Getting background noise on a recording is one of the most frustrating experiences to
have when trying to create music. You may of course immediately look at your
microphones and wonder why they are picking this up. But rarely is it due to a
problem with your microphone. In fact it’s usually because your microphone is
doing exactly what it’s supposed to do – very well. The problem usually lies in
everything else around it.

Parts of a Microphone

Diaphragm: The diaphragm is a thin, sensitive membrane that vibrates in response to sound
waves. It acts as the primary sound-capturing element of the microphone.

Capsule: The diaphragm is usually part of a capsule, which consists of a backplate and a
diaphragm separated by a small air gap. The sound waves cause the diaphragm to
move relative to the backplate, generating an electrical signal.

Transducer: The diaphragm and the backplate form a transducer, which converts sound waves into
electrical signals. When the diaphragm moves, it changes the capacitance
between the diaphragm and the backplate, resulting in an electrical output
proportional to the sound waves.

Magnet or Electret material: Some microphones use a magnet and a coil to convert the
mechanical vibrations of the diaphragm into electrical signals. These are known
as dynamic microphones. Others use an electret material, which is a permanently
charged material, to generate the electrical signal. Electret condenser
microphones are common examples.

Pre-amplifier: In many microphones, the electrical signal generated by the diaphragm or the
transducer is very weak. To boost the signal to a usable level, a pre-amplifier
circuit is often integrated into the microphone. The pre-amplifier increases
the signal strength and prepares it for further processing or transmission.

Output Connector: The microphone is typically equipped with an output connector that allows it to be connected to other audio equipment. The connector type may vary depending on
the microphone, such as XLR, TRS (1/4-inch), or USB.

Housing and Grill: The components of the microphone are enclosed within a housing or body, which provides physical protection and helps reduce unwanted noise and vibrations.
The housing often includes a grill or windscreen that helps to minimize the
effect of wind and plosive sounds on the diaphragm.

How Microphones Work

Now, let’s understand exactly how microphones work. Microphones work by converting sound
waves into electrical signals through the interaction of a diaphragm, a coil or
capacitor, and a magnet. As sound waves reach the diaphragm, it vibrates,
causing the attached coil to move in dynamic microphones or changing the
capacitance in condenser microphones. These variations generate weak electrical
signals that can be amplified and further processed for recording or
transmission.

The diaphragm is a thin, flexible membrane typically made of materials like metal or plastic. It
serves as the primary element that responds to sound waves. When sound waves
reach the diaphragm, they cause it to vibrate in sync with the variations in
air pressure. The diaphragm’s movement corresponds to the changes in the sound
waves’ intensity and frequency.

In dynamic microphones, the diaphragm is attached to a coil of wire. This coil is
suspended within a magnetic field generated by a permanent magnet. When the
diaphragm vibrates, it moves the attached coil within the magnetic field,
inducing an electrical current to flow through the coil. This movement of the
coil generates an electrical signal that mirrors the audio waveform.

In condenser microphones, the diaphragm is placed in close proximity to a fixed backplate,
creating a capacitor. The diaphragm acts as one plate of the capacitor, and the
backplate serves as the other plate. When sound waves reach the diaphragm, they
cause it to move, altering the distance between the diaphragm and the
backplate. This change in distance results in the variation of capacitance,
which leads to an electrical signal being produced.

In both dynamic and condenser microphones, the electrical signal generated by the diaphragm’s
movement is typically weak. Therefore, it needs to be amplified before it can
be recorded or transmitted. This is where preamps or audio interfaces come into
play, as they boost the microphone’s weak electrical signal to a level suitable
for further processing or recording.

Different microphone designs and technologies offer unique characteristics and
applications. For example, dynamic microphones are robust and versatile, making
them suitable for live performances and recording instruments. Condenser
microphones, on the other hand, are more sensitive and capture a wider
frequency range, making them ideal for studio vocals and capturing intricate
details.

It’s important to note that microphones also have various pickup patterns, determining their sensitivity to sound from different directions. Omnidirectional microphones capture sound
equally from all directions, while cardioid microphones are more focused on the
front and reject sound from the sides and rear. There are also bidirectional
(figure-8), supercardioid, and shotgun microphones, each with their own unique
directional characteristics.

Why Microphones Pickup Background Noise

Microphones are sensitive devices, designed to capture a wide range of frequencies. This
sensitivity allows them to faithfully reproduce audio, but it also means they
can pick up subtle sounds that may go unnoticed by the human ear. This includes
low-level noise generated by electronic components within the microphone
itself, known as self-noise.

Interference can also contribute to background noise. Electromagnetic interference (EMI) and
radio frequency interference (RFI) can disrupt the microphone’s electrical
signal, resulting in unwanted noise. EMI can be caused by nearby electronic
devices or power lines, while RFI can originate from sources like radio
transmitters or wireless communication equipment.

Additionally, mechanical vibrations can be transmitted to the microphone through its stand,
cables, or the surface it is placed on. These vibrations, whether from foot
traffic, handling the microphone, or other physical sources, can introduce
background noise into the captured audio.

How To Reduce
Microphone Background Noise

Now, let’s get to it. Reducing background noise on your microphone relies on mostly external factors.

Select the right microphone: Different microphones have different characteristics and pickup
patterns. Choose a microphone that is suitable for your specific application
and environment. Directional microphones, such as cardioid or shotgun microphones,
are often more effective at rejecting background noise compared to
omnidirectional microphones.

Use a shock mount: A shock mount is a device used to suspend a microphone and isolate it
from vibrations and handling noise. Its primary purpose is to reduce or
eliminate unwanted mechanical vibrations that can be transmitted through the
microphone stand or mounting system. By doing so, a shock mount helps to
improve the overall audio quality by minimizing the impact of these vibrations
on the microphone’s diaphragm.

Control the environment: Minimize or eliminate sources of background noise in the recording
environment as much as possible. Close windows to reduce outdoor noise, turn
off noisy equipment, and choose a quiet location for recording. Consider using
soundproofing materials or acoustic treatment to reduce reverberations and
external noise.

Adjust microphone placement: Proper microphone placement can make a significant difference.
Position the microphone as close to the sound source as possible while
maintaining a suitable distance to avoid distortion. This helps capture more of
the desired sound and reduces the impact of distant background noise.

Use a pop filter or windscreen: Pop filters or windscreens placed in front of the microphone can
help reduce plosive sounds (such as “p” or “b” sounds) and
wind noise. They act as physical barriers that disrupt the airflow, minimizing
unwanted noise caused by air movement.

Reduce electronic interference: Keep the microphone away from sources of electromagnetic
interference (EMI) or radio frequency interference (RFI). Move away from power
lines, electronic devices, or wireless communication equipment that can
introduce noise. Additionally, use shielded cables to minimize interference.

Use noise reduction software or hardware: Post-processing techniques can be employed to
remove or reduce background noise. Audio editing software often includes noise
reduction tools that allow you to analyze and remove specific frequencies or
constant background sounds. Alternatively, dedicated hardware processors or
noise gates can be used to reduce noise in real-time during recording or live
performances.

Minimize handling noise: Handling the microphone or touching its stand can introduce unwanted
vibrations and noise. Use a shock mount or a microphone stand with vibration
isolation to reduce handling noise. Avoid unnecessary movements or impacts near
the microphone during recording.

Check microphone sensitivity and gain settings: Adjust the microphone’s sensitivity or gain
settings appropriately. If the microphone gain is set too high, it can amplify
background noise. Find the optimal balance between capturing the desired sound
and minimizing background noise.

Use noise reduction plugins or devices: Consider using dedicated noise reduction plugins
or external devices, such as audio interfaces or mixers with built-in noise
reduction capabilities. These tools can help suppress background noise during
recording or live performances.

Practice good microphone technique: Encourage proper microphone technique among speakers or performers. Teach them to speak or perform close to the microphone while
avoiding unnecessary movements or rustling noises that can contribute to
background noise.

Microphones With Low Background Noise

Dynamic Microphones: Dynamic microphones are known for their excellent off-axis
rejection, meaning they are effective at minimizing sound coming from
directions other than the intended source. They are less sensitive and have a
more limited frequency response compared to condenser microphones, which can
help reduce background noise. Dynamic microphones like the Shure SM58 and
Electro-Voice RE20 are popular choices known for their ability to reject
background noise.

Shotgun Microphones: Shotgun microphones are highly directional microphones with a
narrow pickup pattern that focuses on sound sources in front of them while
attenuating sound from the sides and rear. This makes them great for isolating
the desired sound and minimizing background noise. Shotgun microphones such as
the Sennheiser MKH 416 and Rode NTG3 are widely used in film, broadcast, and outdoor
recording settings.

Noise-Canceling Condenser Microphones: Some condenser microphones feature built-in
noise-canceling technology, which actively detects and reduces background noise
during recording. These microphones use digital signal processing algorithms to
analyze and subtract unwanted noise, resulting in cleaner recordings. Examples
include the Neumann U 87 Ai and Audio-Technica AT2035X.

Lavalier Microphones with Windscreens: Lavalier microphones, also known as lapel
microphones, are typically omnidirectional and can be attached to clothing for
hands-free recording. While they may not have the same level of background
noise rejection as directional microphones, they are often used in environments
where minimizing handling noise is crucial. Using a windscreen or a foam cover
on the lavalier microphone can help reduce wind noise and minimize certain
types of background noise.

Be sure to check out our article on modeling microphones too!

What are you listening to tonight?