Above the sea, under the blue sky, the Zhong Jun sailed lonely on the sea.

It's not a common shipping lane, so it's very quiet.

The sailing speed of the Zhongjun is very slow, only about seven or eight knots, and many staff members on the Zhongjun are busy testing and debugging various equipment and testing various underwater acoustic data.

And behind the Zhongjun, thousands of meters underwater, a submarine has been quietly following in the rear for two hours.

"Not found!"

"Aha, I'll just say, we weren't found!"

"Sure enough, our stealth is invincible!"

It's been two hours, and we haven't even been discovered, we must have deceived the Zhongjun!

The captain stood there, tears streaming down his face.

We've finally made it!

Our experiments are a success!

Just as he was about to announce it loudly, he suddenly heard a "bang".

Knocked!

Knocked on active sonar again!

The captain's expression immediately froze.

What's going on?

On the Zhong Jun, Gu Xiaobai finally finished a small project of his own, pushed the notebook in his hand away, stood up and stretched.

Ah, so tired.

It's time to listen to something and take a break.

Gu Xiaobai walked to the headphones of the full-band transducer array next to him and put them on.

As soon as he put on his headphones, he heard a small melody that seemed to be humming in the midst of the noise of the ocean.

The melody lurks beneath the noise of the ocean, like a splash brought by a bluefin tuna inadvertently turning around, like a shark swinging its tail from side to side, like a school of panicked fish, merging and abruptly parting.

Its voice is so harmonious that even the occasional hearer of it would probably think that it was actually some unknown sea creature, and would not think that it was actually a submarine.

A behemoth capable of diving in the sea for up to a month!

But such a voice really can't hide from Gu Xiaobai.

At this moment, Gu Xiaobai really couldn't cry or laugh.

Why is this big guy here again?

In Gu Xiaobai's ears, the behemoth has nothing to hide in the ocean.

It's like a big guy hiding in a crowd, stealthy, trying to follow the person in front of him.

Hey, your big guy has been exposed, okay!

Forget it, give you some face!

After a while, Gu Xiaobai found that this big guy was still following behind brazenly.

Moreover, there is a tendency to get closer and closer.

Gu Xiaobai couldn't bear it anymore.

Is this bullying me for being deaf?

Gu Xiaobai's hand was pressed on the console, and in the next second, there was a loud "bang", which once again resounded through the cabin of the submarine.

Knocked!

Knocked again!

It was like a basin of cold water splashed on everyone's heads, and the joy just now was suddenly gone.

In the submarine, there was a dead silence.

How did we get found out again?

Is it really our technology that doesn't work?

The officers and men in the submarine fell into deep doubt again.

At the critical moment, the captain encouraged everyone:

"Don't be discouraged, at least we lasted two hours before we were discovered!

"Oh!" everyone replied weakly.

"Come, don't be rude, and say hello to Zhong Jun too!"

"Bang", the active sonar hit the bottom of the Zhong Jun, on the Zhong Jun, Gu Xiaobai heard the submarine in the rear stop, and then slowly turned and sailed into the distance.

Let's go?

After a few hours, Gu Xiaobai put on the headphones again, and then he heard that the voice came again!

Gu Xiaobai didn't know what to say, he thought about it, and knocked on another active sonar.

"Boom!"

After a long time, there was a "knock", and the other party also responded to him.

Gu Xiaobai: "????"

He didn't understand what the hell these guys were doing.

It's a bit confusing......

How does it feel a little childish?

This feeling is like a big man, following behind the small man in front, and when the other party finds out, he will say hello with a smirk: "Hi!"

What exactly do you want to do?

Do you always feel like you're being followed by an idiot?

Gu Xiaobai tilted his head, puzzled.

In the submarine, the captain clenched his fist: "This time, we held out for two and a half hours before being discovered!"

"Come on!"

"Let's do it again!"

The submarine turned around and sailed away again.

One more time, we'll go back!

On the Zhongjun, Gu Xiaobai thought for a while, then returned to his notebook and typed.

Pan Guoxiang watched from the side for a while, not understanding at all.

Hydroacoustics involves fluid mechanics and acoustics, but the electroacoustics that Gu Xiaobai is now engaged in is completely the work of code and code farmers.

He asked Chen Jingshan, who was sluggish next to him, "Xiaobai, what is he doing?"

"He's writing a sonar filtering algorithm......" Chen Jingshan looked sluggish.

Filtering algorithms?

"What's it for?"

"From the noise of the sea, find a certain sound in a specific pattern and separate and mark it......" said Chen Jingshan.

At this moment, it was Pan Guoxiang's turn to be shocked.

Although Chen Jingshan is engaged in electroacoustics, he is actually mainly engaged in high-fidelity compression, high-fidelity playback, streaming music streaming, and other electroacoustic processing of sound.

He had never been exposed to anything military-related before.

But Pan Guoxiang understands.

This thing, in fact, overlaps with the function of modern sonar, which can automatically identify and fix different motors and boats through the sound pattern, and automatically tag them.

In most cases, it can be very accurate.

But this kind of thing has almost no effect on military submarines, and the identification data of major military powers are absolutely secret.

But for Gu Xiaobai, there is nothing in this world that cannot recognize patterns and find characteristic sounds.

Once you find effective patterns and characteristics, it's easier to identify them.

"The accuracy of his algorithm is very high...... It can raise the level of noise control by several notches for recognition......" Chen Jingshan watched from behind for a long time and explained to Pan Guoxiang.

Then, Gu Xiaobai added a few lines of code to the back, and wrote these things into the control code of the hydroacoustic transducer matrix.

"What is this for?" Although Pan Guoxiang didn't understand it, he could clearly see that the genetic code behind it was not the same as the previous one.

"As long as the target mode is detected from the ocean noise, it will automatically emit active sonar...... "Chen Jingshan muttered: "Why do I think Xiaobai wants to fight whack-a-mole?"

Whack-a-mole?

Who are gophers?

Why does Xiaobai play whack-a-mole?

Pan Guoxiang had no idea what was happening.

Behind, the sneaking big man quietly approached the Zhongjun from afar.

There were still dozens of nautical miles away from the Zhongjun, and the captain took a breath and said, "Get ready, stay silent!

According to their experience, the Zhongjun will probably monitor the data in the vicinity of about 30 nautical miles, and as long as it enters the range of 30 nautical miles near the Zhongjun, it is a matter of time before it is discovered.

The question is, how long will it last this time.

Then, the captain heard a "thump".

"What's the situation? Didn't you say don't make any noise?" exasperated the captain.

The sonar soldier looked at him with a blank expression.

"Wait, we're knocked?"

The sonar soldier nodded.

"How could we have been knocked!" the captain furious, "Come again!"

It went around in a circle and had just entered the thirty nautical miles of the Zhongjun.

"Boom!" was another sound, and at the moment when they had just entered thirty nautical miles, it hit the submarine accurately.

Captain: "......"

Sonar: "......"

Other officers and soldiers: "......"

Why?

"This can't be, it must be a coincidence!"

"Is he shooting active sonar indiscriminately everywhere?"

The sonar soldier looked at the screen for a long time, then put on the headphones and listened for a while, shook his head and said, "No." ”

"I don't believe it, come again!"

The captain raised his wrist and looked at his watch: "We will come back in the evening, I don't believe that he doesn't sleep!"

The submarine wandered around the rear for another half a day, and at about 11 o'clock in the evening, it quietly entered the range of the Zhongjun.

"Boom!" was knocked again!

At this moment, the captain felt like he was the reincarnation of the Buddha, and he was beaten all over his head!

Mom, you see I'm getting taller!

Mom, I'm getting taller again!

Mom, I'm getting taller again!

I'm in so much pain!

In the submarine, day and night are not distinguished, and in the dim light, the captain commands the submarine, constantly circling around the Zhongjun.

2 a.m.: "Boom!"

3:27 a.m.: "Boom!"

5:15 a.m.: "Boom!"

7:30 a.m.: "Knock ......"

"Doesn't he sleep?" the captain was going crazy.

We don't sleep, why don't you sleep either!

He didn't know that Gu Xiaobai had already gone to sleep, and at this moment, it was not a human being who was playing a "whack-a-mole game" with him, but a program.

Gu Xiaobai's notebook was connected to the console, and it was running quietly at this time.

The algorithm that Gu Xiaobai just wrote was running in the background.

It's like a thin layer of gauze, filtering the sound of the bottom of the sea over and over again.

Once, twice, three times......

It's like water has been filtered through layers of sediment and turned into a piece of clarity.

All the noise was gone, leaving only the sound of a propeller that seemed to be humming a melody, which appeared on the screen.

And then "knock".

Whack-a-mole.

Gu Xiaobai slept, but there were still people who didn't.

Chen Jingshan sat in front of the computer, staring at the program on it.

Watching the sound being filtered layer by layer, the feeling is like seeing someone and finding an orange from millions of oranges at a glance.

He'd read the code, but anyway, he couldn't believe why anyone could play with sound pattern recognition and noise filtering to such an extent.

It's impossible!

He felt that his previous worldview was about to be turned upside down.

At eight o'clock in the morning, Wang Guanshan came to change shifts with the first mate.

He ran around the boat, sweating a little, and was stretching comfortably at this time, and when he came in, he found Chen Jingshan's red eyes.

"You haven't slept all night?" Wang Guanshan glared.

Chen Jingshan answered in a hoarse voice, staring at the picture.

Wang Guanshan shook his head, another half an hour passed, and Gu Xiaobai also finished breakfast, finished exercising, and ran to the cabin.

He saw Chen Jingshan staring at his notebook, but he didn't care, took out a book, and read it seriously beside him.

After a while, he heard Chen Jingshan shouting: ", it has appeared again!"

Gu Xiaobai turned around and saw a group of people gathered around Chen Jingshan, including graduate students, other professors, and crew members.

They were discussing curiously.

"What is this doing?"

"Is Xiaobai looking for a deep-sea monster?"

"It seems to show up every once in a while, like it's playing hide and seek with us. ”

"It's so pitiful, just 30 nautical miles into us, you'll be knocked back......"

"I think it could be a whale, you see this tiny noise, it's definitely not a boat. ”

"Maybe it's an underwater monster!"

"I think it could be an undersea person. ”

"Aliens!"

"But it's amazing, such a small waveform can be found!"

"If this recognition algorithm is published, it will be ......"

Wang Guanshan also watched with relish on the side and participated in the discussion.

He was the one who guessed it was an underwater monster.

Then he heard the radio go off.

"Captain, someone is looking for ......," the staff called him with a strange look.

Then he heard a crying voice inside: "Hey, you guys are too much! Our captain is crying, can you be a human being!"

Wang Guanshan: "???"

"Who said I cried, I'm sleepy! Lao Wang, you kid Niu, did you stare at us all night without sleeping? It's too much! Don't you give us a little face! Are we still good brothers?" From there, there came the hoarse voice of the captain.

Wang Guanshan heard this voice at once, his old classmate, who is also a good friend for many years, and his comrade-in-arms Sun Junliang.

"Old Sun, why are you contacting me? aren't you going...... Wait, are you with us?"

Wang Guanshan subconsciously looked left and right.

In the past, when he was still on the warship, he was teased by Sun Junliang.

In the rear, the submarine threw out the floating antenna, and in order to make a phone call, it sent a bloody and tearful complaint to Wang Guanshan.

At this moment, Sun Junliang really burst into tears: "I didn't know before, Lao Wang, you are this kind of person, how long has it been since you saw you, you are so ruthless, is it really good to abuse us like this......? Give me back the Wuliangye I gave you!

Wang Guanshan: "?????"

He looked back at the people behind him, and suddenly he understood......

This night, what was Gu Xiaobai teasing.

"Oh...... It turns out that the guy who was knocked out as soon as he showed his head was you......" Wang Guanshan suddenly realized, "Ahahaha, do you think my brother I don't sleep to play with you? I don't know how fragrant it is to sleep at night! The one who knocked you is not a person, it is a piece of code made up by my boss, and it is knocked as soon as I show up, isn't it very cool, ahahahahaha...... Happily killed me, finally someone avenged me...... Wait!"

Wang Guanshan was suddenly stunned.

The most advanced submarine in the country will be caught as soon as it shows its head, and the sonar filtering algorithm will be knocked out......

Wang Guanshan thought of a possibility in his head.

I'm going to have a new member of the Black Square family!