How to filter high frequencies from recorded data?

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Hi,
I do have recorder data of air flow and time. Sampled with 25 Hz. But there is some high frequency noise I would like get rid of.
The blue line is original data. Yellow one is filterd with median filtration. After five negative peaks there is noise but it should be. These peaks should be in one peak. Than i would like to smooth the signal. I was thinking about using Fir filter but don't know which and how.
Thanks for your help!

Accepted Answer

Chandra
Chandra on 2 May 2022
Hi,
To remove high frequency noise, pass the signal through low pass filter.
Low pass filter can be of averaging filter, butterworth filter, Chebyshev filter etc..
Please refer the below example code for low pass filter with butterworth and averaging filter (averaging FIR filter)
load('data_f.mat');
plot(flow_S);
%% butterworth filter low pass filtering
%[b,a] = butter(3,0.1,"low");
%% normal average filter in place of butterworth filter
b = (1/20)*ones(1,20);
a = 1;
%% filtering
out = filter(b,a,flow_S);
hold on
plot(out);
refer to filter function matlab

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