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Thread: fft analysis with microphone electret + amplification

  1. #1
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    fft analysis with microphone electret + amplification

    Hello there,

    I am trying to make a system with teensy 3.2 that be capable to acquire sound between 20 Hz - 20KHz
    and make the FFT analysis to send to my computer via wifi.

    I bought a microphone electret and i think, i'll buy a chip to amplify the signal and connect it to ADC teensy for make FFT Analysis.

    Do you guys know about some chip that can make this work?? i thought about max9814 but i don't know is compatible with the teensy 3.2.

    The other question is about ADC included in teensy. This ADC with 8 bits, it is suficient to make a FFT analysis ?

    I notice about audio teensy shield but isn't what i need, because i only need input system.

  2. #2
    Senior Member PaulStoffregen's Avatar
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    The easiest way is with this shield:

    https://www.pjrc.com/store/teensy3_audio.html

    and this microphone added to it:

    https://www.pjrc.com/store/microphone.html

    You'll also need header pins and optionally sockets to join it to your Teensy 3.2.


    For the FFT part, I recommend starting with the tutorial.

    https://www.pjrc.com/store/audio_tutorial_kit.html

    FFT is covered in part 3-2 on pages 24-29. Or you can watch me & Alysia demo the tutorial material if you scroll down to the video. The FFT part begins 34:56 into the video. Before reading or watching the FFT part, earlier parts like the basic design tool usage would be good to know.

  3. #3
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    Thanks @PaulStoffregen for your answer. I notice audio shield but i only need an input systems.

    I'd appreciate if you guys can recommend one way to do that

  4. #4
    Senior Member PaulStoffregen's Avatar
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    The design tool has most of the audio library's documentation, in the right side panel as you click on each audio object. If you're not yet familiar with how the design tool works, read or watch part 2 of the tutorial.

    While all the tutorial material was created with this shield, and so the shield is by far the easiest way to get started & learn, as you use the design tool you should notice there are currently 7 different input objects. Those are the ways you can get sound input. Each has its documentation in the design tool right-side panel.

    If you are a beginner, I highly recommend going with the audio shield, even if you do not need the output path. It is by far the best documented hardware. If you're learning, you can use the tutorials to get started without the difficulty of needing to adapt to other hardware before you fully understand how everything works.

  5. #5
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    Hi, I have a very similar project and I'm glad I found this thread. Instead of using the mono microphone, I'd like to use the stereo line-in pins. I'm a novice when it comes to the electrical signals and was curios to answer:

    Would it be feasible to solder a 1/8" female audio jack connector to the L/R/G pins on the audio board and use any off-the-shelf microphone? Do off-the-shelf microphones work with line-level strength?

    Thank you very much, I've very much enjoyed working on T3, and can't wait to see whats in-store for T4

  6. #6
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    Quote Originally Posted by RoboRepublic View Post
    Would it be feasible to solder a 1/8" female audio jack connector to the L/R/G pins on the audio board and use any off-the-shelf microphone? Do off-the-shelf microphones work with line-level strength?
    I'm guessing that microphone's output will be too low for line-level input. You would need gain between mic and Line input.

    Maybe go with a pair of digital microphones (one for left, one for right) connected directly to Teensy's I2S RX interface: https://www.tindie.com/products/oneh...al-microphone/

  7. #7
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    Thank you very much for your insight, I didn't know about this pesky product it look very cool I've since thought up of a better solution, but I still have some additional questions about signal strength and audio processing. Its a bit divergent from this topic, so I'll create a new one

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