Sound waves with frequencies higher than the upper limit of a person's hearing (about 2oooohz) are called sound waves. \.\

The wavelength of sound waves is very short, only a few centimeters, or even thousandths of a millimeter, so the diffraction ability is very poor, and it can propagate in a straight line in a homogeneous medium.

In addition to this, sound waves have a singular property, which is "cavitation":

Due to the high frequency of sound waves, the power of sound waves is very high compared to ordinary sound waves.

When sound waves travel through a liquid, small cavities are created inside the liquid due to the violent vibration of the liquid particles. These small cavities expand and close rapidly, causing violent collisions between liquid particles, resulting in pressures ranging from thousands to tens of thousands of atmospheres.

This violent interaction between particles causes the temperature of the liquid to rise suddenly. In addition, it can also play a good stirring effect, so that two immiscible liquids, such as oil and aquatic emulsification, and add solute dissolution, plus chemical reaction......

At this time, the small puddle in front of Ding Bao, in addition to the composition of water, also had a layer of animal grease floating on its surface. From the fluctuating temperature to the final emulsification of water and oil, under the subtle characteristics that only his eyes can observe, there are changes that conform to the "cavitation" characteristics, which he can distinguish at once.

Before, the shape shì was urgent, although it was suspected that the sound waves that could not be heard by human ears were remotely commanding the heavenly soldiers, but there was no time to calm down and carefully verify the analysis.

Because as a core backbone who has been immersed in the bioengineering industry for many years, he knows very well that sound waves are beyond the range of human hearing. Except for sound waves. And infrasound.

And these two kinds of sound waves. Each has its own characteristics, and there are also animals in the biological world that can go out and listen, so it is not easy to judge in a short time.

For example, mosquitoes, bats, cats, dogs, and domestic animals can hear sound waves; Elephants, whales, dolphins, and other marine animals can feel infrasound. Therefore, what kind of sound waves are used to control the heavenly soldiers, he can't jump to conclusions.

In fact, at that time, he was more inclined to infrasound in his heart.

Because infrasound waves have a long wavelength, they travel long distances and are not easily absorbed. In some cases. It is even possible to travel hundreds of kilometers, thousands of kilometers, and circle the earth for three or two weeks!

The most important thing is that although the same sound waves are inaudible to the human ear, some frequencies of infrasound waves are similar to or even the same vibration frequency of human organs, and can resonate with human organs. So he speculated whether it would be the use of infrasonic synergistic resonance to manipulate the heavenly soldiers.

The only thing that is difficult to explain is that infrasound waves are mostly seen in earthquakes, tsunamis, auroras, meteors, etc., and they are not easy to come out, and although it is delicate to control the heavenly soldiers through guò organ resonance, it is actually very dangerous. If you don't do it, the organ blood vessels will be ruptured, and it will inevitably be too cumbersome to control.

But. At this time, the obvious "cavitation" in the puddle proved that the celestial soldiers were controlled by sound waves.

This makes it easier to understand.

Because Ding Bao knew that in Scotland and Ireland in Europe, people like to use a whistle called the canine flute to call and command their dogs. The canine flute is blowing sound waves, and the pedestrians around are at a loss, and the puppy has already acted according to the command from the canine flute.

In this way, in fact, the reason is not so complicated, and the heavenly soldiers are equivalent to puppies, simply accepting specific orders and slogans.

It's just that I don't know how these heavenly soldiers "hear" sound waves.

The cave was pitch black, but fortunately there was snow outside, so it wasn't very obscure. His eyes were used to it, and he could barely see the scene within three or two steps of his surroundings.

Ding Bao stared at the puddle in front of him, raised one palm, and signaled Lao Feng not to make a sound first. Waited until the puddle gradually calmed down, the cavitation disappeared, lying at the entrance of the cave and swept away with extreme eyesight, there was no trace of the heavenly soldiers, and it was suspected that he had been searched, and then he turned back, but was shocked to find that the old wind had passed out.

"Old wind, wake up, haven't told me yet, where is the box?"

The old wind, who had already run out of oil and dried up, immediately tried his best to open his eyes, and his cloudy eyes suddenly burst out with a kind of sunset-like brilliance, shining so brightly that Ding Bao's heart was sour, and he moved his lips and said, "...... The box is not on the old man. To avoid ...... Let you bear unnecessary dangers, and go to the peak,...... You just need to send a message to the little fox fairy for me. …… She'll take it. ”

Ding Bao nodded silently, and solemnly promised: "Don't worry, old wind." I'm sure I'll get it done. ”

The old wind made him promise, the brilliance in his eyes brightened, and it dimmed again, and he tried to raise his neck, leaned into Ding Bao's ear, and confessed: "That box...... Just put it in ......"

"What?!"

Ding Bao clasped his ears with his hand, suspecting that he had heard it wrong, and immediately said in surprise: "Are you sure you are not mistaken?" In that kind of place, how can the little fox fairy get it?! ”

Lao Feng wanted to laugh proudly, but only a few coughs were heard. Ding Bao hurriedly patted his back for him, but he heard Lao Feng say excitedly: "Ahem...... You can't think of it, and neither can the enemy. …… The old man was a cat for three months before he ...... Finding an opportunity to hide the box there is a first-class place. …… But don't worry, even if there are only two people in the world who have the ability to touch there, one of them must be this little fox fairy......"

Ding Bao nodded, and said strangely: "What about the other person?" ”

"You." Lao Feng did not hesitate.

"......" Ding Bao opened his mouth, but he didn't speak. Looking at Lao Feng's complicated but extremely trusting gaze, his mood was as heavy as lead, and his fists were clenched with a rattling sound.

"Ning Bao, hurry, hurry, the time has come. Left Chest ...... Inner bag, small silver bottle. ”

When Ding Bao was feeling uncomfortable, Lao Feng suddenly straightened up, grabbed his collar, and said eagerly.

Ding Bao didn't know why, but he still found a small silver bottle the size of a small thumb in a very delicate and secret inner pocket inside his clothes. As soon as the silver bottle was touched, Ding Bao's nose moved, and his face immediately changed greatly: "Eroded ossified muscle fluid!" Old wind, you're going to ......"

"It's ...... The ...... of every wind family Home. No bones remained, no dust. ”

After the old wind finished speaking, he grabbed Ding Bao's arm and hung down weakly, his eyes closed, and he passed away.

Boom! Ding Bao slammed his fist on the rock wall next to him, blood flowing down his fingers, but he was unmoved, his face was gloomy and terrifying.

After a long time, he recovered from his stiff body, took a deep breath, picked up the small silver bottle, uncorked it, and poured it all on the old wind and withered body.

I had just taken two steps when I suddenly felt something soft under my feet.

Looking down, it's a dead little animal.

The size of a mouse, with a snout like that of a fox and an outer ear protruding forward, which is large. The neck is short, the chest and shoulders are broad, the breasts are up to the chest, and the hips and legs are slender. The whole body is covered with hair, and the back is gray in different shades, while the ventral side is lighter in color. A pair of wing membranes are born on the back, faintly light brown.

"Bats?"

Ding Bao exclaimed, his heart moved, and he immediately turned around and walked towards the cave.

If he remembered correctly, bats were masters of using sound waves. Because it is not only acceptable, but also cums.

The lower the frequency of the sound, the longer the wavelength, the greater the linearity of the obstacle that needs to be reflected. A big wall can reflect our shouts, but a telephone pole can't reflect our sounds.

Bats can emit bursts of sound waves, with very short wavelengths, and even a single wire can be reflected by a mosquito, which allows bats to locate and avoid wires and catch mosquitoes.

He hadn't gone far before he saw the rows of bats hanging upside down on the top of the cave.

It is said that bats are diurnal and nocturnal animals, and it is night, so it is time to go out to forage. But in fact, many people don't know that bats also have the habit of hibernation.

It's just that it doesn't hibernate deeply, and sometimes excretes and eats during hibernation. It only reduces the ability of metabolism, breathing and heartbeat only a few times per minute, slowing down blood flow, and lowering body temperature to coincide with the ambient temperature. Once awakened, it can immediately return to normal.

At this time, because of the sound brought by Ding Bao, some bats had already woken up and were about to fly lamely.

Looking at these dazed and panicked little animals, Ding Bao's expression instantly became hideous. (To be continued!)

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