4.7.5. Signal Processing

You can perform data filtering and smoothing of graphs in the chart view. At least one graph must be selected for the operation as in the following steps.

Figure 4.30: Signal Processing operation

Figure 4.31: Steps for the Signal Processing operation

Step	Description
1	Click the chart view.
2	Select the target graphs for the Signal Processing operation.
3	Select Signal Processing from the menu bar.
4	Select the Type from the following options: Filtering, Smoothing, and Frequency Weighting.
5	Set the parameters for the operation.
6	Select Remove Ori. Curve if you want to remove the target graphs.
7	Click the button to create the graph.
8	Click the button to close the operation.

Figure 4.32: Parameters for "Signal Processing"

Signal Processing	Parameter	Description
Filtering	Filtering Type	Used to select the filter type. LowPass allows frequencies below the cut-off frequency to pass through. HighPass allows frequencies above the cut-off frequency to pass through. BandPass allows frequencies between lower and upper frequencies to pass through. BandStop blocks frequencies between lower and upper frequencies.
	Order	Used to set the filter order. When the value is smaller, the resultant curve may be smoother.
	Cut off Frequency	Used to set the cut-off frequency.
	Low Cut off Frequency	Used to set the lower cut-off frequency.
	High Cut off Frequency	Used to set the upper cut-off frequency.
Smoothing	Smoothing Method	Used to select the smoothing type. Moving Window Averaging reduces the large variation like peaks in the local region of the data by using local averaging. Savitzky-Gloay performs the local polynomial regression around each point to get smoother data. This is superior to "Moving Window Averaging" because it tends to preserve data features such as width or height of peak.
	Points of Window	Used to set the half-number of points for the moving window. As this value increases, the degree of smoothing increases.
	Polynomial Order	Used to set the polynomial order for the Savitzky-Gloay method. The larger the value, the more the peak will be preserved.
Frequency Weighting	Weighting Type	Used to select the weighting type. A-weighting is the most commonly used to measure the sound pressure level. B-weighting and C-weighting are alternative weighting functions. See the definition for Weighting.
Frequency Weighting	Frequency Axis	Used to set the base of the log scale.

4.7.5.1. Weighting

The weighting functions of A-weighting, B-weighting, and C-weighting can be defined as follows.

Figure 4.33: Weighting Functions, sourced by Wikipedia