  In this work, we experimentally report the acoustic realization the
two-dimensional (2D) Su-Schrieffer-Heeger (SSH) model in a simple network of
air channels. We analytically study the steady state dynamics of the system
using a set of discrete equations for the acoustic pressure, leading to the 2D
SSH Hamiltonian matrix without using tight binding approximation. By building
an acoustic network operating in audible regime, we experimentally demonstrate
the existence of topological band gap. More supremely, within this band gap we
observe the associated edge waves even though the system is open to free space.
Our results not only experimentally demonstrate topological edge waves in a
zero Berry curvature system but also provide a flexible platform for the study
of topological properties of sound waves.
