This paper proposes a method to evaluate excitation force considering the planar spread of multiple people on the ground. The excitation force is divided into before and after ground input, and each reduction rate is evaluated using a simple envelope. The reduction rate before ground input is calculated by comparing cases with/without considering the sound arrival time difference. The reduction rate after ground input is calculated for receiving points by comparing planar excitation and point excitation. Using a finite element analysis of a two-layered ground model, it is shown that the reduction rates can be evaluated with a simple envelope.
