Masking toilet noise may date back to Edo
Local Japanese News In English
Today there are colorful portable gadgets and iPhone applications to cover up the sounds people make when using the toilet, but a museum here has a large bronze urn dating from the 19th century that could be the earliest form of such devices. Because many Japanese women are embarrassed to have other people hear the sounds of the more private bodily functions, most ladies' rooms in department stores and office buildings are equipped with a device commonly known as the Otohime - originally the brand name of a product developed by Toto Ltd. - that emits the sound of a toilet flushing.
Toto put on sale its first Otohime product in 1988 to cater to the delicate sensibilities of women and save water at the same time. Before the device was introduced it was customary for women to flush the toilet twice - the extra flush being to mask the bodily sounds. (Japan Times)
Source: cleanup