System information

____________________________________________________
Blastware Advanced Module
Blastware Operator Manual 6–29
a. Process Waveform
Define the area you want to filter by using the analysis cursors within the Analysis window.
Within the Analysis window, select Filter from the Process menu. Select the waveform, or
channel, to filter from the drop down menu, Process Waveform.
b. Display Result In
Within the Filter Channel dialog window, select the location which you want the results of the
filtering to appear. The resulting filter can be shown in an existing waveform location or in a new
channel.
c. Name Result
Enter a Name for the filtered results. The new name is limited to 5 characters in length.
d. Window
The Window functions, reviewed in detail below, are used to reduce spectral leakage and apply
smoothing to assist in the analysis of recorded waveforms. Spectral leakage is where small
amounts of the signal energy are seen in frequencies that do not exist in the original waveform,
and have moved out of the original signal spectrum.
Each Window function within Blastware performs like a predefined narrowband, low pass filter,
and multiplies the time record by a length window that results in a smooth and gradual end at zero
of the defined window edges. The defined window edges are created by moving the cursors
within the Analysis window of Blastware.
Blastware offers the following windowing functions: Hanning Window at cursors, Hamming
Window at cursors, Blackman Window at cursors, Triangular Window at cursors, Welch
Window at cursors, and Bartlett Window at cursors.
Note: It is important to remember that Windowing distorts the original signal. Applying
a Window function narrows the frequency spectrum by suppressing distortion and signal
to noise ratio, avoiding the broadening of the signal. Selecting a Window function
depends on the knowledge of the original signal and the desired outcome.
A brief description of each Window function: