This helps them determine where they are, where they are going, and what if anything is near.
Here is a poignant metaphor. We call out to find our place, to see if anyone is near, if anyone responds. A response helps us know where we are, where we are going, and whether or not we are alone.
For many with CFS results of echolocation are bleak.
Too often they call out and find, there is no response.