YAKAGE, Okayama Pref. — 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.

Toto spokeswoman Akiko Yamasaki said a major drought that hit the city of Fukuoka in 1978 partly motivated the company, based in the nearby city of Kitakyushu, to develop the product.

Several other cities also faced water shortages in the late 1970s due to factory construction, and Toto, known for its high-tech Washlet toilets, came to realize the need to address the female habit of flushing toilets twice.

The company came up with the name Otohime, which literally means “sound princess,” to symbolize the shyness and modesty of Japanese women, according to Yamasaki.

“Most foreigners are amazed at and give high marks to sophisticated Japanese toilets with bidets, warm seats and many other functions. But they don’t understand the necessity for Otohime and think it’s strange,” she said.

South Korea is the only other country where the Otohime is marketed, while Washlets are available around the world. In Japan, the cumulative shipments of Otohime products surpassed 1 million units last August.

Shigenori Yamaji, an expert on toilet culture and a researcher at Osaka University of Tourism’s Institute of Tourism Studies, also reckons being embarrassed at other people hearing such sounds in the lavatory is peculiar to Japan, at least to the extent that masking natural sounds is a desirable option.

According to Yamaji, the sensibility can be traced back to at least the 19th century, a time of feudalism, as the residence of a wealthy family in Yakage that also served as a designated inn for dignitaries was equipped with an urn traditionally called an Otokeshi-no Tsubo (Urn for Covering the Sound).

The urn, now kept in storage at the Yakage Folk Museum and expected to be put on display there in the near future, has a water outlet in the shape of a dragon. A curator said the urn was originally placed on a platform near the lavatory, which was exclusively for high-ranking guests of the inn and not for family members or servants.

When a guest wanted to use the room, it is thought his attendant would be standing by to lift the plug on the urn and let the water out from the dragon’s mouth to cover the sound of the nobleman urinating, Yamaji said.

Women who use modern equipment for the same purpose in the 21st century say their shyness is not the only reason they activate the sensor every time they use the bathroom.

“I’m more concerned about the unpleasantness for other people if they hear the sounds I make than my own embarrassment at being heard,” said a 22-year-old student in Tokyo.

Another student in her 20s said she uses it out of “consideration” for other people.

But some are critical of the custom. “I think the Japanese sometimes read too much between the lines,” said a housewife in her 30s in Chiba Prefecture.

“My own excretory sounds never make me embarrassed. It’s much more embarrassing to put on makeup on the train,” said a Chiba dance instructor in her 50s.

Meanwhile, the flushing sound device, which is either attached to the wall of the cubicle or part of the toilet itself, has evolved into a new stage as several companies launched portable gadgets last year that women can carry with them to use in places lacking the conventional device, such as when they travel overseas.

The toilet flushing sound has also been made into applications downloadable to iPhone, so people can take their handsets into the restroom and play the sound.

Among the recently introduced portable products is the Keitai (Portable) Otohime sold by toy maker Takara Tomy Arts. The Tokyo company said the product is selling well, with the initial 30,000 units sold out in trade with wholesalers soon after its launch in late November.

Priced at ¥1,449, the battery-operated device can be locked so the powerful flushing sound doesn’t suddenly blare out on a train.

If such sensibility in toilet culture dates back to feudal lords, a question arises — don’t men in modern Japan want to use the Otohime?

In a survey by Toto on about 200 male college students in 2007, 36 percent said they always or sometimes flush the toilet while “doing the business” in campus restrooms, with 66 percent of the flushers saying they do so because they don’t want others to hear them.

Mariko Shibasaki, another Toto spokeswoman, said she has heard that “herbivorous boys” — a catchphrase referring to men who are reluctant to be involved in romance or have sex — are pleased to see such portable devices being sold. One of them said, “I’ve always wanted something like that.”

If the trend grows, it could give rise to another catchphrase — Otohime Boys.