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
• Binaural recording
• 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, directional microphones, or a mix of omnidirectional and directional 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.

In case the array consists of omnidirectional microphones they accept sound from all directions, so electrical signals of the microphones contain the information about the sounds coming from all directions. Joint processing of these sounds allows to select the sound signal coming from the given direction. So, microphone array selects the sound coming from a given direction by processing multichannel signals. ^[1]

An array of 1020 microphones , the largest in the world until August 21st 2014, was built by researchers at the MIT Computer Science and Artificial Intelligence Laboratory.

Currently the largest microphone array in the world was constructed by Sorama, a Netherlands-based sound engineering firm, in August 2014. Their array consists of 4096 microphones.

Soundfield microphone

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

See also

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

Notes

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.
• Literature on source localization with microphone arrays.
• An introduction to Acoustic Holography
• A collection of pages providing a simple introduction to microphone array beamforming