Earplugs!

Here's a quick tip. If you're doing mental practice and are as easily distracted by noises as I am, try a set of earplugs. (I highly recommend the "leight-sleepers" brand.) I find that wearing them increases my ability to concentrate and audiate. 

(In case you don't know, "audiate" means to hear the music in your head...I used to say visualize but of course that's not quite right.)