We all know that YHWH created by speaking. He "said" and there was.

At Mt. Sinai, YHWH also spoke:

Exod 19:13-19
13 'Not a hand shall touch him, but he shall surely be stoned or shot with an arrow; whether man or beast, he shall not live.' When the shofar sounds long, they shall come near the mountain."
14 So Moshe went down from the mountain to the people and sanctified the people, and they washed their clothes.
15 And he told the people, "Be ready for the third day; do not come near your wives."
16 Then it came to pass on the third day, in the morning, that there were thunderings and lightnings, and a thick cloud on the mountain; and the sound of the shofar was very loud, so that all the people who were in the camp trembled.
17 And Moses brought the people out of the camp to meet with Elohim, and they stood at the foot of the mountain.
18 Now Mount Sinai was completely in smoke, because YHWH descended upon it in fire. Its smoke ascended like the smoke of a furnace, and the whole mountain quaked greatly.
19 And when the voice of the shofar sounded long and became louder and louder, Moses spoke, and Elohim answered him by voice.

Remember that Yom T'ruah is a remembrance or reminder of t'ruah, shouting or the blast of a trumpet. What is it to remind us of? The creation of the universe "in the beginning"? The creation of a set-apart people at Mt. Sinai?

Let's look at "in the beginning." In Hebrew we would say b'reyshith. The letter beyt makes the "b" sound. It means "in, on, by, when, or with" when placed before a word. The rest of the word, reyshith, is from the word rosh, which is commonly translated as "head", but comes from a more ancient meaning of "to shake." Therein lies something awesome. "In the shaking" YHWH formed the heavens and the earth.

Heb 12:3-13
3 For consider Him who endured such hostility from sinners against Himself, lest you become weary and discouraged in your souls.
4 You have not yet resisted to bloodshed, striving against sin.
5 And you have forgotten the exhortation which speaks to you as to sons: "My son, do not despise the chastening of YHWH, nor be discouraged when you are rebuked by Him;
6 For whom YHWH loves He disciplines, and flogs every son whom He receives."
7 If you endure disclipining, YHWH deals with you as with sons; for what son is there whom a father does not discipline?
8 But if you are without disciplining, of which all have become partakers, then you are illegitimate and not sons.
9 Furthermore, we have had human fathers who corrected us, and we paid them respect. Shall we not much more readily be in subjection to the Father of spirits and live?
10 For they indeed for a few days disciplined us as seemed best to them, but He for our profit, that we may be partakers of His holiness.
11 Now no disciplining seems to be joyful for the present, but painful; nevertheless, afterward it yields the peaceable fruit of righteousness to those who have been trained by it.
12 Therefore strengthen the hands which hang down, and the feeble knees,
13 and make straight paths for your feet, so that what is lame may not be dislocated, but rather be healed.

Heb 12:18-29
18 For you have not come to the mountain that may be touched and that burned with fire, and to blackness and darkness and tempest,
19 and the sound of a trumpet and the voice of words, so that those who heard it begged that the word should not be spoken to them anymore.
20 (For they could not endure what was commanded: "And if so much as a beast touches the mountain, it shall be stoned or shot with an arrow."
21 And so terrifying was the sight that Moses said, "I am exceedingly afraid and trembling.")
22 But you have come to Mount Zion and to the city of the living Elohim, the heavenly Jerusalem, to an innumerable company of angels,
23 to the assembly and gathering of the firstborn who are registered in heaven, to YHWH the Judge of all, to the spirits of just men made perfect,
24 to Yahshua the Mediator of the new covenant, and to the blood of sprinkling that speaks better things than that of Abel.
25 See that you do not refuse Him who speaks. For if they did not escape who refused Him who spoke on earth, much more shall we not escape if we turn away from Him who speaks from heaven,
26 whose voice then shook the earth; but now He has promised, saying, "Yet once more I shake not only the earth, but also heaven."
27 Now this, "Yet once more," indicates the removal of those things that are being shaken, as of things that are made, that the things which cannot be shaken may remain.
28 Therefore, since we are receiving a kingdom which cannot be shaken, let us have grace, by which we may serve YHWH acceptably with reverence and fear.
29 For our Elohim is a consuming fire."

So Yom T'ruah is to remind us of YHWH's discipline. The voice of the shofar is a call to righteousness to those who have been trained in righteousness. It says, "get your act together and receive correction." It is a time of shaking to prepare us for Yom Kippur. It is to make us honest about ourselves so that we might truly afflict our souls on Yom Kippur, and then move on to joy at Sukkot.

One more thing. There is a correlation between the seventh month and the seventh day:

Gen 2:2-3
2 And on the seventh day Elohim ended His work which He had done, and He rested on the seventh day from all His work which He had done.
3 Then Elohim blessed the seventh day and sanctified it, because in it He rested from all His work which Elohim had created and made.