Filtering before changing sample rate
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Filtering before changing sample rate

 
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Richard Owlett
Guest
Posted: Sat Dec 03, 2005 1:16 am    Post subject: Filtering before changing sample rate Reply with quote
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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Jerry Avins
Guest
Posted: Sat Dec 03, 2005 1:16 am    Post subject: Re: Filtering before changing sample rate Reply with quote
Richard Owlett wrote:
Quote:
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.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
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Jon Harris
Guest
Posted: Sat Dec 03, 2005 9:15 am    Post subject: Re: Filtering before changing sample rate Reply with quote
"Jerry Avins" <jya@ieee.org> wrote in message
news:3cGdndRqqOuTVg3enZ2dnUVZ_tOdnZ2d@rcn.net...
Quote:
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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Rocky
Guest
Posted: Sat Dec 03, 2005 5:15 pm    Post subject: Re: Filtering before changing sample rate Reply with quote
Jon Harris wrote:
Quote:
"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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Richard Owlett
Guest
Posted: Sat Dec 03, 2005 5:15 pm    Post subject: Re: Filtering before changing sample rate Reply with quote
Rocky wrote:
Quote:
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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Steve Underwood
Guest
Posted: Sat Dec 03, 2005 5:15 pm    Post subject: Re: Filtering before changing sample rate Reply with quote
Richard Owlett wrote:
Quote:
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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Peter K.
Guest
Posted: Sat Dec 03, 2005 5:15 pm    Post subject: Re: Filtering before changing sample rate Reply with quote
Steve Underwood <steveu@dis.org> writes:

Quote:
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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