Table 1.

Summary of previous work identifying clinically relevant cepstral peak prominence (CPP) cutoff values.

Author	Year	Language	Study size	CPP method	Group classification	Sustained vowel CPP cutoff	Running speech CPP cutoff
Heman-Ackah et al.	2003	English	281 patients (176F/105M)	CPPS (Hillenbrand)	Perceptually mild vs. severe dysphonia	10 dB	5 dB
Heman-Ackah et al.	2014	English	835 patients, 50 controls	CPPS (Hillenbrand)	Perceptually normal vs. dysphonic	n/a	4.0 dB
Yu et al.	2018	Korean	214 patients (142F/72M), 74 controls (47F/27M)	ADSV CPP	Perceptually normal vs. dysphonic	12 dB	7 dB
Núñez-Batalla et al.	2019	Spanish	72 patients, 52 controls	CPPS (Praat)	Normative values (not cutoff values)	Female: 16.0 dB Male: 16.4 dB	Female: 7.9–11.3 dB Male: 7.8–10.9 dB (cutoff varies with sentence)
Aydinli et al.	2019	Turkish	27 patients, 27 controls (40M/14F, pediatric)	ADSV CPP	Nodules diagnosis vs. normal voices	No thresholds, but found significantly lower CPP in pediatric speakers with nodules vs. age- and sex-matched controls for most, but not all, speaking tasks.
Delgado-Hernández et al.	2019	Spanish	136 patients, 47 controls	CPPS (Praat) in two configurations	Perceptually normal vs. dysphonic	Configuration 1: 23.62 dB 2: 13.96 dB	Configuration 1: 18.4 dB 2: 8.37 dB
Lee et al.	2019	Korean	1,029 patients (512M/517F)	ADSV CPP	Normal vs. mild	10 dB	7.7 dB
					Mild vs. moderate	7.5 dB	5.4 dB
					Moderate vs. severe	4.1 dB	2.9 dB

Note. F = female; M = male; CPPS = smoothed cepstral peak prominence; ADSV = Analysis of Dysphonia in Speech and Voice.