TFR	Time-frequency representation
Jitter (absolute)	inter-cycle variation of the fundamental period
Jitter(relative)	relative period
Jitter(rap)	relative perturbation
Jitter(ppq5)	five-point period perturbation quotient
Shimmer(dB)	Variability of the peak-to-peak amplitude
Shimmer(relative)	relative amplitudes of consecutive periods
Shimmer(apqP)	three, five and eleven-point amplitude perturbation
HNR	harmonics-to-noise ratio
HNR(mean)	mean HNR
HNR(SD)	standard deviation of HNR
WD	Wigner distribution
CWD	Choi-Williams exponential function
pD	joint probability density distribution
E(t)	average instantaneous spectral energy
$f_{mi}\left(t\right)$	average instantaneous frequency
$f\_Cres\left(t\right)$	instantaneous frequency peak
H_t	instantaneous information entropy
H_f	spectral information entropy
H_tf	joint Shannon entropy
IE(f)	spectral information
K	kurtosis
$〈t^n{f}^m〉$	joint time-frequency moment
SVM	Support Vector Machine
NN	Neural Networks
LDA	Linear Discriminant Analysis
LR	Linear Logistic Regression
RF	Random Forest
C	control group
B	group of ALS participants diagnosed with bulbar involvement
NB	group of ALS participants not diagnosed with bulbar involvement
A	group of ALS participants with or without bulbar involvement