Linked Questions

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1answer
23 views

FFT/PSD/IFFT analysis on single axis piezoelectric accelerometer signals for curb impacts

I'm trying to denoise the signal by performing PSD analysis and followed by IFFT. Ultimately, I want to generate Force and Displacement plots from the denoised acceleration signal. Noisy Acceleration ...
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2answers
32 views

Time Series processing using fft

I have a set of real data (timestamp and value) with an unstable step between samples (5sec, 30sec etc.). The data is the % of fillage of a vehicle's tank through time. Due to the harsh volatility of ...
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1answer
43 views

Using DFT Rotation for Frequency Down-Mixing

Is it possible to perform Frequency Down-Mixing (sometimes referred to as Down-Conversion) by simply rotating the DFT sequence? If so what are the Advantages and Disadvantages of this method?
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37 views

How can I generate an ideal 2D low-pass filter in MATLAB?

I've been tasked with creating a 32 x 32 half-band low-pass image filter in MATLAB. My thinking is to generate the ideal filter mask in the frequency domain and compute the corresponding convolution ...
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2answers
31 views

filtering difference b/w freq and time domain

When you want to get the specific frequency (ex. around 1000Hz), you might take FFT, remain the frequency you want, and reduce the power of the other frequencies you do not. ex.) if fs=16khz and ...
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0answers
60 views

FFTW audio artifacts when modifying magnitudes in frequency domain

I'm currently working with FFT (FFTW3) that I'm using to apply treatments on audio files frequencies. The Forward/Backward test is passed, since I can get the exact same soundfile when processing ...
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2answers
96 views

Question about ideal filters

Following shows the discrete time Fourier transform of an ideal low pass filter with cutoff frequency $\omega_c$: $$H\left(e^{j\omega}\right) = \begin{cases} 1, & \text{if $|\omega| \le \omega_c$...
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1answer
81 views

Is resizing of frequency spectrum a valid method of resampling?

One method of resampling is to perform a Fourier Transform on a signal, resize the resulting frequency spectrum, and then return to the resampled version of the signal with an inverse fourier ...
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1answer
40 views

Find signal power in a band by integrating the PSD in a frequency band (and zeroing the out-of-band DFT bins)

I know that directly zero DFT bins outside a frequency band has the side effect of introducing ringing, as this post says Why is it a bad idea to filter by zeroing out FFT bins?. But what about ...
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2answers
49 views

Digital filtering based on frequency component amplitude… why not?

I've got a very general question. I've just implemented a filter working in frequency domain that simply cuts every frequency component whose modulus amplitude falls below a certain threshold value. ...
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1answer
46 views

Downsampling - how many extra samples to include

I want to downsample a finite section of an equidistant time-series $$x_i, \qquad i=0\dots n-1$$ by doing an FFT and dropping the upper part of the spectrum. Since the FFT looks at $x_i$ as a cyclic ...
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1answer
287 views

Building a FIR filter from an arbitrary frequency-magnitude response curve (eg. Least Squares fitting) [duplicate]

I'm trying to create a FIR filter from a magnitude equation, where my starting equation provides the magnitude (amplitude) between 0 and 1 for any given frequency in Hz. I posted the magnitude ...
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2answers
87 views

Time domain to frequency domain conversion of audio signals to extract 1/3 octave frequencies

I am writing first time in this forum and I am not expert in programming and FFT. We have developed an android app (Noise Tracker) for noise measurement using smartphones. It displays noise levels in ...
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1answer
117 views

How many things can they be done with a spectrogram?

I found some things that can be done with a spectrogram. filter frequencies by setting the bins to zero observe what frequencies make up the signal. observe the energy or amplitude of each frequency, ...
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3answers
53 views

Filtering using fourier series

Suppose I have a measured signal $M$ that has frequency components from 0 to 50 Hz. I plot the specturm of this signal using FFT and I observe its frequency content (power vs frequency). Then, I ...

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