How to test the microphone?

By dirt or moisture, the sensitivity of the BATLOGGER microphone may be impaired. With a simple method one can test the functionality of the microphone:
(Caution: The various microphone types have different noise spectrums, please consider the microphone type)

  • Go to a maximal quiet environment
  • Place the protective cap onto the microphone or gently press a sound-absorbing object (eg earplugs) onto the microphone
  • Make a manual recording (press >>)
  • Select approx. one second silence of the recording (wav file) and display the spectrum (eg. with Audacity -> Analyse -> frequency analysis)

Microphone OK (FG):

  • Noise level of approx. -49dB @ 65 kHz
  • Flat spectrum +/- 3dB @ 15 - 90 kHz

Microphone OK (SPM):

  • "W shape"
  • Peak at about 55 kHz and about -46dB
  • Reduction at approximately 100kHz by about -10dB
  • A few scattered peaks are normal

Microphone bad:

  • Low sensitivity (<-50 dB) @ 20 - 50 kHz
  • High noise (>-40 dB) over entire bandwidth
  • Lots of peaks over the whole spectrum

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