Friday, December 21, 2012

A Lukewarm Apocalypse

For people making disaster preparations for the 'apocalypse', as far as things go, I'm not certain how helpful a few tins of food and some tea candles would be in the event of, say, the end of the world.

If the world is doomed, I wouldn't want to live. Imagine the total loss of modern infrastructure; I don't think we'll be able to climb out of such a mess anytime soon, if anything on that scale happens.

Now of course most people taking in the end of days nonsense will say, well, we're not expecting a disaster on that scale. Maybe something less severe, but a disaster nonetheless. A sort of lukewarm threat, perhaps.

I find that the scenarios where the 'disaster preparations' would come in useful are pretty much on the harmless side of the continuum. Surely, anything worth worrying about such that it deserves a special mention must have a greater impact, otherwise the Mayans are not only alarmists, but alarmists with a great tendency for omission.

Of course, it's much easier to say that everyone is nuts.

Thursday, December 20, 2012

Binaural Hearing

We have, of course, two ears which jointly allow us to localize the direction of incoming sound. But our ears are much more than simple point hearing devices; there must be some more advanced mechanisms contained within. Why? Because we can tell whether a sound is coming from our back or our front.

Imagine the case in our ears were replaced with two simple mono microphones of appropriate sensitivity. Any sound would be picked up by the two microphones, though at different delays. Knowing the speed of sound, it is simple to calculate the distance of the source from each microphone and hence, the intersections (locii). Note the word intersections. With two point microphones, there are two intersections (in a 2-D scenario) and infinite intersections (dispersed in a circle in a 3-D scenario).

If our ears were only point microphones, we would not be able to differentiate sounds coming from behind us. 

But of course, we can. That is because our ears are directionally sensitive, or at least, structures in our ears serve as directional filters.

One interesting result of this line of thought is that with headphones, it is not possible to duplicate full directional sound. Headphones are merely two point sources of sound; there will be ambiguity of direction, leading us to confuse front-back sounds.

Tuesday, December 18, 2012

Hashing Web Services for Spam Detection

For many web services, it is necessary to provide your email address as well as other related personal information, such as your name or date of birth. The problem with this is that you have no idea what they do with your information.

One approach that several people use is to put in false information, which sidesteps the privacy issue. Still, for several web services an email address is still required, if only to provide an authentication link to verify your account. A secondary email address dedicated for such purposes is often used.

It is possible to detect the origin of the spam by clever selection of the personal details provided. For example, when prompted to provide a name or user name, the title or address of the web service can be used instead. Thus, when the information is sold and used to address spam to you, the name the spam mail identifies you by can be used to determine the source.

Similarly, more complex hashing schemes can be used to encode such identifier information into birth dates.