Saturday, September 4, 2010

Quefrency, Lifters, New House and Fine Dining

Howdy y'all!

So now I'm moved.  Scott and I are settling into the new place and refactoring our organizational methods.  Before I get into the house/food stuff, I wanted to tell you about something kinda cool that I learned today.  Like anything worth learning, this tasty morsel requires just a tad bit of background...

Signal processing is the science/art of modifying or analyzing some sequence of values for useful purposes.  An example might be checking the stock market value of some particular stock every day for a year, then taking those values and taking the moving average of every week of values as they come out to have a better "Feel" of that stock and then making some decision based on it.  Here is a wikipedia article with a little more precise language if you'd like to explore (I would if I were you =)  http://en.wikipedia.org/wiki/Signal_processing

Some more interesting (to me) applications of signal processing are things like filtering an audio signal so that you can turn up the bass and really "bump" in your car or house...  lol.  At any rate, like any technical domain, there are plenty of cool terms and a few that are just made-up because whoever invented it had a good sense of humor. 

For example, in signal processing we talk about the frequency spectrum (a range of frequencies we are interested in), we talk about low-pass filters who "allow" low frequencies through and "stop" higher frequenices (this really kind of a generalization a moving average, when you think about it).

So now to the funny part.  I have been working on a rather challenging filter for a while now (I posted about it a while back), and I keep my nose to the grindstone trying to research and find the right solution to the problem.  Since I had some time today, I was looking at something called the "Cepstrum" which is sort of an odd animal.  its name originates from rearranging the word "spectrum," reversing the first four letters.  I have to tell you the definition because even though it's abstract, it is kinda funny to say (copied from wikipedia):

"verbally: the power cepstrum (of a signal) is the squared magnitude of the Fourier transform of the logarithm of the squared magnitude of the Fourier transform of a signal"
http://en.wikipedia.org/wiki/Cepstrum

lol. But wait!  there's more!  for only $19.99 you can hear the other terms associated with various cepstrum operations!  (okay, fine.  I'll give it to ya for free!)

Instead of talking about time, even though strictly speaking, the unit is time, but we went into the frequency domain and then back to the unit of time but not the time domain) so we are not in the frequency domain either, the independent variable of the cepstrum of a signal is called "Quefrency" (mangled version of frequency) of the signal.  Further, whereas in the frequency domain one has filters, in the quefrency domain there are "Lifters" (mangled version of filters).  Which is another whole pun in and of itself because you can use lifters to "lift" particular frequency components and their harmonics from a signal. 

Let's say that you are recording audio signals and somebody is talking in the room next door.... very annoying.  now you have someone else's voice that you didn't intend to have in your recording.  You can use lifters to lift that voice out of the signal and kinda erase it.  Or maybe you wanna know what the person was saying, then you could isolate it!  Super cool.  I am of course very new to the concept, but it is almost as if the cepstrum is like a second order frequency transform, allowing you to see the spectrum of the spectrum.  Here is a cool pic of a spectrum and the cepstrum of that.



So that was great find for the day.  Thanks for reading though that bit of techy stuff, I hope you enjoyed it.

On another note, my girlfriend Elisa is now in Switzerland on vacation for about 10 days, but before she left she stopped by to see the new place (and maybe to see me too).  Since I had recently failed at a dinner I intended to make, I thought I'd give it another shot and make dinner for both Scott and Elisa...  and the result?  Success baby!  haha, it ended up being very good, in spite of my inexperience.  I fixed penne chicken alfredo with black olives and artichoke hearts, with brocoli, cauliflower and carrots.  2% milk was also available as a beverage.  See, see, see!

I suppose presentation leaves a little to be desired...  all I had were sippy cups and plastic plates and silverware, but I think everyone enjoyed the meal.  That makes me happy.  So that you can see the house, I decided to give you a "flash" tour that wasn't too long.  so I basically ran through the house with my camera.  Here ya go.


And I guess that will conclude my remarks for this afternoon.  I'll be sure to take some nice HD pictures when I get my room more organized and cleaned up.  Until then, via con Dios, my friends!