Noise Reduction
Noise reduction is a process that often times is not really necessary if a recording has been done with standard equipment such as analog or digital. There usually is no room for noise to be accumulated on a track if the recording were done properly.
There are times when noise reduction is important when it comes to recording unplugged such as acoustic instruments, or the human voice. These sounds have to be captured through the open air where other sounds can be present as well.
Sound proof booths usually handle this problem very well an there is no need for concern. There is a lot of ambiance that can be heard through a microphone in the studio and that is one of the needs of the booth. The result of a recording with background noise would be hard to clean up afterwards.
Unless a recording is going to be recorded live outdoors like a concert or even a venue, club, or auditorium, then you obviously will want to capture all the noise of the background ambiances. It all depends on what type of recording you are going to do that will help you decide if a silent or ambient background is what you want for your music.