A parametric sound is generated from a nonlinear interaction of two or more intense ultrasounds at different but neighboring frequencies. The purpose of this study is to visualize the generation process of the parametric sound in a time domain using a numerical simulation. In particular, we focus on the generation of length-limited parametric sound beam, which is generated from a pair of parametric sound sources and indicates a truncated array length with a special radial beam pattern like a Mexican hat. To visualize nonlinear components, a simulated nonlinear sound wave is transformed into spatial spectra in a wave number space, and a nonlinear component such as the difference frequency sound is extracted using wave number filtering. The visualization of length-limited sound generation indicates discontinuities of wave fronts near a sound source. From the result, it is suggested that the discontinuity of wave front causes the special radial pattern of the beam with narrow width.