I use decimation filter plus IIR filters to do octave filters (20Hz-20kHz). Sample frequency is 48K. I found the filter shape distortion at high frequency band (16k). I thought this might be related with the sample frequency, so I increase the sample frequency, but nothing is improved. what's wrong?
help with my octave filter
Started by ●October 20, 2009
Reply by ●October 20, 20092009-10-20
On Tue, 20 Oct 2009 09:05:41 -0500 "boozy" <boozy@sina.com> wrote:> I use decimation filter plus IIR filters to do octave filters > (20Hz-20kHz). Sample frequency is 48K. I found the filter shape > distortion at high frequency band (16k). I thought this might be > related with the sample frequency, so I increase the sample > frequency, but nothing is improved. what's wrong? > >Simple, you screwed something up. If you were to post your Octave code, and be a bit clearer as to what you're trying to accomplish, someone might even be able to take a stab at what. -- Rob Gaddi, Highland Technology Email address is currently out of order
Reply by ●October 21, 20092009-10-21
the problem is when there is a high frequency (such as 16k) sine wave get into my octave filters. the octave 16k band is fine while there are unwanted high output from other octave bands (such as 31Hz band 63Hz band,) I am expecting -70dB from these lower bands.>On Tue, 20 Oct 2009 09:05:41 -0500 >"boozy" <boozy@sina.com> wrote: > >> I use decimation filter plus IIR filters to do octave filters >> (20Hz-20kHz). Sample frequency is 48K. I found the filter shape >> distortion at high frequency band (16k). I thought this might be >> related with the sample frequency, so I increase the sample >> frequency, but nothing is improved. what's wrong? >> >> > >Simple, you screwed something up. If you were to post your Octave >code, and be a bit clearer as to what you're trying to accomplish, >someone might even be able to take a stab at what. > >-- >Rob Gaddi, Highland Technology >Email address is currently out of order >
Reply by ●October 21, 20092009-10-21
I have the anti-aliasing filter before downsampling. any idea what's wrong?>the problem is when there is a high frequency (such as 16k) sine waveget>into my octave filters. the octave 16k band is fine while there are >unwanted high output from other octave bands (such as 31Hz band 63Hz >band,) >I am expecting -70dB from these lower bands. > > >>On Tue, 20 Oct 2009 09:05:41 -0500 >>"boozy" <boozy@sina.com> wrote: >> >>> I use decimation filter plus IIR filters to do octave filters >>> (20Hz-20kHz). Sample frequency is 48K. I found the filter shape >>> distortion at high frequency band (16k). I thought this might be >>> related with the sample frequency, so I increase the sample >>> frequency, but nothing is improved. what's wrong? >>> >>> >> >>Simple, you screwed something up. If you were to post your Octave >>code, and be a bit clearer as to what you're trying to accomplish, >>someone might even be able to take a stab at what. >> >>-- >>Rob Gaddi, Highland Technology >>Email address is currently out of order >> >
Reply by ●October 21, 20092009-10-21
what I found more is some frequencies (such as 16.2k, 16.3k) may contribute more errors in the lower octave band than other frequencies (such as 16k) do.>I have the anti-aliasing filter before downsampling. > >any idea what's wrong? > >>the problem is when there is a high frequency (such as 16k) sine wave >get >>into my octave filters. the octave 16k band is fine while there are >>unwanted high output from other octave bands (such as 31Hz band 63Hz >>band,) >>I am expecting -70dB from these lower bands. >> >> >>>On Tue, 20 Oct 2009 09:05:41 -0500 >>>"boozy" <boozy@sina.com> wrote: >>> >>>> I use decimation filter plus IIR filters to do octave filters >>>> (20Hz-20kHz). Sample frequency is 48K. I found the filter shape >>>> distortion at high frequency band (16k). I thought this might be >>>> related with the sample frequency, so I increase the sample >>>> frequency, but nothing is improved. what's wrong? >>>> >>>> >>> >>>Simple, you screwed something up. If you were to post your Octave >>>code, and be a bit clearer as to what you're trying to accomplish, >>>someone might even be able to take a stab at what. >>> >>>-- >>>Rob Gaddi, Highland Technology >>>Email address is currently out of order >>> >> >