In the Beginning

In the very beginning, in the very first book of the old testament, God is speaking. He is always speaking, and HIS word never returns void.  The words HE sets forth always go forth, keep going forth.  They don't stop.

In this book and chapter, in HIS speaking, HE is creating all things. And everything HE speaks comes about, and everything HE creates is Good. All the examples are below from Genesis Chapter 1 (In ESV): 

On the very first day, HE spoke light into existence:

3 And God said, “Let there be light,” and there was light.

And on the second day, HE spoke to create the expanse (firmament) that separated the heavens from what became the earth

6 And God said, “Let there be an expanse[a] in the midst of the waters, and let it separate the waters from the waters.”

And in order to name something, It seems likely HE spoke:

8 And God called the expanse Heaven.[c]

On the 3rd day, HE spoke to separate the water and seas under the heavens, and then named them.

9 And God said, “Let the waters under the heavens be gathered together into one place, and let the dry land appear.” 10 God called the dry land Earth,[d] and the waters that were gathered together he called Seas.

Also on the 3rd day, HE spoke again to create the vegetation. This is the first day HE spoke twice and had two acts of creation:

11 And God said, “Let the earth sprout vegetation, plants[e] yielding seed, and fruit trees bearing fruit in which is their seed, each according to its kind, on the earth.”

On the 4th Day, HE created the lights in the heavens and described their purpose.

14 And God said, “Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons,[f] and for days and years, 15 and let them be lights in the expanse of the heavens to give light upon the earth.”

On the 5th Day, HE created the creatures that fill the waters and the air (these HE let Adam name).

20 And God said, “Let the waters swarm with swarms of living creatures, and let birds[g] fly above the earth across the expanse of the heavens.”

Also on the 5th day, This is the first time that HE blessed something and gave a command.:

22 And God blessed them, saying, “Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth.”

On God's last day of creation, HE created the creatures the fill the land, again leaving them unnamed until Adam named them:

24 And God said, “Let the earth bring forth living creatures according to their kinds—livestock and creeping things and beasts of the earth according to their kinds.”

The 6th day is another day where GOD did two separate acts of creation, for HE also made Man in HIS likeness and described their purpose.

26 Then God said, “Let us make man[h] in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth.”

And here also, God spoke again to bless them and give them their commands (purpose):

28 And God blessed them. And God said to them, “Be fruitful and multiply and fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth.” 29 And God said, “Behold, I have given you every plant yielding seed that is on the face of all the earth, and every tree with seed in its fruit. You shall have them for food. 30 And to every beast of the earth and to every bird of the heavens and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food.”

In Summary, here God spoke to create. No one was there to hear, no human that is. We know that the Sons of God were there to hear it because HE tells us that in the Book of Job. And then when HE created living beings, whether beast, fish, bird, or man, HE spoke to them, blessed them, and commanded them (telling them the purpose for which HE created them). Based on this passage, it seems like all of these heard HIM speak and understood what HE was saying.... or at least since it was the word that went forth, that word created what HE said. 

Many believe HE spoke in Hebrew, as many believe Hebrew was the first language. I don't know currently about the truth of that. Not saying it was not true, just saying that I personally have not even tried to study that out. All I know is that HE SPOKE, and continues to speak in many ways, to many, for a variety of reasons.  And when HE speaks, it comes about and we are blessed.