Self-killing advantage

"Your Majesty!"

"His Majesty!"

"Your Excellency!!"

Everyone inside the tent stood up without exception when they heard Robin's clear voice in their ears, but their hopes were quickly disappointed when they looked around them in all directions and did not find anyone...

*ruff ruff*

"Look.. there..." Alexander finally raised his finger and pointed in a certain direction, when everyone followed the path he was pointing at, they found Robin riding a Draco kilometers away!

"..How?!" Victoria said it, but everyone was thinking about the same question. Robin's voice a while ago was very clear and quiet, as if he was sitting next to them, but he was talking at such a distance. 

As the soldiers and servants around didn't seem to hear him either, how could he send his words to reach only their ears?

Rather, how did Robin hear Alexander's words in the first place and respond to him?!

*Gulp*