Muted voices heard

     This occurred last friday. I've been rather involved and hadn't a chance to enter it. Last friday my wife was in town, I was alone in the house with my dog. I first noticed the sound of voices in the upstairs bath. As this house is almost soundproof to anything but very loud noises (when the doors and windows are shut) I figured it must be persons very near the house. The voices were very muted, I could tell it was more than one person but I could not make out what was being said. I looked out the eastern window of the bath which shows most of the side and backyard; there was no one evident. I checked out the western side which has a clear view of the garage, storage building next door, garden area and part of the backyard, again no one was there. But the sound of voices continued. I went from room to room upstairs and the voices continued neither louder nor lower. I went downstairs, they were still evident. It made no sense to me that whoever they were they sounded the same in every room of the house. I stepped outside to determine if a group of people were looking over the town. This is not uncommon in the warmer months, but it would be a first during such a cold period. There was no one in sight up or down the street. The voices were not heard while I was outside; but were auditable again as soon as I came back inside. Frustration began to set in. I went to our 3 TV sets and made sure they were off; they were. We have one radio set to pick up weather and closings, but it was not on. By this time the voices just seemed to get ever fainter until they were gone. Thinking back on it, I would say there were both male and female voices. The voices being so low sounded a bit like the babble that goes on at a party or general gathering of people. There was nothing of the kind in the area. Unfortunately I lacked the presence of mind of getting my recorder and attempting to tape the voices. Its just that , at first, I was sure I'd find where they were originating from. But the hubbub was pretty much the same in any room of the house.