The phenomenon recounted in Acts 2.5-11 was this: Now there were staying in Jerusalem God-fearing Jews from every nation under heaven.  When they heard this sound, a crowd came together in bewilderment, because each one heard them speaking in his own language.  Utterly amazed, they asked: “Are not all these men who are speaking Galileans?  Then how is it that each of us hears them in his own native language? Parthians, Medes and Elamites; residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia, Egypt and the parts of Libya near Cyrene; visitors from Rome (both Jews and converts to Judaism); Cretans and Arabs—we hear them declaring the wonders of God in our own tongues!”[1]  These were the surrounding facts.  The number of disciples speaking in tongues was 120[2], and they were doing it at the same time.  They were all packed in one room, and the room was on the second storey[3].  The crowd was on the first storey, and outside the house.  In the circumstances, it was impossible for any one Jewish proselyte in the crowd to hear specifically any one disciple speaking distinctly in any one language.  The only thing the crowd could have heard was the distant combined din of 120 persons speaking simultaneously.  Hence, it was recorded that each one in the crowd heard “them”, that is to say, the whole 120-strong congregation, not one or two believers among the congregation, speaking in his own language.  They were all in fact just speaking in tongues but, to amaze the crowd, God wrought the miracle of enabling each of them to hear a message in his own language from that cacophony.

[1] Acts 2.5-11.

[2] Acts 1.15.

[3] Acts 1.13.