After dinner, Kaichi came to the side of the ship with a pan and Kissin.

"Jiayi, what are you doing with this array? does it have anything to do with bats?" Kissin looked at the so-called array disk in Jia's hand, he didn't understand this, but he felt very strange when he looked at it. This is a two-dozen wide discs, and a dozen is the distance from the tip of the thumb to the tip of the middle finger of the palm of the hand, about 20 centimeters.

The array plate was not thick, no thicker than four fingernails, and it was covered with mystical patterns, filled with white metal, and there were four gems between the four corners, which looked more like a handicraft.

Unbeknownst to him, the white metal was Mithril alloy. Filled in the array plate to build the magic through, the reason why the Mithril alloy is used, of course, is because it is so cheap. There is also a small trumpet-like thing at the outermost end of the array disk, which makes this array disk look like a turtle shell, and the horn in front is the head.

Jia Yi took the array disk and said to Kissin: "This is used to simulate the sound of bats, and then the array disk will receive the wave emitted by the sound, and you can detect if there is anything in front of you." ”

"Why do you want to imitate the sounds of bats?

"Bats can see at night, not because their eyes can see things in the dark, but because they can make sounds from their mouths, and when they hit an obstacle, they bounce back and hear it with their ears, and they know that there is an obstacle in front of them. ”

Kaichi explained, but seeing Kissin's blank eyes, he knew that he still didn't understand.

"It's like an echo, you know what, you're shouting in the canyon, you can hear the echo, the speed of the sound is the same, and depending on the time of the echo, we know how far away the obstacle is ahead. Bats are the same, but the sound of bats is inaudible to the human ear, so people have not found that bats are located by sound. ”

Kissin felt that he understood something, but he still couldn't accept it, and he had never heard of seeing with his ears: "Can you really see with your ears?"

"Your martial arts are pretty good, aren't they?" Kaiichi saw Kisin nodding and continued, "Then do you have that feeling, when someone wants to attack you, you will have a sense, and you can detect someone on the other side when you hear the sound?"

Kissin continued to nod.

"That's right, you don't see through your eyes, do you? As long as the senses are sharp enough, it's fine. "Jia Yi actually secretly changed the concept, but in this way, Kissin is much easier to understand.

Jia Yi doesn't want to explain this thing anymore, Kissin lacks the corresponding foundation, as long as he knows a rough idea, if he wants to explain it clearly to him, Jia Yi doesn't have the ability to do so.

Jia Yi picked up the array disk and was about to activate the magic circle, when he suddenly remembered something, is the sound here still the transmission speed of 340m/s? If it is in water, what is the speed? If this is also wrong, then the distance measured is too different.

After thinking about it for a while, Kai decided that it would be better to measure it himself.

He let down a small boat from the ship, came to a relatively flat cliff, then ran to the opposite shore, used magic to measure the distance, determined the distance, he used his array disk to shoot ultrasound waves at the opposite cliff, and at the same time used the hourglass to start the timer, and when the array received the returning ultrasound, he stopped the timer. After dividing the distance by time and dividing by two, the speed of sound transmission is not much different from that on Earth, about 360 m/s, which is 20 meters per second faster than that on Earth, and the difference is not too big.

After calculating the transmission speed of the sound, Jia Yi continued to experiment with his own detection array, at least when it was used to measure the speed of sound, it was still easy to use, and it was no problem to use it as a sonar radar.

When Kaichi returned to the big ship, many sailors had already gathered around him, because they had heard that Master Kaichi was going to use his ears to see things, and everyone came to see the strange.

"Get out of the way, get out of the way, don't get in the way. ”

"Jiayi, how do you use this thing, can you really see it? With a sound?" Even the captain heard the wind and came to watch.

Kaichi has also seen the boredom of sailors, he said: "This is still a beginner version, theoretically you can only find things on the water, and after improvement, in addition to being able to find things on the water, you can also find things underwater, even at night or when the sight is not good, there is no problem." ”

With that, Kaichi came to the side of the ship and lined up the sailors around him, leaving only Kissin and the two captains by his side.

Theoretically, this piece of light and shadow is used as a display screen, showing the real-time dynamics around it according to the feedback of sound wave detection, but unfortunately it has not yet been completed, and can only display a line or a point.

After the array disk was activated, the small horn began to release ultrasound waves intermittently, and the rest of the people couldn't feel anything, but Kaichi himself applied the listening technique, so he could hear intermittent sound waves being transmitted one by one.

The sound waves that were transmitted quickly received feedback, and it was the cliffs on both sides, and two irregular lines were displayed at both ends of the display, symbolizing the cliffs on both sides. Then, there were some sporadic bright spots, and these were the boats in the river. It's just that in addition to these, there are a lot of noise spots, which are background noises caused by some multiple reflections, which should be filtered out.

Although it didn't reach the point of holograms, but now Jiayi is more satisfied with this look, at least it's a little bit like it, isn't it?

"This point is supposed to be a ship, sailing towards us. Depending on the reaction time, there should be a distance of 2 miles. Kaichi said, pointing to the big spot closest to his side.

"Let's go to the lookout and see if there's a ship in the waterway ahead?" said Captain Hewlett.

Immediately at his words, a sailor climbed onto the ship's mast and looked straight ahead. It would be nice if he had a telescope, so that he could see farther, but he didn't have the energy to do it. Jia Yi didn't know that he was actually looking forward to the telescope, but he didn't know it.

However, the two-mile road was not too far, and when the sailors went up and searched casually, they saw that there was indeed a large ship heading ahead, and the distance was similar to what Kaichi had said.

The sailor immediately spoke to the people below.

"Is this really detectable, really by sound? Why can't you hear it?" asked Captain Hewlett.

"People can only hear part of the sound, and if the frequency is too high or too low, they can't hear it, and even if this sounding circle emits a high-frequency sound, you can't hear it. ”

Jia Yi explained, but no one understood, looking at their blank eyes, Jia Yi could only explain simply: "This is magic!"

Oh, now, everyone understands, wouldn't it be nice to say that this is magic, everyone will be able to understand, I said so much earlier, but everyone is confused.

Jia Yi was also helpless, I wanted to do a popular science for everyone, but I didn't expect everyone to understand it at all. But Kaichi doesn't have to feel disappointed, because even in modern times, where basic education is almost universal, people don't really know the principles of many things, and they can only be forcibly classified as science, which is not much different from this strong name magic.