Back to the Roots

I have had the very exciting and unique opportunity to partake in a private investigation. To maintain the integrity and respect of the space, I will not be divulging the location until after the completion of the investigation. After joining up with the group I've been generously offered to assist, we had a preliminary walk-through to iron out details. Once we completed that, we took a little time to sprawl out throughout the gorgeous space and see if we could experience anything and, possibly, debunk any of those experiences.

For the most part, it seemed fairly quiet. A few conversational sessions yielded little discomfort or out of ordinary happenings. However, there was one instance that we're trying to determine any explanation for. While in one room, sitting and holding a conversation session, a very brief, young, sing-songy female voice was heard in the doorway/hallway of the room we were in. 
The other groups were not near us and there was no body seen where the voice had been heard. It was as clear as day. Currently, I can not explain what I heard or how I heard it. We're trying to come up with explanations and haven't determined any logical source at this time. If we're unable to pinpoint something (as we go through other recordings at the time to see if it was possibly from another group nowhere near us and somehow carried to be brief and right next to us), then this would be the first time I've experienced a disembodied voice. 
I'm curious to see what the actual investigation yields and if we have other personal experiences. This is exciting! I love experiencing odd things and trying to figure out natural explanations.