I have recently been going through some of the earliest books in my collection. I enjoyed Lian Hearn's "TALES OF THE OTORI" books so much that I have decided to read all of them again now.
The books are set in a fictional feudal world that is very similar to the feudal era of Japan. The first book in the series is called "ACROSS THE NIGHTINGALE FLOOR".
The world may be fictional but nightingale floors are very real. They were wooden floors designed to make a noise, similar to a chirping bird, when walked upon. Historians are not sure whether the floors were made intentionally to warn of intruders or the chirping noise was incidental or an accident.
The name comes from the Japanese Bush Warbler (uguisu) a Japanese songbird.
It is quite remarkable how much the floor does sound like a chirping bird. I think it would be impossible for an enemy, or an assassin to creep quietly over such a floor. I would like to think that these floors were intentionally made because they are quite amazing.