butterworth

问题 I am trying to pass my audio through low pass filter, so as to filter out noise from it. However, the output of the wav is very noisy, and I am unable to understand why. Find the original and filtered wav and their resp. spectrograms below link. enter link description here The code I have used is: #https://stackoverflow.com/questions/25191620/creating-lowpass-filter-in-scipy-understanding-methods-and-units import numpy as np from scipy.signal import butter, lfilter, freqz, filtfilt from

问题 I'm trying to use a 20Hz low pass filter on data in R, but when I use the filtfilt function, the plot is different from the matlab. I'm using the following code in R: fc<-20 fs<-100 Wn<-pi*fc/(2*fs) testar<- butter(5, Wn, type="low") L2<- signal::filtfilt(testar,Tabela$posicao) plot(Tabela$tempo, L2, type = "l", col="red") The matlab code is: fc=20; fs=100; Wn=pi*fc/(2*fs); [b,a] = butter(5,Wn,'low'); posfilt= filtfilt(b,a,Tabela.posicao); The plot in matlab is: The R one: why the R one is

问题 I'm trying to use a 20Hz low pass filter on data in R, but when I use the filtfilt function, the plot is different from the matlab. I'm using the following code in R: fc<-20 fs<-100 Wn<-pi*fc/(2*fs) testar<- butter(5, Wn, type="low") L2<- signal::filtfilt(testar,Tabela$posicao) plot(Tabela$tempo, L2, type = "l", col="red") The matlab code is: fc=20; fs=100; Wn=pi*fc/(2*fs); [b,a] = butter(5,Wn,'low'); posfilt= filtfilt(b,a,Tabela.posicao); The plot in matlab is: The R one: why the R one is

问题 From this answer, I know how to create a High-pass Butterworth filter. From this video, I know that, lowpasskernel = 1 - highpasskernel . So, I created the following Low-pass Butterworth Filter, function [out, kernel] = butterworth_lp(I, Dl, n) height = size(I, 1); width = size(I, 2); [u, v] = meshgrid(-floor(width/2):floor(width/2)-1,-floor(height/2):floor(height/2)-1); % lp_kernel = 1 - hp_kernel kernel = 1 - butter_hp_kernel(u, v, Dl, n); % fft the image I_fft_shifted = fftshift(fft2

问题 This question already has answers here : High Pass Butterworth Filter on images in MATLAB (2 answers) Closed 2 years ago . According to Page#14 of this link, the equation for a high-pass Butterworth filter is, And, according to Page#17, the output should be something like the following, Now, I have looked at this answer in SO, and has written the following Matlab code using the formula given in the linked pdf document. The output looks different than that of the one given above. What is the