My wife worked for many years for a radio company, United States Broadcasting. The office she worked in ran seven stations on the seventh floor of a ten story office building in the middle of downtown Macon, Ga. As you can imagine with the location of the building you have quite a lot of city hustle and bustle to deal with. Most of their studio rooms were dead as a door nail and very small. Some of the rooms were barely large enough to accommodate the host and one other guest besides the mixer and computer they used. A couple of them were larger, could accommodate several guests, host, and equipment. These studios were rather old school in that the host or DJ had to mix the show and operate the playlists on the computer themselves. All the stations were pumped into the main transmission room where there were placed in strategic positions rack units that had EQ, compression, limiting, gating, etc. for each station before it hit the final transmission coil. Believe me when I say that those cubicles are slammed so hard with compression and gating it would make your mama cry! I can't speak for NPR but I have appeared on or done the audio for commercials for every radio and TV station around here and the use of HEAVY compression and gating is a standard. I generally would just do mixes without any limiting at all and when they played that spot it would sound like it was cut in NY!