The other day, I read about "otohime", also known as "sound princess":
Many Japanese women are embarrassed at the thought of being heard by others during urination (see paruresis). To cover the sound of bodily functions, many women used to flush public toilets continuously while using them, wasting a large amount of water in the process. As education campaigns did not stop this practice, a device was introduced in the 1980s that, after activation, produces the sound of flushing water without the need for actual flushing. A Toto brand name commonly found is the Otohime (音姫, lit. "Sound Princess," also homophone with a legendary goddess Otohime)
As a male, is it possible to hear one in real life?
Do they exist in mixed gender / unisex toilets? If so, where are mixed gender toilets most common? (I haven't noticed any in my previous two trips)
Otherwise, should I try finding an otohime in an Akihabara shop, or possibly some sort of museum?