Feature space It is sometimes desired to observe the distribution of raw features either within a syllable or within a longer time scale. This is a qualitative method, and its analytic equivalencies are the principal component analysis (PCA) and a variety of cluster analysis and feature classification techniques. Launch
SA+, go to ‘explore and score’ and open Example 2. Now outline Syllable 1:
Click the feature space tab. On the top right you will find two radio-buttons groups titled ‘Select sound’ make sure that sound 1 Draw All button position is down. Select the red button from the color palate on the top and click Draw .
The image should look like this:
Next, outline the second syllable, click on the blue color and on the X marker, and then click Draw:
Now rotate the image and pan it using the mouse, until you can only see Wiener entropy versus pitch:
Clearly, the two syllables differ in pitch and in Wiener entropy, but less different in FM. Now, outline syllable 1, select Red, and Draw, outline syllable 2, select Blue and Draw, outline syllable 3, select Green and Draw:
What is this exercise good for? Well, it is a way of examining the emergence of categories of sounds in a continuous space. For example, if you suspect that ‘
Dee’ notes of two populations of chickadees are distinct – you may examine the data in feature space. Outline each note type and use a color code to distinguish between the populations. Select several examples from each population and see how it looks like before you get yourself committed into heavy quantitative analysis.