Suddenly (apnw). Old adverb, but in the N.T. only in Acts ( Exodus 2:2 ; Exodus 16:26 ; Exodus 28:6 ). Kin to exaipnh ( Acts 22:6 ). A sound (hco). Our eco. Old word, already in Luke 4:37 for rumour and Luke 21:25 for the roar of the sea. It was not wind, but a roar or reverberation "as of the rushing of a mighty wind" (wsper peromenh pnoh biaia). This is not a strict translation nor is it the genitive absolute. It was "an echoing sound as of a mighty wind borne violently" (or rushing along like the whirr of a tornado). Pnoh (wind) is used here (in the N.T. only here and Luke 17:25 though old word) probably because of the use of pneuma in verse Luke 2:4 of the Holy Spirit. In John 3:5-8pneuma occurs for both wind and Spirit. Filled (eplhrwsen). "As a bath is filled with water, that they might be baptized with the Holy Ghost, in fulfilment of Acts 1:5 " (Canon Cook). They were sitting (hsan kaqhmenoi). Periphrastic imperfect middle of kaqhmai.