how to smooth Fourier Spectrum of an acceleration-time history

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Muhsin
Muhsin on 18 Oct 2017
Commented: Muhsin on 25 Oct 2017
Hello; I would like to smooth the fourier spectrum of an acceleration-time history. The Acce-time history is attached. Can anyone help me please? Thank you.
Muhsin

Answers (1)

Christoph F.
Christoph F. on 18 Oct 2017
To make the spectrum appear smoother, you can either apply a window function to the signal in the time domain by element-wise multiplication (MatLab offers window functions like blackman()/hamming()/hanning()/kaiser()/triang()/etc) before calulating the Fourier transform.
Or you apply a lowpass filter to the spectrum; however, in this case you need to make sure that no frequency shifts occur, for example by using filtfilt() instead of filter or by manually compensating any shifts the filter produces. The most practicable type of filter for this task is a symmetric FIR filter with even order.
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Muhsin
Muhsin on 25 Oct 2017
Dear Christoph; I already have the fourier spectrum. So How can I smooth this fourier directly? Thanks

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