Linked Questions
78 questions linked to/from Why is it a bad idea to filter by zeroing out FFT bins?
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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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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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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
86 views
Question about ideal filters
Following shows the discrete time Fourier transform of an ideal low pass filter with cutoff frequency $\omega_c$:
$$H\left(e^{j\omega}\right) =
\begin{cases}
1, & \text{if $|\omega| \le \omega_c$...
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72 views
Is resizing of frequency spectrum a valid method of resampling?
One method of resampling is to perform a Fourier Transform on a signal, resize the resulting frequency spectrum, and then return to the resampled version of the signal with an inverse fourier ...
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Find signal power in a band by integrating the PSD in a frequency band (and zeroing the out-of-band DFT bins)
I know that directly zero DFT bins outside a frequency band has the side effect of introducing ringing, as this post says Why is it a bad idea to filter by zeroing out FFT bins?. But what about ...
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2answers
44 views
Digital filtering based on frequency component amplitude… why not?
I've got a very general question.
I've just implemented a filter working in frequency domain that simply cuts every frequency component whose modulus amplitude falls below a certain threshold value. ...
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1answer
41 views
Downsampling - how many extra samples to include
I want to downsample a finite section of an equidistant time-series
$$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
231 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
80 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
115 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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2answers
505 views
How do Anti-Aliasing Filters filter the signal?
I have programmed a anti-aliasing filter that uses the fourier-transformation and makes a perfect cutoff on my desired cutoff frequency for downsampling without aliasing.
I have read about other ...
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30 views
Use Cases of FFT in Signal Processing [duplicate]
I am trying to learn about signal processing and fft's applications within it. My understanding is that a classical use case for fft is to remove "noise" (ex. high frequencies that are not supposed to ...
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1answer
54 views
Reducing one frequency in song
How would I take a song input and output the same song without certain frequency ranges?
Based on my research so far, the song should be broken down into chucks, FFT it, reduce the target frequency ...