understand him.... then kill him.....

20.9.08


The private buses of the city along with their friends and enemies always make me annoyed with the enormous amount of noise they produce. Some times during traffic blocks we feels that a horning competiotion is goin on. What ever it is the only thing we could do was to sit silent, exactly as our father of nation told. We were helpless.

Sciene and technology started their sci-fi journey years back fascinating the common man with technologies ans instrument that were supposed to be completely imaginary. Here also technology comes for our help. The active noise control technology got a very simple principle that anyone can think, but most of us never got time to think about. The technology uses "anti noise" which kills the villain "noise" by canceling it with himself leaving behind nothing. Looks like attacks on an animation movie? ill now explain what happens here.
All of us knows the fundamental thing, sound consists of compressions and rarefactions meaning that sound is a pressure wave propagating in some media. Anti noise, our hero is nothing else its also pressure wave with compressions and rarefactions but with a small difference, he is in opposite phase with noise, they got 180 phase difference. So the next simple thing come, another chapter from high school physics, what happens when two of these waves meet. The answer is obvious, destructive interference resulting in nothing left behind. This is how technology works, and eliminates noise and re-establishes peace.
What was the problem hat existed ? why is it that no one else did this before? the answer is simple, the circuits and technology of yesterdays were not efficient enough to be employed in this area. They had to process enormous amount of data in real time and produce accurate results. Digital signal processing came for help in thiss ituation. DSP and DSP chips studied and understood incoming signals very fast using the complex underlying mathematical principles ideas of convolution, correlation etc. DSP then generated the pattern of the anti noise which cancells the noise for a good extend.


The introduction of smart digital signal processors and the availability of cheaper and smaller signal processing chips made companies think of realising the concept. Bose, a hi-fi speaker manufacturing company have come up with their product, Aviation headset X which is now used by pilots to help them from aviation noise. The headset costs $995 at present.



We can wait for the cost and size to come down and buy one for ourselves when entering our cochin streets. As usual this will also happen autmatically, we just need to wait.

PS: i was studyin for DSP supplementary exam with the help of some online book when i came to see this topic.
I refer the book to anyone who want to study DSP http://www.dspguide.com/

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