Diary of a Criminal Investigator-Chapter 275: Voice Analysis

Wang Guojun’s expression kept changing, the light in his eyes flickering.

Chen Feng stood up and handed a cigarette to Wang Guojun.

"Think it over carefully. I’m going to grab some food; I haven’t eaten all day and night."

"Let me know when you’re ready."

Having said that, Chen Feng turned around and left.

Although Chen Feng wasn’t as skilled in interrogation techniques as the Criminal Investigation Team members,

he had his own ways of dealing with common thugs and hooligans.

Talking about morals with them was useless.

Scaring them?

Also useless.

This gang had been in and out of prison and weren’t easily intimidated.

For someone like Wang Guojun, who had no other family, just a sick old mother,

the only approach was through this angle.

Now, Wang Guojun was showing signs of giving in.

However, too much pressure can backfire; sometimes, he needed time to think on his own.

Just as Chen Feng was about to leave the interrogation room, Wang Guojun suddenly spoke.

"Stop!"

Chen Feng turned back: "Have you thought it through?"

Wang Guojun shook his head: "I want to know, how did you confirm it was me who kidnapped Liu Bai?"

He thought the plan was flawless.

How did Song Hui get exposed?

Did he betray me?

Erpi and Pang couldn’t have; they’d been with me from the start of the kidnapping.

Song Hui was the only possible flaw.

But why would Song Hui betray me?

The two million gambling debt wasn’t fake; that was concocted by Wang Guojun and others.

For Song Hui, this plan had to succeed, no room for failure.

Even at worst, Song Hui only knew me as Wang Laohu.

In the entire Haizhou, there must be at least a hundred people with this name.

It’s just a nickname after all.

Can’t quite figure it out.

And precisely because he thought everything was perfect, Wang Guojun dared to boldly go home to cook for his mother.

"Was it Song Hui?"

Chen Feng stopped, turned around, Wang Guojun’s eyes were wide open, staring intently at him.

"Not exactly."

The information Song Hui provided couldn’t directly tie down Wang Guojun.

At least, not in a short time.

They had to get a professional sketch artist to create a portrait based on Song Hui’s description for comparison.

This process isn’t completed in just one or two hours.

"You and Song Hui had a pinhole camera in the room where you kidnapped Liu Bai. Through the footage, we identified Song Hui."

"As for you... the video didn’t capture your face clearly, but you left a fingerprint on the luggage cart used to transport Liu Bai. Our Crime Scene Investigation officers identified you through fingerprint analysis."

Surveillance footage?

Fingerprint identification?

Wang Guojun had a history of robbery and theft and learned criminal law in prison.

But surveillance...what’s that about?

As for fingerprint identification, he’s seen it on TV and knows what’s involved.

"What...surveillance?"

Chen Feng didn’t reply, just shook his head and left the interrogation room.

The officer recording the session packed up the computer and left as well.

The process of identifying Wang Guojun involved a bit of coincidence.

You could chalk it up to karma.

In the Crime Scene Investigation office, Liu Guodong, Yang Sen, and Old Bai were still studying the phone recording.

Lu Chuan was busy receiving the system reward of Intermediate Voice Analysis skills.

Voice analysis requires a specialized sound spectrum analyzer to convert sounds into strip-like or curve-shaped images.

In voice analysis, these images are referred to as spectrograms.

As a person grows, due to vocal cord development, there’s a change in voice from childhood to adolescence.

After this period, the vocal cords’ development stops, giving an adult voice relative uniqueness.

As long as the vocal cords aren’t damaged, the voice remains relatively unchanged.

This consistency provides a basis for judicial voice identification.

The Intermediate Skill Card loaded quickly.

But the team currently lacked a sound spectrum analyzer for Lu Chuan to capture the phone recording voices.

Besides, capturing it wouldn’t be of use.

Wang Guojun was already caught, so voice identification was moot now.

What Liu Guodong needed was the environmental sound from the call.

"Master, let me give it a try."

Liu Guodong handed the phone to Lu Chuan: "See if you can find anything. You’re young, with sharp ears. We old guys can’t hear anything useful."

Lu Chuan nodded, took the phone, and pressed play.

With the Intermediate Voice Analysis skills, besides using a sound spectrum analyzer, the main method was still human listening to identify distinct sound features.

Otherwise, anyone could buy a spectrum analyzer and perform voice analysis.

In reality, human voices have relatively fixed frequencies; while different voices may sound distinct, they often appear similar in data as strip-like bands.

Without experience, proper analysis is impossible.

"Brother Bai, can I borrow your headphones?"

Old Bai, who practiced vocals in the morning and enjoyed listening to Peking opera when free, had his headphones handy.

It just came in handy now.

Old Bai’s headphones were quite advanced, supporting both wired and Bluetooth.

Lu Chuan connected the Bluetooth, put on the headphones, and gradually increased the volume.

He focused on the timing when Liu Bai was speaking.

When Liu Bai spoke without voice modulation, the recording picked up the surrounding sounds more clearly.

Lu Chuan’s job was to layer the sounds.

Deliberately ignoring and minimizing Liu Bai’s voice.

For most people, or those without training, this is quite challenging.

In noisy environments, we often get drawn to the loudest sound.

But the voice analysis system had a self-hypnosis-like method.

It let Lu Chuan focus on the sound he wanted to hear.

Lu Chuan, with headphones on, closed his eyes and fully immersed himself in the headphone world.

Liu Bai’s voice became a hollow background, gradually screened or deliberately ignored by Lu Chuan.

While all his attention went to that faint part of the background sound.

Clack, clack, clack.

Sound of an explosion-proof hammer?

Woo, woo, woo...

Ongoing alarm sirens.

Listening to this part of the recording over and over, Lu Chuan finally took off the headphones after a few minutes.

"Lu? What’s your take?"

Lu Chuan looked up at Old Bai, but from adjusting the recording too loudly for so long, his hearing hadn’t adapted back.

Old Bai’s voice sounded like it was coming from miles away.

But he could hear clearly.

Lu Chuan shook his head a bit, gestured OK, went to his desk, drank a large glass of water, and started to settle down.

"Got something."

"I heard a clacking sound in the recording, like the striking of an explosion-proof hammer during renovation."

"And a fire truck siren."