When you enter a public toilet in Japan, you are likely to be enveloped by a backdrop of noise. No, not like that. It is the sound of running water, perhaps peppered with happy tweets and birdsong, and it is intended to transform the room into an acoustic image of nature, perfect for responding to its call.
In Japan, noise-producing devices that flush toilets are commonplace. Although they come in various forms, they are often called otohime or “sound princess” and are manufactured by Japanese toilet manufacturer Toto Ltd. manufactured. It's a form of bathroom etiquette in which sounds that can be embarrassing are drowned out by the sound of a rushing river, perhaps sprinkled with other sounds from nature. Some older models only emit the recorded sound of a toilet flushing.
These devices have been standard in Japanese women's toilets for years, both to suppress unwanted noise and to save water: In 2016, a survey by the Nikkei newspaper found that women flushed an average of 2.3 times without a noise device and 1.5 times with one.
Now they are finding a new audience of all genders in offices, malls and other public spaces across the country. And as they become more widespread, the sounds they make get stranger and stranger as exporters and hackers tailor them to more and more niche audiences.
“It became natural for women to use otohime,” said Tsukasa Matsuyama, who works in Toto’s faucets and appliances department. “Because younger men are more sensitive to toilet noises, they are also being installed in men's restrooms. There is a growing movement to not differentiate between genders when designing public restrooms.”
The features built into Japan's famous futuristic toilets – heated seats, body sensors, bidets – were once dismissed abroad as silly extravagances. But it now counts celebrities like Ali Wong, Drake and Jimmy Kimmel among its followers, and Toto's exports to North America have exploded in recent years. The next frontier is noise masking devices, which are also attracting new users in the transgender community in Japan. Toto, for example, has conducted surveys with transgender people about problems they face in public restrooms and shared the results with design firms, said Tomoe Hashitani, a spokeswoman for Toto.
“In a country marked by poor gender equality statistics, the toilet may be the place where gender equality is advancing, faster than society as a whole,” said Ken Mogi, a neuroscientist and author who often writes about the search for “ikigai,” or the search for the meaning of life. “Polite Noise Toilets are Japan’s answer to curbing toxic masculinity, at least when it comes to toilets.”
They also become a playground for fraudulent programmers who upload all sorts of excitement into their toilets. During the pandemic, a hobbyist named Akifumi Kinoshita developed a parody device called Sound Shogun that plays the rousing theme from the popular samurai TV drama “The Unfettered Shogun” at just the right moment. It went viral.
“I was very amused when I found a device called an Otohime in the men's room of a town hall, so I built one, mostly out of scrap parts I had,” said Mr. Kinoshita, who built the Sound Shogun for more solitary pleasure.
“Toilets are places where you can spend time alone,” he said. “Playing background music or other noises would be a popular way to create a sense of solitude, in addition to the original purpose of etiquette.”
Donna Burke, a Tokyo-based voice actress and entrepreneur, is another superfan. Growing up in Australia, she said, she often double-flushed her school toilet out of embarrassment. When she moved to Japan in 1996, she immediately loved Sound Princess and couldn't understand why it wasn't sold abroad.
So last year, Ms. Burke worked with a Japanese manufacturer on her own version, Royal Flushh, a wall-mounted device that emits the sound of a forest stream and birdsong with the wave of a hand. It markets it online, targeting shared apartments and Airbnb accommodations. She plans to release a version with new customizable sounds such as classical music. And artillery fire.
“Once we make the basic model a hit, we will introduce the premium model,” said Ms. Burke, 60, who is heard by thousands of passengers every day as the voice of the Tokaido bullet train. “Among the new sounds is the beginning of Beethoven's Fifth – 'Da da da DAAAA!' – and Rossini’s ‘Wilhelm Tell Overture’.”
She also lends her voice to the popular video game “Metal Gear Solid,” which helps explain the artillery fire. “Because 'Bombs away!' she said. “And it's funny – a war soundtrack that covers male toilet bombs and appeals to my 'Metal Gear Solid' fans.”
Toilet noise masking technology may seem like a modern invention, but the concept dates back centuries. At Rendaiji, an ancient Buddhist temple in Okayama Prefecture, monks have preserved a bronze urn that was placed in 1799 near a toilet once used by feudal lords. The urn has a spout that sprays water onto a roof tile below, drowning out noise. According to Rendaiji's official history, the urns were used throughout Japan, including at Edo Castle, the seat of the Shogun, Japan's supreme warlord.
The basic concept was not updated until the 1970s, when Japan was struggling with nationwide water shortages – in part because large amounts of water were lost through free flushes.
Amid a severe drought in Tokyo in 1979, Orihara Manufacturing, a local toilet distributor, released Etiquettone, Japan's first electronic toilet noise canceling device. It was aimed at women and doubled as a deodorizer. It became so popular that the Tokyo City Council endorsed its use as an emergency water-saving innovation. But Orihara failed to obtain a patent. Over the next decade, competitors such as Toto, Matsushita Electric (now Panasonic), and Inax (now Lixil) rushed to bring their own versions to market.
“We found that women wanted not only masking effects but also soothing sounds when using the toilet,” said Mr. Matsuyama, the Toto technician. This set the stage for the development of Otohime.
At the Toto Museum in the city of Kitakyushu in southwestern Japan, the original wall version from 1988 features a large button that triggers a veritable 25-second water roar. As Otohime gained popularity, Toto gradually updated the sound, replacing the electronic simulation of running water with the organic gurgling of real water in the wild.
Around 2009, Mr. Matsuyama traveled through Japan in search of the perfect sound: ocean waves, waterfalls, caves, rivers, streams. He recorded them all and tested them with focus groups. Finally, on the island of Kyushu, not far from Toto headquarters, he found what he was listening for in a stream and mixed it with the tweets of sparrows and nightingales.
Users have asked Toto to reveal the river's location, but it is a secret.
“We concluded that the sound of a stream was the best, and of all those sounds, this particular stream had the greatest noise reduction effect,” Mr Matsuyama said. “With Otohime, we hope users will enjoy using their imagination and discovering the 'secret' of not providing location.”
Toto has also produced some individual variations, including koto music for women's restrooms and a samurai conch shell beat for men at a rest stop in Gifu Prefecture.
To compete with Sound Princess, Toto rival Lixil teamed up with electronic instrument maker Roland to develop a device in 2018 to leverage its expertise in signal processing. The result was the Sound Decorator, a motion-activated wall device. It also plays recordings of birdsong and a babbling stream and automatically adjusts the sound frequency to match the toilet noise.
“This masking feature is similar to the cocktail party effect, where you can tune in to one sound and ignore others,” said Satoshi Wakuda, software development manager at Roland. “The algorithm amplifies the frequencies that are needed and attenuates those that are not, effectively blocking out toilet noise.”
Lixil has also launched devices with updated sounds, including one that plays the roar of a Formula 1 engine at a rest stop near the Suzuka Circuit race track.
As noise control devices spread across Japan, enthusiasts like Ms. Burke believe it's only a matter of time before the rest of the world catches on. “People just don’t know they need it until someone shows them,” she said. “One of our first sales was a woman who came back to Australia from Japan and whose husband was peeing very loudly in the toilet. She bought two units to save her marriage.”