Difference between revisions of "Geopsy: Taper"
(New page: '''Taper''', reached from the Waveform menu, applies a taper (a.k.a. apodization window, a.k.a. window) to the signals in the active [[Geopsy: Signal Viewer|signa...) |
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'''Taper''', reached from the [[Geopsy: Waveform Menu|Waveform menu]], applies a taper (a.k.a. apodization window, a.k.a. window) to the signals in the active [[Geopsy: Signal Viewer|signal viewer]]. | '''Taper''', reached from the [[Geopsy: Waveform Menu|Waveform menu]], applies a taper (a.k.a. apodization window, a.k.a. window) to the signals in the active [[Geopsy: Signal Viewer|signal viewer]]. | ||
| − | The applied taper is a cosine | + | The applied taper is a tapered cosine window [[Wikipedia:Window_function#Tukey window|(Tukey window)]]. By clicking on Taper, a pop-up window appears with the following options: |
*"Time Limits" allows to specify the time interval out of which the signal will be set to 0. | *"Time Limits" allows to specify the time interval out of which the signal will be set to 0. | ||
*"Width" allows to give the width, in % of the time interval, of the slope of the taper as also defined for the [[Geopsy: Filter#Cosine Taper|cosine taper filter]] but in the frequency domain. | *"Width" allows to give the width, in % of the time interval, of the slope of the taper as also defined for the [[Geopsy: Filter#Cosine Taper|cosine taper filter]] but in the frequency domain. | ||
Revision as of 14:48, 9 March 2010
Taper, reached from the Waveform menu, applies a taper (a.k.a. apodization window, a.k.a. window) to the signals in the active signal viewer. The applied taper is a tapered cosine window (Tukey window). By clicking on Taper, a pop-up window appears with the following options:
- "Time Limits" allows to specify the time interval out of which the signal will be set to 0.
- "Width" allows to give the width, in % of the time interval, of the slope of the taper as also defined for the cosine taper filter but in the frequency domain.
Since the Fourier Transform of a boxcar function (too simple tapering window, equivalent to no taper) is a sinc function, the Fourier Transform of a signal without applying an appropriate Taper will be the multiplication of the true Fourier Transform by the sinc function. On the contrary, appropriate tapers have a Fourier Transform closer to a Dirac function that distorts less the Fourier Transform of the signal. It is therefore necessary to apply a taper before going to the frequency domain.
"Taper" modifies the temporary signals in the active viewer.
See also: Window function (Wikipedia)
