Notating Ambience

I was outside smoking a cigarette on my back porch when I remembered something that Brian Eno wrote about appreciating ambient sounds. I don't remember where I read it, it might have been online or on the back of a record or in this book I have that compiles a year's worth of his journal entries. Wherever I heard it, he suggested this exercise:
While you're outside or in any environment with a combination of patterned and non-patterned noises, listen to the collection of sounds in total and attempt to formulate a notation system for what you're hearing. Imagine each sound individually and attempt to mentally, or physically with a pen and pad if you're really into the idea, notated the rhythm, pitches, and other interesting sonic features of the sounds.
Once you've got a feeling for what the different sounds are and how they work, just sit and interpret how the different sonic features co-exist. Cover up one ear and see which how that changes things. Move around. Pay attention to all the elements you would in music and then pay attention to how you can add to the collage of sounds.