618 World of Warcraft (WoW)

'Sonic attack! Accurately speaking, they are interwoven sound waves. The bats can cooperate to simultaneously emit ultrasonic waves and avoid wasting energy. In that way, they can achieve the strongest killing effects' Ran Xiyu's voice sounded in her teammates' minds. 

The sound wave generated by humans through speech was an omnidirectional on, so the intensity attenuation was also very fast, which was proportional to the square of the distance radius. It was like that because almost all the wave divergence was spherical, and the surface area of the sphere was proportional to the radius. As such, regardless of gravity or electromagnetic force, their primary calculation formulas were similar, obeying the inverse-square law.

In the case that the sound wave did not diverge, it would become a cluster, so its attenuation ratio was meager. This was also the reason that sounds passing through a rolled book sounded louder in another person's ear.