Table 2.

Frequency domain SF’s extracted from the FSFB. The s(k) is the FSFB spectrum, k is the sample of spectrum, and f_k is the value of frequency at spectrum sample k.

Feature Name	Equation	Feature Name	Equation
Mean frequency	$X_{mf}=\frac{{\displaystyle \sum _{k=1}^{K}s(k)}}{K}$	Standard deviation	${\sigma }_{{}^f}^2=\frac{{\displaystyle {\sum }_{k=1}^K{{\displaystyle \left(s(k)-X_{mf}\right)}}^2}}{K-1}$
Root variance frequency	$Xrvf=\sqrt{\frac{{\displaystyle \sum _{k=1}^K{(s(K)-Xmf)}^2}}{K}}$	Spectral kurtosis	$X_{fkurtosis}=\frac{{\displaystyle \sum _{k=1}^K{(s(k)-X_{mf})}^4}}{(K){\sigma }_f^4}$
Root mean square frequency	$X_{frms}=\sqrt{\frac{{\displaystyle \sum _{k=1}^K{f}_k^2{(s(K))}^2}}{s(K)}}$