Frequency Contours

Frequency Contours
 
Open the song “Example 2” and Click the “Contours” button (next to the “Derivatives” button):

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Fig 1: Decrease in contour threshold - show zero crossings

Click back and forth a few times “Derivatives” and “Contours” and as you can see, this display show the zero-crossings of the spectral derivatives. This algorithm is a bit more complex than it seems, details are given in the next chapter. There are two parameters that might need manipulation to obtain contours of good quality with your data. This adjustment is recommended because the contours are used to calculate some of the sound features (continuity and principal contour).

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Fig 2: The contour threshold slider

Decreasing the contour threshold will detect zero crossings in a less contrast background. For example, decreasing the threshold to zero (and then reopen the sound) looks like this:

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Fig 3: Sound with contour threshold set to zero

Now set the threshold back to 10 and reopen the sound looking at the zero crossing, this will give you an intuitive feeling to what the threshold is achieving.
In "options & settings" you will find a second parameter:

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Fig 4: Sound with contour threshold set to 10

The second parameter, contour bias, has no visual effect but it does affect some interpretations of the contours, we will discuss these interpretations in the next chapter.

In "options & settings" you will find a second parameter:
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Fig 5: The contour bias paramenter

The second parameter, contour bias, has no visual effect but it does affect some interpretations of the contours, we will discuss these interpretations in the next chapter.

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