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Measuring Audio With Nox Recorders

The ability of measuring audio with Nox recorders is one of the key differentiators when it comes to our equipment. There are many ways to record audio, but for the purposes of sleep medicine where detecting snoring through audio is very important, the method chosen is very important.

This knowledge base article explains how Nox recorders measure audio and why using calibration for the dBc scale is superior than the more common dBa scale.

  • The Audio envelope of the T3 and A1 is calibrated towards dBc scale rather than dBa.
  • The reason is that dBa is simulating the frequency response of the human ear and the measure is therefore frequency dependent.
  • dBc is measuring the actual sound power independent of the frequency.
  • Using dBa could for example result in a men snoring at 60Hz center frequency being measured approximately 6dB lower than a woman shoring with the same power at 120Hz center frequency.
  • By recording the raw audio, any weighting curve can be applied to the recorded sound in the software and therefore dBa can be derived as well.


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*Please note that not all features or all products are available in all markets. Our products are medical devices and subject to registration/approval in each market area. For more information on product availability please contact

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