08-05-2012, 05:20 PM
ACOUSTIC BEAMFORMING USING LINEAR ARRAY
[attachment=21609]
MICROPHONE ARRAY
A microphone array consists of multiple microphones placed at different spatial locations.
When all are arranged in a straight line, it gives rise to a
Linear Array.
The basic point in beamforming is, a multiple transducer setup produces an interference pattern.
If you select the spacing between your transducers and the delay in the transducers' signals just right, then majority of the signal energy all goes out in one angular direction.
Here, the advantage of the linear array is that background noise can be suppressed, which makes it possible to investigate the sources in reverberant or noisy environments.
Microphone array design
A very important criterion to be considered is Microphone spacing which depends on operating frequency.
To avoid spatial aliasing, the wavelength of the incoming signal must be less than the spacing between the microphones.
Lower frequencies produce wider beam, and higher frequencies produce narrow beam.
Lower frequencies(wider beam) correlate better with their delayed versions,, but narrow beam suits well for spatial filtering.
PROBLEMS OF CONCERN
Unidirectional microphones cause attenuation of oblique signals.
Audio input from microphones are very low, and amplification from both ends is a must.
Assumption of parallel wavefront being received at all times might cause errors.
Compatibility of the processor with PC.
Echoes in the environment concerned, might
hamper the quality of signal processing.
[attachment=21609]
MICROPHONE ARRAY
A microphone array consists of multiple microphones placed at different spatial locations.
When all are arranged in a straight line, it gives rise to a
Linear Array.
The basic point in beamforming is, a multiple transducer setup produces an interference pattern.
If you select the spacing between your transducers and the delay in the transducers' signals just right, then majority of the signal energy all goes out in one angular direction.
Here, the advantage of the linear array is that background noise can be suppressed, which makes it possible to investigate the sources in reverberant or noisy environments.
Microphone array design
A very important criterion to be considered is Microphone spacing which depends on operating frequency.
To avoid spatial aliasing, the wavelength of the incoming signal must be less than the spacing between the microphones.
Lower frequencies produce wider beam, and higher frequencies produce narrow beam.
Lower frequencies(wider beam) correlate better with their delayed versions,, but narrow beam suits well for spatial filtering.
PROBLEMS OF CONCERN
Unidirectional microphones cause attenuation of oblique signals.
Audio input from microphones are very low, and amplification from both ends is a must.
Assumption of parallel wavefront being received at all times might cause errors.
Compatibility of the processor with PC.
Echoes in the environment concerned, might
hamper the quality of signal processing.