MySheepHearMyVoice

To him the porter opens; and the sheep hear his voice: and he calls his own sheep by name, and leads them out.

Jesus is speaking now of the personal relationship that He is preparing for all believers by Grace Through Faith.

And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
I believe He is speaking of the gentiles who will hear His voice through the apostles who will prophesy under the unction of His Holy Spirit who also inspired Christ Jesus.

My sheep hear my voice, and I know them, and they follow me:
What voice?     His Word.
We are saved by hearing, believing, receiving and doing His Word.
A believer in Christ who does not believe the Lord's Word is deceived because they do not hear Christ's voice and hence are not His sheep.
Those that hear, believe, receive and do the Word of the Lord are following Christ Jesus.     see He Be Re Do.

Pilate therefore said unto him, Are you a king then? Jesus answered, You say that I am a king. To this end was I born, and for this cause came I into the world, that I should bear witness unto the truth. Every one that is of the truth hears my voice.
Jesus actually offers some information here regarding His purpose in coming to earth. He is the Truth and draws men to the Truth.

Wherefore (as the Holy Spirit says, To day if you will hear his voice,
The Holy Spirit is the Lord. Christ Jesus is the Word of the Lord. We hear His voice when we listen to the Word by revelation of the Holy Spirit.

While it is said, To day if you will hear his voice, harden not your hearts, as in the provocation.
Make yourself tender to the voice of the Lord - His Word and His Holy Spirit.
When a person hardens their heart toward the Lord it is an overt act of rebellion.     It results in an impenetrable eternal spiritual state from which there is no hope of salvation.
This is not to be confused with running from the Lord which many have done and do today.
No one comes to the Lord purely on their own.     They are drawn by the Holy Spirit as they hear the Gospel.     Those who believe and receive the Gospel are saved.     Those who reject the Gospel have spurned the Holy Spirit and so may never be bothered by Him again.

Again, he limits a certain day, saying in David, To day, after so long a time; as it is said, To day if you will hear his voice, harden not your hearts.
The Lord always speaks in the here and now. He is I AM. Whenever a person is drawn by the Holy Spirit they are hearing the voice of the Lord. To believe or to harden is the act of our Free Will.

Behold, I stand at the door, and knock: if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me.
The fact that this statement is addressed to the church at laodicea implies that they have shut Christ out of their operation. It is in fellowship with Christ by His Spirit according to His Word that we sup with Him.
Who is it that stands at the door knocking? He is the Holy Spirit of Christ Jesus.

And I heard a voice from heaven, as the voice of many waters, and as the voice of a great thunder: and I heard the voice of harpers harping with their harps:
At the end of the Day Of Wrath there will be great rejoicing on earth and in heaven.