Strange voice caught on tape.

I had previously reported that I was hearing what sounded almost like short-wave bursts that appeared to be coming from an interior wall of my house that once housed a dumbwaiter that has been sealed off for over 50 years. The first time I attempted to register anything on a tape, you'll remember, my recorder was moved several feet from where it was placed and all that was recorded was a buzzing sound. I checked the recorder out and it was fully operational. So I again set the voice activated recorder out. This time I discovered that if the downstairs door from the parlor to the front hall is left open the barking of my dogs can be heard. On this trial run they barked plenty, obviously while the wife and I were out. However aside from the barking the recorder did pick up the short "radio?" blasts that we have been hearing in the hall or master bedroom. But again, even though the blasts are loud they were too garbled to tell what was being said. Just prior to my placing the recorder in the hall, I had experienced the "voice" which repeated itself five or six times and sounded almost like it was saying, "Vincent had a heart attack", it sounded like that to me but it was unclear, garbled, so it could have been something else. BTW I know no one named Vincent. But tracking down the origin of these sounds always leads back to an inside wall on the second floor of my house in an area that once had an old dumbwaiter for moving items from the second floor downstairs. But it has been sealed off for decades. I have a pair of walkie-talkies and I have tried them out on the second floor, but nothing comes through on the wall. Its a very perplexing mystery.