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VShuk.1
Visitor II
March 31, 2020
Question

What is the Sampling Frequency MP34DT05?

  • March 31, 2020
  • 1 reply
  • 857 views

I am using MP34DT05 to calculate the A-Weighted output and for this I want to understand the sampling frequency of the sensor.

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    Eleon BORLINI
    ST Employee
    March 31, 2020

    Hi @VShuk.1​ , the nominal working frequency of the MP34DT05 microphone sensor is 2.4MHz. The microphone is fed directly with a clock of 2.4MHz, and returns as output data a 1-bit PDM (pulse density modulated) stream at the same frequency. In order to recover the acquired audible signal (falling e.g. in the audio band 20Hz-20kHz), the PDM must be converted into PCM / I2S format, typically. The audio signal frequency of the converted signal depends on the decimation factor you use to down-sample the stream from PDM to PCM. For example, if you decimated by a factor 32, you will get a "word length" of 2.4MHz/32 = 75kSamples, meaning a maximum detectable frequency of 37.5kHz (from Nyquist theorem). In order to "A-weighten" you signal I suggest you to multiply the signal times the A-weighting filter spectrum in the frequency domain. Regards

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