Back in the Middle Ages, the Japanese learned to install alarms in their homes against thieves and robbers. To make it difficult for a stranger to sneak unnoticed, so-called uguisubari (uguisu - nightingale, bari - tension) or "nightingale floors" were paved inside the palaces and temples.
To the supporting floorboards beams with the help of metal spikes are attached special, abutting against the floor, staples about 12 cm long.When a person walks on such a floor, the staples move up and down, rub against metal spikes and make sounds similar to birdsong. Moreover, walking on tiptoes only enhances the effect, since the pressure on the floor in this case is higher than from a full foot.
By the way, the sound turned out to be not only loud, but also quite beautiful, and the nightingale floor during the day could well be used to delight the ear, as an unusual musical instrument.
The most famous nightingale floor among today's tourists is located in the ancient palace of the emperors in Kyoto.