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Posts by b0dhi

Quote: Originally Posted by eucariote Assessing discrimination abilities in humans from conscious reports is absolutely routine [snip] There is an important difference between assessing conscious discrimination abilities in humans and assessing the effect of something on humans. Listening to music is not simply an exercise in conscious discrimination. There are well established subconscious effects, both long and short term. There may even be as...
Quote: Originally Posted by eucariote But I'm ready to accept the results of such a test, regardless of outcome. Just as I accept the conclusion that L-dopa leads to statistically significant increases of the chemical that is otherwise missing in the brains of people with Parkinson's, so alleviating their symptoms. Which was shown using said technique.. You'll notice they didn't simply ask the patients what their L-DOPA levels were. They measure...
Thanks Nick_charles. To be honest I think what you suggested there, i.e., taking the difference of the files, is the best approach. I'm not at all convinced an FFT is a reliable way of detecting differences in these files since the margin of error seems to be too high. I'll see if these files give more believable results though. Edit: Looks like the differences are there in those reference files too. These are a diff for t5 and t6. Assuming those two files are just...
Just in case anyone's using Wavosaur for any of this analysis - when I was testing RMAA, I noticed that THD increase by 300% after I did something with Wavosaur. So I did some more testing and found that simply opening the RMAA file and re-saving it increases RMAA's THD measurement by 300%. I tested with Adobe Audition and it didn't have this problem. Using Audacity, the THD increased by 100%. I assume/hope it's dithering causing this. Also, Nick_charles, could you please...
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.
I think that will work. Been doing some tests and I got roughly +/- 0.3dB amplitude accuracy with a ~65k FFT and 4-term Blackman-Harris window having ~-90dB side lobe. Blackman (3-term) also worked within that accuracy. I tested with various signals of known amplitude and noise 20, 40 or 60dB down to imitate broadband music. One thing I should point out is that none of my software lets me choose a FFT length smaller than the number of samples in the data, so I don't...
This might be helpful. In particular, see the table near the bottom comparing the type of signal to be determined and the window that would be appropriate for it. I know I have a book here that goes into the math and most importantly shows the amplitude error margins of each of these windows but I can't for the life of me remember where it is. Will post those details when/if I find it. Edit: found something here: http://www.bksv.com/doc/bv0031.pdf. See table 2 on page...
Quote: Originally Posted by nick_charles I downloaded a demo version of Autosignal. It is a serious package. I could not find a way to get the FFT size down, it kept giving me 81K samples so the text files were enormous and the results were a bit dubious. There's nothing whatsoever dubious about those results. Audacity uses an apodizing transform. All apodization windows have limitations as far as their amplitude and/or frequency resolution....
Quote: Originally Posted by nick_charles A 2.3db difference is seriously worrying and not in just a perfectionist way this is way off. Using Audacity at its highest FFT size (16K) the biggest diff found was at 21449hz and was 0.074921db, big enough but... A 2.3dB difference is indeed worrying. I'd like to get to the bottom of this. What exactly is the "sample" you're comparing your reference to?
Here's what I got testing Audacity's fourier transform: Generated 2 dithered sine waves, 2 seconds long, 44.1khz 16bit, each @ -12.0dB (normalised to 0dB) 1khz and 13khz tones were generated this way, mixed, and saved to a single wav file. Used fourier spectrum in Audacity, 16384 pt Hanning window, linear freq. Exported data shows: 13000.671387hz @ 17.752396dB 1001.293945 @ 16.788063dB. Difference: 0.964dB. Used AutoSignal fourier spectrum, Best Exact N algorithm....
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