Unfortunately, due to his lack of ability to be able to objectively measure the frequency of the sound that he produced, he would need to rely on trial and error to a large degree. Furthermore, unlike when he was creating the Flux Earther technique, it would be much more difficult to observe the success or failure of his trial-and-error method.
Since the technique involved constructive superposition of two sound projectiles, he would necessarily need to release two sound projectiles of different speeds.
The first projectile would be the Sonic Bullet technique which moved at the speed of sound, and the second technique would be the Mighty Roar Flash Blast technique, which moved faster than the speed of sound. He would need to use both those techniques and ensure that he timed and placed them and ensured that they were in phase with each other such that they would engage in constructive superposition.
The difficult part was ensuring they would be launched in phase with each other. Because he had no way to ensure that they would have the same frequency, he was at an impasse.
He glanced at the large target barrier more than five hundred meters away.
The barrier wall was made up of Apprentice-level materials, however, they had been extensively engineered with the right kind and mix of esoteric substances that they could withstand even the power of Martial Squires.
Rui had wondered why they couldn't apply such a methodology to weapons to create even stronger weapons that allowed them to be more ubiquitous but thinking about it, he could come up with a rather straightforward answer.
Weapons needed to be strong enough such that even if the power of the wielder was focused across a millimeter square of its surface area, it would not break. It needed to be so strong that every millimeter square of the weapon was individually capable of withstanding the full power of the wielder focused on it, without breaking.
When blades clashed with each other, only such a tiny amount of the blade ends up bearing the primary brunt of both the wielder and the opponent. If it every millimeter of a sword's tensile strength did not greatly exceed that of the user, it was an unfit weapon.
With human-level weapons, it was easy to ensure this was true. No ordinary human could ever break the edge of a sword made with steel alloys no matter how strong their muscles were. The difference between the tensile strength of steel and the muscular strength of swords was like that of the sky and land. It was a large gap. That was why humans could fight with full power without having to worry about breaking their weapons with their own power due to this big gap.
It became increasingly difficult to maintain this same gap for Martial Artists.
This same rationale did not apply to larger structures. With larger structures disproportionately greater than the human body in size, all forms of esoteric materialistic engineering of different esoteric resources could b employed to ensure that these structures could withstand punishment from powerful Martial Artists.
He found it to be an interesting albeit irrelevant detail.
('As long as it fulfills my needs, I am fine,') He mused.
He took his stance before opening his mouth.
THWOOM! content.
He closed his mouth after having shot a Sonic Bullet, preparing the Mighty Roar Flash Blast technique rapidly after.
THWOOM!
The latter trailed three meters behind the former, rapidly catching up to it due to being faster than it.
Soon the two sound projectiles overlapped with each other.
BOOM!
A wind blast emerged from the union of the two projectiles, causing a huge gale.
('Hmph, they were completely out of phase, causing destructive superposition,') He sighed.
And the problem was, as predicted, different frequencies.
('This time, same pitch,')
THWOOM!
THWOOM!
BOOM!
A huge wind blast emerged once again.
The reason the explosion was violent was because the crests of the wave were meeting the troughs. The waves were oscillating in opposite directions when they touched, which basically meant that they were directly crashing into each other, and the molecules of the air were blown away.
That was what caused the violent dispersion of air.
('Wait, can't I judge the degree to which there exists a difference in frequency between the two projectiles based on how violent the superposition is?') Rui realized.
The more violent the blast, the more the waves were out of phase. The less violent it was, the more they were in phase. If they weren't violent and formed a single projectile, then that would b a sign of success; that they were in phase with each other.
He felt better. After all, he had come up with an objective way of measuring the degree to which the two waves were out of phase with each other.
Now he just needed to do it over and over until he learned via muscle memory how to get it right. It was sheer and raw experience needed to master the frequency equalization of the technique and nothing else.
Still, his job wouldn't be over once he mastered just constructive resonance between two sound projectiles. He wanted to learn how to accomplish it between three, and perhaps even four and five.
Of course, he highly doubted that the latter two would be viable in most combat. At most, if he ever happened to be put in a situation where he needs five times the singular offensive power of his strongest attack that he possesses at the moment, then he would be able to muster it up.
In the right circumstances, he could potentially end up outputting power that was on par with Martial Squires who were several grades above him.
('Now wouldn't that be one hell of a technique that the Martial Union would love to get their hands on?') Rui smirked with anticipation. He wondered what Senior Ceeran would think when he learned of this technique that Rui was working on, given his fascination for new techniques!