Hello,

unfortunately seems there is a trouble in the web site.
Even worst Tony Fisher died some years ago so we cannot ask to him for 
help. The university which keep alive his web site may be of help.
I will try to ask them.

The web site was providing a fully functional code with all coefficient 
and C code language (rather easy to translate in Basic or other 
languages). No knowledge of complex math is needed to make it work, when 
it will work...


best regards
Mauro



Il 26/04/2011 16:43, Geoffrey ha scritto:
> Hello Mauro,
> This looks like something called POLES and ZEROS,
> I do not understand it.
> I need someone to explain it to me in layman's terms and not
> the language of higher math.
> Best Regards,
> geoff
>
> I do understand a bit about polar and rectangular notation
> and tiny bit about imaginary numbers but I have
> real trouble relating it to Poles and Zeros ?
>
>
>
> -----Original Message----- From: Mauro Mariotti Sent: Tuesday, April 26,
> 2011 12:45 PM To: psnlist@.............. Subject: Fwd: Fwd: Re:
> Modulated Seismic
>
>
> Hi Geoffrey,
>
> i think you can find this link interesting:
>
> http://www-users.cs.york.ac.uk/~fisher/mkfilter/res.html
>
> it can help you to compute the coefficients and also provide you a C
> code to implement them.
> The web pages related to this one also allow to compute coefficient and
> code for digital filters low-pass high-pass etc.
> With this specific page i linked you can compure a RESONANCE filter that
> can point at a single specific frequency.
> You can choose coefficinet to have this resonator more sharp to cut out
> unwanted frequencyes.
> The use is rather straightforward, computation is fast.
>
> best regards
> Mauro
>
>
> Il 23/04/2011 05:16, Geoffrey ha scritto:
>> Is there some way to pick a frequency
>> like 0.123 Hz then process the sampled
>> seismic signal to see if any energy of only
>> that frequency is present ?
>>
>> Can you point me to a complete subroutine
>> [complete meaning does not use a library of functions]
>> to obtain such an answer ?
>>
>> It would be like an FFT but you give the data,
>> sample rate, and what SINGLE freq to look for ?
>>
>>
>> -----Original Message----- From: Chuck / Judy Burch Sent: Sunday, April
>> 17, 2011 3:44 PM To: psnlist@.............. Subject: Modulated Seismic
>>
>> All,
>>
>> Thanks to Randal for raising this interesting topic. The Teager-Kaiser
>> Algorithm and Randal's rectification scheme are efforts to find the
>> instantaneous amplitude (or envelop) of a seismic record. Think of a
>> short enough piece of a seismic record -- it can be modeled by a
>> waveform of a given frequency, phase and amplitude. Throw away the
>> frequency and phase information and you are left with just the amplitude
>> as a function of time. So you can think of a record (very approximately)
>> as a collection of unit-amplitude waveforms from an appropriate
>> frequency range that has been AM modulated by the envelop.
>>
>> The FFT of the envelop, then, can be thought of as the Fourier Transform
>> of the "modulating" function.
>>
>> There are different ways of approximating the envelop. Many texts on
>> signal processing discuss the "analytic trace" or "analytic signal"
>> method, which is mathematically rigorous. If the original record is X,
>> then the quadrature (90 degree advanced) record, Y, is the Hilbert
>> Transform of X. The envelop of X is SQRT ( X2 + Y2 ).
>>
>> In the (remote) chance that anyone wants to pursue this, contact me and
>> I'll show you an easy way to calculate the Hilbert Transform.
>>
>>
>> Chuck Burch
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>>
>

-- 
Mauro Mariotti
http://www.infoeq.it
http://www.sara.pg.it

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