Infrasonic Radar

After eating and drinking his fill, Umino Sasuke found an excuse and returned to the underground laboratory.

Fortunately, Aburame Shibi was sensible—or perhaps his reconnaissance range was limited. He only deployed Kikaichū around the outskirts of the defense zone and had no intention of monitoring the four of them. Otherwise, it would have been difficult for him to slip away.

Once he reached the underground laboratory, Umino Sasuke could not wait to unseal the Sealing Scrolls and begin setting up the experimental equipment.

The equipment was quite valuable, and it took him two days of spare time to finish installing everything.

Once the laboratory was set up, he immediately took the Water Bat summoning beast that had been cut in two from its bottle of saline solution and began dissecting it for research.

The results were encouraging, though not entirely smooth.

The good news was that after several days of dissection and research, he had basically unraveled the principles behind the Water Bat's ultrasound.

The bad news was that while chakra was versatile, it still followed the law of conservation of energy. To achieve the same meticulous precision as the Water Bat's physiology required considerable amounts of chakra and Chakra Control.

Once the sensing range exceeded the three-kilometer limit, the demands on chakra reserves and control increased geometrically.

Under normal circumstances—for instance, in actual combat, where he needed to keep constant control of the battle's rhythm like the Byakugan—the Sonic Radar Technique's sensing range was best kept under two hundred meters.

Of course, with further research, the Sonic Radar Technique's sensing range could continue expanding for the same chakra expenditure. However, the further he went, the harder it became to improve it, unless he made another breakthrough in Chakra Control or the Transformation Jutsu.

"Continuing research in this direction is starting to feel like more trouble than it's worth."

Umino Sasuke was somewhat disappointed. The path of further increasing the Sonic Radar Technique's sensing range was not a dead end, but the investment and returns were clearly disproportionate.

Still, when one path closed, another opened.

When he tried to draw parallels by reading some research materials on summoning beasts, he discovered several rather interesting documents.

In particular, there were studies related to Tiger Summoning Beasts.

Tiger Summoning Beasts generally possessed extremely high combat power. Alongside aerial summoning beasts such as hawks and falcons, they were practically mandatory research subjects for major institutions.

Those institutions focused their studies of Tiger Summoning Beasts on the composition of their combat power. Yet by chance, he came across an inconspicuous research document—or, more accurately, a set of observation records that had strayed from the mainstream direction of research.

According to those records, the Tiger's Roar of Tiger Summoning Beasts possessed an intimidating force similar to genjutsu. Its range was extremely broad; a casual roar could carry for dozens of li and could even cause ordinary creatures to suffer cardiac arrest.

"In other words, the Tiger's Roar of Tiger Summoning Beasts has incredibly strong penetrating power and can travel over immense distances."

Umino Sasuke was deeply shaken and immediately realized the value of those research materials.

Knowledge he had read in popular science books in his previous life began surfacing in his mind.

According to those books, the frequencies humans could hear ranged from 20 to 20,000 hertz.

Sound waves below 20 hertz were infrasound, while sound waves above 20,000 hertz were ultrasound.

A tiger's roar was infrasound.

Its sound-wave frequency was concentrated between 14 and 18 hertz, placing it squarely within the range of infrasound.

Infrasound had extremely strong penetrating power and could travel great distances.

The saying that a tiger's roar shook the forest meant that a single roar could reverberate across several mountain peaks, which showed just how terrifyingly far it could travel.

Furthermore, studies showed that a tiger's roar could penetrate the human skull and resonate with the brain's alpha waves, causing electric-shock-like illusions and neural paralysis.

The powerful penetration of a tiger's roar could even affect the physiological responses of nearby small animals, causing their hearts to stop.

At the same time, tigers could also use infrasound to sense the signs of an impending earthquake, allowing them to react and warn others in advance.

"A tiger's roar is actually infrasound!"

Umino Sasuke was greatly shocked, and his heart burned with excitement.

The Tiger Summoning Beasts of the Shinobi World had been vastly enhanced in every aspect by chakra, and naturally, the infrasound in their roars was no exception.

Now that he thought about it, the so-called genjutsu-like intimidation of Tiger Summoning Beasts must have come from the infrasound in their roars being amplified by chakra, making the effect even more terrifying.

Umino Sasuke compared the experimental data and conducted further research, only to find that it was indeed just as he had guessed.

"Good thing I already had experience developing the Water Bat's ultrasound. Otherwise, I'd really be going broke this time."

Tiger Summoning Beasts were generally quite powerful, and many institutions researched them. Demand was high, so their prices naturally remained steep. This was also the front line; buying a Tiger Summoning Beast here would require paying an even greater premium.

Now, however, his previous experience developing the Water Bat's ultrasound, together with the relevant research materials in his hands, saved him a great deal of effort.

Having discovered such an excellent new direction for research, Umino Sasuke naturally immersed himself in it and could not pull himself away.

For a long time afterward, whenever he had free time, he would hole up in the underground laboratory. Fortunately, some materials could be stored in the Sealing Scrolls, allowing him to read through them bit by bit while patrolling the defense zone.

"Let's call it here for today."

Umino Sasuke stretched, archived and saved all of the day's research results, then hurried without pause toward the sentry patrol base.

It took more than ten minutes before he finally returned to the sentry patrol base.

"Captain, don't tell me you went to have fun at the military camp trading post again?"

Tejudo walked over with a lewd grin and gave Umino Sasuke a vigorous sniff, only to find him reeking of disinfectant.

Umino Sasuke took out a small bottle of Water Bat No. 6 and tossed it over, scolding him irritably, "If you still want these little darlings in the future, then keep your mouth shut."

"Sure, I'll shut up. Right away."

Tejudo caressed the bottle of poison in his hand, unable to put it down, as if it contained not poison but his little wife.

Seeing Umino Sasuke return, Inuzuka Ryo and Xiao Xiao moved with practiced ease and immediately began setting up the pot to cook.

Umino Sasuke continued to handle the fishing. After exhausting the waters so thoroughly, he was now the only one who could catch Golden Mandarin Fish.

Meanwhile, Tejudo carried a large wooden bucket, standing on the river's surface downstream as he practiced Water Walking.

Infrasonic Radar Technique.

Umino Sasuke stood on the river's surface, formed the Tiger Hand Seal with both hands, and began sensing.

Before long, he discovered several Golden Mandarin Fish hiding in the deep pool to his right.

"Shock!"

Umino Sasuke brought his hands together in the Tiger Hand Seal, and an utterly invisible wave of infrasound silently surged toward the deep pool.

A few seconds passed.

A large patch of freshwater fish floated to the river's surface, unconscious, including several Golden Mandarin Fish.