Phantom messages

When I receive a new e-mail, my mail program makes a pleasant little bl-oong sound. I’ve begin hearing that sound when the computer is off–even when I am far away from all manner of technology. A moment ago, I was out of the shower shaving; bl-oong. The day before yesterday, I was in the Netherlands walking on a dijk in Kruiningen; It was so quiet I could hear a seagull’s wings touch the water. bl-oong. I have to hope that this sound is just similarly pitched to a number of other natural sounds. Otherwise, It may be a mental condition.
At least it’s not the voice saying You’ve got mail! When I had AOL, that would scare the bejeebers out of me. If I heard that whilst walking around in the woods, I would be seriously disturbed.