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#1
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"Richard Clark" wrote in message
On Mon, 19 Feb 2007 15:16:29 -0600, "Henry Kolesnik" wrote: There's a good example of a 3D plot he http://www.spectraplus.com/screenshots.html#3d Has anyone used this software? Hi Hank, Yes, I have. It is exceedingly expensive, but you can probably get 30 days of free use if you have a one-time knock off project. Of course, it may take 30 days to figure it out. FFT analyzers are a dime a dozen, but few know how to use them accurately - or are even aware of what can be done with them. Bob's complaint, notwithstanding, a 1024 bin FFT employing the proper mixing inputs can resolve any note on a guitar to within hundredths of a cycle. I am sure this is of no interest to you, however. Over the years, the most useful FFT software I've had, is the (fairly simple) FFT analyzer in Audition/CEP. It's big plus is the ability to use the Audition/CEP audio editor to select portions of real-world waveforms, and to use the wave generation and modification features to create waves for use in analysis and testing. |
#2
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On Mon, 19 Feb 2007 17:23:32 -0500, "Arny Krueger"
wrote: Over the years, the most useful FFT software I've had, is the (fairly simple) FFT analyzer in Audition/CEP. It's big plus is the ability to use the Audition/CEP audio editor to select portions of real-world waveforms, and to use the wave generation and modification features to create waves for use in analysis and testing. Hi Arny, I am sure this is an useful tool, but without windowing the data, any semblance to reasonable analysis is a house built on sand. I note in your provided link to work you have done that you use Blackman exclusively. This is at least a good first pass to achieving an analysis, but any variety of work is going to be more demanding (the Blackman window has its limitations), otherwise it is like looking through glasses smeared with Vaseline. 73's Richard Clark, KB7QHC |
#3
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"Richard Clark" wrote in message
On Mon, 19 Feb 2007 17:23:32 -0500, "Arny Krueger" wrote: Over the years, the most useful FFT software I've had, is the (fairly simple) FFT analyzer in Audition/CEP. It's big plus is the ability to use the Audition/CEP audio editor to select portions of real-world waveforms, and to use the wave generation and modification features to create waves for use in analysis and testing. I am sure this is an useful tool, but without windowing the data, any semblance to reasonable analysis is a house built on sand. So you think that the FFT analysis tool in CEP doesn't do windowing????? I note in your provided link to work you have done that you use Blackman exclusively. This is at least a good first pass to achieving an analysis, but any variety of work is going to be more demanding (the Blackman window has its limitations), otherwise it is like looking through glasses smeared with Vaseline. So you think that Spectra doesn't provide options for windowing and/or that I have no idea what effect they have on actual results???? |
#4
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On Tue, 20 Feb 2007 10:01:08 -0500, "Arny Krueger"
wrote: So you think that the FFT analysis tool in CEP doesn't do windowing????? With about as much panache as a Yugo in the Indy 500. Hardly a reason to throw $350 into the wind. So you think that Spectra doesn't provide options for windowing and/or that I have no idea what effect they have on actual results???? The designer of Spectra is a local Ham - I know his capabilities, I don't know yours. All I have to go on is the pedestrian choice of Blackman windowing that demonstrates nothing in the way of "ideas on the effect on actual results." As I offered, it is an ordinarily suitable choice if you have no demanding requirements. Hi Hank, There are a world of free analyzers, one quick search found 16: http://freshmeat.net/search/?q=fft&s...o.x=11&Go.y=10 Get your feet wet before throwing the green at bloatware designs that invest their resources in advertising. If you find nothing in this first list, I can certainly 26 find more. 73's Richard Clark, KB7QHC |
#5
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"Richard Clark" wrote in message
On Tue, 20 Feb 2007 10:01:08 -0500, "Arny Krueger" wrote: So you think that the FFT analysis tool in CEP doesn't do windowing????? With about as much panache as a Yugo in the Indy 500. Hardly a reason to throw $350 into the wind. So you think that Spectra doesn't provide options for windowing and/or that I have no idea what effect they have on actual results???? The designer of Spectra is a local Ham - I know his capabilities, I don't know yours. All I have to go on is the pedestrian choice of Blackman windowing that demonstrates nothing in the way of "ideas on the effect on actual results." As I offered, it is an ordinarily suitable choice if you have no demanding requirements. I got it now, I'm dealing with a FFT snob, not someone who just sees them as a tool to get a job done. |
#6
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On Tue, 20 Feb 2007 23:02:18 -0500, "Arny Krueger"
wrote: The designer of Spectra is a local Ham - I know his capabilities, I don't know yours. All I have to go on is the pedestrian choice of Blackman windowing that demonstrates nothing in the way of "ideas on the effect on actual results." As I offered, it is an ordinarily suitable choice if you have no demanding requirements. I got it now, I'm dealing with a FFT snob, not someone who just sees them as a tool to get a job done. Connoisseur is more appropriate, and as for getting the job done, I did that on contract to HP for one of their many FFT audio analyzers 22 years ago. I've written 200,000 lines of fourier code for many products that get jobs done. I also have the seminal work by Blackman and Tukey that predates the math of the Fourier transform: "The Measurement of Power Spectra." An extract bears repeating: "'... we were able to discover in the general wave record a very weak low-frequency peak which would surely have escaped our attention without spectral analysis. This peak, it turns out, is almost certainly due to a swell from the Indian Ocean, 10,000 miles distant. Physical dimensions a 1mm high and a kilometer long.'" The Hann or Hamm windowing functions are preferable as even Blackman would admit and even these two are hardly exemplars of outstanding performance. My designs exhibited a noise floor of -200dB (statistical noise from the transcendentals' math). A poor Blackman window would throw away 120dB of that to offer only -80dB. -80dB is certainly impressive to mundane applications, but most would agree that very little more effort was needed to gain 12 more orders of magnitude in performance. Hi Hank, If you've waded through my prior list of freely available Fourier analyzers, more can be found at: http://sourceforge.net/search/?type_...soft&words=fft Not all are applications however. However, you should probably try to get a copy of HP's Application Note 243-1 "Dynamic Signal Analyzer Applications." Of particular note for your studies into the nuances of investigating construction materials in Guitars (I did it with Violins), you should study the Fourier math relating to "Coherence" suited for a dual channel analyzer. 73's Richard Clark, KB7QHC |
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