Figure 2.

Front panel of the dedicated LabVIEW user interface: (a) reference III-Lead ECG signal; (b) processed ultrasound signal at f₁ = 40 kHz; (c) processed ultrasound signal at f₂ = 39 kHz. Note that US signals are delayed compared to ECG signal for about 200 ms because of the type and place of measurement; (d) measuring error, i.e., difference between the reference signal and experimental method signal instantaneous HR displayed on a diagram; (e) diagram of instantaneous HR of the two methods in question and (f) numerical display of instantaneous HR of all three signals.