When I was listening and I heard birds chirping my mind would say "I hear birds chirping..." and when I heard the water rippling, my mind would say "I hear the sound of water rippling..." and then I would think "but I'm not supposed to recognize the sound as being water or the sound of the birds chirping as being birds chirping..." and then I would think "I'm not supposed to be thinking that I'm not supposed to be thinking about what the sound is..." and so I sort of fell into this ever-recursive, spiraling loop of meditative frustration. Also, this technique relies upon a person's ability to hear. It would do no good for a deaf person.