Guard Frequency Question

As most of us have been doing these days, I spend a fair amount of flight time
listening to 121.5. This frequency has always had some sort of low level hiss
and crackle on it that I don't hear on other communications frequencies. Does
anyone know what causes this?

George Patterson
Some people think they hear a call to the priesthood when what they really
hear is a tiny voice whispering "It's indoor work with no heavy lifting".