Ultrasonic wave generation due to human footsteps on the ground.

@article{Ekimov2007UltrasonicWG,
  title={Ultrasonic wave generation due to human footsteps on the ground.},
  author={Alexander Ekimov and James M. Sabatier},
  journal={The Journal of the Acoustical Society of America},
  year={2007},
  volume={121 3},
  pages={EL114-9}
}
Human footsteps generate broadband frequency vibrations in the ground/floor and sound in the air from a few Hertz up to ultrasonic frequencies due to striking and sliding contacts between a foot and the ground/floor. The high-frequency (above 1 kHz) vibrations from footsteps were detected on a building floor, but were not detected on the outdoor ground… CONTINUE READING