The extracted respiration from all the HARKEN sensors were specially well correlated with the thoracic PG signal. The cross-spectral energies were in all cases concentrated near the peak frequency of the thoracic PG (0.12 Hz on average, with 50% energy between 0.105 and 0.205 Hz, see detail plots for all cases in Annex A.1).
This result confirms numerically the idea that could be visually hinted from the outlines of the raw and filtered signals presented in the previous sections: that the well-defined periodic waveforms that are captured by the sensors were really the outcome of respiration, and specifically of the thoracic volume change.