The composition and color are beautiful, eerie and dramatic. The problem is, in the opening sequence, after we pass through it we see as if we were still seeing it from Earth . In reality, the structure has three dimensions, so it probably looks very different from the backside. Still, this was a very cool effect. So radio astronomers don't have a habit of using headphones to listen to the signals.
Headphones can only check one at a time.
As it turns out, it pays off, because The Message is so strong that it overwhelms the background. Matter of fact, in the movie they mention the power is about 100 Janskys. You can see a few of them in the image above. This is a real site, and they simply filmed the scene there. Bad Reader Ted Brattstrom asked Dave Finley, an astronomer at VLA, about this.