What is the significance of "Kol Kanfeihem"?
Malbim: He tells how he heard the command to the Chayos; they are commanded about the Ofanim. They do not move them via physical contact, not via a force that pulls or pushes, rather, via voice and a spiritual intellectual command. (a) When they fly with their wings, which hints to miraculous conduct based on Hashem's will, above nature and the Ma'arachah. This command is "k'Kol Shakai" - from Hashem, who overrides the Ma'arachah via special Hashgachah. It is "k'Kol Mayim Rabim" - at the time of creation, Ru'ach Elokim hovered above the water (the creation; there was not a Ma'arachah yet). Also refer to 1:24:3:3, 1:24:4:4.
What is the comparison to "Kol Shakai"?
Rashi: Do not say that the sound of much water is soft - "k'Kol Shakai", like the voice explained in Tehilim "Kol Hashem ba'Ko'ach" (Tehilim 29:5).
Radak #1: It is a Gibor's voice -"mi'Shakai Yavo" (Yeshayah 13:6) "v'Hayah Shakai b'Tzarecha" (Iyov 22:25).
Radak #2: It is Hashem's voice; He is called Shakai. Also in the third vision, it says "k'Kol Kel Shakai b'Dabero" (10:5) - like when He spoke on Har Sinai "Kol Gadol" (Devarim 5:19). Below, it was heard "Ad he'Chatzer ha'Chitzonah" (10:5) - the border of the Bayis. Also at Har Sinai, even though it was a great voice, it was not heard outside of Machaneh Yisrael. Also every Nevu'ah, the one for whom it is designated, only he hears it.
Malbim: Refer to 1:24:1:1.
What is the comparison to "Kol ha'Mulah k'Kol Machaneh"?
Rashi citing Targum Yonasan: The voice of their words, when they thank and bless their Master, like the voice of a camp of supreme angels.
Radak: Mulah is like Milah (word), but it hints to a strong word heard when many speak, "k'Kol Machaneh."
Malbim: "B'Lechtam" (when they go without flying, according to the Ma'arachah), the voice was like that of a Machaneh. This is only when the nation is arranged like an ordered army. On the one hand, they hear only one voice, of Hashem based on Hashgachah. On the other hand, they hear many voices - the laws of nature and its orders.
Why do their wings soften when they stop?
Rashi: They slacken from making noise.
Rashi citing Targum Yonasan: They silence their wings in front of Hashem's voice that comes out from above their heads to inform Nevi'im of their mission, like it concludes "va'Yhi Kol me'Al
