DIGITAL FILTERS

[shiva garg1]

What are the digital filters.Is it possible to seprate low,medium,high frequency components from the digitlised signal.

 

[audioguru2]

Hi Shiva,
A digital filter can do a lot more than just separate signals into only 3 bands.
Texas Instruments took a cheap lousy-sounding speaker, and used a Digital Signal Processor IC to equalize it at many frequencies so that it sounded great! And the EQ can easily be changed with programming, at the touch of a memory button.
Modern stereos and car radios use digital filters. My factory car radio has "loudness" that is 'way too strong and a lousy sounding compressor that causes all the music in a song to change volume with each bass beat, but only on FM radio, the CD player in it doesn't compress. I can't turn them off, the radio is programmed that way.
I was in the middle of complaining in an e-mail to the radio station about their lousy-sounding compressor, when I heard the same song on my home stereo and it wasn't compressed. I quickly cancelled my e-mail.

 

[shiva garg1]

Hello audioguru
as far as i know signal is converted into digital signal by sampling it at a particular frequency,so in digitlised signal there is only one frequency which is sampling frequency,so how they seprate different frequencies components of original signal from digitlised signal

 

[audioguru2]

Hi Shiva,
You don't understand that all the sounds are added togerther, then sampled. So the single sampling frequency is digitally modulated (digitized) with all the sounds. A processor can separate anything from the digitized information.

A similar thing happens with a simple loudspeaker. It can reproduce a lot more than just a single tone at a time, it can reproduce an entire orchestra: all the notes, all the instuments and all their harmonics. All at the same time because they are all added together to make the single output from an amplifier.

How about a DVD player? From a single sampling frequency its modulation has in digital form: 3 high-resolution colours, all the millions of locations on a screen, 5.1 channels of very high quality audio, error correction and even has extra information to show text on the player's screen. Since they are all added together, the player's processor must separate all the information and feed it to the proper outputs. Simply separating some audio frequencies would be easy.

 

[shiva garg1]

SIR
I am still unable to understand plz explain me with the help of block diagram

 

[surajbarkale]

Here is a large dose of theory ;D http://www-ccrma.stanford.edu/~jos/filters/
[urlhttp://www.mlssa.com/pdf/Upsampling-theory-rev-2.pdf
the google i used -
http://www.google.com/search?q=digital+filter+theory
;D ;D ;D