Signal Processing Stack Exchange
Signal Processing Stack Exchange

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What is the difference between the PSD and the Power Spectrum?

Can any one explain the difference in the amplitude between the two and what does each one represents? For example, when using the pwelch algorithm in MATLAB how do the two different options ('psd','power') affect the units of the output? (I know…
havakok
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How can I decompose a signal into square waves?

I am dealing with signals that are a superposition of different square waves with different amplitudes and phases. Normally, one would decompose a signal into sine waves with help of the Fourier transform, but in this particular case a decomposition…
Sentry
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Phase correlation vs. normalized cross-correlation

I asked this over at Mathematics Stack Exchange, but since this sort of lies on the border of the questions normally asked over there and the questions you see over here I'll ask it here as well. (As of now, there's been no activity on my question…
Eric
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How/why are the $\mathcal Z$-transform and unit delays related?

The $\mathcal Z$-transform uses the same notation as the unit delay $z^{-1}$, but in $\mathcal Z$-transform $z$ is a complex number. What's the relation between the $\mathcal Z$-transform and the unit delay concept? Also, is there a complex number…
mavavilj
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Is it correct to subtract a low-pass filtered signal from the original signal and use the result as a "high-pass"?

I am having a hard time trying to find documentation to implement band-pass or high-pass filter with python/scipy/numpy. I can easily create and apply a low-pass filter, though, so I ask: Would it be conceptually correct to low-pass-filter a signal,…
heltonbiker
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Why LTI system cannot generate new frequencies?

Why $Y (\omega) = X(\omega)H(\omega)$ implies that an LTI system cannot generate any new frequencies? Why if a system generates new frequencies, then it is not LTI?
USER
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References on the MP3 encoding algorithm

Does anybody have a reference describing the MP3 algorithm in a step-by-step manner and clear to understand? These references were a little bit confusing: Audio compression using modified discrete cosine transform,The MP3 Coding Standard,…
ali ha
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Estimating the input to a system from a system state using EKF

[ Cross-posted from: https://math.stackexchange.com/questions/164169/estimating-the-input-to-a-system-from-a-system-state ] I have a system for which I have obtained a non-linear time-varying state-space representation. For this system I am able to…
IainCunningham
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Filtering of streaming audio

Given something like 103 data points ($N=103$), a DFT will give back 103 frequency values. Then to do something like filtering the high frequencies involves setting the high frequency values from the DFT to zero, and doing the inverse DFT to get…
user782220
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DFT of discrete signals, why do we only analyze frequency bins equal to number of input samples?

If we have a signal $x[n]$ such that we have $N$ samples i.e. $n=0, \ldots, N-1$, then when we analyze the DFT $X[k]$ we only analyze for $k=0,\dots,N-1$ as well. Why is the range of $k$ tied to the range of $n$? Why don't we analyze more, or…
GrowinMan
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What is the difference between natural response and zero input response?

I am new to DSP and was going through different responses of a system subjected to an input. My understanding of zero input response is: it is the response/output of the system when the input signal is set to zero. In other words if a system is…
rotating_image
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Ultrasonic speaker calibration and emitting calibrated signals

I'm trying to calibrate an ultrasonic speaker with the aim of emitting predictable signals, but alas I keep running into trouble, probably due to my lack of DSP-fu. A little background I want to be able to playback sounds as close as possible to a…
Thor
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Algorithms for detection of fingertips or nails

Can you give me some advices on what could be the best algorithm(s) to use for detection of fingertips/nails in image. First thing that crossed my mind was Viola - Jones. After rethinking I concluded that maybe it would be possible to use just Hugh…
Srđan
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1 answer

Recognizing data clustered into shapes

I am working on a project in Python to detect and classify some bird song, and I have found myself in a position where I need to convert a wave file into frequency vs. time data. This hasn't been too much of a problem, but to be able to classify the…
smckee
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Denoising by DCT and hard thresholding

If I have an image and I find the DCT and then apply hard thresholding on the coefficients and then IDCT then I have attenuated the noise. Can someone please explain in detail or point me to the answer as to why this works? I understand why a…
Dino
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