Hanning window on Imported data

Question

David Harra 2022-3-29

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https://ww2.mathworks.cn/matlabcentral/answers/1683649-hanning-window-on-imported-data

回答： Chandra 2022-4-5

Hi everyone

I am trying to add a hanning window to my time signal before I FFT it. I am not sure exactly what do. Looking at other examples I feel like I have information missing. I selected the time portion where my front wall signal is evident as you can see in the diagram below.

I have a Time & Data vector which are 1480 x 1 arrays (for the part of the selected signal) and the inspection frequency of my transducer is 10 MHz. If anyone can point me in the right direction, would be grateful.

Thanks

FName = 'Tit_10MHz_110F.flxhst';
MyData = read_history(FName);
Time = MyData.TimeRecB.Time;
Data= MyData.DataRecB(1).Data;
Transducer_Frequency = 10e6  %10MHz
%%
%Select the front wall signal
select= find(Time>=2.4e-6 & Time<=3.6e-6);
Time= Time(select);
Data= Data(select);

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Mathieu NOE 2022-3-30

hello

your signal start and stop with zero values

you don't even need to apply a window here - you can simply do the fft on the raw signal

a window would be needed if you had a persistent signal (non zero at both ends)

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Answer 1

Chandra 2022-4-5

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Hi,

To pass a filter over signal we can use "filter" function with appropriate coefficients

>>w = hann(64);  % we can use desired window size according to requirement
>>x = filter(w,1,Data); %w and 1 are coefficients, generally there are
                        % numerator and denominator of a transfer function

refer to the hanning window by using this link

https://www.mathworks.com/help/signal/ref/hann.html

refer to filter function using this link

https://www.mathworks.com/help/matlab/ref/filter.html

This can be achieved by using filtfilt function also, refer the following link

https://www.mathworks.com/help/signal/ref/filtfilt.html?s_tid=doc_ta