Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Sampo Syreeni
On 2014-10-31, Theo Verelst wrote: if I have a sampled noise signal of some kind, regardless how I got it, it isn't going to make a difference for the main characteristics of the proposed measurement which transformation I use, [...] Oh, but it is. Suppose you derived your so called noise seq

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Sampo Syreeni
On 2014-10-31, Ethan Duni wrote: Transforms between orthogonal bases are basically rotations. I.e., they are linear operators that produce each component of the output as a linear combination of input components. Generally, then, the Central Limit Theorem tells us that the output distributions

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Sampo Syreeni
On 2014-10-31, Bjorn Roche wrote: I am not sure if the PDFs are preserved across transforms from one orthonormal basis to another, and the answer to your question would depend on that They most certainly are not. As two concrete examples of bases which lead to different induced PDFs upon tra

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Sampo Syreeni
On 2014-10-31, Theo Verelst wrote: Now, how probable is it that we get "all equal" frequency amounts as the output of the this FFT transform (without regarding phase), taking for instance 256 or 4096 bins, and 16 bits accuracy ?! Or, how long would we have to average the bin values to end up e

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Ethan Duni
>The expectation value of the signal over the ensemble of all unitary transforms >with a suitable measure (like Haar). The expected value you describe is equal to the zero signal (this follows immediately from symmetry), not a "Gaussian white noise signal" (whatever that is - you insist that it do

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Andreas Tell
On 01 Nov 2014, at 00:06, Ethan Duni wrote: >> The correct statement would be >> that an arbitrary unitary transform of a Gaussian white noise signal is >> *expected* to give a gaussian white noise signal. > > What does "*expected*" mean in that sentence? The distribution of a unitary > transfo

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Ethan Duni
>The correct statement would be >that an arbitrary unitary transform of a Gaussian white noise signal is >*expected* to give a gaussian white noise signal. What does "*expected*" mean in that sentence? The distribution of a unitary transform of an i.i.d. Gaussian vector is i.i.d. Gaussian. >My po

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Theo Verelst
it's funny how you guys seem to go off in all kinds of not so connected directions. Just to make clear my question is a serious one, with more normal undergrad material connected than I have ever seen mentioned here, consider this: if I have a sampled noise signal of some kind, regardless how I

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Andreas Tell
On 31 Oct 2014, at 23:31, Ethan Duni wrote: > If you have Gaussian i.i.d. noise, you can apply any unitary transform you > want and you will still end up with Gaussian i.i.d. noise. I believe that > this is the result Bjorn is referring to. Note that this doesn't work with > arbitrary distributi

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Ethan Duni
>> There is a theorem that goes something like this: >> >> If you have white noise expressed in one orthonormal basis, and you >> transform it to another orthonormal basis, the result will still be white >> noise. > >There is certainly no such theorem. For any noise signal you can define >a basis t

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Andreas Tell
On 31 Oct 2014, at 19:50, Bjorn Roche wrote: > There is a theorem that goes something like this: > > If you have white noise expressed in one orthonormal basis, and you > transform it to another orthonormal basis, the result will still be white > noise. There is certainly no such theorem. For

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Ethan Duni
>I am not sure if the PDFs are preserved across >transforms from one orthonormal basis to >another, and the answer to your question would >depend on that (Of course it would also depend >on several other parts of the phrasing of your question >that aren't clear to me). My intuition is that PDFs >ar

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Ethan Duni
>Say we're only taking one length of the FFT transform, and >are only interested in the volume of the various output "bins". >Now, how probable is it that we get "all equal" frequency amounts as >the output of the this FFT transform (without regarding phase), taking >for instance 256 or 4096 bins,

Re: [music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Bjorn Roche
There is a theorem that goes something like this: If you have white noise expressed in one orthonormal basis, and you transform it to another orthonormal basis, the result will still be white noise. The phrasing of that is obviously imprecise, but the point is this: since the time and Fourier dom

[music-dsp] Statistics on the (amplitude) FFT of "White Noise"

2014-10-31 Thread Theo Verelst
Hi music DSpers, Maybe running the risk of starting a Griffin-Gate, but one more consideration for the people interested in keeping the basics of digital processing a bit pure, and maybe to learn a thing or two for those working and/or hobby-ing around in the field. Just like there is some dou