Directional Of Arrival Estimation In Beamforming
The direction of arrival (DOA) of a sound source is an important piece of information for any beamforming system. With this knowledge, the beamforming can direct itself to capture signals coming only from the direction of arrival while ignoring others. One of the most popular methods for DOA Estimation is based on time delay of arrival, also known as phase differencing.
Delay Estimation For Direction Of Arrival
A sound source is located in the far field, two microphones on the same plane will recieve the signal at slightly different times. The exact value of this arrival difference is dependent upon the angle of the sound source relative to the microphones. Hence, the delay information can be used to estimate the direction at which the source is impinging upon the array. The situation is described in the following figure.
Figure 1: Sound Source Impinging Upon Two Microphones
Upon examining this figure, it is clear that the propagation delay between the microphones is given by:
Where λ is the wavelength, which is dependent upon the speed of sound c. Therefore, the direction of arrival can be calculated as:
This estimate can then be used to steer the beamformer to capture signals in the desired direction while rejecting all others.
VOCAL Technologies offers custom designed beamforming solutions with a robust direction of arrival estimation. Our custom implementations of such systems are meant to deliver optimum performance for your specific signal processing task. Contact us today to discuss your solution!