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Thread: Faint high pitch noise when using Audio Board & USB

  1. #1
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    Faint high pitch noise when using Audio Board & USB

    There is a very faint continuous high pitch noise when I'm using the Teensy Audio board and USB Audio as an input device to the computer.

    I have a Teensy 3.1. Arduino 1.8.8. Teensyduino 1.4.5. Audio Shield Rev B. MacOS 10.14. But problem also heard on Windows 10.

    Steps to reproduce on Mac (similar to Windows)

    1. Open Examples / PassThroughUSB.

    2. Compile & upload.

    3. Plug in headphones to audio adapter.

    4. Go to the Sound Preferences (speaker icon on top menu bar)

    5. Click Input tab and select Teensy Audio.

    6. High pitch sound starts.

    7. If you click a different input it stops.

    When trying to diagnose this I was able to get rid of the noise if I make the following change that basically disables sending any USB Audio data back to the computer.

    usb_audio.cpp:318

    Code:
    unsigned int usb_audio_transmit_callback(void)
    {
    return 0; // BUG: eliminate buzz
            static uint32_t count=5;
            uint32_t avail, num, target, offset, len=0;
    Is anyone else experiencing this problem? My "fix" isn't really a fix, but more of a clue.
    Last edited by ftrias; 12-28-2018 at 09:31 PM.

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