  The non-Hermitian skin effect is a distinctive phenomenon in non-Hermitian
systems, which manifests as the anomalous localization of bulk states at the
boundary. To understand the physical origin of the non-Hermitian skin effect, a
bulk band characterization based on the dynamical degeneracy on an equal
frequency contour is proposed, which reflects the strong anisotropy of the
spectral function. In this paper, we report the experimental observation of
both phenomena in a two-dimensional acoustic crystal, and reveal their
remarkable correspondence by performing single-frequency excitation
measurements. Our work not only provides a controllable experimental platform
for studying the non-Hermitian physics, but also confirms the correspondence
between the non-Hermitian skin effect and the dynamical degeneracy splitting,
paving a new way to characterize the non-Hermitian skin effect.
