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CALIBRATION.md

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DFSDM calibration for Knowles MEMS microphones

This page shows if pre-emphasis works or not.

Condition

  • Coefficient for pre-emphasis: 0.95
  • 7000 Hz sine wave is generated by a tone generator running on my PC, and the MEMS mic receives the tone via air.

Measurement result

"System clock 80_000_000 / clock divider 32 / FOSR 128" outperformed System "clock 80_000_000 / clock divider 64 / FOSR 64": SNR is better at 7000Hz.

System clock 80_000_000 / clock divider 64 / FOSR 64

Pre-emphasis disabled

FFT pre-emphasis disabled

Pre-emphasis enabled

FFT pre-emphasis enabled

Spectrogram pre-emphasis enabled

Mel-spectrogram pre-emphasis enabled

System clock 80_000_000 / clock divider 32 / FOSR 128

Pre-emphasis disabled

FFT pre-emphasis disabled

Pre-emphasis enabled

FFT pre-emphasis enabled

Spectrogram pre-emphasis enabled

Mel-spectrogram pre-emphasis enabled

Confirmation with Welch's method

Welch's method with pre-emphasis disabled

Welch's method with pre-emphasis enabled