Sound: To Harmonicity (ac)...

A command that creates a Harmonicity object from every selected Sound object.

Purpose

to perform a short-term HNR analysis.

Algorithm

The algorithm performs an acoustic periodicity detection on the basis of an accurate autocorrelation method, as described in Boersma (1993).

Settings

Time step (standard value: 0.01 s)
the measurement interval (frame duration), in seconds.
Minimum pitch (standard value: 75 Hz)
determines the length of the analysis window.
Silence threshold (standard value: 0.1)
frames that do not contain amplitudes above this threshold (relative to the global maximum amplitude), are considered silent.
Number of periods per window (standard value: 4.5)
4.5 is best for speech: HNR values up to 37 dB are guaranteed to be detected reliably; 6 periods per window raises this figure to more than 60 dB, but the algorithm becomes more sensitive to dynamic changes in the signal.

Usage

You will normally use Sound: To Harmonicity (cc)... instead of this command, because that has a much better time resolution (though its sensitivity is 60, not 80 dB).

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© ppgb, September 16, 2003