Page 2 - Vibrations 3
P. 2
When looking at a chirp signal it will have an appearance
of,
The upper waveform shows a low frequency start building
up to a high frequency.
The lower trace shows a high frequency start diminishing
to low frequency.
The spectrum is shown on the right, both waveforms
show the same spectrum.
This is a broadband spectrum where no individual
frequency is well defined.
The FFT is not an effective method for frequency analysis
as the frequency contents is not stationary.
Whenever you see a broadband spectral response you will
know the frequencies are not stationary – demonstrated
with the audio in the last lecture.
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