(Joh 16:7) Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
(Joh 16:8) And when he is come, he will reprove the world of sin, and of righteousness, and of judgment:
(Joh 16:9) Of sin, because they believe not on me;
(Joh 16:10) Of righteousness, because I go to my Father, and ye see me no more;
(Joh 16:11) Of judgment, because the prince of this world is judged.
Here we have the Lord Jesus Christ telling us exactly what the Spirit will do when He speaks by the word.
In verse 9 He says that He will convince the world of sin because they do not believe on Christ. That is exactly what He does when He makes the preached word effectual to the heart of a chosen sinner. He reveals his sin and convinces him that God is right and just to condemn him. He puts the sinner in the dust at the feet of Christ begging mercy.
In verse 10 He tells us that the Spirit convinces of righteousness because He will be risen and that it is a sign that God requires no more. The Spirit will convince the sinner that in the death, burial and resurrection of Christ God has righteously put away the sin of all His elect by the sacrifice of Christ and that the sinner is now the righteousness of God in Him.
In verse 11 the Spirit convinces that judgment is past and the sinner is set free.
That is the work of the Spirit through the preaching of the word. He speaks to the heart not the head and it isn't an audible voice or a vision or dream it is the preaching of the Gospel being manifested to be the power of God unto salvation.