For at least 1,000 years, the struggle has continued.

It is a struggle that has united children across cultures, religions and national borders. It has seen multitudes of victims, who have shaken their heads in befuddlement and despair. It is an unusual struggle, one in which each of us has participated, until we slowly, unknowingly, turned traitors and crossed the battle lines. It is the struggle of children to be, and to remain, unintelligible to grownups.

In Japan, the fight has raged for a millennium — Sei Shonagon’s “The Pillow Book’ includes references to wakamono kotoba (young peoples’ words). Yes, even 1,000 years ago, there were conniving young types bent on confusing, confounding, even intentionally repelling the adult population.

Back in the 21st century, the battle continues as the linguistic shenanigans of the young move into the technological realm. Taking their cue from similar products overseas, two Japanese companies _ Dwango and Taito _ are marketing mobile-phone ringtones that they claim can only be heard by “young people.”

You may shudder — if you’re over about 35 years of age. But loaded up with one of these ringers, your average Docomo, au or Softbank mobile phone can be turned into the ultimate “weapon.” Children can be alerted to incoming calls without their parents even knowing. School students can receive incoming e-mails while teachers drone on about history or arithmetic.

What is the world coming to? And more importantly, do these things really work?

At this point I must confess to being a sprightly 33 years old — which means in terms of my auditory faculty I’m currently switching sides. In all probability, I have either recently lost, or am about to lose, the ability to hear these young people’s ringtones.

According to the makers, the tones are mosquito-like buzzes at a frequency of 14-17 kilohertz. When we reach our early 30s, we tend to lose the ability to hear sounds in and above this range.

Dogs, cats and many other animals, of course, are a different story. They can hear high-frequency sounds perfectly well — meaning that any “secret” call to battle broadcast by children could see these four-legged creatures marshaled as well. Luckily for adults, they won’t have to contend with chinchillas, canaries, elephants or tuna, whose hearing is on a par with adult humans, or worse.

But I digress. First, I needed to work out what side I was on. Would I be able to hear the thing?

The Taito-run site “Gurumero” had three types of the ringtones — High (around 17 khz), Medium (around 15 khz) and Low (around 14 khz). Dwango’s “dwango.jp Torihodai Deluxe” had similar ones too. Docomo, au and Softbank phones can access both sites

About ¥60 and as many seconds later my phone was loaded up. I started with the easy one — the Low setting. It hit like a dentist’s drill to the brain. I had to concentrate to hear the Medium and the High setting? Well, I had to turn off the stereo, shut the window and quieten the neighbor — but I could hear the thing.

Great! I was officially a “young person”! I knew an uncorrupted spirit still existed somewhere down inside me. Now all I needed was to live out my days in a hermetically sealed, soundproof box — just me and my “otona ni kikoenai (can’t be heard by grownups)” ringtone, waiting for the revolution.

I was even more pleased when I tried them out on people aged 40, 47 and 53. Only the 40-year-old managed to hear them — and only the Low and Medium tones at that.

Dwango reports that these secretive, kids-only ringtones are popular. In the first six months of this year they said they were the fifth most popular download of the roughly 10,000 on the site.

But never mind Dwango’s claims, what is the evidence from the front line?

A small majority of the 10 teenagers I recently grabbed at JR Tamachi Station near the JT office said they had tried them out — but none were currently using them.

“Actual melodies are more fun,” answered Mika, 14, from Tokyo.

I also put in a call to the Tokyo Board of Education, to see whether any schools had reported usage of the ringtones.

“I had never heard of them until you called,” explained Satoshi Hagiwara, who is in charge of the metropolis’ publicly-run high schools. “None of our teachers have mentioned them.”

He explained that most schools allow students to bring mobile phones to class, but disallow their use.

A call to the Education Board of Tokyo’s central Minato Ward similarly revealed that none of its primary or junior high schools had reported use of the ringtones.

Perhaps in a country with such a long history of linguistic high jinks, the kids have no need of such technological aids. Or perhaps they object to them in principle. After all, these ringtones arose from technology that was originally intended to control their behavior.

Two years ago a British inventor named Howard Stapleton developed what he called “Mosquitoes” — alarms that would emit uncomfortably high- frequency sounds to discourage youths from loitering in public. Adults, of course, would be unaffected. Maybe there are advantages to growing up after all.

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