The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain.

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Plotting convoluted and original signals on the same graph

So I have a frequency response (got it by windowed fft-ing) of a note E4 played on a guitar and now I'm trying to implement a dynamic threshold for finding the peaks (fundamental frequency of the note ...
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1answer
52 views

Extracting original signal from overlapping area

Considering this image, where I have a spectral decomposition of a light bulb. Due to the non point shaped light source, the spectral decomposition using a diffraction grating in front of my camera ...
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43 views

how to calculate the dc component of an energy signal?

Does the energy signal or finite energy signal have 0 dc component always?How to confirm this from the frequency spectrum?
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27 views
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32 views

frequency spectrum of the conjugate of x(t)

Is the frequency spectrum of x*(t) the same as the one of x(t). I'm telling this because I found that X*(f) = (X(-f))* . So to find X*(f), intuitively i would just flip X(f) because of the minus sign ...
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146 views

Purpose of using polyphase filter bank (PFB)

What is the advantage of using a polyphase filter bank (PFB) for spectral analysis over just using the FFT? In the standard "critically sampled" uniform DFT filterbank, the polyphase ...
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37 views

“Undersampled” Polyphase Filter Bank

I'm working on an application where I want to grab high-resolution pieces of the spectrum, but I don't need the whole spectrum-- just a few bands. I've looked into using the Goertzel algorithm (too ...
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22 views

Is negative frequency important in calculating Spectral Moments

A follow on question form this one (What is meant by "spectral moment"?) In answers to the above referenced question spectral moment is defined as: $$ m_k=\int_{-\infty}^{\infty} ...
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1answer
51 views

What is the reason for filtering out the negative frequencies of a signal?

I am reading this tutorial. Quoting the lines from the topic "Analytic signals and Hilbert transform filters": the corresponding analytic signal $ z(t)=x(t) + j {\cal H}_t\{x\}$ has the property ...
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53 views

Fourier Transform of a Pulse Train (Frequency Comb Simulation)

I am trying to take a Fourier transform of a femtosecond pulse train and plot the frequency spectrum. I followed this question and am able to create a pulse train and plot both the time and frequency ...
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43 views

Filtering of complex exponential functions

In my problem the signals $x(t), h(t), w(t), y(t)$ and $y_w(t)$ are defined as follows: $$ x(t)=\sum_{i=1}^M a_i\delta(t-\tau_i) \\ h(t)=e^tExp(-e^t) \\ w(t)=\begin{cases} 1 \quad when \quad ...
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I have a sequence which is made of complex exponentials with arbitrary amplitudes and initial phases. No noise

I have a sequence which is made of complex exponentials with arbitrary amplitudes and initial phases. No noise. That is it is a sum of the complex exponentials of the form $A_i e^{jnw_i+p_i}$. For ...
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94 views

Recover signal from its spectral amplitude and envelope

I am given an amplitude spectrum (no phase) and the envelope of a signal. What I know about the original signal is, that it can be thought of as wavepacket like structure (sinusoids under a bell ...
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3answers
118 views

Reflecting negative frequency to positive frequency

I am trying to synthesize sinusoids by using window function in the frequency domain. It involves: In frequency domain, shift the window to center around the peak frequency To generate a DFT ...
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1answer
18 views

How to estimate carrier frequency & amplitude for several overlapped template signal

As is shown in the picture, a template signal is delayed and overlapped in time domain, the shape of template signal is already known The positions of each template are already known. Each ...
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2answers
111 views

What is spectral entropy?

Can anyone explain what spectral entropy is? Does noise with a restricted bandwidth have the same spectral entropy as white noise?
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1answer
39 views

Ways to identify if music has vocal timbres in it?

The human voice is singular because it has a specific frequency spectrum and fast transitions between vowels and consonants. What are good and computationally fast ways to detect if there is probably ...
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22 views

FIR/IIR approximation of known frequency response

I have two different sets of data from compatible signal sources but recorded off two different transmission line characteristics. I am trying to equalize out the transmission line in the two data ...
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22 views

Classifying sleep stages from only EEG

I'm currently working on a project that requires me to classify sleep stages (Awake W, N1, N2, N3 and REM) based on only an EEG. Various algorithms and classifying standards (such as Rechtschaffen ...
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32 views

amplitude compensation after filtering and mixing audio

I am working on a mixer which lets me mix dry and wet signal in a user defined ratio. Wet signal is basically just the all pass filtered signal. The mixing takes place in frequency domain and so does ...
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122 views

Compare phase and magnitude spectrum results of 2 Images [duplicate]

I have read that from Fourier transform we obtain magnitude and phase spectrum. The magnitude spectrum tells you how strong are the harmonics in a image and the phase spectrum tells where this ...
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41 views

Can a infinite bandwidth signal Be a infinite Time SIgnal?

While Decomposing the impulse train using the Fourier series the no. of the samples are infinite hence representing a infinite length of train. But while studying the Nyquist Criteria in the ...
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33 views

Getting wrong periodogram

I'm driving a white noise signal $e(n)$ through an AR random process: $$ x(n)=e(n)+\sum\limits_{k=1}^N \alpha_k x(n-k) $$ I got five values of $\alpha_k$ and plotted its power spectrum in Matlab for ...
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1answer
43 views

What is sound output delay of a band pass filter at different freqencies?

I measured that a 2-pole band pass filter, given imput audio of different frequencies, outputs an audio signal with different time delay. At 440Hz, the time delay between of the input audio and the ...
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41 views

Are there any pictures of a sample accurate spectrogram on the web or in books?

I programmed a sample accurate spectrogram some time ago and i still have never seen a picture of another one. It's interesting maths, i was told it's trivial, so why has no one else posted research ...
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199 views

What is the most precise frequency analysis spectrography algorythm?

Everyone uses Fast Fourier Transform, which is fast at the detriment of precision. The input audio has sample accuracy and the FFT has 1/64 sample accuracy. What algorithms can output high resolution ...
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122 views

Power Spectrum in dBFs

I'm trying to get the spectrum of my signal in dBFS units. I'm not sure what is the refernce that I should devide by. I computed the power spectrum as follows: 1) FFT normalized to the number of ...
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310 views

Is it only me or matlab's periodogram's function is confusing?

I am really confused with matlab's periodogram. First of all, it says in the documentation that its unit is "dB per unit frequency". What does that really mean? I just don't quite get it. Second of ...
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87 views

Dominating frequency in a “clear” 50 Hz signal

I am trying to find out the dominating frequency of a signal with a frequency of 50 Hz (sampled at 200 Hz - every 5 milliseconds). The python code I am using to do this is the following (based on ...
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46 views

Harmonic estimation from a single note

I have a recording of a single note played several times on a violin. I'm working with Matlab to estimate the amplitude of the first N harmonics. I already know which note is played but there can be ...
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21 views

estimating frequency spectrum from power spectrum

I am passing white noise of known variance through filter, and I get the ouput signal.I estimate the filter response from PSD of the output. Is the following code correct when implemented in matlab? ...
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25 views

Is it possible to calculate the variance of signal in real time implementation? [duplicate]

In communication system, when we received some signal which contain our message of known variance sigma_s which is corrupted in noise of unknown variance. If I need the variance of the signal in ...
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206 views

Can anybody explain about phase shift and phase spectrum terms in case of multidimensional signal?

I know about phase of a 1D signal. But when I go into higher dimensions like 2D,3D etc, it becomes headache to grasp the concept. What are the terms phase shift and phase spectrum mean in case of ...
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2answers
53 views

Phase spectrum range

I computed spectrum analysis of sine wave (without windowing and zero-padding) and I got plots as follows: As far as I know they are correct. When I learnt about DSP, I got the huge problem with ...
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18 views

Predict auditory masking with a crude estimation?

If I had a vector containing the spectral centroid, spread, skewness and kurtosis (all normalised) of an audio clip and found the distance between it to the same kind of vector of another audio clip. ...
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Spectrum density estimation in R. Plot scale

I used spec.pgram to estimate the spectrum of a sequence. It gives a plot, I wonder what exact does it plot? It is not spec in the return value it is not log of that, it is not log10 of that. I fail ...
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72 views

Frequency spectrum of signal - Matlab

Here is the code I use to plot a function in frequency domain in Matlab: ...
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1answer
53 views

Average spectrum representation - SonicVisualiser

I try to have a signal (speech) represented in time and frequency domain (waveform, spectrum and spectrogram). I use Sonic Visualiser and for spectrum representation it shows an analysis at a given ...
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3answers
155 views

How to estimate the period of a pulse train?

I am trying to find the period of a pulse train like signal. I have reviewed the following questions but I did not find a clear-cut answer to the problem, 12892, 16502, 6260. I do not know the ...
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16 views

What is the best way to detect audio drops (audio level drops irregularly) in a video?

While recording a video, due to some problem in microphone (like low battery ) audio level go down inconsistently (voice____Voice__), I am trying to figure out an solution for this, is there any way ...
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1answer
33 views

What is the Sound of a Solution to the Wave Equation?

What is the sound of a solution $y(x,t)$ to the Wave Equation $\frac{\partial^2y}{\partial t^2}=c^2\,\frac{\partial^2y}{\partial x^2}\enspace$? To be clear, I don't look for a solution of the Wave ...
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71 views

How to define cyclic frequency for cyclostationary signal in terms of signal parametrs?

I am trying to detect cyclostationary signal. For that it is required to know its cyclic frequency. But I am unable to figure out how it can be related to signal parameter. Is it possible to define ...
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73 views

Detect repetitive units within signals

I have several signals that consist of repetitive units. In the figure you'll clearly see the variability of the signals, that increases top down. The first signal is super repetitive and units are ...
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3answers
102 views

How to add pitch-shifted version of signal to itself?

I want to write an algorithm to add pitch-shifted version of audio signal to itself (like Electro-Harmonix POG does). And I need to do it in realtime. How to implement it? My guess is: break signal ...
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1answer
67 views

Increasing the number of points in the frequency spectrum

I have an image with few pixels in length and height. For this image I calculated the two dimensional Fourier transformation. What I got for the frequency spectrum in one direction was a very ...
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1answer
36 views

Do I need an overlapping in STFT if I want to play the signal back?

I want to write an algorithm to implement a pitch-shifter, like in this article: http://www.guitarpitchshifter.com/matlab.html. And I need to do it in realtime, not with a signal already defined ...
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0answers
33 views

Computational model for spectrum analyzer - how to model resolution?

I'm trying to model a spectrum analyzer which may be used experimentally for visualizing the spectra of signals. I have a numerical data signal with excellent resolution (...
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0answers
51 views

Spectral centroid range between 0.45 to 0.5, almost doesn't react to mic input

I am implementing some feature extractors in Swift for an application. One of these features is Spectral Centroid. For some reason I keep getting values ranging between 0.45 and 0.5, and these don't ...
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Determining the point in a temporal signal when a periodic behavior begins to occur

I'm a newcomer to digital signal processing, so I'm looking for some general advice and direction on this problem I have. I have a signal like that shown below. Starting around x=40000, you can see a ...
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Extract features from video based on temporal frequency

Situation is as following: there is a video, 2d sequence of frames, each of which contains still picture of beating heart, or some other oscillating object. Also each picture contains some features, ...