\begin{table}%t4
\caption{\label{tab4}Frequencies found in data Subset~2.}
%\centering
\begin{tabular}{ccc}
\hline\hline\noalign{\smallskip}
Frequency   &  Amplitude & Comment   \\
(c~d$^{-1}$)        &    (m~s$^{-1}$) & \\
\hline 
0.0447   &  5.23 $\pm$ 0.41 & $f_{\rm rot}$ \\
0.1108   &  7.75 $\pm$ 0.40 & $f_3$  \\
0.2707   &  5.60 $\pm$ 0.34 & $f_2$ \\
1.1716   &  5.25 $\pm$ 0.38 & $f_1$  \\
0.0227   &  6.42 $\pm$ 0.38 & \\
0.1342   &  7.94 $\pm$ 1.35 & \\
\noalign{\smallskip}
$\sigma$ = 1.89~m~s$^{-1}$ & \\
\hline
\end{tabular} 
\end{table}