Microphone array

A microphone array is any number of microphones operating in tandem. There are many applications:

• Systems for extracting voice input from ambient noise (notably telephones, speech recognition systems, hearing aids)
• Surround sound and related technologies
• Locating objects by sound: acoustic source localization, e.g. military use to locate the source(s) of artillery fire. Aircraft location and tracking.
• High fidelity original recordings

Typically, an array is made up of omnidirectional microphones distributed about the perimeter of a space, linked to a computer that records and interprets the results into a coherent form. Arrays may also be formed using numbers of very closely spaced microphones. Given a fixed physical relationship in space between the different individual microphone transducer array elements, simultaneous DSP ( Digital signal processor ) processing of the signals from each of the individual microphone array elements can create one or more "virtual" microphones. Different algorithms permit the creation of virtual microphones with extremely complex virtual polar patterns and even the possibility to steer the individual lobes of the virtual microphones patterns so as to home-in-on, or to reject, particular sources of sound.

An array of 1020 microphones[1], the largest in the world, was built by researchers at the MIT Computer Science and Artificial Intelligence Laboratory.

Microsoft's Windows Vista computer operating system has built-in support for microphone arrays for increasing the accuracy of its speech recognition feature, letting users connect multiple microphones to a single system, so that the inputs can be combined into a single, higher-quality source.

Soundfield microphone

The Soundfield microphone system is a well established example of the use of a microphone array in professional sound recording.

See also

• Microphone
• Stereophonic sound
• Decca tree
• Surround sound
• Ambisonics
• Acoustic source localization

External links

• Acoustic Camera, System for online and Real-Time Sound Sources Identification in 2D and 3D.
• Fukada's tree, in an AES paper about Multichannel Music Recording.
• Hamasaki's square, in an AES paper about Multichannel Recording Techniques.
• HEAD Visor, System for Real-Time Identification of Sound Sources.
• Squarehead Technology makes microphone arrays for directive sound pickup for conference and broadcast use.
• Trinnov Audio's SRP microphone array for surround recording.
• Dr Theile's OCT array.
• hauptmikrofon.de, a website about Stereophony, Surround Sound, Binaural and Wave Field Synthesis (WFS).
• Core Sound's TetraMic A first-order Ambisonics microphone using a tetrahedral array.
• An introduction to Acoustic Beamforming
• Literature on source localization with microphone arrays.
• An introduction to Acoustic Holography