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-2
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1answer
44 views

Effect of frequency shift on a sound signal

I had two sound files and did the following to it: ...
0
votes
2answers
124 views

filtering in frequency domain

I am performing decorrelation of two channels of audio using all pass filtering. The two all pass filters for two channels are of very high order (>1000 but with not all coefficients non zero). I have ...
0
votes
1answer
39 views

Calculate amplitude of noise added Sine Gaussian signal from frequency domain

How to calculate the time domain amplitude of noise added Sine Gaussian signal from corresponding frequency domain. Here time domain amplitude is 2. How to get this from frequency domain. ...
0
votes
1answer
71 views

Applying Gaussian Blur in frequency domain

Please see second update I'm trying to implement gaussian blur in frequency domain using c#. Those are steps that I'm doing: Load bitmap. Split bitmap into separate color channels. Convert every ...
-1
votes
1answer
56 views

fft2 of interferometric image - how to interpret the result in term of dominant frequency

I have an interferometric image which shows fringes at a certain frequency, basically a dominantly periodic signal overlaying the information that I want to extracthere are the fringes that I want to ...
9
votes
3answers
155 views

What is the type of noise in this image?

what reason could make the noise/effect in this image? Below is the original Thanks!
2
votes
2answers
160 views

Perform Convolution in Frequency Domain Using FFTW?

I'm trying to convolve two signals $x(n)$ and $h(n)$ in C by using the FFTW library's functions to perform a Fourier transform on each, multiply the appropriate complex components together, and take ...
0
votes
1answer
65 views

Oversampling and Aliasing

I am really confused about oversampling and upsampling. I know that upsampling means stretching our signal in time domain by a factor of K, then interpolating some values or using just zeros. As I ...
0
votes
0answers
142 views

DFT and Inverse DFT in Image Processing

I have implemented DFT from this link. 1) Tried taking dft for the three Channels(R, G and B) and reconstructed the original image by taking inverse dft for all three channels and merged them ...
0
votes
1answer
48 views

Discrete Time Fourier Transform to Frequency Domain

I failed to do this question on the exam and finding it very difficult, I would be glad if you can help me solve it. How shall I start?
1
vote
0answers
11 views

Creating synthetic frequency domain box filter vs 4 pixels in corners

Creating two 10x10 black images. 1st image, adding a 2x2 white box in the middle (Low pass filter). 2nd image, adding 1 pixel in each of the corners. Then performing the following steps in that ...
1
vote
2answers
103 views

Using only positive frequencies in fourier domain, How will it affect the ifft?

I am going to do some kind of transformation and transform a data to another domain, and again back to the first domain. For this, I take a fourier transform of the data and separate the positive part ...
0
votes
3answers
142 views

Time period to Instantaneous frequency

I have simple smooth time signal with different time period. I would like to transfer period over the time to frequency, and to track frequency changing over the time, I would call it Instantaneous ...
0
votes
1answer
42 views

How to convert filter into frequency domain to do filtering?

I have this filter: filter_2 = firceqrip(2,0.6,[0.05 0.03]); I want to convert it to the frequency domain to multiply it by a signal (i.e filter in the frequency ...
0
votes
0answers
35 views

Constant-Q transform - summing complex DFT coefficients vs. summing DFT magnitudes

The constant-Q transform computes a spectrum on a logarithmic frequency axis. When analyzing music signals, this can be a more meaningful representation than the Discrete Fourier Transform (DFT), as ...
0
votes
0answers
303 views

How to perform Wiener deconvolution in Matlab

I have an output signal y which is an input signal x convolved * with an impulse response ...
3
votes
2answers
193 views

How does taking the absolute value of a complex signal reflect in the frequency domain?

I have a frequency-domain representation $X(e^{i\omega})$ of the complex discrete one-dimensional signal $x[n]$: $X(e^{i\omega})=\mathcal{F}\{x[n]\}$. Is there a frequency-domain transformation of ...
0
votes
0answers
53 views

Simplest approach to classify signal based on its 'smoothness'?

First of all, I have no experience with signal processing whatsoever and I may not even use proper terms so please bare with me. I am just humble software developer trying to find the simplest and the ...
1
vote
0answers
67 views

Why does my overlap-add integrator in frequency domain result in distorted signals?

With help from the dsp guide and DSP-Related, I tried to implement a leaky integrator in octave/matlab. It seems to work in general, but there are a few problems. So that's what I do: Calculate the ...
0
votes
1answer
171 views

What is doppler tolerance

Can anybody explain the meaning of Doppler tolerance for the waveforms(Linear frequency modulated, Barker code, Polyphase codes) used for Pulse compression. The Doppler frequency shift $f_{d}$ due to ...
3
votes
1answer
131 views

How does the number of frequency-domain sampling points influence the outcome of an inverse FFT?

Given some frequency-domain representation of an impulse response. How does the number of frequency-domain sampling points influence the outcome of an inverse FFT, if I keep the sampling frequency ...
0
votes
1answer
104 views

how to get the phasor(frequency domain) representation of a digitalized signal?

I know that we can get the phasor representation(frequency domain) of a signal through Fourier transform, but the picture above gives a method that can get the phasor representation of a signal in a ...
1
vote
2answers
66 views

Convolution theorem

As stated by the convolution theorem, a convolution in spatial domain is equivalent to a multiplication in the frequency domain.Nevertheless, when should the first be preferred over the latter?
0
votes
0answers
35 views

Poles and zeros from FRF

How can I determine the poles and zeros of a system given its frequency Response? I can understand how one can find the Frequency response from poles and zeros of a system. Is it possible to do it ...
2
votes
1answer
135 views

Magnitude of gradient in frequency domain

I'm learning some basics of image processing. Recently I've read about image filtering and two-dimensional Fourier transform, because I'm preparing for exam. And I have one question I don't know ...
0
votes
1answer
21 views

2 by 2 bit orthogonal encoding mult-kronecker expansion matrices?

What is the name of the following bit encoding generator matrices?
1
vote
1answer
77 views

Why multiplying frequency kernel with sinusoid results shifting frequency domain

I am having great time while reading "The Scientist and Engineer's Guide to Digital Signal Processing" book. In "Chapter-14 Introduction to Filters" author indicates we can create high pass filter ...
1
vote
1answer
56 views

Similarity theorem in Fourier analysis

I have a homework problem that I'm not quite sure how to complete. The problem is as follows: PROBLEM Write the definition of the Fourier coefficients, and show that $$f(t + \frac{1}{2}T) = f(t) ...
0
votes
1answer
827 views

Convert normalized frequency to real frequency in AR model

Let us suppose that we have modeled signal using AR model, and suppose we have following model: I used spectral estimation function from MATLAB pyulear Now ...
1
vote
0answers
41 views

question about the frequency of Gabor filters

The Fourier transform of 2D Gabor filters is shown below: F is the radial frequency of the Gabor functions. Another parameter Fm is denoted as highest central frequency. Fr is the constant ...
0
votes
0answers
71 views

Determining Valid DTFT's

Are the following frequency domain signals valid DTFT's (Discrete Time Fourier Transforms)? Answer yes or no, and justify your answer. a) $X(\omega) = \omega + \pi$ b) $X(\omega) = i + \pi$ c) ...
1
vote
2answers
1k views

Convolution in the frequency domain

We often hear that "convolution in time is the same as multiplication in frequency", and vice versa, that "convolution in frequency is the same as multiplication in time". So in a typical windowing ...
1
vote
1answer
82 views

What's the frequency transform of a random matrix?

Assume the following: img = 255*rand(512); %Generating a 2D matrix with random numbers between 0 to 255. fftimg = abs(fft2(img)); %FFT of the image. The frequency transform of this image is a ...
1
vote
1answer
74 views

Standard deviation of Gaussian corresponding to perfect low pass filter [1,1]

For a time discrete signal, the rect-filter (for 1D signal [1,1]) is a perfect low pass filter. I was wondering, what is the best gaussian approximation of this filter? For a current problem, I ...
1
vote
3answers
234 views

What does the negative sign mean in the image frequency domain?

When I transform an image from the spatial domain to the frequency domain, some frequencies are negative. What is the meaning of the negative sign? For example:
1
vote
3answers
390 views

How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT?

My understanding if a frequency in my signal doesn't line up exactly with a bin, it is smeared over a few bins to the right and left. How can the instantaneous magnitude be determined? (do I have to ...
-2
votes
1answer
159 views

WIDELY UNKNOWN?? Wireless Channel Transfer Function or freq response - frequency vs attenuation

We know that the signal attenuates out with distance and according to the channel transfer function or frequency response, the signal frequency components attenuate to different values based on ...
0
votes
1answer
262 views

Frequency domain to time domain conversion-(varying sample count)

I need to convert 150 Frequency domain samples to the time domain. The problem is, I have been provided with 250 time domain samples for comparing my results. How am I supposed to relate the 150 ...
1
vote
2answers
279 views

What is relationship between entropy and frequency in image

When I was studying spatial frequency and entropy, it occured to me that "is there a relationship between entropy and frequency?". As you can see, if we consider only horizontal line, the frequency ...
1
vote
0answers
227 views

Adding shot noise in frequency domain

I have a current signal represented by an array in python, which I would like to add shot noise to. Shot noise is defined as $$ σ_i = \sqrt{2qI \Delta f} $$ where $q$ is the elementary charge, $I$ ...
-1
votes
1answer
107 views

what I'll get if I take FFT of a frequency domain data

What I'll get if I take FFT of a frequency domain data. I have two questions related to this. For ex, x is a time domain data where X = fft(x), now fft(X)= what i'll get ? While reading SCFDMA, ...
2
votes
1answer
44 views

Stability varying with order

I have been doing some research into modelling acoustic spaces, and (with help from this site) I've managed to take the frequency response of fibrous layer model, convert it to a reflection response ...
0
votes
0answers
161 views

FFT frequency domain averaging and zero padding

I'm trying to get the average frequency response of an entire piece of audio by splitting it into segments, doing an FFT on each one, and averaging the magnitudes together. Its working great until I ...
0
votes
0answers
68 views

How to optimize a wavelet transform?

I am using complex morlet wavelet to estimate frequencies and damping ratios in a 1-D signal. I have done it so far, and the results are accurate enough. Now my question is how can I modify or ...
8
votes
1answer
498 views

How to circularly shift a signal by a fraction of a sample?

The shift theorem says: Multiplying $x_n$ by a linear phase $e^{\frac{2\pi i}{N}n m}$ for some integer m corresponds to a circular shift of the output $X_k$: $X_k$ is replaced by $X_{k-m}$, where ...
1
vote
2answers
246 views

Examples of Causal and Complex Wavelets?

I'm looking for wavelets that are both: causal (a wavelet coefficient $W(j,k)$, where $j$ is scale and $k$ is translation, does not use data from $t > k$ to be estimated). complex (such as the ...
3
votes
1answer
214 views

Spectral Leakage, Phase and other questions about FFT

I'm currently implementing a voice recognition algorithm using FFT and now some questions came up to me: Spectral Leakage: I know what it is, why it appears and how to solve it using a Windowing ...
7
votes
2answers
1k views

When should I calculate PSD instead of plain FFT magnitude spectrum?

I have a thirty-second speech signal that was sampled at 44.1 kHz. Now, I would like to show what frequencies the speech has. However, I'm not sure what would be the best way to do that. It seems ...
2
votes
2answers
213 views

Does the number of samples matter for FFT, and how to get a specific frequency visible?

If I have a signal that has 740 samples, the sampling frequency is 1000 Hz, and I take an FFT of length 1024, are the frequencies I get now 0, fs/1024, 2*fs/1000, ..., 511*fs/1024? I mean, do I get ...
0
votes
1answer
86 views

Image with specific frequencies

I have created a frequency domain image filter and would like to test it against some images where it is known that the frequencies only occur within a given band. Trouble is, I don't know how to go ...