I heard one of these at Velim test track a few days, and I was a few metres away, it was very loud. It sounded like fans were blowing very hard, sadly didn't see it moving, just heard it starting up. But they look fantastic!
Two images attached, sadly it was too far away and dark for anything good (delayed train caused me to arrive there late).
Two images attached, sadly it was too far away and dark for anything good (delayed train caused me to arrive there late).