Sounds of Idling ES44C4's - GE Whoop and Other Air Noises

Whoop at 2:21
In the idling train, three of the four engines were ES44C4's (4400 was a dash 9 and was not running). The second engine from the front kept making air noises, and it whooped several times, however, I only got one good recording it the whoop.
After the the air compressor ran for a bit, there was a loud revving-up sound that I have seen with other GE's. In an earlier video of an ES44C4, I had said it was the GEVO 12 revving up, but the actual engine makes a chugging sound when running hard. I think the air compressor, or something else, is doing it.
Previous Video of ES44C4
• GEVO 12 Idling and Rev...
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