# Questions tagged [ifft]

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### Cepstrum calculation with 5-smoothing zero padding

I am trying to compute cepstrum of a signal x An implementation of this in python is: ...
99 views

### FFT of square wave: maths and actual numbers do not coincide

this fact is driving me insane... Theory states that the Fourier transform of a square wave is a sinc function, but if I compute the fft of a synthetic (perfect) square wave of amplitude 1 and ...
81 views

### What is the meaning of the length of diagonal lines in FFT

I am relatively new to FFT analysis of images and have a question about them. I like to think I understand the basics but many of the properties shown in a FFT image are beyond me. My main question ...
52 views

### White noise generation in frequency domain (stfft) produces a periodic pattern

I have created a set of spectral processing modules for SynthEdit next to be released, implenting short time fft, so I am now quite experienced with the matter, but recently encounteted an unexpected ...
49 views

### Scaling issue after doing manipulations in FFT

I have two filters which must apply (in series) to same input data $x[n]$ e.g of length 256 (real time asio input buffers). One filter is e.g. an impulse response $h_1[n]$ of a speaker and other one ...
44 views

### Yet another fft question - a vocoder

Lets assume a pipeline X: ...
43 views

### IFFT of a complex, conjugate-symmetric transfer function - Value at Nyquist frequency

Using the MATLAB 'symmetric' flag to compute the IFFT of a complex-valued, length-N (with N even), transfer function, the imaginary part of the complex value at the index ((N/2)+1) corresponding to ...
87 views

### fft and inverse fft error size and applying impulse response matlab

I have a signal called noise. I am using the following command to calculate the mean squared error after fft and inverse fft process: ...
42 views

### What happens if I zero out the initial terms of the fft output and take inverse fft? [duplicate]

I am new to signal processing domain. When I run fft on data of length 1000, I get 1000 complex numbers. Now, if I want to extract the low frequency information or signal approximation, I take the ...
391 views

### inverse discrete fourier transform with plain python

I am trying to calculate inverse discrete fourier transform for an array of signals. I am using the following formula: $$x[n] = \tfrac1N \sum\limits_{k=0}^{N-1} X[k] \, e^{j 2 \pi k n/N}$$ And my ...
62 views

### What is the proper way to filter out unwanted noise from accelerometers?

I'm a beginner in signal processing and have a hard time to filter out environmental noise from the floor vibration data collected using accelerometers. I have tried using butterworth filter (IIR) ...
92 views

### My impulse response does not tend to zero

I am doing an IFFT of frequency response data achieved with Simulation tools. When I plot my impulse response it looks wrong as the response does not tend to zero as it should. Instead there seems ...
96 views

### Inverse FFT of complex exponential with time delay - window leakage?

I am working in MATLAB with a frequency domain signal that is a sum of complex exponentials, e.g. $X(\omega) = \sum_i e^{-j\omega t_i}$ where $t_i > 0$ $\forall$ $i$ I expect the output to ...
76 views

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### How to implement discretized CWT with FFT?

I tried to make circular convolution (correlation actually because it is easier to understand for me) look like the Continuous Wavelet Transform (CWT) but got stuck because the conjugation was on the ...
863 views

### OFDM - why do we need IFFT?

This question is really related to - is there any need for IFFT in the first place? If we want to send a bunch of complex-numbers (vectors), then most OFDM discussions involve presenting those ...
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### Cepstrum: IFFT or FFT to enter the cepstral domain?

I'm trying to implement source-filter separation of some pre-recorded speech in Max/MSP. I'm unsure of whether one uses an FFT to enter the cepstral domain, or an IFFT. Some of the textbooks and ...