The Japanese are known for producing gadgets, purpose and potential buyers are — closely guarded secret. So this time craftsmen from the country of the rising sun created a "keychain" for determining a person's age.
The idea is simple — the listener through the earpiece fed high-frequency sound, like a mosquito squeak. Depending on the intensity of the sound and the ability to hear the test is calculated approximate age. The older man — the less he hears.
No idea who it might be needed — except that to police officers to determine the age of young people drinking alcohol on the streets. However, the gadget is now available at online stores at a price of $ 10.