In the video, they both talked about the steep seating and how vertical it was. IMO, that is a sign that it is going to be loud in there. In a way it reminds me a bit of George Mason's arena. I've been there several times and I recall it being pretty loud there. I don't think the AUB seats as much, but it does look like the AUB has the upper deck more on top of the action than at GMU. As was mentioned, there aren't walls where the sound will get swallowed up so I think we're good there.
I think there are two major factors in terms of the buildings acoustics- seating (which appears to be on point) and the roof.
I think the roof is going to be the reason that place is as loud or quiet as it will be. I cannot imagine that they did not consider acoustics in relation to an arena. Especially when they are planning to have concerts in there. It doesn't matter how many seats you have for a concert if the place sounds like garbage. I've got to believe they seriously considered sound and its impact in there.
I'm really going out on a limb here, but I am basing this on previous builds. I really believe the AUB is going to be LOUD. And not only will it be loud, but a great venue for concerts. They have knocked it out of the park with practically every single thing that's been built at JMU. And this arena is a big, big deal for JMU. Not only is it good for JMU, but for Harrisonburg. To go through all this time and build a place where it would either: a) sound quiet, or b) sound terrible.... I just cannot fathom them screwing it up. And either of those would be a massive mistake. There's nothing to indicate that they would make a mistake that big.