth read on microphone sensitivity, check out the following My New Microphone articles:
• What Is Microphone Sensitivity? An In-Depth Description
• What Is A Good Microphone Sensitivity Rating?
How do I rid of microphone feedback? Microphone feedback happens when a live microphone picks up the sound of its own amplified signal from a loudspeaker. To rid of feedback, we must reduce the amount of sound the mic picks up from the speaker. Methods to do this include:
- Turning down the speaker
- Decreasing the microphone gain
- Increasing the distance between the mic and speaker
- Pointing the mic and speaker away from each other
- Filtering out the problem frequencies
To read more about microphone feedback, check out 12 Methods To Prevent & Eliminate Microphone/Audio Feedback.
Choosing the right microphone(s) for your applications and budget can be a challenging task. For this reason, I've created My New Microphone's Comprehensive Microphone Buyer's Guide. Check it out for help in determining your next microphone purchase.
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Make the right decisions at the right times to craft professional mixes!