During a casting call, the actors present will act out a role by reading lines from the script. Therefore, the acoustics of the room should be excellent if the venue is a large one. Some casting rooms are smaller in scale, like
classrooms, audition rooms, and studios. Since actors won't be far from the producers, the acoustics aren't quite as important. That said, the space should still be as soundproof as possible, to keep distractions like traffic noise or nearby conversations from intruding.
Casting rooms may also come with extra spaces like waiting rooms, lounges, bathrooms, and kitchens. These give actors a place to lounge or go over notes before their auditions. Extra rooms also keep noise from interrupting an audition. Rather than having people waiting in the auditorium, it's better to separate them so everyone is free to speak at full volume.