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

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46 views

Spectrogram, time vs frequency localization, and length of signal

So I'm having some trouble conceptually and am hoping somebody can clear something up for me. This is long and I apologize for that but I want to provide as much information as possible so that the ...
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1answer
24 views

What is the spectrum of modulated noise?

I use a white-noise generator in an rf bridge to measure antenna impedance. The receiver is an ordinary AM/CW/SSB communications type, nothing fancy, nothing 'coherent'. As I approach the null of the ...
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45 views

How to Flip Spectrum Around DC?

Is it possible to flip a signal's spectrum around DC? I have a simple spectrum that I made up (MATLAB code): ...
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49 views

Additional peak after resampling

I prepared a Matlab script, which re-samples spectrum from 24kHz to 20kHz. When I used up-sampling, a fir filter, and then up-sampling again at the end, I get an additional peak at 4kHz which is not ...
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36 views

Encounter 0 when calculating log power spectrum

To convert power spectrum to a log-scaled one, how to define log10(X(k)) if X(k)=0 for some ...
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12 views

How to estimate the power spectrum in yule walker method?

I'm trying to estimate the power spectrum using yule walker method in C++ . After finding the coefficient ,how to estimate the power spectrum ? Example: I got the coefficient up to 30 ...
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21 views

How to attain the frequency vs time graph of a .mp3 file

I'd like to plot a graph of frequency vs time for a given mp3 file using either Processing or freemat, any clue on how to do that. Also this might be overkill, but if I were to get a frequency vs time ...
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0answers
34 views

Fourier of a function in Matlab

I have a function describing a fourier transform of type : \begin{equation} \mathcal{F}(C(t)) = 1.42 \mathcal{F}\left( \exp^{-1.192t} u(t)\right) - 12.44 \mathcal{F}\left(\exp^{-1.192t} u(t)\right) ...
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2answers
63 views

MATLAB : How to filter a data signal

I have a data signal (column vector) with N values taken over at specific sample rate (dx) at a fixed frequency. After taking the Fourrier transform of this signal and representing it in the Fourier ...
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12 views

Where can I find images corrupted by periodic/coherent noise?

I found one here https://scipy-lectures.github.io/_images/moonlanding.png I would be more interested in photographs which are naturally corrupted by such noise. I am seeking them in order to use ...
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1answer
44 views

How to calculate resolution of DFT with Hamming/Hann window?

The frequency resolution of a DFT with a rectangular window of size $N$ is given by $f_s/N$. However, when using other window functions like a Hamming or Hanning window the resolution gets worse. How ...
2
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1answer
100 views

Why is the magnitude of the second component of my FFT spectrum always the largest one?

While working with FFT, I have a strange case with a current experimental setup. I am working with beat frequencies (intermediate frequency output) and using a standard FFT algorithm (complex to ...
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1answer
71 views

How to interpret these different Fourier analysis of this audio signal?

This is my first dive in DSP. I would like to familiarize myself with frequency analysis. I have two audio tracks which should be digitized at 16bit-44.1kHz and 24bit-192kHz (music, presented as a ...
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1answer
22 views

Bandwidth of a trimmed sinus wave

I generate a sinus which duration is 15ms and frequeuncy of 13KHz. Is its bandwidth is (1/15ms) ? Or in other words, BW = 66.6Hz? I ask that because I have two freqs in my system: 13K & 13.1K. I ...
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1answer
28 views

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 ...
2
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1answer
68 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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1answer
52 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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42 views
1
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1answer
36 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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2answers
189 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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1answer
41 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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28 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} ...
2
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1answer
60 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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1answer
134 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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60 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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29 views

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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2answers
112 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
125 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
19 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 ...
2
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2answers
130 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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32 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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0answers
27 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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35 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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1answer
149 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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42 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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52 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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1answer
43 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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1answer
216 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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1answer
146 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 ...
2
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1answer
372 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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116 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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2answers
61 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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0answers
22 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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0answers
27 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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2answers
224 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 ...
0
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2answers
72 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 ...
0
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1answer
19 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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15 views

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 ...