One of the most popular analysis methods for time/frequency analysis is a Time-FFT. You can
perform this analysis in SIGVIEW automatically to see how signal spectrum changes through
time. The resulting graphics is a 3D graphics with time and frequency as X/Y axes and signal
amplitude on Z-axis. This function simply divides your signal into possibly overlapping segments,
calculates FFT for each segment and puts all FFT results next to each other in a 3D graphics.
1. In this How-To, we will show you how to apply the same concept to other analysis functions
and to see how, for example, probability distribution of a signal changes through time. Of course,
you can use it to track any other function, for example autocorrelation, integral curve, ...
2. As a first step, you should load one signal in SIGVIEW, for example guitar.wav from Examples
subdirectory of SIGVIEW installation directory.
3. Zoom-in to a smaller part of the loaded signal by using "Edit/Zoom to X samples/values" menu
option. Choose 1024 samples length.
4. Use "Signal tools/Probability distribution curve" menu option to calculate distribution curve for
zoomed signal part.
5. Click on new Distribution curve window and select "3D Tools/Track changes as 3D graphics..."
from main menu. In the settings dialog leave default value of 50 for "Last changes to track
option". That will be number of columns in your 3D graphics. The resulting Control Window
should look like this:
6. Click on signal window and then click on "Play" button in toolbar (Play & Navigate/Play (no
sound) menu option). Your signal part will move through the whole signals, distribution curve will
change and add new column in 3D graphics on each change. The speed of moving is determined
by the Step property of the window which can be
changed by using Play & Navigate/Step
change... option". At the end, last 50 changes of the curve will be stored in a 3D graphics. The
result will look like this:
7. Note that X-axis units on 3D graphics is "change" - it is simply a column index starting from 0
8. By using combination of 3D-ruler and
Ruler extraction options, you can even use this graphics
to restore each of columns as 2D graphics again.