>On 4/24/2013 3:16 AM, radams2000@gmail.com wrote: > >> One common technique is to design a high pass filter and then >> substitute Z^-n for Z. > >The same substitution could be done with basic lowpass as well. That >produces regular comb type response with adjustable pass/notch. > >It gets interesting if you insert frequency dependent delay into the >basic lopass/hipass filter. The result is irregular comb. > >Vladimir Vassilevsky >DSP and Mixed Signal Designs >www.abvolt.com >For a substitution from a lowpass filter, does one substitute Z^n for Z, rather than the Z^-n for highpass?
Filtering out 60Hz + harmonics
Started by ●April 23, 2013
Reply by ●April 24, 20132013-04-24
Reply by ●April 24, 20132013-04-24
>>On 4/24/2013 3:16 AM, radams2000@gmail.com wrote: >> >>> One common technique is to design a high pass filter and then >>> substitute Z^-n for Z. >> >>The same substitution could be done with basic lowpass as well. That >>produces regular comb type response with adjustable pass/notch. >> >>It gets interesting if you insert frequency dependent delay into the >>basic lopass/hipass filter. The result is irregular comb. >> >>Vladimir Vassilevsky >>DSP and Mixed Signal Designs >>www.abvolt.com >> > >For a substitution from a lowpass filter, does one substitute Z^n for Z, >rather than the Z^-n for highpass? >Scratch that, swapping the polarity of n flips the spectrum about w = 0. I knew that.
Reply by ●April 24, 20132013-04-24
On Tue, 23 Apr 2013 20:21:37 -0500, "Tic Tac" <95008@dsprelated> wrote:>Hello all, > >I am quite new to the world of DSP and am required to perform some DSP for >my student job using Matlab. I need to remove the noise ofthe utility >frequencies (60 Hz + harmonics) from a number of signals. I have been >reading many forums on this topic and tried many possible solutions but was >unable to get it to work properly. > >For instance, I tried using a notch filter and also tried a comb filter >which worked for the first few harmonics but then started to overcompensate >and would create spikes in the opposite direction. > >I also tried modifying the magnitude of the fft (I made a new variable of >the absolute value of the fft, averaged over the whole time span >intervals). I modified it so that the spikes at the harmonics is removed >and interpolated a value in between them. However, all I am left now is the >magnitude and no phase info. so I am unable to transform that into the time >domain. > >Is there a standard way of filtering out these frequencies which I am not >seeing? > >Please let me know. > >Thanks, >VicHello Vic, I sure seems to me that there should be a way to reduce your '60 Hz + harmonics' to acceptable levels. Send me your Matlab code of what you've done so far and I'll have look. (Your FFT scheme, as you've described it, has no chance of doing what you want. But send me the FFT code anyway.) Who knows, I may be able to help. [-Rick-]
Reply by ●April 24, 20132013-04-24
Another factor to consider is how stable the mains interference signal is. In my experience it can change quite rapidly if someone is operating a dimmer, for example. If you make the notches too narrow then every time the harmonic content of the mains changes, you will hear a long "acquisition" period where the buzz is allowed through for several seconds. This is particaurly true if you are using this to remove buzz from a guitar, where the orientation of the guitar relative to the magnetic field is dynamically changing as the guitarist gyrates madly around the stage, as guitarists often do. Bob
Reply by ●April 25, 20132013-04-25
Adaptive line enhancer. Here's a MATLAB example that I stumbled across: http://www.mathworks.com/help/dsp/examples/adaptive-line-enhancer-ale.html. Greg
Reply by ●April 26, 20132013-04-26
On Thu, 25 Apr 2013 09:15:31 -0500, Greg Berchin <gjberchin@chatter.net.invalid> wrote:>Adaptive line enhancer.By the way (taking this off topic), given recent Bing advertisements that they are the "best on the Web's most popular searches"; a good demonstration of the difference between Google and Bing can be found by searching for "adaptive line enhancer". On Bing, the ad that appears at the top of the list is for "Ron Jeremy Rates Them All - Male Enhancement Shocking Truth!". And Bing's RELATED SEARCHES list consists of: Lash Enhancers Bra Enhancers Male Enhancer Jewelry Enhancers Ring Wraps and Enhancers Natural Libido Enhancers Enhancer Definition Biology SmartLash Eyelash Enhancer Review Meanwhile Google just return a list of hits that are actually relevant (no ads), beginning with "Scholarly articles for adaptive line enhancer".
Reply by ●April 26, 20132013-04-26
>On Thu, 25 Apr 2013 09:15:31 -0500, Greg Berchin ><gjberchin@chatter.net.invalid> wrote: > >>Adaptive line enhancer. > >By the way (taking this off topic), given recent Bing >advertisements that they are the "best on the Web's most popular >searches"; a good demonstration of the difference between Google >and Bing can be found by searching for "adaptive line enhancer". >On Bing, the ad that appears at the top of the list is for "Ron >Jeremy Rates Them All - Male Enhancement Shocking Truth!". And >Bing's RELATED SEARCHES list consists of: > Lash Enhancers > Bra Enhancers > Male Enhancer > Jewelry Enhancers > Ring Wraps and Enhancers > Natural Libido Enhancers > Enhancer Definition Biology > SmartLash Eyelash Enhancer Review > >Meanwhile Google just return a list of hits that are actually >relevant (no ads), beginning with "Scholarly articles for adaptive >line enhancer". >That's hilarious!
Reply by ●April 26, 20132013-04-26
On Fri, 26 Apr 2013 07:58:57 -0500, Greg Berchin <gjberchin@chatter.net.invalid> wrote:>On Thu, 25 Apr 2013 09:15:31 -0500, Greg Berchin ><gjberchin@chatter.net.invalid> wrote: > >>Adaptive line enhancer. > >By the way (taking this off topic), given recent Bing >advertisements that they are the "best on the Web's most popular >searches"; a good demonstration of the difference between Google >and Bing can be found by searching for "adaptive line enhancer". >On Bing, the ad that appears at the top of the list is for "Ron >Jeremy Rates Them All - Male Enhancement Shocking Truth!". And >Bing's RELATED SEARCHES list consists of: > Lash Enhancers > Bra Enhancers > Male Enhancer > Jewelry Enhancers > Ring Wraps and Enhancers > Natural Libido Enhancers > Enhancer Definition Biology > SmartLash Eyelash Enhancer Review > >Meanwhile Google just return a list of hits that are actually >relevant (no ads), beginning with "Scholarly articles for adaptive >line enhancer".So you're saying an Adaptive Line Enhancer isn't going to help me be more attractive? Damn. That changes everything. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●April 26, 20132013-04-26
On Fri, 26 Apr 2013 16:29:45 GMT, eric.jacobsen@ieee.org (Eric Jacobsen) wrote:>Damn. That changes everything.Correction: That changes everything ADAPTIVELY. Greg
Reply by ●April 27, 20132013-04-27
On 4/25/2013 9:15 AM, Greg Berchin wrote:> Adaptive line enhancer. > > Here's a MATLAB example that I stumbled across: > http://www.mathworks.com/help/dsp/examples/adaptive-line-enhancer-ale.html. >Interesting. You mean, do the opposite of what conventional ALE does: estimate the stationary part and subtract it from signal ? There should be optimum adaptation rate vs rejection vs artifacts. I wonder how well it does with realistic audio. Vladimir Vassilevsky DSP and Mixed Signal Designs www.abvolt.com
