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Question about application note AN-1140

Question asked by ag09 on Apr 30, 2013
Latest reply on May 1, 2013 by JeradL

Hi I have a question on the Microphone Array Beamforming ap note by Jerad Lewis.

 

I am having a hard time understanding/visualizing the response of the Endfire beamformer configuration. Lets say I have the basic 2 microphone beamformer in the endfire configuration and sound is coming from the rear of the array. The Rear microphone will be delayed and inverted to be 180 degrees out of phase with respect to the front microphone, which when summed together will give maximum attenuation. However, if the source is coming from the front, the summed signals will be the and the inverted rear signal delayed by (mic spacing)/(speed of sound) with correct delay samples set by the DSP. I do not see how this will give 0 db attenuation because it is very similar to the case where sound is coming from the rear. Can someone help me understand why it should be 0 db attenuation.

 

Also, is the aliasing frequency and null frequency the same thing? if not what is the formula to calculate the aliasing frequency

 

And what software is being used to generate the polar plots of the responses?

 

Thanks

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