The squarewavesource is an impulse source in which digital technique is used. It has the advantages of rigid phase, high frequency stabilization and high antijamming.
方波电源是采用数字技术的脉冲电源，具有相位严格、频率稳定度高，抗干扰能力强等独特的优点。
2
When a wave travels uniformly in all directions from a small source, the intensity varies inversely as the square of the distance.
当波从小扰动源向各个方向均匀传播时，其强度的变化与距离的平方成反比。
3
Sound waves travel outward like balloons expanding around their source. The sound's power is distributed on the surface of the wave which increases with the square of the distance from its source.