"And suddenly there came from heaven a sound like a mighty rushing wind, and it filled the entire house where they were sitting. And divided tongues as of fire appeared to them and rested on each one of them. And they were all filled with the Holy Spirit and began to speak in other tongues as the Spirit gave them utterance."
Acts 2:2-4 (ESV)
The Spirit of God is not merely a "still, small voice."
He is outrageous!
He is loud, powerful, visible, audible, miraculous, and even earth-shaking!
"And when they had prayed, the place in which they were gathered together was shaken, and they were all filled with the Holy Spirit and continued to speak the word of God with boldness."
Acts 4:31 (ESV)