Preliminary experience with the modified tapping machine proposed by T. J. Schultz [J. Acoust. Soc. Am.60, 645 (1976)] revealed some problems with lightweight floors covered with soft carpeting. Measurements of impact velocity and internal impedance of human walkers with a variety of footwear are described. A modified tapping machine based on the measurements of foot impedance was produced. The peak levels produced by this modified machine are compared with those produced by live walkers and standard machines.