Audacity Forum

Well, at least I know this kind of things the Fourier Transform is something involving coefficient of Exp with i^2=-1 but the argument of the exponentiel may be defined differently and this influence the normalization of the function too. There is of course a set of definition that garantee the fact...

No news to answer to the question pf the FFT convbentions made by Audacity ?

Well I do not manage to match Mathematica 9 to the Audacity results but I guess this is a convention missmatch more than a bug.

Do you know the convention for the Fourier Transform parameters (a and b just below) used ?

1/n^((1-a)/2)Underoverscript[[Sum], r=1, n]Subscript[u, r] e^(2[Pi] i b(r-1)(s-1)/n)

steve wrote:For implementation details, please refer to Spectrum.cpp in the source code http://code.google.com/p/audacity/sourc ... ectrum.cpp

ha! I find my way in FFT.h/cpp sorry for previous post...

For implementation details, please refer to Spectrum.cpp in the source code http://code.google.com/p/audacity/source/browse/audacity-src/trunk/src/Spectrum.cpp Thanks a lot I have dived to the code and now I'm looking for the WindowFunc and PowerSpectrum definition but I cannot managed to catch the...

Ok
But does this shift is independant of sampling rate AND/OR sample length ?

I get -24dB for 8000Hz sampling rate, 2048 sample length and Blackman-Harris windowing & 50% overlaping.

steve wrote:The peak amplitude is normalized such that a 0 dB sine wave will show (approximately) 0 dB.

Do you mean also that the
spectrum 20*Log10[PeriodogramArray[data,4096,2048,BlackmanHarrisWindow]]
is shifted such that the max is set to 0dB even if "data" are not from a sin func with amplitude = 1 ???

The peak amplitude is normalized such that a 0 dB sine wave will show (approximately) 0 dB. I have just generate sin 440Hz freq. with Amplitude=1 and with Blackman-Harris window 1024 sample size I get 0dB at peak value. Ok By the way is the windowing follow Welch rule with 50% overlapping ? (ie. 51...

Hello, I'm sure this question has been answered already but I cannot fionf it... So please can you tell me the following thing. I'am using version 2.03 And I plot the Spectrum Analysis using Blackman-Harris Windows, 4096 samples, 8000Hz sampling rate over 1sec resord. I would like to know what is th...