Chen Hao placed the recorder on the table, the casing hitting the metal surface with a dull thud. He stared at Nana's back as she stood in front of the control panel retrieving data streams.
"That tremor just now was not accidental," he said.
Nana didn't turn around, her finger sliding across the virtual panel: "The resonant frequency of the thruster motor is 183 times per second, and the peak of the frequency drift of the communication module's receiving band appears between 181 and 185. The two coincide."
"So, we killed our own signal?" Carl pulled a detection cable from his toolkit and flicked it casually. "My crappy machine just shook, and the whole team went silent?"
Susan leaned against the wall, holding a printed copy in her hand: "It wasn't just the silence. Do you remember the silence during the evacuation? The three of us backed away using hand gestures, like a silent movie. What if the swarm had gotten a few steps closer then? Who would have given the order?"
The air was silent for a second.
Chen Hao raised his hand and scratched the back of his head: "So the problem now is not 'whether it can be connected,' but 'when it will be disconnected.'"
Nana finally turned around. A flash of blue light appeared in her eyes, as if the program had switched to a new task: "I have extracted all the anomaly logs. The source of the interference has been identified as harmonic leakage in the power system. There are two solutions—change the frequency, or add shielding."
“Changing the frequency is troublesome.” Karl shook his head. “Each thruster has different factory parameters, and it takes half a day to calibrate each time. Moreover, the pressure changes greatly in deep water, and the frequency band may deviate again at any time.”
“Then there’s only one way left,” Chen Hao decided. “Weld a shell over it.”
For the next 48 hours, the main control room was transformed into a modification workshop.
Chen Hao was in charge of disassembling and assembling the communication repeater casing. He sat at his workbench, his screwdriver stuck in the connector for ages, sweat beading on his forehead. "This thing wasn't designed to be repairable, was it?"
“The original structure was designed for lightweight construction.” Nana handed over a miniature wrench. “What you’re doing now is reverse engineering.”
“I know.” He gritted his teeth and pried open the last protective panel, “but right now I just want it to live a little longer.”
Susan and Carl were welding a shielding layer next door. The rare metal sheet was as thin as paper, but extremely hard; it wouldn't melt in if the welding torch wasn't hot enough. After the third failure, Carl pushed his mask up: "This material is too weird; it doesn't melt when it's hot, and it becomes brittle when it's cold."
“No wonder the thing we dug out in Chapter 677 is so unusable.” Susan adjusted the current setting. “Try it again, this time feed the wire more slowly.”
Nana didn't leave the console the entire time. Her program had three main threads: one to analyze the time points of each test interruption, one to simulate the electromagnetic response curve after the new shielding layer was added, and the other to secretly record the flashing rhythm of the leader creature from the previous chapter, to be used as a test sample.
The first high-pressure test was conducted in the simulation chamber.
All six nodes were online, and the voice channel was open. Chen Hao had just said, "Number one is normal," when the signal started to drop. In the playback recording, his voice sounded like something had gnawed at it, with a small piece missing in the middle.
“The frequency band is still fluctuating.” Carl looked at the waveform graph. “Although it’s more stable than before, it can’t withstand the pressure at 800 meters.”
“The shielding layer is not thick enough.” Nana pulled up the material stress model. “The current version can only filter 62% of the interference. To achieve the ideal state, at least three layers are needed.”
"Then add it." Chen Hao wiped his face. "Anyway, this thing isn't heavy."
In the second test, they used a shielding sheet three times thicker. The voice recording was stable, but a low-frequency buzzing sound appeared in the headphones, continuous and causing a throbbing sensation in the temples.
Susan was the first to spot the problem: "This isn't external noise. It's the metal itself vibrating."
“Infrasound resonance,” Nana confirmed. “The material will produce slight self-excited vibrations under specific pressure, which fall right at the edge of human hearing.”
"It sounds like a refrigerator making noise by itself in the middle of the night." Carl rubbed his ears. "If I listen to this for another two hours, I'll go crazy."
No one laughed.
They knew that in the deep sea, any persistent anomaly could affect their judgment. Not to mention that they would have to rely on this system to communicate with those blue-light creatures in the future—if even the signals they received were distorted, who knew if they would misinterpret a "greeting" as an "attack."
Nana activated the adaptive filtering algorithm. This was an old technique she had dug out of the database, originally used for early space communications. Its principle was to capture noise characteristics in real time and then generate an inverse waveform to cancel them out.
After the first iteration, the buzzing decreased by 40%.
Round 2, 71.
The third time, the system successfully identified the resonance pattern and completed dynamic compensation within 0.3 seconds. The playback recording was so clear it sounded like a face-to-face conversation.
"Alright." Carl listened to the test clip. "This time it really sounds like a human voice."
The final step is short-range field verification.
They left the base with the new equipment and set up a node in the shallow sea area 500 meters away. The ocean currents were more turbulent than expected, and when the searchlights swept across the area, the water was clearly distorted.
"Let's begin." Chen Hao pressed the call button.
Everything is normal. The audio is clear, and the delay is almost imperceptible. The four people take turns speaking to check the synchronization.
Just as they were preparing to retrieve the equipment, an undercurrent suddenly struck.
The monitoring screen flashed, and the three nodes instantly went offline.
The channel fell silent.
Chen Hao looked up at Nana. She had already made her move.
A finger swipes across the terminal, and the backup link is automatically activated. Three seconds later, all signals are synchronized again.
“Reconnection successful,” she said. “The firmware has been updated to enhance the network self-healing mechanism.”
"So, it can reconnect itself if it breaks next time?" Chen Hao asked.
“As long as the physical connection of the nodes is not damaged, the link can be rebuilt.” Nana nodded. “Now the system supports dual-channel redundancy, with the main frequency transmitting voice and the auxiliary frequency performing verification. Even if the main channel fails completely, the content can be restored through error correction codes.”
Chen Hao smiled and put the repeater into the waterproof box.
Back at base, he sat down at the control panel and opened the test log. The last line of the log showed: continuous operation for two hours and seventeen minutes, zero signal interruptions, and an audio distortion rate of 0.38%.
He clicked save and casually added this version of the equipment to the standard equipment list.
Susan and Carl signed the acceptance form together. The two took the equipment to the warehouse to register it. Before leaving, Carl muttered, "If it breaks again, I'll stick it on my forehead."
Nana returned to the charging station, and the device entered standby mode. The core program continued to run, constantly monitoring the health of all terminals.
Chen Hao stood up and stretched his shoulders. He walked to the window and looked out at the sea; it was pitch black, and he couldn't see anything.
But he knew that next time he went down, no one would make wild guesses because they couldn't hear clearly.
He turned and walked toward the rest area, pressing the replay button as he passed the control panel.
Nana's voice came through the recording, steady and clear.
"The communication link is stable, and all six nodes are synchronized."
Next, Susan reported: "Received, no issues reported in position two."
Carl: "I'm finally getting some peace and quiet."
Finally, it was his own voice: "Okay, let's set off then."
He paused for two seconds, then pressed it again.
The same recording played again.
This time, however, before anyone else spoke, there was a very short interlude—like a rhythmic ticking sound—that repeated three times.
Chen Hao frowned, pulled the progress bar back, and played it frame by frame.
The sound was not in the original record.
It only appears during playback.
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