Microphone array
Encyclopedia
A microphone array is any number of microphone
s operating in tandem
. There are many applications:
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 microphoneshttp://cag.csail.mit.edu/mic-array/, the largest in the world, was built by researchers at the MIT
Computer Science and Artificial Intelligence Laboratory.
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.http://msdn.microsoft.com/en-us/windows/hardware/gg462985
system is a well established example of the use of a microphone array in professional sound recording.
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
s operating in tandem
Tandem
Tandem is an arrangement where a team of machines, animals or people are lined up one behind another, all facing in the same direction....
. There are many applications:
- Systems for extracting voice input from ambient noiseAmbient noise levelIn atmospheric sounding and noise pollution, ambient noise level is the background sound pressure level at a given location, normally specified as a reference level to study a new intrusive sound source.Ambient sound levels are often measured in order to map sound conditions over a...
(notably telephoneTelephoneThe telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
s, speech recognitionSpeech recognitionSpeech recognition converts spoken words to text. The term "voice recognition" is sometimes used to refer to recognition systems that must be trained to a particular speaker—as is the case for most desktop recognition software...
systems, hearing aidHearing aidA hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as "ear trumpets" or "ear horns", were passive funnel-like amplification cones designed to gather sound energy and...
s) - Surround soundSurround soundSurround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...
and related technologies - Locating objects by sound: acoustic source localizationAcoustic source localizationAcoustic source localization is the task of locating a sound source given measurements of the sound field. The sound field can be described using physical quantities like sound pressure and particle velocity. By measuring these properties it is possible to obtain a source...
, e.g. military use to locate the source(s) of artillery fire. Aircraft location and tracking. - High fidelityHigh fidelityHigh fidelity—or hi-fi—reproduction is a term used by home stereo listeners and home audio enthusiasts to refer to high-quality reproduction of sound or images, to distinguish it from the poorer quality sound produced by inexpensive audio equipment...
original recordings
Typically, an array is made up of omnidirectional
Omnidirectional
Omnidirectional refers to the notion of existing in every direction. Omnidirectional devices include:* Omnidirectional antenna, an antenna that radiates equally in all directions* VHF omnidirectional range, a type of radio navigation system for aircraft...
microphones distributed about the perimeter
Perimeter
A perimeter is a path that surrounds an area. The word comes from the Greek peri and meter . The term may be used either for the path or its length - it can be thought of as the length of the outline of a shape. The perimeter of a circular area is called circumference.- Practical uses :Calculating...
of a space, linked to a computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
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
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
) 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 microphoneshttp://cag.csail.mit.edu/mic-array/, the largest in the world, was built by researchers at the MIT
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
Computer Science and Artificial Intelligence Laboratory.
Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
computer operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer 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.http://msdn.microsoft.com/en-us/windows/hardware/gg462985
Soundfield microphone
The Soundfield microphoneSoundfield microphone
The Soundfield microphone is an audio microphone composed of four closely spaced subcardioid or cardioid microphone capsules arranged in a tetrahedron. It was invented by Michael Gerzon and Peter Craven, and is a part of, but not exclusive to, Ambisonics, a surround sound technology...
system is a well established example of the use of a microphone array in professional sound recording.
See also
- MicrophoneMicrophoneA microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
- Stereophonic soundStereophonic soundThe term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
- Decca treeDecca treeThe Decca Tree is a spaced microphone array most commonly used for orchestral recording.It was originally developed as a sort of stereo A–B recording method adding a center fill. It is the most commonly used spaced-pair technique...
- Surround soundSurround soundSurround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...
- AmbisonicsAmbisonicsAmbisonics is a series of recording and replay techniques using multichannel mixing technology that can be used live or in the studio. By encoding and decoding sound information on a number of channels, a 2-dimensional or 3-dimensional sound field can be presented...
- Acoustic source localizationAcoustic source localizationAcoustic source localization is the task of locating a sound source given measurements of the sound field. The sound field can be described using physical quantities like sound pressure and particle velocity. By measuring these properties it is possible to obtain a source...
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