If you went to sleep in the Edo period also or Tokugawa Japan did not know you, whether you will wake up the next morning. In the 17. Century was the threat of Ninjas big enough, so the architect in Japan designed a special alarm system, to protect aristocrats.
The design is called Nightengale Floor, roughly translated the Nightingale Floor. The following example from the Nijo Castle in Kyoto shows, as the boards are fixed to the support with metal clips. Diese Klammern kratzen aneinander und wenn jemand auf diese Stelle tritt, produce the brackets a sound like the chirping of a nightingale.