Microphone array
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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
- Environmental noise monitoring[1]
- Robotic navigation (acoustic SLAM)[2]
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. The application of these algorithms can produce varying levels of accuracy when calculating source level and location, and as such, care should be taken when deciding how the individual lobes of the virtual microphones are derived.[3]
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 selecting the sound signal coming from the given direction.[4]
An array of 1020 microphones,[5] the largest in the world until August 21, 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 DLR, the German Aerospace Center, in 2024. Their array consists of 7200 microphones with an aperture of 8 m x 6 m.[6]
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
- ^ Environmental Noise Compass
- ^ Evers, Christine; Naylor, Patrick A. (September 2018). "Acoustic SLAM" (PDF). IEEE/ACM Transactions on Audio, Speech, and Language Processing. 26 (9): 1484–1498. doi:10.1109/TASLP.2018.2828321. ISSN 2329-9290. Archived (PDF) from the original on 2020-05-05.
- ^ Jesse Tribby (9 November 2016), Assessing the accuracy of directional real-time noise monitoring systems (PDF), archived (PDF) from the original on 2017-03-16, retrieved 2020-05-09
- ^ Stolbov M.B. (2015). "Application of microphone arrays for distant speech capture". Scientific and Technical Journal of Information Technologies, Mechanics and Optics. 15 (4): 661–675.
- ^ LOUD: Large acOUstic Data Array Project
- ^ Enhancing Aeroacoustic Wind Tunnel Studies through Massive Channel Upscaling with MEMS Microphones
External links
- 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