Among the other Japanese products and technologies having to do with the lavatory, there are sound-effect units made especially for public restrooms, or more specifically, for women's restrooms. Japanese women tend to be embarrassed about other people hearing the sound they produce when relieving themselves. So in public restrooms, many of them flush the toilet once when they sit down and a second time after they are done. This leads to a great waste of water.
In 1988 Toto started selling the Otohime, a device that produces the sound of flowing water, for use in public restrooms and office buildings. The name, literally meaning "Sound Princess," is a pun on the name of a princess in a Japanese fairy tale. The product is attached to the wall of each stall and plays the sound of running water from a small speaker for 25 seconds when it is activated. By activating the Otohime when they use the toilet, even self-conscious women can make do with just one flush.
Toto estimates that this saves as much as 20 liters of water each trip to the lavatory. In an office building with 400 female workers, installing sound makers can save over 10 million liters of water in one year, assuming that each woman goes to the bathroom five times daily (and that without a sound maker, all of them would double flush). This translates into a reduction in the water bill of ¥7.74 million.