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What is a Microphone Array? – For a Myriad of Uses!

Did you know that microphones are not just used for entertainment purposes? Most people would picture a large stage with performers on it, whenever they talk about microphones. But in reality, these devices are much more versatile than you think. Want to know more about its uses? Then you need to learn what is a Microphone Array!

In my opinion, today’s subject is really straightforward and easy to understand. However, at the same time, I feel that this topic is rarely discussed in-depth, even among audio professionals (just my opinion). Hence, we are going to learn about the various functions of the microphone array and how they benefit various audio related projects!

Microphone Array – A Complex System?

In principle, any number of microphones that are designed to operate in tandem, is called a microphone array. There are many applications in the world of audio engineering, that utilizes this recording concept. A microphone array is usually is made up of omnidirectional microphones, unidirectional microphones, or a mix of both types.

Neumann U87

The Neumann U87, a popular microphone that can be used as an omnidirectional mic / Photo by Will Fisher / CC BY-SA 2.0

In many cases, these microphones will then be positioned along the perimeter of a space, and connected to a computer (with a running software) that analyzes the recording and interprets it into coherent information. There are also situations where arrays are designed to include a number of microphones that are arranged to be very close together.

Since there is a fixed physical relationship in space between the different types of microphones within the array system, one or more “virtual” microphones can thus be created by having every one of the signals from each individual microphone array element to be processed simultaneously by a DSP (digital signal processor).

AKG C451B

The AKG C451B, a well known microphone with a unidirectional polar pattern / Photo by Harumphy at en.wikipedia / CC BY-SA 3.0

By using the different software algorithms available, it is possible to create virtual microphones with extremely complex virtual polar patterns. Some software even has the capability to allow attenuation of the individual lobes of the polar patterns of all the virtual microphones, in order to focus on, or to reject specific sounds coming from a particular source.

Design Considerations

It is important to take note that in such applications, the algorithms that are used to calculate the source level and location, will produce varying levels of accuracy. Hence, careful considerations should be practised when deciding how the individual lobes of the virtual microphones will be shaped.

Omnidirectional Polar Pattern

A diagram showing an omnidirectional polar pattern / Photo by Galak76 / CC BY-SA 3.0

Furthermore, if the array consists of only omnidirectional microphones (which captures sound from all directions), then the audio signals from the mics will contain information on sounds coming from all directions. These signals will often be routed to multiple channels, and can then be processed in order to allow the selection of a sound signal coming from any given direction.

Various Applications

A microphone array is used in many applications within the professional audio industry. Here are some of them:

  • Systems for extracting voice input from ambient noise (notably telephones, speech recognition systems, hearing aids)
  • Surround sound and related technologies
  • Binaural recording
  • Acoustic source localization (locating objects by sound), e.g., military use to locate the source(s) of artillery fire, aircraft location, and tracking
  • High fidelity original recordings
  • Environmental Noise Monitoring

The largest microphone array in the world (until August 21st 2014), consisting of 1020 microphones, was built by researchers at the MIT Computer Science and Artificial Intelligence Laboratory. Shortly after, Sorama (a Netherlands-based sound engineering firm), broke the record in the same month, by building an array consisting of 4096 microphones.

A very well known example of the use of a microphone array in professional sound recording, is the Soundfield microphone system. This system is not only very versatile and powerful, but is also portable, which makes it ideal for outdoor recordings.

This is all the information I have for you guys today. Have you seen any microphone arrays being used in public areas before?

Let me know your thoughts down below, and share this article with your friends!

Farhan

When I'm not rocking out to great music, I'd prefer to be sleeping on a field on a windy day =)

2 Comments

  1. Aw I loved this article. I’m really into music, listening as well as playing, and just recently bought a mike for my go – pro to catch better audio on it. There seems to be an improvement for sure. What sparked my interest about this one in the article is the ability to pick up on ambient noise, which I could see as a big plus.

    • Hey JP!

      GoPro is becoming more popular with many recording enthusiasts these days. I might just get one soon, to use during my travels. Its good to know that you have experience using one with an on-board microphone. Would be great to know how the quality is like!

      Thanks for dropping by, and do keep in touch!

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