音姫 "Sound Princess"
Many Japanese women are embarrassed at the thought of being heard by others during urination. To cover the sound, many women used to flush public toilets continuously while using them, wasting a large amount of water. Becase of that, Otohime was introduced which produces the sound of flushing water without the need for actual flushing. (音姫 "Sound Princess").
This device is now routinely placed in most new public women's rooms from an environmental friendly point of view. The device is activated by pressing a button, or by the wave of a hand in front of a motion sensor. When activated, the device creates a loud flushing sound. This sound either stops after a preset time or can be halted by a second press on the button. This can save a lot of water!
I think this is one of the very Japanese inventions because whenever I travel outside Japan, nobody cares the sound as we do. There is no judgement of good and bad, this is just one of the unique cultural aspects. :-)