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I'm an absolute beginner. I'm doing a project that involves estimating the time delays between the sound signal arriving at different microphones in an array (the project is a bit complicated but I'll find my way through). I'm planning to use a panda board and connect the microphone array to it. But before going about implementing the array, I thought I should first learn how to do some DSP on an analog input. Basically, how would I connect ONE microphone to the panda board and do, for eg, an FFT on the signal?

The panda board has an audio in port but that wouldn't help much when I have to use multiple microphones. Can I connect the condenser mic (the really cheap one ) using 2 wires to a general input pin? How would I read input from it? Will I be able to record sound using such a setup? And I understand that I have to do the Analog to digital conversion (In fact I WANT to do it by myself, so that I would better understand how stuff work).

And now the million dollar question : If I connect a few more microphones to different input pins of the panda board and give them the same sampling rate (I have no idea how but I'll learn it) will that make a microphone array?

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  • $\begingroup$ Any particular reason why you chose panda board? There are proper DSP kits which allow real time dsp processing like analog devices 8191M $\endgroup$ – Ram Oct 31 '13 at 18:28
  • $\begingroup$ No particular reason. As I said, I'm a beginner. I did not know that better solutions existed. So are you saying that using 8191M would be more efficient/feasible than the panda board? $\endgroup$ – Kevin Martin Jose Nov 1 '13 at 4:40
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To connect one microphone to the Panda board, use its audio input. The homepage says it's a stereo input, so yo can actually connect two microphones assuming your microphones are mono. To apply any DSP on the analog signal it must first be converted to a digital signal, of course. For that you need an analog-to-digital converter (ADC). It's an electronic device. You cannot do analog-to-digital conversion by yourself. I suspect the Panda board audio input to have a dual-channel ADC, otherwise it would be quite useless.

I haven't dived into the technical specs of the Panda board but I'd be very surprised if its general input pins were made for analog signals. So you cannot use those for recording audio, because they're lacking ADCs (unless you manage to use the ADCs of the RF interfaces present on the OMAP platform). For each microphone you need an ADC and an interface to the Panda board. Any selfmade solution will be a real hassle here, I would not recommend it.

A possible alternative solution is to use a professional audio interface that has multiple microphone inputs and a USB output. Then connect this audio interface to the Panda board via USB. The challenge here is to get a driver running on the Panda board. But I think it should be feasible. Keep Linux support in mind when choosing an audio interface.

If you've managed that, and you arrange your microphones in a reasonable way you have a microphone array.

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  • $\begingroup$ Can u suggest a cheap USB audio interface that can have 4 microphones connected? $\endgroup$ – Kevin Martin Jose Nov 1 '13 at 4:38

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