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12-02-2005, 09:54 PM
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Filtering before changing sample rate
I think I know the answers, but then again
 I have a "hobby" project to evaluate intelligibility of speech with varying parameters ( primarily sample rate and bandwidth ). [ for perspective, in a previous incantation I "discovered" formants ;] My sample universe is a reading of the Bible recorded under studio conditions. As it is a commercial recording, I'm assuming Nyquist is the least restrictive criterion it meets. Am I correct thinking that if I digitally filter my source to less than 3 kHz i can safely decimate to 8 kHz sample rate? 
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12-02-2005, 10:30 PM
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Re: Filtering before changing sample rate
Richard Owlett wrote:
> I think I know the answers, but then again > > I have a "hobby" project to evaluate intelligibility of speech with > varying parameters ( primarily sample rate and bandwidth ). > > [ for perspective, in a previous incantation I "discovered" formants ;] > > My sample universe is a reading of the Bible recorded under studio > conditions. As it is a commercial recording, I'm assuming Nyquist is the > least restrictive criterion it meets. > > Am I correct thinking that if I digitally filter my source to less than > 3 kHz i can safely decimate to 8 kHz sample rate? Yes Jerry -- Engineering is the art of making what you want from things you can get. ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
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12-03-2005, 06:10 AM
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Re: Filtering before changing sample rate
"Jerry Avins" <jya@ieee.org> wrote in message
news:3cGdndRqqOuTVg3enZ2dnUVZ_tOdnZ2d@rcn.net... > Richard Owlett wrote: >> I think I know the answers, but then again >> >> I have a "hobby" project to evaluate intelligibility of speech with varying >> parameters ( primarily sample rate and bandwidth ). >> >> [ for perspective, in a previous incantation I "discovered" formants ;] >> >> My sample universe is a reading of the Bible recorded under studio >> conditions. As it is a commercial recording, I'm assuming Nyquist is the >> least restrictive criterion it meets. >> >> Am I correct thinking that if I digitally filter my source to less than 3 kHz >> i can safely decimate to 8 kHz sample rate? > > Yes And if you filter is good enough, you can push the cut-off further up toward 4kHz.
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12-03-2005, 12:53 PM
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Re: Filtering before changing sample rate
Jon Harris wrote:
> "Jerry Avins" <jya@ieee.org> wrote in message > news:3cGdndRqqOuTVg3enZ2dnUVZ_tOdnZ2d@rcn.net... > > Richard Owlett wrote: > >> I think I know the answers, but then again > >> > >> I have a "hobby" project to evaluate intelligibility of speech with varying > >> parameters ( primarily sample rate and bandwidth ). > >> > >> [ for perspective, in a previous incantation I "discovered" formants ;] > >> > >> My sample universe is a reading of the Bible recorded under studio > >> conditions. As it is a commercial recording, I'm assuming Nyquist is the > >> least restrictive criterion it meets. > >> > >> Am I correct thinking that if I digitally filter my source to less than 3 kHz > >> i can safely decimate to 8 kHz sample rate? > > > > Yes > > And if you filter is good enough, you can push the cut-off further up toward > 4kHz. You might want to consider a slightly heretical approach and set the filter ABOVE nyquist! Use aliasing as one of the parameters. Try about 5KHz cuttoff with 8KHz sampling rate. I think you might be surprised at the results if it is only speech you are evaluating. Regards Rocky
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12-03-2005, 01:40 PM
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Re: Filtering before changing sample rate
Rocky wrote:
> Jon Harris wrote: > >>"Jerry Avins" <jya@ieee.org> wrote in message >>news:3cGdndRqqOuTVg3enZ2dnUVZ_tOdnZ2d@rcn.net. .. >> >>>Richard Owlett wrote: >>> >>>>I think I know the answers, but then again >>>> >>>>I have a "hobby" project to evaluate intelligibility of speech with varying >>>>parameters ( primarily sample rate and bandwidth ). >>>> >>>>[ for perspective, in a previous incantation I "discovered" formants ;] >>>> >>>>My sample universe is a reading of the Bible recorded under studio >>>>conditions. As it is a commercial recording, I'm assuming Nyquist is the >>>>least restrictive criterion it meets. >>>> >>>>Am I correct thinking that if I digitally filter my source to less than 3 kHz >>>>i can safely decimate to 8 kHz sample rate? >>> >>>Yes >> >>And if you filter is good enough, you can push the cut-off further up toward >>4kHz. > > > You might want to consider a slightly heretical approach and set the > filter ABOVE nyquist! Use aliasing as one of the parameters. Try about > 5KHz cuttoff with 8KHz sampling rate. > > I think you might be surprised at the results if it is only speech you > are evaluating. > > Regards > Rocky > Moi. Heretical? All I've done is suggest DSP be done in TECO, COBOL, or VBA in MSWord ;}
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12-03-2005, 01:46 PM
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Re: Filtering before changing sample rate
Richard Owlett wrote:
> Rocky wrote: > >> Jon Harris wrote: >> >>> "Jerry Avins" <jya@ieee.org> wrote in message >>> news:3cGdndRqqOuTVg3enZ2dnUVZ_tOdnZ2d@rcn.net... >>> >>>> Richard Owlett wrote: >>>> >>>>> I think I know the answers, but then again >>>>> >>>>> I have a "hobby" project to evaluate intelligibility of speech with >>>>> varying >>>>> parameters ( primarily sample rate and bandwidth ). >>>>> >>>>> [ for perspective, in a previous incantation I "discovered" >>>>> formants ;] >>>>> >>>>> My sample universe is a reading of the Bible recorded under studio >>>>> conditions. As it is a commercial recording, I'm assuming Nyquist >>>>> is the >>>>> least restrictive criterion it meets. >>>>> >>>>> Am I correct thinking that if I digitally filter my source to less >>>>> than 3 kHz >>>>> i can safely decimate to 8 kHz sample rate? >>>> >>>> >>>> Yes >>> >>> >>> And if you filter is good enough, you can push the cut-off further up >>> toward >>> 4kHz. >> >> >> >> You might want to consider a slightly heretical approach and set the >> filter ABOVE nyquist! Use aliasing as one of the parameters. Try about >> 5KHz cuttoff with 8KHz sampling rate. >> >> I think you might be surprised at the results if it is only speech you >> are evaluating. >> >> Regards >> Rocky >> > > Moi. Heretical? > All I've done is suggest DSP be done in TECO, COBOL, or VBA in MSWord ;} You missed one of the critically important ones - Excel and OpenOffice spreadsheets. :-) In the Lotus 123 days I did a lot of DSP experimentation in spreadsheets. I had some fairly usable filter design stuff too. I wonder if that is still on an old disk somwhere? Steve
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12-03-2005, 01:57 PM
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Re: Filtering before changing sample rate
Steve Underwood <steveu@dis.org> writes:
> In the Lotus 123 days I did a lot of DSP experimentation in > spreadsheets. I had some fairly usable filter design stuff too. I > wonder if that is still on an old disk somwhere? That'd be cool to see, if you can post it somewhere. :-) Ciao, Peter K.
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