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Microphone Specification Nox T3


This knowledge base article provides information about the accuracy of the built-in microphone on Nox T3 in addition to the regularly provided specification.

General Specification

Sampling Frequency Sound (Microphone)

1 MHz

Storage Frequency Sound (Microphone)

8 kHz


3.6 kHz

Accuracy Sound

< 3 dBc error

Bandwidth / accuracy characteristics and relation to Sleep

Built-in microphones for Nox T3 have been checked against calibrated industrial sound level meters with a frequency sweep measured in a specially setup insulated sound box with speaker.

Used Sound meters:

  • CEM DT-8851 Sound Level Meter, SN/ID: 11043884 / V010
  • REED SC-05 Sound Level Calibrator, SN/ID: 131210834 / V027-3



The figure above shows the Audio Volume signal of the T3 recorder above (grey) and the sound level reference meter below (blue) during a “volume sweep”. The vertical line (red) marks where the T3 microphone goes into saturation.

The audio signal on the T3 device goes into saturation when the reference meter shows 106.4 dB. However, sounds that have the sound level of >105dBc are very loud and unlikely that a sleeping person could produce sounds with such a high volume.


In the figure above the frequency characteristics of the T3 device (black) can be seen in relation to the reference meter (blue). The frequency sweep extends from 50 Hz up to 4000 Hz. The T3 audio circuit has a low-pass filter at 3600 Hz, which explains the sharp cut-off seen in the figure. The largest deviation of the device from the reference is [plus 4 dB] at the end of the sweep (3600 Hz) and [minus 5 dB] (at 50 Hz) in the beginning. For the expected bands of major interest to audio power of snoring the maximum deviation is -3 dB.


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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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