Strange recorded sounds

     A couple of weeks ago, I had the sound activated recorder set up in the Green room. I had a lot of my dogs barking on it, and a few household voices could be heard coming from elsewhere in the house. Then I got the sound of what sounded like a bell ringing, like it was being carried. It had the sound of a pretty good sized bell. The sound appeared to be in the same room as the recorder, that is, it did not have a far away or outside sound. I figured since it was so lound and clear I'd find its source. The only bell anywhere near the Greenroom is a small shipsbell that hangs beside the western rear entrance to the house. I tried ringing it with the recorder on; the result was both higher in pitch and sounded farther away; much much further away; the first attempt didn't activate the recorder; hitting it really hard did, but the results were not the same. So I have no immediate explaination for the ringing bell. HOWEVER, I had the recorder ,last week, in an alcove in the wall in the turn of the wall of the front winding staircase. The recorder was located beside a lamp we keep in that alcove. The external mike was a good inch from the wall and hanging just about 4 inches up from the stairway carpet. We rarely use the front stairs so I felt that external noises would be at a minimum. The recorder was on sound activation for three days before I got around to checking it. It had about 4 minutes of tape that had run. When I ran that four minutes of tape I had my own voice on part of it as I was setting it up. Then a silent period of a few seconds, then the strangest sounds; almost, but not quite like a stringed instrument being plucked. I have no explaination. I'm sure there must be one. But I don't have it. I'm going to try again the same place this week and see if it should reoccur.