Fig. 4. (a) Illustrating the setup to check the signals for the STP. The STP
is placed on a tripod. Walks are done at different distances to observe the
corresponding signals, (b) Illustrating the variation in the signal strength for
a human walk with variation in distance. The signal strength decreases as the
distance increases (considering the flat frequency response for the range of
frequencies of interest), and (c) Illustrating the variation in the signal strength
for walk and run by human at 5m. The signal strength decreases for run due
to attenuation introduced by the frequency response.