Diary of a Criminal Investigator-Chapter 282: Simply Unbelievable

Of course, it’s true.

Lu Chuan rubbed his hands together, completing the voiceprint identification for four voices in one go was no easy task.

Moreover, this was Lu Chuan’s first time conducting a voiceprint analysis.

He was somewhat inexperienced, and many details needed repeated analysis and deliberation.

For example, the second male voice showed signs of a long-term habit of eating peppers.

Although the second male voice had an accent from the southern Zhezhou, in reality, Zhezhou doesn’t particularly have a strong habit of eating spicy food.

"Chili peppers are a stimulating food, and long-term consumption can cause some irritation to the vocal cords, leading to significant changes in a certain frequency of the voice."

The voiceprint analysis report produced by Lu Chuan didn’t just contain conclusions; every conclusion process was detailed.

"Generally, people without special training won’t reach extreme frequencies in their voice range."

Lu Chuan pointed to a chart in the report: "Only very skilled bass singers can lower the frequency of their voice to 82 Hz."

"Let alone 82 Hz, even those who can lower it below 90 Hz have an inherent talent for bass."

"Long-term consumption of chili peppers can cause low-frequency changes in a person’s voice."

"In simpler terms, it creates a pattern in the low-frequency band of the voice."

"Among the four voices, only the second male voice had a pattern show up at the 89 Hz frequency band."

"And this pattern was irregular, unlikely to be naturally occurring, probably due to vocal cord stimulation, so I concluded that the second male voice frequently eats chili peppers."

The three people listening to Lu Chuan’s explanation exchanged glances, truly gaining knowledge.

"What about weight? How can you determine weight by listening to a voice?"

"This comes down to the structure of the vocal cords."

As Lu Chuan spoke, he gestured: "The vocal cords have a wedge-shaped structure, composed of vocal cords, vocal muscle, and a mucosal covering layer, with a small slit-like space in a relaxed state on each side."

"The shape of the vocal cords shows slight differences in people of different weights."

"On the voiceprint spectrum, specific prominent features appear in different frequency ranges."

"And this feature, like eating peppers, is hidden in the sound, hard for the human ear to detect but can be found through sonograph analysis."

This is the identification analysis of the voiceprint spectrum; using a sonograph, anyone can analyze a voice.

However, extracting the sound spectrum at different adjusted frequencies and then analyzing the result based on specific frequencies is not something anyone can easily do.

"People of different weights will show different characteristic patterns at 306 Hz, 803 Hz, and 902 Hz."

"By certain calculations, you can deduce the weight of the voice owner."

"Of course, this might be hard to understand, but some singers maintain constant weight because changes in weight affect the thickness of the vocal cord’s mucosal covering layer."

"This indirectly causes changes in their voice, making it hard to sing with the same tone as before."

"Wow, there’s such a thing?!"

Old Bai, having lived a long life, truly heard of this for the first time.

Upon thinking it through, it seemed to make some sense.

"What about the fourth person? The fourth female voice sounds like she’s in her forties or fifties, how can she be in her twenties?"

Actually, when Lu Chuan was listening to the recording, he already had some skepticism about this.

However, lacking the aid of a sound spectrum, Lu Chuan wasn’t quite sure three days ago.

Now it was different; the fourth female voice’s sound spectrum confirmed Lu Chuan’s suspicions.

"The fourth female voice indeed sounds quite hoarse and aged."

"However, this hoarseness and aging aren’t naturally formed, but due to vocal cord damage, resulting in such an illusion."

Lu Chuan opened the report and turned to the third-to-last page: "Here’s the sound spectrum of the fourth female voice, in the 800 Hz range, her voice spectrum is extremely irregular, which is the main reason her voice sounds hoarse and aged."

"But, look here," Lu Chuan pointed to a break in the spectrum.

Indeed, the fourth female voice’s sound spectrum had a watershed break at 803 Hz, appearing disconnected there.

"What does this mean?"

Yang Sen was puzzled.

"This break means that, at this frequency, the fourth female voice has no sound present."

"In other words, at this frequency, her vocal cords can’t produce sound."

"In a normal sound spectrum, continuity runs, the difference lies in each person’s sound fullness at different frequencies, so the only cause for this kind of gap is vocal cord damage."

"Is it possible she was born this way?"

Lu Chuan shook his head: "This relates to the development of the vocal cords, which should naturally grow as a person ages."

"It’s impossible to have a section in the middle undeveloped like this."

"Even in cases of poor development, one can still produce sound, just not perfectly, without sudden breaks like this."

"Then why a laceration injury?"

Liu Guodong voiced his doubt: "I’ve heard of vocal cord damage resulting in a tear injury before."

"This conclusion also comes from the characteristic of breaks in the voiceprint."

"After a tear injury to the vocal cords, short-term, there’s a possibility of spectral breakpoint occurrence."

"But since tear injuries are typically one or partial, such breakpoints are unlikely to be singular."

"Laceration injury differs; cutting the vocal cords is possibly due to a sharp object, rendering one unable to produce sound at the time of injury, and even after recovery, can’t be restored."

The conclusions in Lu Chuan’s voiceprint identification analysis were all supported by the voiceprint spectrum.

Therefore, each conclusion here could serve as forensic evidence.

"I suggest the Criminal Investigation Team in the High-tech Zone focus on looking for the fourth female voice."

"The occurrence of such vocal cord damage is exceedingly rare."

"Moreover, the fourth female voice has a local accent from Haizhou, and among us, only a few top-tier hospitals can perform vocal cord recovery surgery."

"Considering the person’s age, the surgery should have been done when she was between eighteen to twenty-three years old, making it relatively easy to filter through."

"Great! I’ll call Yuan Shaokang right now."

After hearing this, Liu Guodong felt a surge of confidence.

The fourth female voice having experienced vocal cord damage made finding her relatively easier.

Yuan Shaokang, upon receiving the voiceprint analysis report, was utterly bewildered.

Could such detailed information be obtained just from listening to a voice?

Early the next morning, Yuan Shaokang arranged for three groups to investigate at Haizhou City’s three large top-tier hospitals.

The result was a delightful surprise for Yuan Shaokang!