  The pole-skipping phenomenon is a special property of the retarded Green's
function of black hole perturbations. We turn to its analog in acoustic black
holes, which may relate to experiments. The frequencies of these special points
are located at negative integer (imaginary) Matsubara frequencies
$\omega=-i2\pi Tn$, which are consistent with the imaginary frequencies of
quasinormal modes (QNMs). This implies that the lower-half plane pole-skipping
phenomena have the same physical meaning as the imaginary part of QNMs, which
represents the dissipation of perturbation of acoustic black holes and is
related to the instability time scale of perturbation.
