You went on a blind date and presented an A-level wanted criminal as a meeting gift?

Jiangcheng No.1 Middle School.

It is a full-time key high school with 2,300 students and more than 150 faculty and staff members.

At 6:07 a.m., it was the time when boarding students started getting up and washing up.

The incident broke out during this period.

When Lin Chen's RS7 braked suddenly at the school gate, the area outside the school gate was already full of police cars.

Red and blue police lights spun in the morning mist, illuminating the entire street with alternating light and shadow.

A ring of special police officers in riot gear stood outside the cordon at the school gate, but no one rushed in.

Li Mingyu stood at the front, holding a riot shield in one hand and a walkie-talkie in the other, his lips trembling slightly.

The young special police officers behind him didn't look much better either.

The sounds emanating from the teaching building were enough to explain everyone's hesitation.

That wasn't the sound of smashing or yelling.

It is a dense, mixed, hoarse roar emanating from hundreds of throats simultaneously, like a group of caged wild animals expressing some kind of uncontrolled instinct through their vocal cords.

"We can't get in!"

When Li Mingyu saw Lin Chen jump out of the car, he immediately rushed over, his voice urgent and broken.

"Hundreds of students inside have gone mad, wandering and bumping into things in the corridors, lunging at anyone they see. Three security guards who tried to evacuate have already been bitten and taken to the hospital! We can't possibly shoot the students!"

Lin Chen didn't look at him.

He looked up at the teaching building.

The four-story building has an L-shaped structure. The west wing contains regular classrooms, while the east wing contains music and art classrooms.

Su Ke'er is trapped in the music classroom on the third floor of the east wing.

Lin Chen strode towards the school gate.

"Wait! You're just going to go in like this? Without even any protective gear..."

Li Mingyu's voice automatically became quieter the moment Lin Chen stepped across the cordon.

It wasn't because of what Lin Chen said, nor because Lin Chen glared at him.

It was because the thing Lin Chen was wearing when he walked past him made his mouth close on its own.

That thing wasn't murderous intent, but it made people instinctively want to back away even more than murderous intent.

Like an invisible wall.

He had met Lin Chen many times and was always afraid of him, but this was the first time he had felt this level of oppression.

Lin Chen walked across the main road of the campus and pushed open the side door on the first floor of the west wing of the teaching building.

The lights in the corridor flickered, and several of them had been smashed, with broken glass and notebooks scattered all over the floor.

At the other end of the corridor, about twenty meters away, a dozen or so students in school uniforms were making a wandering motion.

Their walking was aimless, random, with dragging steps, arms hanging low at their sides, and occasionally they would suddenly tilt their heads and bump into the wall or grab at the bulletin board in the corridor.

Lin Chen did not rush forward.

He stopped in place and closed his eyes.

[God-level Insight], now activated.

[God-level Sense of Smell] Activated.

[God-level Hearing Ability], activated.

The three sensing skills simultaneously scan the entire teaching building at full power.

The sense of smell was the first to provide an option for elimination.

There are no molecular characteristics of any known chemical toxins in the air.

It has no bitter almond smell of cyanide, no garlic smell of organophosphates, and no special sour smell of the dark blue nerve inhibitor that is associated with prajna.

This is not a chemical attack.

Hearing then picked up the key information.

Beneath the cacophony of roars and crashes, there is a persistent, extremely low-frequency background noise.

Extremely low.

It fell so low that it far exceeded the lower limit of human hearing.

19 Hz.

This number triggered a series of precise knowledge chains in Lin Chen's mind.

19 Hz infrasound.

The frequency happens to fall near the natural resonant frequency of the human eyeball. Prolonged exposure can cause slight vibrations in the eyeball, leading to blurred vision, anxiety, and even hallucinations in extreme cases.

Even more deadly is that infrasound in this frequency range can interfere with the vestibular system's sense of balance and the rational control areas of the cerebral cortex, causing the exposed person to gradually lose higher cognitive functions without being aware of it, retaining only the most primitive stress responses—fear, aggression, and escape.

The prefrontal cortex of adolescents' brains is not yet fully developed, making them at least three to four times less resistant to infrasound interference than adults.

This is the real reason why these students "went crazy".

It's not poisoning.

It's not hypnosis.

It is a physical-level interference with brain nerves.

Lin Chen opened his eyes.

The sound source was the school's broadcasting system.

Wall-mounted speakers are hung on the ceiling of each corridor in the teaching building, which are normally used for get out of class bells and campus broadcasts.

At this moment, the loudspeakers were outwardly silent, not broadcasting anything that anyone could hear.

However, their speaker diaphragms are vibrating at a low frequency of 19 Hz, invisible to the naked eye, continuously emitting infrasound waves throughout the building.

Lin Chen did not go to the broadcast control room.

He can find it, and he can also disassemble the entire broadcast system's circuit board into parts.

But he can't do that.

Infrasound isn't a switch that you press to stop.

These students had been exposed to continuous 19 Hz radiation for at least thirty minutes, and their brains were in a state of constant overload oscillation.

If the infrasound source is suddenly cut off, and the external forced oscillation is lost, the brain will not immediately return to normal. These students' nervous systems are likely to experience a severe rebound effect after the sudden loss of external stimulation, falling directly from a state of being out of control into a deep coma or even causing irreversible nerve damage.

We must use another method.

It's not about cutting off infrasound, but about neutralizing it.

In physics, this is called "destructive interference".

When two waves with the same frequency, equal amplitude, and a phase difference of exactly 180 degrees meet in space, the wave crests match the wave troughs, and the wave troughs match the wave crests, completely canceling each other out, resulting in a net amplitude of zero.

He needs a sound source that can produce a canceling waveform that perfectly matches the frequency of the 19 Hz infrasound wave and has a precisely reversed phase.

This sound source cannot be an electronic device, because it is uncertain whether Prajna has implanted a countermeasure program in the broadcast system. Once the countermeasure signal from an external electronic sound source is detected, it may automatically adjust the frequency to make the countermeasure disappear.

It must be a physical sound source.

A sufficiently large resonant cavity capable of generating extremely low-frequency vibrations.

Lin Chen looked up towards the third floor of the east wing.

Music classroom.

There was a Steinway D-type nine-foot grand piano in that classroom.

Model D-274 has a fundamental frequency of 27.5 Hz for the lowest note A0 of the strings. However, if a beat frequency effect is created by using a specific chord combination, the frequency difference between two adjacent bass strings can generate a beat frequency vibration of 19 Hz in the air.

The phase of this beat frequency is determined by the time interval between when the player presses the keys.

Accurate to the millisecond.

It is possible.

Lin Chen began to move.

The dozen or so out-of-control students in the first-floor corridor sensed his presence. The closest ones turned around, their eyes bloodshot, their pupils dilated to almost swallow their irises, and thin lines of saliva trailing from the corners of their mouths.

A burly boy roared and pounced on Lin Chen, faster than a normal sprinter. The adrenaline stimulated by the infrasound made his muscle explosiveness far exceed his usual level.

Lin Chen sidestepped, dodging his attack.

Then, he gently pressed the back of his head with his right hand, the force so precise that it caused a brief overload on his vestibular nerve, causing his eyes to roll back and him to fall limply to the ground.

There was no harm done, just a temporary loss of memory.

He neutralized seven students who lunged at him in the same way, each strike precise and controlled to the point of not causing any external injury, but merely using the temporary overload of the vestibular nerve to temporarily incapacitate them.

Walk through the west wing corridor, pass through the connecting passage, and go up to the third floor of the east wing.

The door to the music room had been smashed open from the outside, creating a crack.

Behind the door was a table that had been pushed over to act as a roadblock, and three chairs. The wooden door panel was covered with marks left by fists and fingernails.

There were five or six students blindly banging on the door in the corridor.

Lin Chen took them all down in four seconds.

He knocked on the door three times.

"Ke'er, it's me."

There was a moment of silence inside.

Then he heard the sound of tables and chairs being hurriedly dragged away, footsteps, and a "brother" that was almost swallowed up by a sob.

The door opened.

Su Ke'er's face was covered in tears, her eyes were red from crying, and she had bitten teeth marks on the cuffs of her floral dress.

The moment she saw Lin Chen, she threw herself into his arms, clutching his clothes tightly with both hands, her whole body trembling like a leaf.

Lin Chen put his left arm around her shoulder and his right hand on the back of her head.

"We're safe now."

Three words.

Su Ke'er's cries grew even louder, as all the fear she had been holding back for who knows how long finally burst forth.

Lin Chen made her cry for ten seconds.

Then gently pry her hands open.

"Ke'er, I need that piano."

Su Ke'er sniffled and looked up at him with tears streaming down her face, not understanding why he needed the piano at this moment.

Lin Chen walked up to the Steinway D and opened the piano lid.

The black lacquer reflects a deep luster under the light, and the eighty-eight piano keys are neatly arranged.

His right hand rested on the A0 key in the lowest pitch range, his fingertips feeling the faint vibrations transmitted from the key.

The building’s public address system was still silently emitting 19 Hz infrasound.

In the corridors and upstairs and downstairs, thousands of students are losing their minds in this invisible sonic cage.

Lin Chen sat down on the piano bench.

Ten fingers hovered above the piano keys.

[God-level vocal mastery], full power activated.

The two skills simultaneously unfolded two maps in his mind.

One is a mathematical model of the acoustic wave equation, which precisely calculates which two notes, under the conditions of the space size, wall reflectivity, and air temperature and humidity in this music classroom, can generate a beat frequency of 19 Hz in the air, and how many milliseconds the time interval of the playing needs to be accurate so that the phase of the beat frequency is perfectly 180 degrees different from the broadcast infrasound.

The other one is the complete score of a piece of music.

It is not any known classical piece of music.

This piece was composed by Lin Chen on the spot within three seconds of sitting down at the piano, based on acoustic calculations.

The selection of each note is based on precise principles of physics, and the structure of each chord serves the sole purpose of "generating cancellation waves of a specific frequency and phase in the air."

But it was not a simple physics experiment. Lin Chen arranged those notes into a real piece of music with melody, ups and downs, and emotional tension.

Because simple wave cancellation can only neutralize infrasound.

To awaken a brain that has fallen into a state of neural oscillation, something else is needed.

melody.

When the human auditory cortex receives a structured, predictable melody signal, it automatically initiates a "pattern recognition" process.

This program is an instinct that evolution has endowed humans with; millions of years ago, our ancestors used it to distinguish the sound of the wind from the calls of their companions.

When the signal strength of a melody is strong enough and its structure is clear enough, it can cover up the chaotic noise running in the brain and pull the firing rhythm of neurons back from disorder to order.

Lin Chen's fingers landed on the piano keys.

The first sound.

When the bass notes A0 and B0 are pressed simultaneously, the two notes, with a frequency difference of exactly 19 Hz, produce a deep resonance within the piano's massive soundbox.

Sound waves originate from the strings, are amplified by the soundboard, pass through the open lid, and spread in all directions.

The sound wave met the infrasound output by the broadcasting system in the air.

The crest met the trough.

"Buzz—"

A strange auditory experience spread throughout the entire teaching building.

It wasn't that the sound got louder or softer, but rather that a sense of oppression that had always been there but had never been noticed suddenly lessened.

It's like walking for a long time wearing a very heavy pair of headphones, and suddenly someone takes those headphones off.

But it only alleviates the symptoms.

One note isn't enough.

Lin Chen's ten fingers began to truly play.

The melody rises from the low register, heavy and slow, like the deepest layer of darkness before dawn being torn apart by the first ray of light emerging from below the horizon.

The chord progressions maintain a precise 19 Hz beat frequency throughout each inversion, while the melody itself unfolds a warm, ascending line in the mid-to-high register.

Su Ke'er stood beside the zither, tears still streaming down her face, but she could no longer open her mouth.

She studied piano for twelve years.

She knows what a good performance is and what a masterful performance is.

But she had never heard of such a thing before.

This is not a performance.

This is a story about a person waging war against all the unseen sound waves in the entire building using eighty-eight piano keys.

As the middle section of the piece arrives, the mood of the melody shifts from somber to bright.

Lin Chen's right hand played a series of rapid arpeggios in the high register, each note so clean that there was not a single millisecond of lingering sound.

The left hand maintains a stable and powerful chord progression in the bass register, continuously outputting a canceling waveform.

Changes occurred in the corridor.

The students closest to the music classroom were gradually lowering their shouts.

Their steps went from chaotic, aimless stumbling to staggering, then to swaying, and then to slowly, slowly bending their knees and collapsing to the ground as if all their strength had been drained.

Their eyes were no longer bloodshot.

The pupils are slowly shrinking back to their normal size.

This change started on the third floor east wing and spread like ripples to every floor and corner of the entire teaching building.

The sound waves from the piano, conducted through the solid surfaces of the floors and walls, and then propagated directly through the air, covered the entire space of the L-shaped teaching building within three minutes.

The last section of the piece.

The melody returns to the initial bass theme, but this time it is no longer heavy.

All the dark harmonies were replaced with the bright colors of the major key, the canceling waveforms in the bass register completed their mission in the last set of chords, and the 19 Hz beat frequency completely smoothed out the last trace of residual vibration of the broadcast infrasound in the air.

Lin Chen lifted his fingers off the piano keys.

The overtone of the last note reverberated within the Steinway D's resonant chamber for three seconds before fading into silence.

The entire teaching building fell silent.

It wasn't the chilling roar of before that was now drowned out by silence.

It was truly quiet.

In the corridors, stairwells, and classrooms, hundreds of students slumped on the ground, some leaning against the walls, others slumped over their desks, their expressions blank and bewildered, as if they had just been awakened from a long nightmare whose contents they could no longer remember.

Some people started crying.

It wasn't a screaming cry, but a normal cry after waking up and realizing you didn't know what had happened, with aches all over your body and being terrified.