  We give bounds on Kazhdan constants of abelian extensions of (finite) groups.
As a corollary, we improved known results of Kazhdan constants for some
meta-abelian groups and for the relatively free group in the variety of
$p$-groups of lower $p$-series of class 2. Furthermore, we calculate Kazhdan
constants of the tame automorphism groups of the free nilpotent groups.
