From the New York Times:
The story of Toto, a Japanese company that created the Otohime, or “Sound Princess,” illustrates the great divide. Now installed in thousands of restroom stalls across Japan, the device mimics the sound of flushing water. The Sound Princess solved a problem of affluence: women were continuously flushing public toilets to mask the sounds that come with using them. Toto’s innovation saves them the embarrassment. The portable, purse-friendly version is a best-selling consumer product in Japan.