Noise that is. One person talking is understandable. 2 is manageable,maybe. 3 at once makes understanding incomprehensible. Little can be understood in a crowded room full of people. The same thing I think could be said for train noise. On larger layouts 3 or more trains run at once. Can the human ear segregate and make sense of it or does it become a cacophony of noise? Beethoven,my favorite composer was a master at blending sounds,he wrote his music that way and has many masterpieces. Train sounds are random and not composed and not Beethoven.
I live near the CSX. I hear one train occasionally, very rarely 2 at once passing each other. On many layouts and train shows many trains run continually on loops all with sound units and crew chatter,not pleasant to me. I put mine on timers. Only 1 train (2 or 3 per loop) runs per loop at a time and at spaced intervals. With 6 loops and the use of timers only 1 or 2 trains usually run at once.IMO time and time intervals is the least modeled aspect in model rail roading. Peace in the valley! To each his own but I do not like layouts too busy or too active. They are not prototypical to real life and not enjoyable to me. I am a toy train guy without realistic scenery but still pay attention to this aspect. To each his own. I also design my layout so trains appear and disappear like real trains. I do this with tunnels and putting the layout in 2 rooms. I also time accessories such as carnival rides to turn on and off, not run continually. The ferris wheel has to stop so the riders can get on and off! Same thing with the passenger trains. What is your opinion and preferences?
Dale H
Our guests find it exciting. The human brain allows us to concentrate on one thing and block out the rest. 
I'm still happy at the end of the day when we shut all the noise off. 
Then after it's all over I like to run one train and relax. 
