I actually wondered the same thing when I saw the news this morning and froze the picture to observe. It is possible that it was not the fairing that was being shown. It could have been an environmental test chamber for controlling temperature or acoustics. If it was the fairing those might have been acoustic absorbers on the inside surface.
Doh! I didn't notice your link which is a much better picture than I saw. I would say that is the fairing with tuned acoustic dampers inside. The fairing can vibrate like a drum head at its natural frequency. The acoustic energy from the engines is quite high,and at low frequency.
