It seems to be that it's the same building, and possibly the same room being used for each of the auditions. When they say they are in Chicago, the room looks the same as L.A., etc. At least with some of the other reality shows with tryouts/auditions you can tell it's a different city, like Last Comic Standing. The show did this last year. It's so phony.
Sometime in the first or second episode this season, they had a quick shot of the entire set used to film the auditions. It's a portable set that they take with them to each city and assemble in a convention center or someplace. That's why it looks the same. Also probably why people keep trying to leave the wrong way. It's not a real room, so people (especially those who unceremoniously lose and just want to get off-camera as fast as possible) just try to leave via stage left or stage right instead of throught the "entrance." The waiting areas look different because they are real locations.
Last year someone noticed that some design center was being used in LA. Basically they said it was different rooms in the design center. I forget who said it. It was on some message board.
Last year, the L.A. Design Center was used for the 350 people that were sent to L.A. Same room with different backdrops and colors depending on which city was being represented. This is the place where you saw everyone bust through the fake door hootin' and hollerin' to a waiting Matt Galant. The judges never went to any of the audition cities. None of us saw them until going to L.A. After the first round from 350 to 50 everyone left L.A. and went home for 3 weeks. The top 50 returned and filmed in a studio complex called "The Lot" in the heart of Hollywood and stayed at the Renassaince hotel which is part of the Kodak Theater. When I auditioned in Chicago, it was 15 degrees and snowing. I wore a heavey sweater. We had to wear the same clothes in Hollywood so I had the same sweater on to make it look like I was in chilly Chicago. Let me tell you, a heavy sweater along with 80 degree temps and a hot studio filled with lights, was no picnic. I believe the judges actually went to each city this year. They saved millions by not sending so many inventors/finalists to Hollywood right away. So, I think it is the same set moved to the different cities. That's Network television for you.
The celebrity judges were in each city. The auditions were in differnent cities & the set is mobile & setup in each venue.
I was there for the finals in Houston.