Knocking in the Corner of a Room That Answered Questions

p, first off. Was passing by and decided to clarify: a couple of years ago a "knocker" showed up, it knocked in response to questions, both to it and not. I noticed it when I was talking in the room where I sleep. Usually it knocked monosyllabically, I'd ask it something and there could be from one to four (!) knocks. And sometimes it responded in time: yes - one knock, no - two knocks. It passed a test on knowledge of the date the Great Patriotic War began (not to be confused with the date of WWII), on the first flight into space (not about Gagarin).

At first it scared me. It knocked right in the corner of the room at any time of day, which is important, though I knew that above and below there are families with children and they're not there at lunch, and behind the wall is an empty apartment. Then it started to interest me. It answered questions, was an adviser. And then it disappeared.

This went on for about half a year. Relatives didn't die, and nobody died - it couldn't have been souls. What/who was it