In my project I use electret mic + opamp to capture audio, which is later used for speech recognition on a remote site. This works well when operates in a silent environment, but not when there is some interference that comes from another direction (for instance, a conversation near by).

I wonder how hard it would be to perform some simple analog voice cancellation by adding another mic + opamp a few centimeters from the first one (the device's total size is a few centimeters), in order to filter out audio signal that comes from the side and only keep the audio signal that comes from a source perpendicular to the two mics.

I tried to search a little and found some info about beamforming. However, I'm looking for a solution which is simple and cheap, and doesn't require digital signal processing.


If you simply summed or averaged your two signals from the two microphones you'd end up with double your signal amplitude in the direction you're after while your noise floor would remain the same in the other directions. Depending upon your S/N ratio to begin with, that could be significant.

I'm not sure if there's a better as simple method to get better gain than that without adding more mic's or smarter circuitry.

  • \$\begingroup\$ Thanks, but I'm looking for a way to remove the component which is not in front of the mic, not only to change its amplitude. So if I was willing to add a "smarter circuitry" or another mic, what would be the simplest way to go? would a simple microcontroller be any good or do I need a serious DSP? \$\endgroup\$ May 8 '14 at 18:24
  • \$\begingroup\$ By changing the amplitude you are able to remove the noise. Once you have your summed signal, lower the signal amplitude until sounds from the other directions matches the noise floor of your system. The more mic's you use in an array and the further apart the mics are from eachother, the more directional you can get. I doubt a simple uC would do much anything for you. A serious DSP would allow you to potentially amplify the directional signal you want without increasing the noise floor, even then though, you need at least 2 mics. \$\endgroup\$
    – horta
    May 8 '14 at 19:45

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