Many supernatural things took place on the Day of Pentecost, like a sudden sound coming to earth from heaven, a roaring wind that blew through the room, flames resting on each person and those present speaking in languages they had never learned. This is what took place at the birth of the Church. It was a very supernatural experience.
As we read the account of that day, the real message of Pentecost can be obscured behind all the supernatural things that took place. In Acts 2:11 the people said, "And we all hear these people speaking in our own languages about the wonderful things of God has done." The sound of heaven, spoken through the Church, was be heard as "the wonderful things God has done."
It seems to me the message of the Church today should still be this wonderful message of the great things God has done. These "wonderful things" is the sound of heaven. When the voice of heaven speaks through the Church of the wonderful things God has done, the culture's response will be the same today as it was on the Day of Pentecost.
The sound of heaven is a message filled with a wonder at the love of God. This sound of heaven is our message to the world and this is truly the evidence that we are Spirit-filled believers.