Squeaky floors are annoying, which is why when you search for “squeaky floors” in Google, you get hundreds of articles offering you tips and advice on how to make your floors squeak less. But in ancient Japanese societies, especially among royal families, squeaky floors were not hated but desired—because a floor that screeched and groaned with each step was an effective anti-burglar alarm system.

Some Japanese castles built during the Edo period had these kind of flooring in the hallways. They are known as uguisu-bari, where uguisu refers to the Japanese bush-warbler or the Japanese Nightingale—a very shy bird that prefers to stay hidden among the foliage, but its distinctive breeding call can be heard throughout much of Japan from the start of spring.

It is said that these specially designed creaking floors sound much like the bush warbler singing. In English, they are known as nightingale floors.

Inside Ninomaru Palace of the Nijo castle where nightingale floors are installed. Photo credit: Fran Sastre/Flickr