Last week my wife sent me a short essay that she had found. In the essay is a reference to “nightingale floors”. (Many thanks to Mary for sending this to me!)
What is a “nightingale floor”, you ask? It is a floor that sings like a nightingale. Apparently.
Tell me more, you say. Indeed.
In various ancient palaces in Japan, these floors were built as security systems. When you walk on them, they “sing” (of squeak, depending on how you hear such things.) The most famous such floor is in the Nijo Castle in Kyoto, built in the early 1600s.
Here you can see the floor, from above and below.
According to Wiki, the etymology of the name is as follows:
“The first character (鴬) is read as uguisu and refers to the Japanese bush-warbler. 張り is read as bari, which comes from 張る haru meaning to stretch. Together this means “the sound of a Nightingale from the stretching/swelling/straining [of the floor]”.”
You can hear one of the floors here. You will notice how they really do sound like chirping birds!
Here you can watch a video of people walking on one of the floors.
Here you can read more about the floors and see another video.
One site asked the question:
“If your security needs are high enough that you decide to put in nightingale floors, odds are you also have guards keeping an eye on your castle. So how do you tell if those chirping footsteps you’re hearing are coming from a trusted sentry or enemy ninja?
The answer? Quite simple, really:
“The solution is, like the floors themselves, elegantly simple. In order to tell friend from foe, the lord of the castle or captain of the guards would designate a set rhythm for allies to adhere to when walking on the nightingale floors. If they heard their “nightingales” singing at a different speed, they knew they had an uninvited guest, and that it was time to sound the alarm.” (http://en.rocketnews24.com/2015/04/17/nightingale-floors-the-samurai-intruder-alarm-system-japans-had-for-centuries/)
If you would like to learn how to walk across such a floor, like a ninja, and perhaps not get caught, check out this link, which shows you a basic ninja walking technique.