Good Morning 
I have some old audio book recordings that have terrible noise issues. So far, I’ve been removing the noise track by track. I was worn plum out after doing this for 38 individual tracks. I have a program that will allow me to combine multiple my audio files into one. My question is, if I combine all of them together and remove the noise that way, will it be just as effective as if I did it track by track?
OS: WIndows 7 Home Premium
Audacity Version: 2.0.5
Thanks for your help. 
If the noise is the same in all of the recordings then you can import all of the files into Audacity and apply Noise Reduction to all of the tracks at the same time (though of course it will take longer to process, but you can leave it working while you have a cup of coffee).
The quality/effectiveness of Noise Removal is very dependent on the “noise profile”, so if the noise is different in each file then it will be better to process them one at a time, creating a new noise profile each time.
Thanks so much Steve. I was not the original importer so I can’t say for sure if it’s the same, although they sound a lot alike. I think I will have no choice but to process each track. Oh joy 