Cepstral Peak Prominence (Smoothed) and Voice Disorder Screening

1. A healthy voice with no suspected voice disorder.

2. A voice where voice disorder is suspected through subjective observation skills and confirmed by CPPS analysis.

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A sound cepstrograph showing production of [ ɑː ]. Notice the clear band of energy with little noise above or below, corresponding to the Cepstral Peak Prominence. This indicates a clear signal with little jitter or shimmer. This is a strong indicator that the vocal folds are meeting smoothly and that there is no voice disorder present.

A sound cepstrograph showing production of [ ɑː ].

Note the weaker bands, and the fact that there are 3-4 bands instead of one single band.

Note the lack of a substantial peak, and the very low CPPS value compared with the typical vowel production (left).
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See the CPPS peak graph above for my production of [ ɑː ] (segment of 2-3 seconds taking from the middle of the vowel).

Note that the value for both with and without voice detection are essentially the same as this is a single vowel, rather than connected speech with voiceless segments.

Note also that the value is 17.46 dB, well above the threshold of 14.45 dB, below which a voice disorder might be suspected.

The value of 9.07 dB is below the threshold value of 14.45 dB and therefore a voice disorder is very likely to be present.

This indicates a voice disorder.

CPPS Threshold values

A free plug-in for Praat by Elizabeth Heller Murray (2022) provides figures relating to CPPS thresholds.

See the Voice Assessment: Objective vocal assessment and analysis for download links.

Guide to free software to evaluate vocal pitch, loudness and screen for voice disorders

Recording considerations

CPPs picks up on noise and distortion (jitter and shimmer). For this reason:
  • Only use recordings made 'live'. Do not analyse recordings made online over Microsoft Teams, Zoom, or similar.
  • Only analyse recordings made with a high-quality microphone is a quiet room.
  • Always consider the service user interview (case history) and subjective observations of voice.

CPPS is sensitive enough to detect vocal fatigue and post-viral infections affecting the vocal folds.

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