The Voice from Heaven (John 12:27-36)

After Jesus spoke with certain unidentified Gentiles (12:20-26), He turned His face to heaven and said for all to hear, "Father, glorify Thy name!" Jesus exclaimed as He did knowing that the hour of His passion was upon Him. Then for the sake of those that stood by a voice from heaven answered Jesus, "I have both glorified it and will glorify it again." What did this voice from heaven mean?