In the next picture the trend line is of exponential decay type and consequently the peak prominence value has changed a little bit. Note that the first four lines in the script are only necessary to generate a PowerCepstrum of a part of a vowel.Ĭreate KlattGrid from vowel: "a", 0.3, 125, 800, 80, 1200, 80, 2300, 100, 2800, 0.1, 1000 Next picture of a PowerCepstrum with its straight blue trend line and its corresponding peak prominence value was generated with the following script. To be compatible with the past, a standard least squares line fit can also be chosen but it is much less precise than the other two because a least squares fit is much more influenced by the peak cepstral values than the other two. The "Robust" method corresponds to the incomplete theil regression and is computationally faster but somewhat less precise. The default method, "Robust slow", corresponds to Theil's robust line fit. Or, we could use an exponential model in which the background cepstral amplitudes decay in a non-linear fashion.ĭefines how the line that models the cepstrum background is calculated. The slope of this line will generally be negative because the background amplitudes get weaker for higher quefrencies. We can model it with a straight line as was done in Hillenbrand et al.
#Cepstral peak prominence praat how to#
If you choose the "Least squares" fit method then it matters more.ĭefines how to model the cepstrum background. In our analysis this value is not so critical if we use the robust fitting procedure. (1994) article was chosen as 0.001 s in order to reduce the effect of very low quefrency data on the straight line fit. Both programs provide a smoothed version of the CPP (referred to as CPPS (Cepstral Peak Prominence Smoothed) in Praat and simply as the CPP in ADSV), and both programs have been included in a substantial body of clinical voice research. The lower value for this range in the Hillenbrand et al. The quefrency range for which the amplitudes (in dB) will be modelled by a straight line. A pitchCeiling of 300 Hz will correspond to a lower quefrency of 1/300≈0.0033 seconds.ĭetermines how the amplitude and position of a peak are determined. The lower quefrency is determined as 1 / pitchCeiling and this value is in general more critical than the value of the upper quefrency which equals 1 / pitchFloor. The CPP measure represents how far the cepstral peak emerges from the cepstrum background.ĭetermine the limits of the quefrency range where a peak is searched for. The CPP measure is the difference in amplitude between the cepstral peak and the corresponding value on the trend line that is directly below the peak (i.e., the predicted magnitude for the quefrency at the cepstral peak). Calculates the cepstral peak prominence measure (CPP) as defined by Hillenbrand et al.
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