One aspect of the project that we never truly got working was the automatic pitch calibration algorithm, for calibrating the RPM of the stepper motor to achieve the correct air flow rate. To achieve this, a method of measuring the frequency spectrum (or fundamental frequency of the spectrum at a minimum) produced by the recorder is required. Our aim was to do all signal processing onboard the micro-controller, but with its limited memory and speed, this is challenging. We welcome further work on this issue.
One aspect of the project that we never truly got working was the automatic pitch calibration algorithm, for calibrating the RPM of the stepper motor to achieve the correct air flow rate. To achieve this, a method of measuring the frequency spectrum (or fundamental frequency of the spectrum at a minimum) produced by the recorder is required. Our aim was to do all signal processing onboard the micro-controller, but with its limited memory and speed, this is challenging. We welcome further work on this issue.