In most of the schools in the United States, as in most of the schools everywhere, the mobile phones are prohibited. And that's quite normal, finally. But on another hand, the students can be smart enough. And the big trick is to have a ring tone that you can hear, because you're young but your teacher can't, because he's old.

The story starts with Compound, a security company, and their main product: the mosquito. An alarm which outputs an ultrasonic sound that only the young people can hear it. The idea is to prevent the gatherings of teenagers. An idea of Nicolas Sarkozy?

Here, it looks like adults won the game. But the idea has evolved and the mosquito was adapted into a ring tone for mobile phones! In United States of course, in UK and I guess soon everywhere in the world... 'Cause even Compund proposes its own, like the official one, called Mosquitone.

So, the fashion trick: receiving an SMS during the class, the teacher does not hear it, everyone laughs. You could use the vibrator but it's less funny anyway.

How does it work?
The drawing here above represents the spectrum of the audio frequencies a human being can hear. When he's young, this spectrum goes from 2000 to 18000 Hz, maybe more. But he gets old, the spectrum narrows. Not for everyone of course, but for most of people, it decreases as indicated above.

A test?
All right, but be sure to use good speakers and a correct PC sound-card, and first turn the volume down, then turn it up slowly. It can be surprising!
The sounds are not compressed (wav, not mp3). Otherwise, it's sure you could not here it...

4000 Hz, like piano :

12000 Hz, more than 60 you can't hear...

15000 Hz, more than 40...

17000 Hz, the Mosquitone's frequency:

20000 Hz, personally I can't hear:


Source : New-York Times, middle of June.
For those who do not know: One hertz (Hz) simply means "one per second" (1 / s); 100 Hz means "one hundred per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. Frequency of aperiodic events, such as radioactive decays, is expressed in becquerels.

sciences

Deb Roy is the chief of the MIT Media Lab' S Cognitive Machines research group (!!) and the project on which he's currently working is at the very least unusual. The project is very serious and is called “The Human Speechome Project”. Speechome is the compression of speech and home. Good. ok.

The purpose is to understand how a human being acquires its language thanks to the social and physical context when he's a child. For doing this, Deb decided to record (almost) every moments of his baby's life, 9 mongths old. 400,000 hours audio and video during 3 years, from 12 to 14 hours a day.

Let's calculate: 3 years equal 15,000 hours. So there is redundancy: Roy installed 11 multi-directional video cameras and 14 microphones that will record every activity in the house. Hey hey, there is a button, called "ooops", that deletes the last minutes. True!
A disk of 5 terabytes stores the data temporarily before they're sent to Media Lab for analysis.

The analysis of this huge data flow, it is precisely the most interesting part of the project. To confirm their assumptions on the learning, the team of Roy must develop a software that's gonna take the place of his son, by analyzing the sights and the sounds perceived during these 3 years. Algorithms of speech or video processing are under development, for a better understanding of the all types of communication included in the images. New techniques of visualization already emerged from the project: distinguish a person who walks from one room to another, who drinks, who clean a baby...

sciences

False !
At the eclipse lottery, we're the only winners.

Mercury and Venus, if we don't look at the mortal atmosphere, would be good places for an eclipse: the sun is big in the sky. But they have no moon. Checked.

The others planets have a lot of moons but all too small or too big. For example, the 4 moons of Jupiter hide absolutely nothing. When they arrive in front of the sun, you can't see anything: no more sun, no luminous ring, nothing!

Janus, the satellite of Saturn, could be a good candidate... but it has the shape of a potato and it's quite hugly. Moreover, because of its speed, the phenomenon last less than 10 seconds.

Finally, the moons of Uranus have a good size but they are ugly, too, and the sun, viewed from Uranus, is just a small luminous pinhead. Like a star for us.