Alfred0
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    • Alfred0
      Yes, my form teacher doesn't understand also how is happening, because using a standard PC also introduce noise, and the PC is grounded too, it uses typical clover shaped plug, and the laboratory is grounded, so, yes, pretty strange how we're...
    • Alfred0
      Hello, so, just an update, the system is not working as intended yet, but I'm discovering some interesting things. First of all, I want to know if there's something that I should have in mind when assembling the teensy and audio boards because...
    • Alfred0
      Yes, the concept is the same, I've testing with some precalculated coefficients in MatLab using FX-LMS algorithm and seems kind of working, is not clear. Due to the deadline I had, I can't do more now, so the new deadline is for January, I'll...
    • Alfred0
      Hi AntiLoop, no problem with the thread, is here for learning 😊 I can´t remember properly, but I'm pretty sure that cardioid microphones mostly are dynamic microphones, they use electromagnetism to generate electric pulses that represent the...
    • Alfred0
      Sorry, this is a mistake, d(k) is the signal measured at the point where I want the cancellation to be done, so it's the input from the second Line In, because it is measure with the microphone. The rest of terms are properly label, y(k) is the...
    • Alfred0
      Thanks for your answer. Regarding to option 1, I've seen that there was a queue block, but having to analyze three different points of the flow per channel, which means six in total, I think it's going to be a big problem in terms of latencies...
    • Alfred0
      Oh, I mean, if I use the FIR filter example, all is working, if I use the FIR filter as I intended, now is also working, but my new issue is how am I supposed to convert the input and output signal to numbers in order to recalculate the filter...
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    • Alfred0
      Ok, update, I've found the issue. If I use any FFT the sound is destroyed, so I have to find a way to convert the analog input signals to digital, and operate them to get the coefficients of the fir filters, I thought the fft1024 blocks would be...
    • Alfred0
      Thank you for this information MarkT, it has been very useful, but right now I'm very lost with this, I have spent all week trying to get it to work in different ways and it does nothing. This is what I was thinking that will work, but even...
    • Alfred0
      Update: I change firFilter_Left.begin(FIR_PASSTHRU, numCoeffs); firFilter_Right.begin(FIR_PASSTHRU, numCoeffs); Just to directly pass the input to output as the description says, but is still not working, I'm very confused right now.
    • Alfred0
      Good morning. First, I've learn one big issue, is obvious, but I didn't realize until now, I should define the array as int16_t to be properly used in the FIR filter module. So I comment the begin() from the loop and initialize this in setup()...
    • Alfred0
      Ok, that's right. I need to update the coefficients in real time because they have to adapt to the changes in the reference signal that I'm trying to cancel, so that's why I want to change the filter. I think there's an example of FIR in the...
    • Alfred0
      Well, to keep continuity with the theme, I don't know if I'm using the FIR filter wrong, but there is no sound at all, it's like a dam for the sound. I've been thinking about using part of the idea of the convolution code I mentioned here to do...
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    • Alfred0
      So, short answer: praying The long one, I think the latency isn't going to be the biggest problem because the point where the cancellation should take place will be enough further to give some room to processing all. The idea is to demonstrate...
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    • Alfred0
      There are two main problems with that preamp board: 1. Lack of biasing resistors for the electret capsule. They can be added externally, like this: Looking at the preamp board pics the gain is set to about 9x (30C=20K / 2K2), inverting...
    • Alfred0
      So, the easiest way to approach this would be to use a "good" external amplifier, I mean, anything better than the boards I'm finding around. For example, I could connect the microphones to the computer, route to outputs and connect it with a...
    • Alfred0
      I'm sorry, I know you are trying to help me in the best way possible and I don't mean to hinder you. I will try to be as clear as possible about what I want to do. To begin with I think it is important to clarify the objective I am looking for...
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    • Alfred0
      I really didn't answer to this, yes, in practical is like having 4 separate microphones, or 2 stereo (that is the same), but everything points to the use of amplifiers.
    • Alfred0
      No exactly, first of all, thank you very much for your quick response Paul. I use the Line In because the idea is to have the best sample possible, so how is an electronic subsystem is not strictly necessary to use directly connected...
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    • Alfred0
      Looking at this a bit more.... I'm guessing you actually have 4 separate microphones? If that's what you're really doing (not actually said in your question) then you really need to build 4 amplifiers to turn each into a proper line level...
    • Alfred0
      Hi Chip, I sketched out the different connections and it seems like you have all the pin numberings OK. The mods also look OK. Yes, I would remove the CS pull-up resistor on pin 6 of both audio boards. Not sure whether the audio data on pin 6...
    • Alfred0
      Second attempt at attaching pics...
    • Alfred0
      Hello. I'm working on my final degree thesis, and I'm trying to make an electronic subsystem capable of active noise cancellation. To achieve it, I'm using two Audio Shield (Rev. D) boards and a Teensy 4.0 connected in Quad Channel mode and...
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