We naturally hear ambient noise in our waking lives (unless we live in an anechoic chamber), so it's often necessary to have ambient sound in our audio recordings. Rather, it's uncanny not to have ambient sound in our recordings. One method of capturing ambient audio is by using an ambient microphone.
What is an ambient microphone? An ambient microphone is really any microphone set up for ambient miking (where the diffuse sound is greater than the direct sound). An ambient microphone is often, but not always, purposed with capturing ambient sounds (i.e., crowd noise, distant sound and reverberation, room tone, and field ambience).
In this article, we'll cover the definition of ambience in more detail and discuss the different kinds of ambient microphones and ambient microphone arrays.
What Is An Ambient Microphone?
An ambient microphone is really any microphone that is set up for ambient miking.
Ambient miking techniques have their microphones positioned at such a distance that the room sound (reflections and reverberation) is more prominent in the mic signal than the direct sound of the sound sources.
Therefore, ambient mics are positioned far away from sound sources and best serve large acoustic environments with rich character and reverberation.
Of course, some microphone types outperform others when it comes to capturing ambient sound.
So what are some of the key specifications of a quality ambient mic?
Omnidirectional Polar Pattern
Omnidirectional ambient microphones are generally preferred over directional ambient mics.
This is because the role of the ambient mic is to capture ambient sounds (i.e., crowd noise, distant sound and reverberation, room tone, and field ambience). Ambient sounds happen in all directions, and omnidirectional microphones are equally sensitive to sound from all directions.
Therefore, omnidirectional mics are commonly chosen as ambient mics.
To learn more about the omnidirectional polar pattern, check out my article What Is An Omnidirectional Microphone? (Polar Pattern + Mic Examples).
High microphone sensitivity could refer to 2 things:
- A high microphone sensitivity rating
- The amount of sonic detail a microphone will capture
A microphone's sensitivity rating refers to the signal strength the mic will output when subjected to a given sound pressure level.
Typically this rating is given as a millivolts or dBV (signal strength) per Pascal or 94 dB SPL (sound pressure level at the mic diaphragm).
Active microphones have higher sensitivities than passive microphones since they have internal signal amplifiers.
An ambient microphone with higher sensitivity is generally preferred since the mics will be positioned further from the sound source and will, therefore, be subjected to less sound pressure level. A higher-sensitivity mic will require less preamp gain to get to line level in the mixing console/DAW.
Condenser microphones and active ribbon microphones generally have high sensitivity ratings. Note that all condenser mics are active.
For more information on microphone sensitivity ratings, check out my article What Is Microphone Sensitivity? An In-Depth Description.
Sensitivity could also refer to the amount of detail a microphone is capable of recreating.
Ambient mics are positioned so that they capture distant sounds and reflections. This creates a sonic blend with a lot of intricate characteristics that are best captured by a detailed microphone.
Condenser and ribbon microphones tend to be more detailed than moving-coil dynamic microphones due to their relatively light diaphragms.
Active microphones have self-noise specifications to tell us how much inherent noise their mic signals have.
Self-noise is caused largely by the active electronics in the microphone that add small amounts of noise to the microphone signal.
So active microphones have higher sensitivities but also have self-noise. Passive microphones have lower sensitivities but no self-noise. However, preamp gain will typically add a small amount of noise to the mic signal, and passive mics generally require more gain to get to the same level.
That being said, choosing an active mic with a low self-noise rating gives us a strong mic signal with a good signal-to-noise ratio.
This is important for ambient mics because they generally pick up low sound pressure levels (the sound intensity drops over distance). So when capturing lower sound pressure levels, we need lower self-noise to maintain a strong signal-to-noise ratio.
To read a more detailed article on microphone self-noise, check out My New Microphone's post What Is Microphone Self-Noise? (Equivalent Noise Level).
Flat Frequency Response
A flat frequency response means a microphone is equally sensitive to all the sound frequencies within its frequency response range.
This means the microphone will not accentuate (or mask) any particular frequency bands and will, therefore, sound very natural.
When capturing the sound of an acoustic space and the blend of multiple sound sources (as with ambient microphones), it's best to have a natural-sounding microphone. A flat frequency response is a major indicator that a microphone will sound natural.
For a detailed read on microphone frequency response, check out My New Microphone's Complete Guide To Microphone Frequency Response (With Mic Examples).
A Note On Condenser Microphones
When looking for a microphone with an omnidirectional polar pattern, high sensitivity rating, low self-noise, and flat frequency response, chances are a condenser microphone will be your best bet.
These active microphones generally sound very natural and will perform very well as ambient microphones.
What Is Considered “Ambient Sound?”
The most commonly accepted definition of ambient sound is the background noise present in a given acoustic environment. This definition is typically used in film but is also important to consider in any audio recording location.
So ambient microphones do not necessarily capture ambient sound, which is fairly confusing.
Ambient Microphone Applications
So what are some common applications for ambient mics and ambient miking techniques?
- Distant room mics: ambient microphones are sometimes used in studio environments as “room mics.” These mics are positioned far from the sound sources and act to capture the reverberation in the acoustic space.
- Crowd mics: ambient mics are often used for capturing the sound of an audience. Where closer distances will capture specific members of the audience more than others, ambient mics will effectively capture the overall sound of the audience.
- Field ambience: ambient mics can be used to capture ambient sound in outdoor and large environments. They may also be used to record room tone.
- Reverb channels: positioning ambient mics along with closer mics on a single sound source gives a reverb-heavy signal and a clean audio signal, respectively. Cool production can be done by mixing just these two channels and more microphones give more creative options.
What is a room mic? A room mic refers to a microphone set up at some distance from sound sources so that it captures a fully developed and/or blended sound from the source(s). Room mics are also tasked with capturing the “room sound” (reflections and reverberation within the room). Multiple room mics are often used in stereo placements.
To learn more about stereo miking techniques, check out my article Top 8 Best Stereo Miking Techniques (With Recommended Mics).
What are the different types of microphones? There are many types of microphones in the world, but the three main mic types are moving-coil dynamic, ribbon dynamic and condenser. Dynamic mics work on electromagnetic induction, while condenser mics work on electrostatic principles.
To learn more about the different types of microphones, check out the following My New Microphone articles:
• Full List Of Microphone Types And Sub-Types (With Mic Examples)
• Microphone Types: The 2 Primary Transducer Types + 5 Subtypes
• Differences Between Dynamic, Condenser, & Ribbon Microphones
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.