14:2 And I heard a sound from heaven like the roar of rushing waters and like a loud peal of thunder. The sound I heard was like that of harpists playing their harps.
And I heard a sound from heaven
This may be redundant as we have already established in the previous verse that this is taking place in heaven. Perhaps the voice is coming from another part of heaven.
On earth the audio spectrum is a very limited spectrum. Perhaps this is John's way of saying the frequency range is expanded on both ends. That is, the RUSHING WATERS expands the high frequencies and the LOUD PEAL of THUNDER expands the low frequencies.
Likewise on earth, sound requires a substance to travel through like air, water, or other solid material. Now if there is no substance in heaven which is likely since it is spiritual in nature, then this voice is communicating the song (next verse) by a totally unknown mechanism. This method of communications also is described in Revelation 1:15, Revelation 19:6, and Daniel 10:6.
The sound I heard was like that of harpists playing their harps.
God is a HAPPY God, and harps are instruments of JOY. When the LAMB shows up, a song breaks out (Psalms 40:2-3 and Ephesians 5:18-19)
Harps express the emotions a person is going through. On the bright side, Psalms 33:1-3 and 1 Samuel 16:14-23 show a lifting emotion. On the cloudy side, Job 30:31 and Isaiah 24:1-8-13 show the silence of a harp is like 'mourning'.