Why did the sound come suddenly? Why did the wind represent the Holy Spirit? Like the wind, the Holy Spirit is a powerful, invisible force. Since wind normally increases gradually, the suddenness had the psychological effect of showing that the sound was not a natural occurrence. Also, the suddenness of the sound would have startled the apostles and the others into attention. Having been in “one accord,” they may even have been praying, but whatever they were doing, they would have stopped and hearkened (Acts 1:14).
The sound of a violent wind (but not the wind itself) “filled all the house” like a powerful presence. The “sound … of a rushing mighty wind” means a continuing roar, not one blast. All in the room received the Holy Spirit and a tongue of fire. This incident marked the introduction of the Holy Spirit in the sense of doing extraordinary things in a marked, miraculous fashion in the early Church.